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MG MGA - 3' carb intake blower neatly installed

The thread a few months ago prompted the search for a neat unobtrusive blower in the "A's" carburettor air inlet duct to especially reduce the carbs temperature in stationary traffic.
The suggested 3" Attwood blower looked good and coincidentally an MGA pal discovered the perfect rubber pipe reducer (Code NAC0752 from Evolution Aqua) which by a pure fluke is a nice push fit both onto the blower (see pic here) and into the duct. As well as cutting off the feet, I removed 12mm from the outlet end where it pushes onto the reducer to clear the bend in the front flexible 4" duct. (not removed in pic)
As yet we haven't had any really hot (by English standards)weather yet this summer to test it out, but so far any restriction of aiflow by this stationary 3" fan has not appeared detrimental at normal driving speeds. I have fitted a manual switch so I can play with this new toy properly when the 'vapours' hit!
See the following for the installed pic.
Pete

P N Tipping

Here the assembly is simply pushed in and that's it. I find the lack of holes or mods to the car the important thing here. I'll neaten up that wiring later - at the time I just had to see it run... With engine running I can't hear the fan which is quieter than the upfront Kenlowe anyway. What do you think?
Pete

P N Tipping

Nice job Pete,

I think it looks like a very neat solution. Really interested to see how it performs...
N McGurk

Pete, -- Are you sure about the part number foe the rubber adapter? Evolution Aqua web site lists NAC0752 as 3" to 2" Adaptor, and a picture shows it as a long rubber cup (stepped tube) with two band clamps. See here:
http://evolutionaqua.com/acatalog/Flexible_PVC_Boots_.html
I get it that the larger end must fit inside the steel pipe on the car body, Does the small end fit inside of the blower outlet end?
Barney Gaylord

Peter,
Well done. By coincidence I have just fitted the 4 inch attwood blower. Like you I have not really been able to test it properly until the weather improves.
I am grateful to Lindsay who did the pioneering work, and I just followed his design. The pump is completely invisible looking through the grille so I was pleased with the final result.

Just hoping for some warm weather so I can see if it has cured the vapour lock problem.
Graham M V

Barney
Yes I'm quite sure about the adaptor, it took a few tries to discover it! The clamp bands are discarded. You are exactly right, it is actually a 3" to 2" (Nominal bore) reducer. So, by a pure fluke, the large O/D of this particular reducer fits tight in the car's duct as in the installed view and the blower fits tightly over the O/D of the small end - as in the first pic. As I say I had to cut off 12mm(1/2") off the outlet end of the blower to get it further onto the small end of the reducer to allow the blower clearance inside the downward curve of the flexible duct.
Here's to some really hot weather for the MGA - never thought I'd say that..!

Graham - I think with that 4" thing of Lindsay's fitted you've got no chance of vapour lock ever again mate!
Pete
P N Tipping

Pete

Interestingly I had been suffering poor starting recently following heat soak after a run with the ensuing rough running for some seconds. A couple of weeks ago I richened the mixture on both carbs and the problem has completely gone away.

Steve
Steve Gyles

Steve
I guess with a hot-start the carbs are suffering from vapour lock and you were always advised to start using say 1/4 throttle for a hot engine start. If you are using 95RON fuel with 5% ethanol, the boiling point will be lower. Also with ethanol around I've seen richer needles can be recommended. Richening your mixture will probably have led to cooler running = less heat-soak?
Currently, for my higher compression ratio, I'm using the higher octane fuels that have no ethanol as yet and the engine is running like a dream. (V-Power has 5% ehanol - beware)
Pete
P N Tipping

Pete..that is a very good solution.....the rubber surround use is ideal. I put a 3 in in the duct and hose but further forward because I had to partially push the metal duct to clear the Judson pulley.....so I can't use your idea but wish I could.
Neil Ferguson

Well, I got enthused and ordered the 3" blower from Walmart for $18.88 plus tax and $1.97 for shipping. Should have it in less than a week. I have in mind to cut the legs off and wrap it in stiff foam rubber, then just stuff it inside the steel pipe duct with little or nothing protruding out the back end of the steel pipe.
Barney Gaylord

Barney..it does wedge in very well like that. I tried it and I added the screws as a 'belt and braces ' solution. I have decided to leave the control on a hidden switch under the dash ( behind a new two dial pod I put in with the )..seemed a better option than wiring up to a thermostat...and I can use my pre-programmed grey cells to judge the time.
Neil Ferguson

Barney, that sounds good to me. At least worth trying and again with no mods to our precious motor's metal.
My switch is under the dash too Neil after a rummage for the switch amongst all those bits you keep forever...you know the scene. Nothing like a fumble under the dash!
Pete
P N Tipping

I have fitted a marine 4 inch blower and found it to be very effective from the amount of forced air emitted through the vents on the side of the bonnet. I have sanded down the moulded parts on the outside of the unit to make it round like the pipe and sprayed it black both outside and inside . I fitted a short length of pipe on the front edge to make the unit less conspicuous. I used the fog lamp switch for on off.

c vassallo

Mine iis the same as C Vassallo's except I used some left over vent tube, cut it down the length and wrapped around the exposed middle part of the pump, to disguise it completely.
I use the F switch too.
Graham M V

I have often wondered about this issue and I take my hat off to you guys who have designed and built the systems shown above.

I have mentioned before on this forum that I created an immediate 5 degree drop in water temperature and therefore probably engine compartment temperature by accidentally leaving the gear box filler bung out of the tunnel on one occasion. The blast of air out of the 'pressurised' engine compartment was very strong and I have often thought about an extractor fan arrangement at the rear of the engine compartment. I have yet to come up with a realistic solution that could be incorporated into an assembled car, but I keep my thinking cap on.

Steve
Steve Gyles

Steve,

The problem with your solution is that it will surely only really work well when the car is moving. I have only encountered the vapourisation problem when stuck in slow or stationary traffic.

I am waiting for the 3 inch versus 4 inch debate to come to a conclusion and then will be joining the bilge blower club.

Malcolm

Malcolm Asquith

Malcolm

Correct, but my idea was much the same as above, assuming a switchable fan is installed. It is just that I have already proven that it works extracting from the back of the engine bay and I was looking at means of harnessing my findings. On the big minus side, the cockpit environment was not healthy during my accidental experiment!

Steve

Steve Gyles

Steve..I agree ..it is truly difficult to think how a suction fan could be positioned to do much good without gross inconvenience and/or modifications..and why do you need it or want it when you have excellent positions for locating a pusher bilge type fan? The affect of the latter can also be focussed on the area of maximum need and is supplied with fresh cool air from in front of radiator...plus ram affect when moving.
Neil Ferguson

I have just been doing a few basic experiments using a thin metal wire rod with cotton lengths attached to it. At idle I made some observations the best I could with the hood/bonnet closed (lying underneath at times):

1. More air vented out of the left 'MG' vent than the right.

2. Air vented forward out of the duct where the guys are now placing the fan.

3. Airflow aftwards round the front carb was good. It then changed direction to outwards between the 2 carbs toward the vent. Airflow appeared to be stagnant or may be forward around the rear carb.

Looking at the way the ducting is set up I cannot help feeling that most of the blown air with this modification, when combined with existing airflows is going to take the line of least resistance around the back of the front canister and straight out the MG vent.

Steve

Steve Gyles

Neil

Sorry, I did not answer your question in my last post. Don't you guys ever go to bed down there? It must have been about 3 in the morning when you posted!

I just have this hang-up about all that hot air getting trapped under the bonnet when stationary. Big slab of a shelved firewall at the back where it all hits and where are the vents? Half way forward. A bit also gets down the tunnelling and underneath. It just seems so obvious to me to keep the airflow going backwards instead of it hitting this wall and coming back forwards again. I think that the bilge pump is just going to ramp up the pressure at the back resulting in most of its air going straight out the MG vent. There again, I really do hope I am wrong.

Steve
Steve Gyles

how 'bout the louvered vents in the Twin Cam inner fender panels -- have these ever been evaluated for their effectiveness in heat removal from the engine bay? Not an easy mod for a push rod car though....

George
G Goeppner

Steve, my thinking... At speed, cool, intake air comes in through the carb duct and the bonnet vents. Hot air comes in through the rad. The air round the engine will be whipped out underneath.
Stationary, with the standard set-up, only a reduced flow of hotter air comes through the rad with engine and exhaust heat building up in the reduced, hotter flow and only a small flow out through the bonnet vents and the rest trying to push out underneath AND forward out the carbies cool air duct!
With our blown air duct idea, when sationary, you still have the same hot air coming through the rad, but now cool air will be really moving across the carbs to keep the fuel float chambers and carbs cooler and still feeding the intakes with much needed cool air. This must reduce the chance of vapourisation which is our aim here. This extra blown cool air will also have some cooling benefit around the engine compartment.
I don't think your gearbox bung hole idea will introduce the necessary cool air for the carbs when stationary...
Pete
P N Tipping

Pete

I agree entirely with your first paragraph. In your second paragraph I am happy to accept that the front carb receives a good cooling from the prime fan and from your bilge pump. I am yet to be convinced that the rear carb will benefit, especially as the float chamber is back against the firewall in stagnant air. It is possible that the common gallery will reduce the effect but it won't remove it entirely. In my view the rear carb has to have a good airflow past it to rectify the problem and this won't happen by bouncing hot air back off the firewall.

Happy to be proved wrong.

Steve
Steve Gyles

I may have given the wrong impression about the gearbox bung hole. I am not advocating fuming us all out in the cockpit, nor running a chimney stack up through the roof. It was intended as a demonstration of a moving car, with the bulked up, relatively high pressure stagnant air sitting at the back of the engine compartment with no where to go. However, from memory, when stationary there is relatively little air going out of this hole. All that I have been trying to get across is that the current remedies at cooling have all been geared towards blowing more air into an already inflated balloon. That balloon could really do with an exit at the end rather than half way down. My exit, for which I have no design, would nevertheless consist of a fan assisted extraction rearwards, thus creating a flow around the rear carb (and perhaps the exhaust manifold) that takes the heat away rearwards instead of it heat soaking its way forward to the MG vents.

Steve
Steve Gyles

If i recall there was once produced a wind tunnel test report that showed the oval grilles actually suck in air, not vent it out, due to high pressure air in front of the scuttle. Words from this article are;

"1- The MGA grill alters the course of the air flow entering the front off the car in such a manner as to deflect it away from the entrance to the carburettor air duct and heater duct.

2- The high-velocity air passing beneath the car reduces the pressure within the engine compartment to the extent that it is lower than the pressure on the hood.

3- The air outlets on the hood are located in a position at which air pressure outside the hood is greater than inside and results in air flowing in rather than out.

4 - A strong stagnation vortex exists at the base of the windshield, disturbing the flow and giving rise to problems with rain and the operation of the windshield washers."

Sounds like an undertray might be a better solution.

Ref George's question, On my Twin Cam i have removed the inner wing access panels and it runs no cooler, or indeed, no hotter. A suggestion once made to me was to place spacers under the bonnet (hood) hinges to lift the rear of the bonnet up and possibly provide a scavenge effect - this would spoil the panel line up, and if the wind tunnel test was right, would not work.
regards
Colin
C Manley

Colyn

That is correct when the car is moving, but they vent outwards stationary.

Steve
Steve Gyles

I haven't had an opportunity to properly test the effectiveness of my 4 inch blower but have just re-read Lindsay's comments from last June when he installed his 4 inch pump.
His experiments showed conclusively that the blower cured lumpy running from vapour lock. So whatever the science behind air flow, etc, it does the job!

In my view, the only question is will we get enough sun to make it worthwhile? Lets hope so!

Graham M V

Steve..your wire and thread experiment is a good one. I have not done such detail with my 3 in blower in place but I did do a basic survey after intalling the unit and found air gushing out of the local bonnet vent and also pushing out underneath the car below the bulkhead.
I also remember the report summarised so well by Colin .The key relevant issue is that the wind suction affect under the car at speed will further pull airflow down and probably reduce or stop the local vent flow . I believe a large volume of cool(er) air from in front of the radiator will be passing to the bulkhead past the carbs ( or one carb way back with the Judson )and diverting to the only place it can go.....down.
Neil Ferguson

In standard configuration, air flow through the cowl vents transitions from outward to inward at about 25 mph. This is entirely due to build up of air pressure in front of the windscreen, which reaches farther forward at higher speed.

I have some practical experience with this from my more active autocross days in the late 90's. After a hot lap around the track I would open the bonnet for cooling in between runs. It was common to find the rear carburetor dashpot warm, but I could hold my hand on it, while the front carb was too hot to touch for more than a couple of seconds. It was quite obvious that cool air was entering the cowl vent to cool the rear carb more than the front one.

The Attwood blowers running free flow at discharge end produce a 30 mph wind from the 4" unit (230-cfm) and 33.6-mph wind (145-cfm) from the 3" unit. Attwood defines a "system" with a 3-foot duct, one 90-degree bend, a collector box, and a louvered discharge vent. This might be fairly close to the flow resistance you have in this MGA application. Then Attwood shows 125-cfm for the 4" unit and 100-cfm for the 3" unit. This is more like 16-mph for the 4" unit and 23 mph for the 3" unit. This is why I like the idea of placing the 3" unit in the steel duct blowing directly at the carburetors. It would be a smaller diameter air stream at higher velocity.

These will definitely do a good job of cooling the front carburetor. Some of this induced air flow (maybe most of it) will flow out the cowl vent at slow ground speed, meaning the cool air will flow right past both carburetors (or at least past the air cleaners). It will be interesting to find at what ground speed it might transition from outward flow to inward flow (if ever). If it does ever transition to inward flow at the cowl vent, then both the inward cowl vent flow and the blower flow will be directed at the carburetors. Considering the input air velocity from the blower, and the direction of travel, I suspect this would create a swirl effect in the engine bay where some of the cool air would travel to the rear corner and then somewhat across the heater shelf area before exiting below the chassis. This may even have some small cooling effect on the upper bulkhead and heater shelf (although I doubt that anyone will even notice that or ever measure it).

The more we chat about this the more anxious I am to give it a try. Does anyone have an idea how to put a temperature sensor in the engine bay to monitor while driving?
Barney Gaylord

Medium level VOM now commonly can be had with temp sensing and various probes. Small bead probes (the usual supplied as standard, but a bit short, maybe 30") are quick response items. Plug in probes in infinite variety to any length can be found at Omega Engineering. The giant set of books from Omega on measuring nearly anything is or was free for the asking.

I use my meter all the time for temp measurements, with one small bead and an optional rigid straight probe; mine came from MSC. I've seen meters as low as $30 with
K thermocouple capability. Cheap ones are often limited to 1600F, mine goes to 2200F - I use it for heat treating parts in an enameling furnace.

FRM
FR Millmore

Agree with you totally Barney and agrees with my bit above but so much more eloquently... Funny I was thinking the same as you, we need a temperature sensor, say between the carbie intakes to give an average inlet temperature when driving along, without blower and when stationary with the 'blower' on. Wonder if we could do it somehow with an ordinary thermometer? Need to be a bit quick I guess!
My pal who had this 3" blower set-up on his "A" first is currently driving around France with the intention of doing the Le Mans Classic before his return - so he should be seeing 30deg C temps - perhaps we will get some hot running results this way...
Pete
P N Tipping

Interesting stuff from Barney. It has just made me do a few more experiments this morning with bits of cotton and tissue paper.

First of all I attached a few square inches of tissue paper to a length of cotton and attached it inside the front left duct where the bilge pump is fitted on the subject car. After 3 runs up to 40 mph the paper was still inside the duct. i.e. it had not been blown into the engine compartment. It was only when I reduced the paper to a miniscule amount (photo) that I found it hanging inside the compartment after a similar speed check. From this rough and ready experiment it would appear that airflow into the engine compartment from this duct is very low until speeds above about 30-40mph are reached. I will experiment at higher speeds and different paper weights once it stops raining and after I have fitted the new starter which was going to be my main job today before I got sidetracked!

I also put some small cotton threads on the MG ducts. I took the car on a longer and faster run up to 70mph and never got them to go inwards. In fact they laid aftwards towards my windscreen throughout. Then I realised that of course I have a sports windscreen that is also fitted with the more raked Le Mans stanchions. I was therefore not getting that pressure build-up over the vents that Barney described. So it seems a lot of my tests and findings are not relevant to the standard MGA! Incidentally, I was able to handle both carb bowls, although I will agree that the rear was a tadge cooler. They would both have probably got a bit hotter if I had been on a longer run.

Steve

Steve Gyles

Steve, if I remember correctly, when the "A's" were very new I recall a piece of film showing the air entering the top ducts at 100mph just using pieces of cotton or was it smoke? This showed the depression under the bonnet. Maybe your tissue idea is a bit too big for the bonnet duct test?
You could be right about the front duct, as when our summers get up to proper temperature my water temperature gauge runs coolest at 45mph either faster or slower it appears to get hotter. Could this be due to increasing cool air getting to the carbs up to 45mph and after that the increased power requirement bangs more heat into the equation than the rad can cope with?
Pete
P N Tipping

Pete

I have just been for another run. I stuck the cotton and tissue wad inside the MG vent. I never went faster than 40mph and I found the wad hanging down inside, so despite my other bits of cotton showing no discernible inwards flow there obviously was some.

Fascinating. Kept me out of trouble today!

Incidentally, whilst peering down inside I noticed that on our RHD drive cars there would be room to bolt one of your bilge pumps on the blanked off LHD steering assembly bolts on the vertical bulkhead, pointing downwards. Now that interests me. Possibility putting my extraction theory to the test!

Steve
Steve Gyles

See air flow testing here: http://mgaguru.com/mgtech/history/hs130.htm
Barney Gaylord

Interesting article Barney, so that's what they did over the pond. I definitely remember something similar going on over here too. It seems the screen isn't badly affecting the bonnet vent's pressure, the inward flow then basically being due to under bonnet depression. Shame we do not know what speed that test was being run at.
Pete
P N Tipping

Steve, with respect I think your vertical fan idea would be a waste of time here mate. Using this idea how would cool air get to the carbs?
Pete
P N Tipping

Pete

Mass flow out, mass flow in. Stationary it would pull the air through the front and top ducts and blow it through underneath. I think that the vacuum cleaner (suction) effect would lower the overall engine compartment temperature more effectively than the blower into the compartment. After all, that is what is found to be most satisfactory with the radiator. Although I do accept that the blower would provide a better spot cooler for the front carb.

Steve
Steve Gyles

Now the question for the other side of the car.

If one of these was put in the heater hose, and the standard heater motor cage fan removed, would this be a way to get more air into the footwell and make temperatures more comfortable, particularly for coupe owners?
dominic clancy

Now we're off..! Good thinking Dominic
Pete
P N Tipping

Dominic. I would hazard a guess at yes. I doubt if the standard caged fan gets anywhere near 100cfm.

Steve
Steve Gyles

I have in mind to try that. The 4" bilge blower was originally recommended by John Twist for lots of vent air through the heater. I don't think you need to remove the original heater fan, as the bilge blower will likely blow nicely right through the original fan wheel. Squirrel cage fans are used because then provide good pressure head in a duct system while running quietly. The bilge blower axial fan will likely make more noise even when inside the air duct.

The 4" fan would provide more air flow for venting the cockpit. The 3" fan buried inside the air duct is likely to be substantially quieter than the 4" fan up front. They should both improve summer venting and winter heating. I have no idea about the subjective difference in air flow until I could try them both.

Since I installed full under carpet padding plus the under dash pad, cockpit heat in my roadster has not been a problem, but extra vent air would likely help the Coupe, and maybe also the roadster with top up in full sun.
Barney Gaylord

My 3" blower arrived today. I promptly cut the legs off, wrapped 1/2-inch of foam weather strip around the center, stuffed it into the metal air duct ahead of the carburetors, and installed some temporary wires.

First observation is, it seems to blow plenty of air to cool the carburetors, although it blows more directly on the air cleaners. I may make some attempt to point it a bit more inboard.

Second observations is, it makes about the right whining noise that I expected, not as quiet as a squirrel cage fan, but with bonnet closed and engine running, not terribly objectionable (for what it is expected to do).

Third observation is, the thing transmits an audible vibration through the body shell that is very noticeable in the cockpit (and anywhere around the car). It sounds very much like a 60-cycle electrical hum from a transformer, and fairly loud. I am significantly displeased with this feature. I may try relocating the blower a little farther forward where it will be supported inside of the flexible duct with no direct contact to the metal car body. For those mounting the 4-inch blowers on the factory legs, you might try rubber isolation mounts to reduce mechanical noise.

No hot weather road test yet.
Barney Gaylord

Reference to Dominic's idea of putting a blower in the heater ducting, anyone know if the existing blower switch and wiring would be up to the job (2.5Amp for the 3" i recall)?
regards
Colin
C Manley

Interesting about the vibration Barney. Using your foam packing idea it should be quite isolated from the body. With the rubber reducer I have also put some 1/4"x1/2" sticky-back foam around the front end of the blower just in case it touched the front fexible. From my right-hand driving position I can't even hear when its on with the engine running. Re: Air only blowing on the air cleaners thinking, I reckon just the fact of getting some cool air around the carbs has to make a difference and that blown air won't be just a "straight rod of air", I'm sure it'll get quite well disturbed with the engine and Kenlowe fans blowing too. Let's wait for that hotness...
Pete
P N Tipping

Not a hot day I appreciate, but I thought I would conduct an experiment with my air extraction theory. I got the car up to temperature then returned to my garage where I left the car idling. I put my famed marmalade thermometer (water temp gauge calibration saga from last year) on the shelf immediately in front of the heater unit. It stabilised at 140 whilst the water temperature gauge settled at 182 degrees. I then got my 'George' vacuum cleaner into action with its suction spout pointing upwards behind but below the rear carb. Max suction is 84 cfm. In 2 minutes the thermometer dropped to 135 whilst the engine temp remained steady. The theory worked. I guess the next step is to repeat it with the temperature probe in other places, probably starting off with the subject front carb.

Steve

Steve Gyles

A couple more comments from the experiments I did yesterday.

1. Although my extractor worked, I would be concerned about the hostile environment of placing the bilge pump there. My vacuum got very hot with 140+ degree air blowing through it (any bugs in the dust bag would have got roasted) and I wonder how the bilge pump would fare? I also noted that even with the vacuum sucking away at full blast there was still a reasonable outward vent of hot air through the MG vents (more on the left than right). Barney mentioned that he thought a lot of air from the bilge pump might go straight up the vent and I am inclined to agree, bearing in mind that even my 85cfm extraction downwards did not remove the escape of air courtesy of the main fan and natural hot air rising. I was sort of expecting air to go inwards with my extraction system. There again, maybe the 100cfm bilge pump with no dust collection bag to contend with would have more of an effect on the airflow?

2. Barney mentioned the difference in carb temperature after his competition driving. My warm-up was just a routine drive in comparison, down the local roads up to 70mph over a 20 minute period. I placed the thermometer against each carb on return and they read the same at 125 degrees. Perhaps one reason may be that the steering shaft on LHD vehicles alters the airflow in that area?

Rough one off tests I appreciate, so as I have frequently said with these types of experiments I am happy to be shot down.

Steve
Steve Gyles

Steve
I make the 4M3/min of the 3" blower over 140cfm. So this amount of cool air is being directed roughly at the carbies which has to do something to keep them cool.
I just think your vacuum's sucking of hot air at just 85cfm from under the bonnet which is being fed by huge amounts of air through the radiator fan(s) hasn't got a hope of cooling the carbs. Hot air rises too, so its hottest up at bonnet(/hood) level, just where the carbs are AND being cooked by the exhaust manifold.
All this talk has made me order a digital thermometer - hope it works. Watch this space...
Pete
P N Tipping

Pete

I was quoting Barney's more realistic figure of 100cfm than the free flowing 145cfm quoted. My theory has always been on general heat removal similar to the car being in motion rather than a specific cool spot blast. After all the carbs work okay when you get moving and the heat gets dragged down underneath.

Steve
Steve Gyles

Steve
The blower's "cool spot blast" is an attempt at producing the effect at the carbs of going along - when stationary; we just can't get the air coming in the top vents as well. (as yet)
Can't get the idea of sucking out hot air to draw more in
and keep warming the carbies while in that traffic jam.
Pete
P N Tipping

Steve..I have to say that I believe a fan sitting in hot air downstream and with no shroud ( ie prone to recirculation and trying to suck hot air out) cannot compete with the same fan in a short duct shroud sucking cool air and pushing it directly into the hot zone along past the filters etc. This is true in both air temperature and air volume terms . The heat shield also helps to direct the air down a v shaped 'tunnel' under the bonnet past the carbs etc.. Even though air may blow out the bonnet vent when stationary it does come out underneath the bulkhead ( I felt it ). I very very roughly guestimate that the air will move at a significant velocity ( order of 1 to 2 ft/sec ) past the carbs and into the suction of the other pump (which needs not far off the same vol. of air) ..the engine .. Once the car starts moving the air direction trend gets even better with the combined effects of ram air in the plenum upstream of the fan,the pressure build up on the bonnet and the lowering pressure underneath the car.
As an additional point I put my fan in to get cooler air into my carb ( ie more air mols per cubic foot ) for better performance and the blower in the duct does just that very precisely ...

Pete.... After all this chat I also ordered a thermo probe and meter two days ago..keen to see the actual benefit..are we perhaps a little obsessive? good fun though and stops me ruminating alone
Neil Ferguson

Pete and Neil

I have no doubt that the blower in the front duct will achieve localised cooling. My mindset, however, has always been to look at options. I guess it stems from my RAF days. For example, leading an 4 to 8-ship formation of strike aircraft you approach hills with cloud lying across the top. You see light in a valley between 2 of the hills. Do you go blasting through that gap and hope its clear the other side? Or do you look left and right to see if you can go round it all? Or perhaps go over the top into cloud in close formation and, if so, is there a civil airway route immediately above? etc etc.

I rarely take the first and obvious answer as the solution without looking at the alternatives and that is exactly what I have been trying to do here. I have attempted to look at the wider picture of heat soak when stationary. My theory is based on shifting air similar to when the car is in motion, after all that is what normally keeps your carbs cool without the aid of the blower. All I have been doing with the extraction fan is to speed up the flow of, albeit hot, air through the engine compartment. Of course this won't cool the carbs in the way your blower will, but it will slow down the heat soak within the engine compartment and possibly prevent the carb temp rising above that critical vapour lock level.

Although you can claim you are putting 100cfm into the engine compartment, is this necessarily true? It may be, but also it is possible the engine compartment cannot effectively take that volume of additional air, resulting in the bulk of it going straight out through the MG duct. Are there any side effects to your blower? You are altering the circulation. Is some other part of the engine compartment going to get an extra roasting? Perhaps boil off the brake fluid - I hope I am joking on that specific point, but you see where I am coming from.

I have never been against your blower, I supported it in my earlier posts. I am just checking out the alternatives.

Steve
Steve Gyles

fur enuf!!! Nufin rong wiv a bit of lateral finkin....
Neil Ferguson

I have some positive results chaps! The digital thermometer turned up this morning! I checked it in boiling water - spot on (so calibrated) and Ambient temp today was 21C/69F. The bonnet/hood was down on its safety catch for the steady readings taken.
The engine was warmed up ticking over, with its standard mechanically driven fan and as usual the A's perfectly good summer thermostat let the coolant indicated temp rise to 200F and rising, so the Kenlowe was switched on; as eI would expect, the tick-over was getting very 'lumpy' by now too.
The temp recorded in front of No.1 carb got up to 163F and in front of No.2 carb it got to 159F. With the 3" blower switched on these temps dropped pretty qickly to 114F & 145F respectively.
The temperature at the bonnet vent came up to 145F and dropped back to 123F when the blower was run.
I could also here an improvement in the tick-over within about 30secs of the blower being started-up.
Looks like it works fine on my "A" and hope this is useful information.
Pete
P N Tipping

Apologies for the typos... Pete
P N Tipping

Good result Pete. My marmalade thermometer was reasonably accurate. Interesting though that the blower does not get at the rear carb. Did you notice any difference in flow out of the vents? i.e. where did the bulk of the blown air vent?

The only major different observation I found was that with my car in absolutely standard trim and without my experimental suction device, the engine temp stabilised at 182 (fractionally cooler day but not a lot). I don't know much about how the Kenlowes should be set up, but if it was set at say 185, would you not reach the high water temps so quickly?

Steve
Steve Gyles

Bonnet being open at all means temps are not reliable.

When Daughter built her award winning "Differential Expansion Thermometer", we did some high temp experimentation which involved heating stuff to the point of needing alum foil shields, to get even temps, on my shop heating stove. This is around 700F at full tilt, and the experiment was about 30" tall. The smallest gap anywhere near the top caused the measured temps to go precipitously downwards. Mostly - sometimes temps measured at lower levels went UP, as drafts pulled heat down, despite the stove itself producing a very strong updraft at these settings. All much like the configuration here with exhaust heating the bottom and cross flows of assorted characteristics.

No sense setting cooling fans below 200, and 210 makes better sense. But not for the carb issue!

Surely you mad scientists have figured out that the carb fans need some baffles to move heat around the area? Ultimately, a ducted air box surrounding the carbs and their airflow, and completely divorcing it from exhaust heat is the best. I had to do this in reverse to prevent carb icing and oil sludging on my Austin America (1300) in real winter driving. I had it arranged so removing one piece turned it into a decent coolish air feed to the carbs.

Might make a Perspex bonnet to watch the trajectories of small birds whilst motoring. Or a web cam, but that sounds out-of-period!

FRM
FR Millmore

Mad - yes; scientists - no. One way for some of us, in the twilight of our years, is to play around with things, write about it, have it critiqued, and learn.

Mulling things over in my mind (sorry, outside the box again) Pete's temperatures went up more quickly than I would have expected. He has the original fan, plus Kenlowe to get soaring temps back down. It begs the question - why? Is it the old question of a non-standard radiator? Mine sits at 180 to 182 all day at idle in these UK temps. It is cored to as close to original standard as is available. Something strange here.

Steve
Steve Gyles

Hi Steve
I discarded the Kenlowe's thermostat as I like being in control, I don't trust things like stats, they muck up the standard MGA engine bay and the 'stat hose seal leaks if you disturb the top hose connection.
I know my radiator is only 1-11/16" thick, I think your Bob West one is correct at 2". I had mine re-cored before I knew of Bob's rads and its still like new - it can wait. I've had this issue for 15 years now and tried everything as you may recall on this site over the years.
I think the smaller temp drop at the rear carb of 159F down to 145F (14deg)could be due to the heat coming up from the exhaust, the increased distance of the blown air and maybe my approx location of the probe end stuck in the rear of the front carb's air filter and resting over the rear carb.
Even these, shall we say, approx figures at least demonstrate the blower is doing quite a good job without any real under-bonnet changes and the tick-over seemed improved with the flow of cooler air which is what I was after all along.
As you know when the A's bonnet is on the first catch its pretty well shut and much handier to resite the temp probe each time - I thought it worth mentioning. I actually managed to poke the probe through the bonnet vent, so it could be done with it shut.
Oh and Mr.FRM - there will be no weird and wonderful baffles or air boxes on my MGA thank you! I'm trying to retain my car as it was manufactured out respect for its designers. Trouble is we're going to be stuck with this new fangled ethanol not catered for in 1955. Mad scientist?... no sir! A design engineer for 40 years having done a Mechanical Design apprenticeship at the Royal Aircraft Establishment Farborough.
Pete
P N Tipping

I begs to differ - you have defined scientist~!
And, don't let your mind out of its box, that sucker might not come back!

If you are speaking of Pete's coolant temps, I can think of bunches of factors, especially at standstill.
The obvious - rad, fan, coolant, stat etc,
IGN timing
Mixture
Cam overall timing and lobe timing, Valve clearance. Valve seat condition
exhaust system
where is the car parked? sun, wind, in the garage (nose in or out?) Top of a mountain?

Some of these, especially ambient air flow, will have major effects on under bonnet temps at standstill as well. Even cracking the bonnet will change it all. A 2mph breeze one direction or t'other will change it all.

AS you observe for your car, We used to have little trouble with random MGA in temps under '100F, all stock. Problems were usually fixed by standard tune and cooling check/repair. No extra fans, big rads, etc. Problems would sometimes arise when cars got caught in standing traffic in tunnels in summertime (Pittsburgh had a number of those_) Estimated air temps near 150F, no air movement at all, hot exhaust from the 300 cars around you. Got caught on my Royal Enfield in one of those, shut it off and pushed it until I got out of the tunnel, wasn't sure I would live! People used to pass out frequently before AC was widely used in cars. They eventually figured out to stop cars entering the tunnels until they could get out the other end - what idiot traffic engineer puts a major intersection traffic light at the output end of a tunnel anyway?.

(I may pass out meself now - 90+F and dew points over 76F)

FRM
FR Millmore

No probs with Mg's in the UK - just ethanol...
Pete
P N Tipping

I had all good intentions of testing my 3" blower today. Ambient air temperature in Naperville just west of Chicago was at least 104dF (40dC) with full sun, certainly hot enough to give the carburetors apoplectic fits in standing traffic conditions.

Unfortunately got I tied up in the afternoon doing wire wheel balancing and front end alignment on an MG midget. We did take the MGA for a 10 minute run around town to "cool off" after working on the Midget. Nice drive, but didn't even think to look at the temperature gauge. So the blower test waits for another hot day, possibly tomorrow.
Barney Gaylord

Pete-
Stuff keeps disappearing and reappearing on my computer today, so forgive fractured story lines!

OK.
As I have posted sundry and various, we have had 10% ethanol for a zillion years now. There were a lot of problems at first, in some cases with over 10% by back door Pennzoil lab test (the suppliers lied, said it was 10% as law prescribes!). It turns out that the problems came and went with other fuel trickery; we still have the 10% and it works just fine and does not eat stuff.
It does cut mileage more than the chemistry says it ought, can't figure that.

FRM
FR Millmore

To begin with, alcohol has about 40% less energy per gallon than gasoline. Mixing 10% alcohol with 90% gasoline yields about 4% less net energy per gallon. So it requires about 4% more fuel to make the car accelerate at same rate or run at same speed. Since you don't get 4% more air into the engine, it also makes less max power.

My personal experience with both types of fuel says the small reduction of power is hard to quantify (hardly noticeable by common man), but that 4% reduction in fuel economy (increase of fuel consumption) is definitely real (but I don' see it as being much worse than that).

Given a choice in the open market you would think that 10% gasohol should be priced 4% lower than straight gasoline. But of course we are (usually) not given this choice. When both types of fuel are available on the same pump, the price difference may be more like 2%. In that case I will always buy the non-alcohol fuel, as a matter of simple economics (not to mention reduced vapor problems and improved performance).
Barney Gaylord

I have just run across this thread and have some input based on 90-100+ degree driving in my MGA coupe and ZA Magnette. Neither car has ever run hot or had tempature problems while moving during hot weather. However the driver and passenger have suffered heat exhuastion in both cars prior to modifications. In the coupe we got so over heated to the point of being physicly ill while in 30 miles of stop and go traffic on hot day on the 405 coming through LA. Both cars have exibited vaporloc problems on hot star up, especially the A Coupe. Below are some recomondations from my experiance.

A. Insulate the underside of the transmission tunnel with 2 layers of good quality heat barrier. I used 3 layers on my Twin Cam tunnel and 2 on my ZA. My leg used to get uncomfortably hot on long drives while resting against the tunnel, as did the interior of the cars. A huge amount of heat is trapped in the tunnel area. The difference is very noticeable. Now I can feel the cool air blowing in from the heater. Note: You will actually need your heater in the winter now. Insulate the drivers floor board above the exhuast pipe.

B. Insulate the toe boards and heater shelf and all panels that face the engine compartment. Since the heater shelf is so visible in the engine compartment, you probably want to insulate it on the inside the passenger compartment. for cosmetic reasons, even though it is not as effective. I also insulated the inside of the heater box on the TC.

C. Any air flow around the carbs while parked prior to hot start up will help, if not eliminate the fuel vaporization problem. Cool air to the air filters will also help performance as cool air is denser.

D. Steve's idea of drawing hot air out is a good idea but not very efficient when using a fan to do so. Fans are much more efficient at pushing cool dense air then sucking hot air. A better method would be to use the vacuum affect under the car to draw more air out. This could probably be easily done with a properly designed sheet metal panel across the bottom of the transmission tunnel, but this does not help while stationary or parked.

E. Putting the heater fan motor on a relay, so it is getting a full 12 volts and more amperage, will make it spin faster and push noticeably more air. It also helps keep your ignition switch and heater switch from getting over heated.

F. Adding a duct fan will increase the efficiency of the heater fan providing more total air flow. 2 fans in series will move more air then one. Same with pumps. 1+1=2, or at least 1.5 :-) I wish there was a way to add a second fan on my ZA.

G. The main source of heat in the engine compartment is the cast iron exhaust manifold, especially while sitting after being. Ceramic coating it will drop the engine compartment temperature significantly. A well designed header( most I have seen are junk!) will extract the exhaust better and retain much less heat than a cast iron manifold and also help lower engine compartment temperatures, especially if ceramic coated. An added benefit of the ceramic coating is, your much less likely for burn your knuckles while twicking your carbs on a hot motor.


I have not used a duct fan like mentioned, but definitely plan on doing so on my TC coupe. The other modifications have made our cars much more enjoyable on hot days. The passenger compartments are much cooler, although they could still use more air flow. I am considering ducting air in to the foot well on the TC coupe. The attached photos shows a little of the insulation I used on the fire wall and toe boards. I can not find the photos I have of the Trans tunnel and underside of the dash, but I used the same material and then cover it with the foam dash padding to hid it. I hope this helps.

Steve C.

Steve Carroll

One more photo.

Steve Carroll

Barney, will you be at GT37 in Dayton next week? I'd be interested to see your blower installation.
Andy Bounsall

Pete..just read your test results and had some quick thoughts....
It is not surprising the rear carb has much warmer air . It is under two effects...
.....Some cool air ( 15 to 30CFM) has been drawn into the front carb. and remaining air therefore is much hotter and continues to mix with much hotter under bonnet air
.....More general under bonnet air has been mixed with the air passing past front carb and so bigger warm up.
I did some very basic calcs ...only directional but gave reasonable correlation.
Assumptions ( fairly big ones !).
..Air blown out of blower is at ambient ..ie 69F ( likely to be higher when car stationary).
..Air coming through radiator 163f
..Air passing first carb on way to rear carb 114f

Bravely assuming air entering first carb is 50/50 of radiator air and blower air gives an average calculated temp of 119f..reasonably close to actual 114f.
Roughly assuming air entering rear carb is again 50/50 air passing first carb and radiator air gives 140F....compared to actual 145f.
NB...Front two cylinder will be getting about 5% more air mols under above conditions....but academic.
These differentials will be reduced drastically once underway and ram air,over bonnet pressure and under car pressures assist flow.
Also interesting to note that I estimate if we assume the average of the two carb temps i.e. 129F prevails under speed and compare this with the 163F ex radiator temp then about 5% more air mols are getting into the cylinders with a blower ..significant!!
Eagerly await my meter and gauge so I can rig up and get some figs driving..my single SU on the judson has its suction filter near the bulkhead so will locate a thermometer here.


Neil Ferguson

Greetings curiosity seekers, -- I am delighted to report on a successful test of the 3-inch blower in my MGA done on Thursday 7/4 when ambient air temperature was 104dF (40dC). I intentionally pushed coolant temperature far past end of the gauge scale and got the carburetors into serious fuel vapor troubles, running on half choke to maintain idle speed. When the blower was subsequently switched on the carbs cooled to decent running with no choke within 60 seconds, and within 90 seconds it was idling smoothly at 900 rpm, even when coolant temperature was sill rising. Beyond that there was nothing I could do that would affect the carburetors as long as the blower was running. I tried everything I could think of to cook the carbs, and the engine still idles smoothly at 800-900 rpm and runs well for driving like it was a cool day. Find the full report with photos and more notes at http://mgaguru.com/mgtech/carbs/cb208c.htm
Barney Gaylord

Greetings Barney! Glad you had the same good experience as myself with the 3" blower and nice to know it works so well at 40degC ambient..! That's way too hot for me I can tell you. Reading the above and your new webpage I couldn't make out if you were driving along with the fan switched off at all. As the bore is efectively very much reduced through the fan, it is a concern that the carbs may get too hot when driving along with the fan off in such hot conditions. Nice to see it works so effectively with your 10% ethanol though.
Pete
P N Tipping

Good report Barney.

Pete, see above and stop worrying about the bloody ethanol!

Barney, On several Mazda, with a fairly primitive FI/O2 system - no knock sensor - I get a 10% drop in economy with 10% E, much more than theory says but repeatable. My normal mad driving gives about 30/31 with E10, and 33/34 with real gas, but there is not real gas anywhere close anymore. No noticeable performance change, so the FI must compensate. Car runs like a bandit in zeroF weather though, and drinks to match! Also, as I have said previously, "Fuel MAY contain UP TO 10% ethanol" but you cannot know what it DOES contain. I have not had opportunity to do these checks on carb cars, but others with carbs have reported the same change.

FRM
FR Millmore

Barney..just read the full report on your site ..good detail..and the result is excellent...
What temp were YOU cooking at whilst driving ?.....the body fluids could start behaving like E10 fuel on such a day.
Neil Ferguson

Pete, -- Once I switched the blower on it stayed on until end of test when engine was switched off (54 minutes later). If the blower was switched off it might restrict air flow some, but when running it will always be increasing air flow. The blower makes a lot more differential pressure through the 3" duct than natural air flow would ever be in the 4" duct.

When I nay drive it some more in hot weather I will try it with blower off at all times until it may be needed to cure the vapor issue. Then I may get a more subjective opinion on whether it may obstruct air flow in any significant amount at road speed when not running.

It is my impression that the blower literally bathes the carburetors in cool air all around that space in the engine bay, even without any directional baffles. It would be interesting to have temperature sensors inside the air cleaners and on the float chambers. I suspect the intake air is significantly cooler, which should make more power as well as nicer running. I also think there is so much cool air flowing past the carbs that both carbs likely see similar intake air temperature.

I know for a fact that it cools the carbs and fuel considerably, certainly well below the boiling point for the fuel, but so far no absolute numbers for actual temperatures, not that it matters much. The primary objective has been met, in spades. The carb cooling was dramatically fast and effective when the blower was first switched on. Then the engine runs sweet like it was a 60dF spring day, even when coolant temperature had the temperature gauge pegged. Possible increased power due to cooler air intake would be a collateral bonus.

The only time coolant temperature was rising was at ground speed below 25 mph or standing still at slow idle. When temperature would run off the scale at idle, just kick the idle speed up to 2000 rpm, and the temperature would drop. That sounds like a candidate for a different cooling fan that would move more air at idle speed, like an electric fan for instance.

Neil, -- I wasn't cooking too bad while driving. T-shirt, shorts, sneakers and ball cap, and I do well as long as the car is moving 30mph or faster, and not standing still for more than a minute at a time. The only time I feel abused in the MGA in stop and stop "rush" hour traffic, creeping along at 0-10-mph for extender periods of time. Then only when it's over 90dF ambient and more than 120dF in the roadway. The asphalt canyons can be a killer if you have to stand still long in hot weather. Carry something to drink if you're out for more than an hour, and don't be to proud to sweat.

My MGA now has 3/8" carpet padding (felt or urethane foam) all the way through. The under dash pad makes a HUGE difference in cockpit comfort in hot weather, also a nice improvement in winter, and notably good sound deadening. The most important improvements for both hot and cold weather are to insulate the tunnel and to plug every damn little hole in the bulkhead. One pencil size hole in the firewall is about equal to switching on a hair dryer.

I have a few articles on my web site about plugging holes. For winter driving it is paramount to plug two 1" holes on each side behind top of front kick panels (windscreen mount bolt access holes). With those holes open in winter you get icy cold air pouring over top of the kick panels like a waterfall. Plastic snap plugs area dime each and work miracles.
Barney Gaylord

Thanks for all your input as usual Barney and glad our little blower worked for you too in those incredible temperatures you have there. I guess we can look on our efforts here as a simple, hidden and successful solution to cooling our carbies and proving that duct flow is a necessity, moving or not on a hot day...
Pete
P N Tipping

Just got my new temp probe plus lead and meter this am and rigged the probe up as shown on the attached pic. It is just above the air intake on the K & N filter and SU carb fitted to my Judson i.e. it is just in front of the firewall and slightly after of the air vent scoop. The probe is tied by the two yellow tie wraps and feeds through the firewall to the cockpit where the meter is placed. I had just been out for a drive and the engine was already warmed up but the car was stationary and only on tick over for following quick test...
Conditions..
Ambient 15c ( 59f )
Radiator temp 87c ( 190f)...electrical fans were blowing through radiator
Temp of probe without bilge fan 52c (125f )
I turned on the fan and almost immediately the probe temp came down to 42c ( 108f).
i.e. The blast is penetrating way back into the engine compartment and giving a 10c ( 17f) temp. reduction on tick over. Ambient conditions are not demanding right now but local temperature suppression around the air filters is very welcome.
I will take the car for a fast hilly drive soon and see how the blower performs

Neil Ferguson

awful pic..attach better one below ...I biased the location towards the exhaust manifold side but latter is wrapped and there is a good heat sheild.

Neil Ferguson

Neil, G'day mate! That's a pretty warm area for the SU's super-charger intake but I'm sure there's nowhere alse to go...
Interesting you intend testing the blower blasting around hills. Do you experience problems on the move in hot weather or are you hoping to drop the intake temp for more power??? We were purely looking at keeping the tick-over smooth when stationary, which is the only time I intend to run the blower. It will be interesting to see if there is any intake temp reduction at speed.
Pete
P N Tipping

pete..never had any carb boiling problems when I had standard carb set up but changed to Judson a few months ago ( and replaced the standard holley carb with an su ) and thought it was a potential hot spot for the intake. After reading Barneys site bumf I installed the 3in bilge fan to get more cool air down to the carb filter with consequent power benefits.
I have just tested and it gives a good result ..about 10c reduction ...and I reported the results...along with other rebuttal trivia ..on the adjacent post " Extra Power on the cheap...."
Neil Ferguson

Ok. There has now been quite a lot of 'probing' going on. Time for you guys to set up some meaningful tests against which others can make comparisons for the variety of MGAs we all run. For instance we have different engine sizes, Kenlowe fans, standard fans, original radiators, Moss radiators etc.

When I get back from my hols towards the end of the month I am going to buy one of these blowers. Before I cut its legs off and stuff it into the front duct I intend to run it as a 'Sucker'. It would be interesting to compare data from a set test scenario.

Over to you.

Steve
Steve Gyles

Neil

You bashed the duct tube to make room for the Judson pulley, I removed, trimmed and reinstalled, so I do not have enough flange to put a tube on any more. But the bilge blowers do have a huge throughput so I am sure that even without the ducting to the carb it will bring benefits.

What I am interested in knowing is whether the blowers will survive being run for long periods, as I have only experienced them in use trolling around harbors or to vent engine bays of potentially dangerous fumes before staring a boat engine (not doing that is often the reason for those rare cases of a boat exploding). So they usually don't run for much more than 30 minutes at a time max, and normally only for five minutes or so.
dominic clancy

Dominic..not 'bashed' ..such a brutal term ...and best saved for a Kings Cross or Soho Saturday night out.. I re-contoured the duct in a controlled series of steps
I am only going to try it ...but will be a week or so off ...I have to go into Hospital for a procedure to 'cure' Atrial Fibrillation that has been pestering me for about 6 months.
I recollect the fans were continuously rated ..but an experience base will now be building up amongst the converted.
I agree re the 'without duct' argument you use and if the result is not a big improvement over the 10c reduction then will not install.
One interesting test i intend to do with this lovely meter and probe is to put the probe in the outlet from the vent duct scoop underbonnet and see when the air flow reverses in-out to out-in and how close it approaches ambient with speed. This seemed to have a great affect on my recent test ....
How is the manifold coming on?
Neil Ferguson

There has been some comment about the windmilling fan obstructing free airflow through the front trunking when at speed (we need feathering blades!). Has anyone considered mounting it in the MG vent? There could be conflicting airflows when stationary but might it just work? You could perhaps consider 2 options:

1. Blowing inwards. This would prevent hot air coming out of this vent, but a lot of cooling air would be forced in, resulting in a greater flow out of the other vent and also underneath. Whilst this may not give the direct and significant spot temperature drops on the carbs as found above, it might keep the overall engine compartment temps lower.

2. Blowing outwards (my suction theory, albeit located in a different position). In this mode 100cfm extra air would be forced out of the MG vent. That air needs to come from somewhere, some of which would be cold air dragged in from the front left duct, resulting in cooling air entering from the front as if the fan was in that duct.

Is the fan reversible? If so it could be run in blowing mode into the engine bay at speed and out of it when stationary. At speed the normal airflow through this duct is inwards, although I do not believe it is significantly large, so, when switched off, a windmilling fan would not cause so much of a problem compared to being in the front duct.

Food for thought.

Steve
Steve Gyles

Ok, so today I received my 3 inch Attwood blower. When the rubber pipe reducer arrives I will mount it the same way as Pete describes earlier on in this thread.

Since owning my MG I have only experienced vapour lock twice & on both these occasions this has been when caught up in stationary traffic on one of those rare hot days that we sometimes get in the UK.

The engine is 1622, no Kenlowe fan & a standard radiator. I intend initially to take manual control of the blower using the F switch. If this proves successful I may think about some sort of automation.

When we get our summer I will report back with observations & conclusions.

Steve .. An interesting idea that you have on the control of the air direction through the MG vent. Perhaps if I had more time I might have considered trying this.

In answer to your question, yes the air direction of the blower is reversible by changing the polarity of the connections. However as the body of the blower has an arrow showing the air direction this implies to me that the efficiency will not be good whilst running in the reverse direction that it was designed to do. Before purchasing your blower you may want to consider an alternative device that is designed for both suck & blow.

Richard


R A Evans

As Richard says polarity reversal will reverse the fan Steve but the aerofoil blade shape would mean awful efficiency, the bearings may not accept thrust reversal, the reversed flow of hot air might destroy the fan and you are strangely sending hot air out of the front of the air duct for it to be drawn back through the radiator again. No thank you!
We know the air flows in through bonnet vents to the engine bay at speed and I like these nice open vents to also let out the hot air after everything is shut down. I'll leave mine just like that.
When on the move I find my "A" is just fine, its just when you come to a halt with a red hot motor, especially after running at motorway speeds, it must suddenly get very hot under that bonnet, that's when I intend to use this blower here in the UK so I have no worries about continuous use.
Pete
P N Tipping

Steve--- I have just rerun the Hogren -Girkin-Burke calculation for airflow though the front vent on your car configuration and applying an Inverted-Firkin correction the conclusion seems to indicate that you need to procure a variable windscreen extender ..one that increases the height (better results if rake also adjusted ) using a double log derivative of speed. This would apparently force about twice the vol of air into the engine compartment compared to a multi direction variable aero foil fan installed in the same vent and infinitely more than the windscreen without extender.. Try following site...

www.windscreenextenderforsgmga.com.nk
Neil Ferguson

I think the cheap little blower will hold up just fine for continuous use. Anyone want to test it? If you connect it to a 4-amp 12vdc power supply (or a small battery charger) and run it 24 hours per day, in 12 weeks it will accrue the equivalent of 100,000 miles at 50 mph. Cost of household electricity is about $1 per week for continuous running.

I would be more worried about the heat exposure immediately after shutdown. From the installation instructions: "Do not operate in area of high heat over 160
Barney Gaylord

Barney

Perhaps placing it right at the front of the flexible ducting behind the radiator slats as c vassallo shows in his picture above? He used the 4" fan in that position.

Steve
Steve Gyles

Pete

Why would the additional air be drawn through the radiator? With an extra demand for 100+cfm out of the engine compartment I think a lot of it would come through the socking great bypass hole of 4" diameter alongside it - on the basis that airflow will take the line of least resistance. Even if some of it did come through the radiator, the extra 100+cfm of now warmer than ambient air out of the engine must have the effect of lowering the engine compartment temperature. As I said in my theory, it may not have the same spot cooling effect of your direct blast but will reduce the the overall engine compartment temperature as yours will also. My thoughts were based solely on the concerns raised of having that bilge fan effectively blocking the duct when the motor is switched off.

Neil I could not get the link to work.

Steve
Steve Gyles

Steve...not surprised link did not work...I made it up.
Have a close look at the reference in the link.....and some of the drivel references in the post....
Neil Ferguson

Neil

Nice one. I was struggling to try to understand it all, but you must appreciate that I read it this morning in an alcoholic haze from last night. I had just got back from a 19 Squadron Lightning pilots reunion from our time in Germany in the 70s. A number of the guys I had not seen in 38 years!

Now if you want to talk really hot air, we had plenty out the back of those machines.

Steve
Steve Gyles

Sounds like a great reunion. ..and talking of jets reminds me of the story I read about a guy in the US who fixed a aircraft booster rocket onto his car and whoosh........he won a posthumous Darwin Award for removing himself from the human gene pool.
Neil Ferguson

Steve
You say "Why would the additional air be drawn through the radiator?" With the reversed bilge pump blowing hot air out in front of the radiator, the engine fan/Kenlowe will draw it back through the rad again. So the average temp of the air coming through the rad is now warmer, winding everything up to get ever hotter.
Loved those Lightnings... Seen the one at the FAST museum???
Pete
P N Tipping

Pete

Wrong scenario. Stationary, the bilge pump would be blowing out through the mg vent, sucking the extra 100+cfm from the engine compartment, not blowing into it.

Great machine for a 50s design, just a bit short on fuel. Bit like an f1 car! Took an airline pilot for a ride once. He said he would be declaring mayday, requesting immediate landing with the fuel endurance I was about to begin my take off run. You could run a lightning dry in 12 minutes with too much burner.

Steve
Steve Gyles

Steve, Have we got our wires crossed here? I assumed you were talking about the reversible blower still being fitted in the front air inlet duct... (I think this thread is getting a bit unwieldy you know)
Pete
P N Tipping

Pete

Probably wires crossed. I am off to the sun early tomorrow morning. When I get back in a couple of weeks I am going to order a fan with the long term plan of going down your route. However, before I cut the legs off I am going to play around with other positions I talked about. I will report back with my findings in due course.

Steve
Steve Gyles

Pete

I am searching for a suitable thermometer with a remote probe without much success. Can you give me a heads-up?

Cheers

Steve
Steve Gyles

Steve..i bought this one on Ebay. It is a multimeter with a small head probe on leads and large LCD readout.Leads are about 30cm long and easily fed via bulkhead grommet from cockpit. ..but not long enough to stretch far along manifold area.. Cheap, $26 and works well ....There must be similar on UK ebay ..
Allows full monitoring while underway ...

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=200786407773
Neil Ferguson

Neil

Yes, on the UK site. Presumably you tape the probes onto the desired contact point? Are the cables single core? i.e. could you extend them? I had been looking at wireless temperature meters!!

Steve
Steve Gyles

Steve..I am a long way away from my car right now ....but I just used a tie wrap and connected the thermocouple close to the air filter ( my filter is close to the bulkhead.) when I did the test runs I referenced earlier. I intend to put the thermocouple in the vent scoop and judge when the airflow reverses etc when I next get back to the car. The leads are both single core and not beyond the whit of man to extend .......
The multimeter is much better than the one I was using so a reasonable bit of kit......enclosed in a rubber protective sheath as well.
Neil Ferguson

Hi Steve
I found this one on A**z*n - Chefs' Thermometer - Digital Kitchen Timer with Meat Thermometer, 11.44 delivered. Give me a shout if you can't find it.
Pete
P N Tipping

Time for a new thread guys? This one's becoming a bit long and dreary! Sorry!
Bruce
Bruce Mayo

Seems like the temperature probes are a good part of this discussion. I still need to get one.

I have a further report on function of the 3" blower. I took the MGA to Road America for the vintage races on July 15 when it hit 100dF by late afternoon. I picked up a friend downtown Chicago in the morning, and dropped him off again in the evening. On the way back from the track we got stuffed by the Sunday evening taffic returning from Wisconsin weekend, resulting in a long stop and stop drag on the Edens expressway. Ambient temperature was about 100dF, and air temperture between the cars and just above the sun-baked pavement was significantly hotter. When the carburetors began to suffer I switched on the bilge blower, and within 60 seconds the engine was purring smooth as a kitten with 800 rpm idle. When coolant temperature was approaching 230dF I increased idle speed to 1500-2000 rpm, and coolant temperature soon dropped back to 220dF. The time spent in the heat and bad traffic conditions was much more tolerable with the blower, almost pleasant (except for the heat affect on the passengers). I suppose this one incident alone is justification for installing the blower.
Barney Gaylord

Barney
Good to hear that it is working so well. Since I installed mine a few months ago, the sun has hardly appeared this side of the pond. I am beginning to think its my fault!
Graham M V

Got my blower. I followed Barney's basic idea of installation. I found that windscreen channel piping makes an excellent seal, perfect width for the channels in the Atwood blower and makes an excellent fit into the duct. I held the rubber extrusion in place with wire, making the seal sit extremely well in place. Before finally installing the blower in the duct I am going to toy around with it in the MG vent to see what effect it makes. That pump certainly shifts some air!

Steve

Steve Gyles

Well, I did a heap of tests this afternoon doing a dozen runs or so with the blower in two positions. Interesting results. Not a hot day, ambient temperature 70F.

Without removing the filters I could not get the blower in the left MGA vent so I put it in the right hand vent with it exhausting outwards. I had the temperature probe positioned in free air just in front of the heater box and in a second test I positioned the probe between the 2 carbs in free air. The engine temp was 175F when running at 40mph and 185F when stabilised at idle. Throughout the tests I was unable to detect any difference in temperature with the blower switched on or off. I was a bit disappointed. I then repeated the tests with the blower in the front vent as shown in Pete's opening post. Somewhat surprisingly I got exactly the same results.

I then taped the probe to the rear of the front fuel bowl. Again, I got no change in temperature both at 40mph, nor at idle with or without the blower.

I then put a deflector plate on the blower to direct the air at the front fuel bowl. At 40mph the front bowl measured 112F with the blower off and 98F with the blower on. At idle the bowl measured 132F blower off and 102F blower on.

I then repeated the tests with the probe at the back of the rear carb. At 40mph it was 112F blower off and 106F blower on. At idle it was 122F and 106F respectively.

Conclusion: For this modification to work to any significant benefit it requires a deflector plate.

Steve
Steve Gyles

Steve - You have been busy. Interesting you are testing the fan when running at 40mph. For me the MGA has always been fine at that speed, surely we just need our blower for the traffic hold ups, that's the only time I intend switching mine on. As you could see above I got good air temperature reductions in front of the air filters and as with Barney's it actually does the business in very hot traffic. How can you stand those temps Barney??? Phew!
Our MG club had a run last week when it was around 32C(90F), I recorded a cockpit temp of 38C (That's b***** hot here Barney!) We had a couple of hold ups on the way and each time when I switched the blower on, the deteriorating tickover was quickly restored to a normal solid 8/900 rpm. It works for me so that's job done.
Steve - I feel that where you are placing the temp probe against the fuel bowls, you are recording the temp of the metal bowl and its fuel which is a relatively large heat sink which would require a very long wait to see any blower cooling results.
It has to be the cooler (as if moving) intake air that does the business.
Pete
P N Tipping

Pete..speak for yourelf re the use of the blower!!. Personally I do not have, or have ever had, carb boiling problems. I installed it to reduce air intake temp. to the engine...and it achieved 10c at 100kph . This is about 3% extra oomph and not far off the results of the steve*2 designed and made stub stack earlier this year ...and even cheaper.
Neil Ferguson

Steve..The results will indeed depend on the configuration of the outlet from the fan and the channeling of the air downstream to and past the carburetors. I got a 10deg c repeatable reduction at 100kph at my filter intake just next to the bulkhead . I had to scientificaaly reshape ( 'bashed' to use Dominic's techical metal working term ) the metal duct outlet to avoid the Judson pulley. Consequently the air is directed towards the bodywork ..it then travels past the large judson charger barrel. Next to the Judson and along most of the the engine length I have a sandwich insulated heat shield ( much longer then the standard one ) and the consequent effect, I believe , is to create a air box/channel minimising the the mixing with the hot radiator and exhaust manifold air.

What temp probe and meter did you buy and use?
Neil Ferguson

Pete

I summarised the tests for simplicity. I also taped the probe to the front of the forward bowl. I got no change in temperature until I installed the deflector. In fact the temp appeared to go up a degree but I assumed that was just normal heat soak and variance. The 40mph test was just for interest to see the effect.

It is possible that my mounting system holds the blower slightly straighter than yours. I only needed a small delector (bent business card) to get the air on target.

Steve
Steve Gyles

I meant to add that the one disconcerting side effect I suffered with the temporary deflector in place was a number of slight hesitations in engine pick-up from low speed (10 to 15 mph turning into T junctions etc) - blower off. I am wondering if I disturbed the cold airflow to the filter boxes. I think my permanent deflector will be across the middle of the blower. I need to give this extra thought but I am thinking of hinging it like a counter-balanced rudder; with power off the plate will align fore and aft; with power on the plate will be deflected by the airflow to the right. I also intend to paint the blower so it blends in with the paint work.

The one thing for certain though is that Pete's blower system really does work well when fettled. Dropping the idling temp of the carb bowls from 132F (ish) down to 106F (ish) is one massive drop and is actually below the normal running temperature of the carbs on my car.

When I originally wired up the system I managed to get cross wires and when I switched the pump on I also got a face full of fluid from the windscreen washers! Now, if I put a water feed pipe into the blower casing I could get a beautiful cold mist into the filters and that would give me a bit more power!!

Steve

Steve Gyles

I have been following this thread as my car like most MGAs is similarly affected by heat soak causing the tickover to slow and go very lumpy when I am stuck in traffic for example.

I was thinking about the idea of a blower fan in the cool air inlet pipe to supply cool air and I then wondered if anyone has ever thought of fitting an air-box to the carbs.
It could be insulated to keep out the heat from the engine compartment and directly fed with cool air by connecting the flexible cool air supply pipe to it.

You probably wouldnt need a fan with this set up as the air coming in would be much cooler than the usual air temp at the carbs

Not sure how big it would have to be to work properly and I know it would probably look strange compared to
the standard filters but I think it may work.

Not sure that I am brave enough to fit one though!

Colyn
Colyn Firth

Colyn,
I think that such an air box would definitely help but maybe not solve the vapour lock problem. As I understand the aim is to reduce the fuel temperature in the float bowls. The big advantage of the blower is that it provides cooling to the carburettors particularly the float bowls and fuel pipes externally. Cool intake air will remove heat via the throttle body only and so will be less effective at low revs.
N McGurk

Colyn & NMcG, Seriously I wouldn't bother with a deflector as I found in practice, whatever the theory, there is so much air coming off that blower it just simply works on a hot stationary MGA. Fit the blower and see the difference - then by all means play about if you just have to.
Pete
P N Tipping

Pete

The findings on my car were for real, not theory. I am more than happy to accept that you found no need for a deflector, but that was certainly not the case in my car. Without the deflector the blower made absolutely no difference to the front carb bowl with the probe taped both to the front side and then rear of the bowl. Interestingly though I note that your carb temp got up to 160F at idle without the blower whereas my starting point was 30F lower stabilised. I presume this is due to the more efficient cooling through the original spec radiator?

My tests were all done with the hood (bonnet) down and locked with the probe sensor wire routed through the firewall. I note you had your hood on the latch for your tests. I wonder if this may have also had some slight effect. I am not tryng to be nit picking, but there is something fundamentally different here and it may just be that my 4" vent tube beside the radiator on my car is set at a fractionally different angle to yours. I have just had a look at it and the line of the inside edge of the vent misses the outside edge of the front bowl by 1.25".

Cheers

Steve
Steve Gyles

This thread was discussed between 24/06/2012 and 07/08/2012

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