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MG MGA - Attwood Blower Deflector

Following on from my experiences with the Attwood blower for cooling the carbs (see Pete Tipping's "3' carb intake blower neatly installed" thread), I am in the process of fitting a deflector plate (see photo).

The reason for only deflecting half the airflow slightly is to retain the rest of the cold airflow for the filter boxes. Also it reminds the Attwood blower of its maritime origins with a rudder!

I plan to make the rudder, sorry deflector, moveable so that when the fan is not in use the deflector is neutral.

Now for the question. I am thinking of using a linear solenoid linked to the 'rudder' bar. I am not that good on electronics so could someone tell me if permanent power to the solenoid for the duration of fan running time is ok? i.e. would the solenoid overheat?

Steve

Steve Gyles

Steve-
Rudder is wonderful - how Brit could you get? But linear solenoid is horribly out of period.

I don't really see the point of having the rudder adjustable, but if you insist, use the heater control cable from many 50s era cars, which was push-pull for flaps and twist for blower.( the alternative to the MGA slide quadrant with pull switch_) Or just divert your heater controls!

If you are truly bound to be out of period, out of time, out of your mind, solenoids are made with strong pull in and much weaker hold coils for continuous duty. Or a push pull solenoid with a detent, since you only need two positions.

FRM
FR Millmore

FRM

You may well have read in the other thread that I found I got no cooling to the carbs without a deflector. I then became concerned that total deflection of the air to the carbs may not be to the benefit of cool air to the air filters, hence the compromise of the central rudder. Yes, I am still considering fixing it at set angle. However, as I don't need deflected air when driving I thought the movable rudder might be novel. I was thinking about your bowden cable option and then remembered my aircraft radio modelling days and thought about a servo/solenoid option, hence the query.

Steve
Steve Gyles

One of these sail rudders on the other side of the radiator in the heater duct and wire them up to the cockpit and you ahould be able to wind-sail the car without the steering...
Neil Ferguson

Steve,
Great post! I am impressed by the levels of analysis and efforts you have put into this. My only question is whether or not the additional benefit would ever be necessary. I might well have missed something in all of this, but as I understand, Barney's results show that vapour lock is eliminated, even under severe hot weather and driving conditions, with the installation of the blower. So the float bowls are cooled enough by the standard blower installation, in which case, for best performance, the air to the filters should be cooled as much as possible? In other words the unguided air flow from the blower is more optimised than the guided flow?
N McGurk

Steve-
I had pretty much ignored the other thread once Barney reported, and I got busy. All v interesting, Still don't really see why you need to steer it variably, aside from being a nice toy. I'd be inclined to use the 4" blower for less restriction in the natural flow with the blower off, and a fixed deflector vane. I think the intake air should still benefit even if some of the air is bouncing off the carbs; remember tat the carbs pull from the entire circumference of the filters, so cooling the area ought to suffice. But by all means keep up the show & tell!

FRM
FR Millmore

Neil

I agree totally. That is why the 'rudder' will be neutral when driving. I also do not intend to keep the blower in all the time, just for the occasional hot day or anticipated heavy traffic on long runs. I have bullet connectors in the wiring so it is simplicity itself to remove the blower.

I would add that I have not suffered over heating so I don't know why I am going to all the trouble!! - perhaps always looking for a project on the car and looking for alternatives. Normal running temperature in the UK ambient temps is 175 to 178, rising to 190 after about 5 minutes at idle.

My last picture gave the wrong perspective of the 'rudder'. This is how it looks; just waiting for my solenoid to arrive. I don't think a solenoid is 'non period', in one form or another there are are a number in the MGA.

Steve

Steve Gyles

Hi Steve
Nothing like a fresh start...
Really you wanted to fly Harriers with nozzles didn't you..! I see you still seem to link this blower with the radiator's water temperature. Obviously the blower will only put cooler air around the carbs and disperse the manifold heat; the water temperature will depend on the day and how much the radiator fan(s) are cooling the radiator. Have you measured the actual air temperature in front of the air filters as I did? There was the instant reduction, it will take ages to cool the fuel bowls once they get hot. If the blower is switched on just as you get to a hold-up the float chambers won't be hot in the first place - so no worries. I throw in - that there were no solenoids on an MGA if you discount the flasher unit(s).
Pete
P N Tipping

Hi Pete

No, not really trying to link it to the radiator temp other than in a queue of traffic you have the potential to 'boil up' and vapour lock quicker than I am!

It's a great idea you had and I know it works. You and Barney have proven it. It's the fine detail that I am trying to get to terms with because, when I set mine up originally I did not get the results you experienced. In fact, as previously stated I got no temperature reduction at all on the front carb, just supercharged cold air to the front air filter! And you know me by now, I am not happy until it is cleared up in my mind.


I have been out in the garage scratching my head over this one. To get any air from my blower onto the front carb I need to deflect the airflow 40 degrees from the blower centre-line. So, yes I guess that makes it of Harrier proportions.

Does your rubber shroud have a lip that goes inside the blower exhaust at all? Is it smooth bore? etc. I am just thinking about the turbulence of the air existing the exhaust, because I also note that you shortened the pipe. Does the airflow alter around that area because you have both a mechanic fan and a Kenlowe? All in all very odd.

The only non standard measurement I am aware of in that area of my engine is that the carb spacers are about 3/32" thinner than standard (non standard - fitted with vacuum tappings). This puts the bowls that much closer to the engine - but we are talking minor measurements here.

I have just re-read your post. I am confused by your statement "it will take ages to cool the fuel bowls once they get hot. If the blower is switched on just as you get to a hold-up the float chambers won't be hot in the first place". Can you explain. I thought the whole thrust of this blower saga was to cool down the chambers which the deflector achieves very quickly.

Cheers

Steve

PS. Windtone hooters?
Steve Gyles

Steve-
There are most elegant and thrifty of space and complexity/weight devices based on "memory alloys", which are just a wire that changes length when an electric current is passed through it. Perfect for this app, as it could be switched along with the blower "ON". Or you could have a c-shaped spring which does the same. They develop a lot of force - some use them for electric door latches and such.

Don't think electromagnetic devices without a moving core count as "solenoids" in this discussion. Control box, horns.

FRM
FR Millmore

Steve
Oh alright then I'll go along with horns having solenoid switches..!
I'm not thinking of cooling the carbs themselves as they are fine when we are moving through the air. The carbs and their fuel are cool so no problem. Come to a halt, the air duct flow stops; hot air keeps coming through and from the rad and mega heat comes up from the manifold and engine block; carbs heat up, vapour lock eventually starts to occur and naturally gets worse the longer the car stands.
All we are doing is to kid the carbs the car is still moving if you like, just as the Kenlowe does.
So in that traffic jam, switch on blower, area round carbs stays cool - no vapour lock just as when moving.
Your tests were excellent, but why heat up the float chambers and measure their temperatures when they won't be getting hot going along or with the blower running when stopped? Go on try measuring the air temperature differences around the air filters as I did. I think the minute details of just where everything is and duct bore differences won't make any noticable difference.
Pete
P N Tipping

Pete

Ignore my blower data from the 40mph tests. I was measuring the normal running temperatures to get a full data set for analysis. I only switched on the fan when running to see the effect. Obviously, in our climes we don't need this artificial boost at speed.

I am cooling the float chambers not heating them with my deflector. In my idling tests I let them heat soak to 132F from their normal running of around 112F, then switched on the blower with deflector and got them down to 98F in less than a minute.

Steve
Steve Gyles

So much for buying an Attwood pump. I am now being inundated with emails from HVAC suppliers and specialists!

Steve
Steve Gyles

Steve,

Ask them what they recommend for cooling MGA carbs.

Malcolm
Malcolm Asquith

And if their AC is bolt-in.

FRM
FR Millmore

Can they recommend them for increased performance when sucking on an MGA exhaust?
Pete
P N Tipping

Just an update on my Attwood Blower that I fitted 4 weeks ago.

Last weekend in hot weather conditions I was caught up in our typical south coast traffic congestion. My temperature gauge was rising to 190 degrees & in anticipation that fuel vaporisation was about to occur I made the switch to turn on the blower.

At idle running the little motor makes more noise than one would expect, however this was reassuring as I do not have a power on indicator on my switch.

I was held in very slow moving traffic for 20 minutes, during that time the idle speed was smooth between 800 – 900 rpm. On previous occasions under these conditions the idle speed would have begun to deteriorate giving me the indication the first indications of fuel vaporisation.

I can therefore report that it works for me. However I seem to be suffering from the same side effect to what Steve was reporting earlier on. On a number of occasions (blower off) the engine shows slight hesitation in engine pick up from slow speed – OK from stationary. I think Steve is right about the disruption of air flow to the filter boxes.

Steve, did you conclude anything with your deflector trials? Do you still get engine hesitation?

Richard
R A Evans

Richard

My ruddered ship is working well. Took a bit of fettling to get the right spring balance against the solenoid but all now sorted. The rudder now centres well when power is off. I had it fitted on a 150 mile round trip to the MGA Register day and suffered no hesitation. Nor did I have occasion to switch it on.

As an aside, I wonder if the EC will make us take our blowers out (see other post about EC regulations)!

Steve
Steve Gyles

They would have to find it first!

The reason I carried out this mod was because it was it was unobtrusive & with the bonnet up almost invisible.

In any case, if it wasn’t for the changes to the fuel since these engines were designed I'm sure that we would not have to carry out these little modifications.

Richard
R A Evans

During the recent hot spell I got a run on a day it was around 32C(86F) and took the opportunity to fit my remote temperature probe centrally between the pancake air filters (average intake temp) with the digital readout magnetically fixed to a bracket tucked into the tunnel carpet overlap.
Driving between 30 & 60 mph in top gear with the blower off I got indicated temperatures from 118F to 123F. Going up or down gradients in top gear the temp remained surprising steady.
This seems to prove that the 3" idle air-duct blower is not causing any undue air-flow restriction.
As soon as the car was stationary the temperature immediately shot up, as it would, and quickly got to around 150F when the tickover started getting lumpy. At around this temp I was switching on the blower and the tickover very quickly settled almost before I got any indicated temperature reduction on the readout. The indicated temp would start to slowly reduce, but once on the move again and with the blower off it would drop rapidly to around its running 120F.
I have also found that the usual run-on I get with my high compression flat top pistons and MGB head is helped by running the blower for a short period towards the end of a run and continue for a short period on tickover before finally shutting off.
So I have to say, to date my rudderless blower seems the perfect solution...
Pete
P N Tipping

During the recent hot spell I got a run on a day it was around 32C(86F) and took the opportunity to fit my remote temperature probe centrally between the pancake air filters (average intake temp) with the digital readout magnetically fixed to a bracket tucked into the tunnel carpet overlap.
Driving between 30 & 60 mph in top gear with the blower off I got indicated temperatures from 118F to 123F. Going up or down gradients in top gear the temp remained surprising steady.
This seems to prove that the 3" idle air-duct blower is not causing any undue air-flow restriction.
As soon as the car was stationary the temperature immediately shot up, as it would, and quickly got to around 150F when the tickover started getting lumpy. At around this temp I was switching on the blower and the tickover very quickly settled almost before I got any indicated temperature reduction on the readout. The indicated temp would start to slowly reduce, but once on the move again and with the blower off it would drop rapidly to around its running 120F.
I have also found that the usual run-on I get with my high compression flat top pistons and MGB head is helped by running the blower for a short period towards the end of a run and for a bit on tickover before finally shutting off.
So to date I have to say my rudderless blower seems the perfect solution.
Pete
P N Tipping

I have just been reading the Chairman's notes in the latest Safety Fast (MGCC magazine). He spends a couple of paragraphs talking about ethanol in our UK fuel. In it he mentions that Super Premium fuel (97 to 99 octane rating) is still ethanol free in most parts of the UK. I always use this fuel in my car, so perhaps that is why I have not been suffering the degree of 'boiling off' symptoms that others have been reporting?

What do others use?

Steve
Steve Gyles

Interesting. Being a cheapskate I always go for the standard grade. Maybe that's my problem? Sadly I will probably have to wait until next year before the hot weather returns to try it out.
Graham M V

I now use the ethanol-free super grades from Esso, BP & the local Tesco. I don't use V-power any more as unlike the others it has 5% ethanol. I used this for 3 years until I noticed it seemed to be eating my sender unit, causing the carbie jet seals to leak (stripping paint off the chassis below!), the floats' bottom halves were a different colour where they were in the ethanol and the inside of the carbies looked far too clean, just like the sender unit. Reading up on this fuel stuff I
left the V-power alone and now appear to have a proper MGA back again. Did you see it rocket up the Brooklands test hill last year?
...and now with my blower - on a hot day? Perfick..!
Running it before shut down in the recent hot weather really seems to have reduced the chance of any run-on I tended to get with my HC flat top pistons.
Pete
P N Tipping

This thread was discussed between 06/08/2012 and 08/09/2012

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