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MG Midget and Sprite Technical Being dumb here.... which way does the coolant go? BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - Being dumb here.... which way does the coolant go?
| I'm looking at the plumbing on the new racecar and wondering if I can dispense with some of the radiator coolant pipework. The heater tap at the rear of the head, does the water come out of the head here or go into the head instead. I know on a standard midget there is a t-junction in the lower pipe that comes out of the block (which we had capped off as our car ran the heater tap to a header tank) on the new car the take off from the heater tap returns back to the top hose via a relocated bottom T hose. The thermostat housing is mounted the same way as standard so in my head the water is going round in a circle at that point..... help! Andrew  |
| Andrew McGee |
| ..and you're Nev's race engineer? tut tut ;-) remember hot air rises, and so does hot water. Conversely cold water falls, so you design the system to take fresh cooled water from the bottom of the rad and pump it into the block. It gets hot, and rises into the head where it gets hotter still, and then returns to the top of the rad through the thermostat housing. A little will flow out the back of the head and into the heater circuit, and then back into the intake (bottom) hose where it gets sucked back into the pump. So when the 'stat is shut, the circulation is through the heater circuit, bypassing the rad so it warms up quickly. Don't ask me what the bypasss hose does; not a lot I suppose as race engines usually have it blanked off... |
| David Smith |
Andrew, for our Spridgets the coolant goes into the block at the rear of the water pump and exits at all other points that are open. The port in the rear of the head is an exit point for coolant. Would normally run from the head through the heater matrix and back to the water pump input side throgh the fitting in the lower hose. There is some debate about the effect of having that port blocked as far as even engine cooling, but it was designed to be run blocked by the heater control valve so I don't see any reason to keep that hose for a race car. Others may well disagree, I'd consult some racers and see what they have to say. I will say that all the racing A series I've seen here in the states run with that port blocked such as shown in the photo.
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| Bill Young |
| Okay so it comes out of the head and goes into the block at the pump. So the current configuration will bypass the thermostat and then go straight into the radiator even if the stat is closed. Dave, I never expressed that I was a race engineer of any kind whatsoever, Nev is more engineering minded than I will ever be, I'm finding I'm needing to find more information out as he keep asking questions (rightly so) that I end up struggling to answer. So my new years resolution is to get to grips with the ways things are and how they can be improved on. Bill, an early engine of mine had a blanking plate on it, however it was found to have hot spots at the read of the head. So we've always run it with an open valve or even no valve at all just a straight pipe connector. Now I'm just bothered that the exit from the heater take off is permanently going back into the radiator and will therefore take it longer to warm up. A. |
| Andrew McGee |
| Andrew, we usually retain the T piece in the bottom hose and pipe directly to it from a fabricated piece that replaces the heater tap. Apparently No4 cylinder is inclined to get hotter than the rest without doing this. |
| Mike Allen |
| Mike, in effect you are simply removing the Heater Matrix. So what effect will the heater feed piped into the top hose have?  |
| Andrew McGee |
| I can't see why that wouldn't work. Try it. At worst you'll just need to re-plumb. |
| Mike Allen |
| That's how it is currently on the race car that we've got to replace my totalled one. So it does work, just there is a hell of a lot of rubber pipes sat above the exhaust manifold which was heavily wrapped in heat bandage.... A. |
| Andrew McGee |
| Leave the heater pipe plumbed into the top hose, your engine will run a lot cooler that way. |
| Dave O'Neill 2 |
| Andrew, plumb the hose from the heater tap back into the lower radiator hose. That will pull the coolant back into the engine and not through the radiator, shouldn't affect warm up at all , in fact it may speed it up a bit. If you're worried about lots of rubber hose around the exhaust area then bend up some copper tubing and route it around the other side if you wish, or over the top like the MGB did with their heater plumbing. Ad an insulating sleeve and you shouldn't have any problems with heat. |
| Bill Young |
| I'll defer to Bill's experience every time. Without measuring temps at various points with both setups it's difficult to know for sure which is best. Maybe in ancient times somebody did this and determined it should be bottom hose and we've all followed along ever since. Maybe not. I've never contemplated plumbing into the top hose simply because every other engine I've seen plumbs to the bottom hose and I've just done likewise. |
| Mike Allen |
| As our engine isn't here but at the other end of the country I could check a couple of things. However I think I recall it having a restrictor plate in it instead of a stat so the top hose set up wouldn't make a blind bit of difference. However on our old car set up, we had the heater tap pick up going to the expansion tank on a large bore pipe. It appears that the expansion tank (which is built into the ali fabrication in the top pic) is connected to the small bore pipe inbuilt into the rad. Decisions, decisions..... A. |
| Andrew McGee |
| The pump pulls water from the bottom of the rad, so this lower hose is a low pressure area. It delivers the water into the block, so everything from here on is high pressure. With a heater, warm water goes through the heater, starting as high pressure, then returns to the low pressure lower hose, and gets recirculated. It does not get cooled other than by the heater, though it is cooled by dilution from the cooler water passing through the rad if the stat is open. That's good for heaters. Without a heater, the recirc has no useful function as far as temperature is concerned, except that it "ventilates" the back end of the head, which could otherwise have stagnant areas and hot spots. Thus it helps keep things even at the back relative to the rest of the engine. With the recirc tapped into the top hose, you have less flow through the ex heater pipe since the top hose is not as low pressure as the bottom one, but it still ventilates, and that warmish water now gets cooled, which was not the case with standard plumbing. So it will take slightly longer to warm up, but will cool somewhat better once it has. The bypass is to keep some water circulating through the head when the stat and the heater tap is closed, again to prevent local hot spots. A small hole in the stat does essentially the same thing, and you need such a hole anyway to prevent airlocks in the engine side of the system. Note that you could simply relocate the heater core to someplace with airflow, thereby really cooling the water that flows through the now "Aux Rad" before returning it to the system. You'd have more flow hence cooling with the standard piping; it would never warm up, and the stat would never open in cold weather, but there would be circulation through the engine and this "Aux Cool" system, none through the main rad. Just like a Spridget in -20F weather! In an apparent attempt to speed up warming, and reduce emissions, some modern systems have deleted the hole in the stat, and I haven't studied how they deal with it, but I have had odd cooling troubles that I cured by drilling the stat hole on these. These stats are just like the ones with the holes, and frequently now you will get them as replacements, which causes airlocks in engines that should have bleeds. I suspect that on the systems that call for "no hole" stats, there are internal bypass bleeds that get plugged up. One was a Ford Taurus, which is certainly no paragon as far as cooling system design, given the number of head gasket failures! FRM |
| FR Millmore |
| Bearing in mind that this is a race engine, the 'heater' function is superfluous and cooling is paramount. When I replumbed the heater take-off on my car (no heater matrix) from the bottom hose to the top hose, the normal running temperature was reduced from 210 degrees F to 180 degrees F. Warm up times aren't that critical, as this is normally achieved while the car is stationary in the paddock. Thermostats are normally removed and replaced with a blanking sleeve. Bearing in mind who built/raced the car, I would be inclined to leave well alone. |
| Dave O'Neill 2 |
| Andrew You won't need a thermostat in a race car - you are running it at peak revs most of the time so a device to warm up the coolant is not required and is a positive handicap if it goes wrong... You need to run one of these http://www.minispeed.co.uk/content/thermostat-blanking-sleeve If its the engine from your other car presumably with David, then it does run such an item. I would never run a thermostat on a race car under the KISS doctrine... David will let you know a simple system to plumb your engine - we adopted it years ago and it has never given us a moments problem... I have never known one of 'our' engines to overheat... Cheers J |
| James Bilsland |
| Fletch, Bill, any comment on Dave O'Neill's temp readings? I've never had >190 running temp, even in Oz summer racing, and that's with a standard crossflow radiator. What are 'ideal' coolant and oil temps in a race engine? |
| Mike Allen |
| David/James That's why I am in a quandry, both folk concerned are highly respected (well by me anyhow!) and they have both had different solutions to the same thing. I'm well aware that the person who built our new car does know what he is doing as he has, previously, been very successful with his other cars. However this one appeared to have engine reliability issues at first which enabled me to regularly run in front of him. Those issues may have got resolved as after I finished racing with him, he got back to his 'normal' results. We will be putting in my latest engine, which as James says is one of "their" engines and the last thing I want to do is to have that one have problems due to something that came on the car. I'm very much in favour of the KISS principle and whilst the self fabricated combined "air blower/catch tank/coolant header tank" is well thought out, I do recall that they had issues with it at first and I'm tempted to remove it and replace it with the Grey car's set up which would then need to have the coolant header tank plumbed into the heater valve feed. James, thanks for the link, yes I can picture that and our engine does have that installed already. FRM, thanks for your input I am learning. Andrew |
| Andrew McGee |
| Andrew I'm puzzled how you had the heater feed plumbed into the header tank. The header tank is not recirculating, the only path back to the rad is via contraction / suction as the coolant cools down. How else is yours modified? |
| David Smith |
| Mike - I'm a little surprised at how much change Dave had, and also wonder under what conditions he was getting a consistent 210, without running a stat. But I've never done back to back tests, and rarely had any situation that stayed static enough to rely on. One possibility is that he had enough hot water from the heater tap, which you will recall does not get cooled, that it alone was enough to stabilise the temps at 210. Vizard talks about "some" Coopers blowing water out, even though they don't overheat, and there are other "mysterious" things with cooling. Could be accounted for by things like casting differences changing flow rates from engine to engine, or plumbing configurations, etc, Just the angles at which a tapping enters a pipe with flow can make a big difference. You will note that the standard lower hose tapping enters at an angle that is slightly contrary to the flow in the pipe, but there certainly still is flow, or nobody's heater would work! Change that angle so it acts as a venturi, and flow in the small pipe might increase drastically. That would mean more uncooled & recirc water in the standard layout, or more cooled & not recirc water with the top hose system. Even exactly where you read the temps makes a big difference. KISS is fine when it's not screwing things up, but engines are much better off if the temps are constant. Too cold and you have to go rich, hot and now it's too rich, etc. Clearances change with temp variations. Engines are much more thermally efficient at higher temps, a big factor in long distance racing, as fuel stops or big fuel loads are SLOW. Cooling is much more efficient at higher temps, so you can use smaller and lighter systems, with less drag inducing through airflow. The Nascar guys run water temps around 235 with oil a little lower c215-220 I think. All the stuff you hear with them about "Putting some more tape on (or Off") is about fine tuning through airflow and running temps. Of course, if you have to run rich and/or cold because your engine will die at optimum temps and mixtures, you pay the penalty. Only thing that saves you is that everyone else is likely off too. I toasted my 1275 Austin/Cooper dirt tracker when they screwed around at lineup enough that I cooked the water out of it. Late in the year and I was mad, so I went after the competition with the temp gauge around about 60psi oil pressure. Hotter it got the faster it went. By the time it melted two pistons, they knew they were beat, and their friends did not let it go uncelebrated! The gudgeon pins on those two pistons looked like someone had attacked them with an acetylene torch - actually melted the pins. Lots of molten aluminum splash, but nothing else wrong with it. FRM |
| FR Millmore |
| Interesting this. What it all boils down to is- If it has a thermostat it has to have some sort of bypass for when the thermostat is shut--- either the original bypass or from the rear. But if it has a restrictor instead of a thermostat a bypass is not required as the circulation of water never gets blocked off Just to prevent the chance of a hotspot in the rear of the head some people run a small hose back to the top of the radiator from the heater fitting on the rear of the head but keep it small. 1/4----3/8 is plenty The hole size in the restrictor is very important-It needs to be small enough to keep the coolant pressurized enough to keep a good surface contact inside the cylinder head while circulating- If the restrictor is too large hotspots will develop while racing------11/16" would be a good starting point and then adjust the size to get the race temp. you want. Coolant temp for a petrol engine while racing 190-195 But if it is a alcohol fuel or alcohol blend 200 plus is the go --Alcohol fuels love heat With a 16 lb cap boiling temp is approx 230 and having had a fair bit to do with a racing Chev on straight methanol I can guarantee you that they go heaps better up round the 220 mark but you must keep a watchfull eye on fuel mixture at these temps as it getts messy real fast if you are a tiddle lean. Cheers Willy |
| WilliamRevit |
Hell's Bells , my '61 Frog doesn't have a heater and after ploughing through all these threads , that's just the way she'll stay...... ;) OTOH might be a good idea to print them off for future ref. Happy Christmas everyone! Arthur. |
| Arthur Jessop |
| Andrew and Mike, I have to defer to those with real world expereince with race cars in the heat of battle like Dave and James. I do heartily agree about the replacement of the thermostat in a race car with a blanking sleeve or a restrictor disc, no sense having anything in the system that would cause real problems if it failed like a thermostat would. I mentioned a restrictor disc because there are circumstances where you can get too much flow through a block or radiator and not allow the coolant time enough to either absorb or release heat, that's when a restrictor disc or experimenting with different diameter water pump pulleys may help. A larger pulley would reduce pump speed and probably save a bit of horsepower, the downside is that the engine may run warm at low rpms. As I stated earlier about plumbing the heater tap as a bypass, that's done by alot of racers, but not all. I'll defer to Dave's experience there, if it worked for him there's not much to loose except for a little hose and tubing. I can understand the reasoning for using that tap as I illustrated in the attached drawing of a standard A series cooling system. I know it's very basic, don't mean to offend anyone but it may come in useful as means for some to understand the system. You can plumb the heater tap to either the upper radiator tank (input side if a crossflow) or the lower tank or radiator hose as is the bypass hose to recirculate the coolant there. Either way, just make sure you have a good flow path from a pressure side to a non pressure side so the flow direction is stable. I favor the lower radiator hose area as it is definitely a "suction" area.  |
| Bill Young |
| Okay lots to get my head (brain!) around now. The car with it's current engine runs really rich, so much so that running it in the garage with the windows open as we did with the old car my eyes start stinging very quickly and it is not at all comfortable to run it at all. By deduction then, it is set far richer than my previous engines are set to. Also looking at the water pump pulley, this is also a lot bigger circumference than I've had on an engine before, there is approximately 8mm gap between this pulley and the alternator pulley which is the same diametre as the alternator body. So I guess that is also slowing down the pump speed along with a slower alternator speed. Now whether the larger pump pulley is compensating for the increased cooling in an effect to bring some heat into it and with the (my) perceived over richness of the set up I'm getting a bit blinded as to what configuration to to install all the ancillaries when we put "our" engine into the new chassis.... I guess the only way forward is to get it onto a rolling road for a proper set up, now the question is.... who is recommended in the UK within sensible travelling distance of West Yorkshire. A. |
| Andrew McGee |
| Andrew, Larger pump pulleys are quite popular in A-Series engines as a means of reducing water cavitation in high-rpm engines, actually improving the cooling. Likewise the larger alternator pulley reduces the load from the alternator and compensates for the fact that the engine will be running at higher rpm. Sounds like someone knew what they were doing when they set up your engine. David "small pulleys" Lieb |
| David Lieb |
| David Oh yes he certainly did, we had similar on our existing engine and intend running with that engine that is known to us. The guy who built the new car has won countless numbers of Championships in his previous Midgets (and MGBs), but wasn't as successful with this one unfortunately. I don't want to change things just for the sake of it, however as James is aware (as he knows this car also), there were reliability issues with it that we don't want to repeat. My first big engine that James had an involvement with ran faultlessly for SIX years without even refreshing it once, it did let go at Zandvoort or I should say that a Valve snapped and destroyed the block and head. The latest 1380cc engine that we had in the grey car was from the same source and I want to use that one in the new car as it has been rebuilt to our spec, whereas the one that came with the new car we don't actually know that much about. Better the devil you know and all that :-) Andrew |
| Andrew McGee |
| Ive always been a little confused by the take off at the rear of the head. The works just blanked it off. I have always run from the rear of the head to the top hose so as to pull hot water to the top of the rad(top hose). With the layout like Dave had with the hose going into the water pump doesnt this act like another bypass hose from the rear? so hot water going into the cold lower hose. I agree with putting a heater matrix in though as this effectively is another radiator in parallel! Its also funny how different same spec engines seem to run at different temps. Ive always run a std metro rad, but I know of a few others that have had this set up (with the same duct as me) with one engine absolutely fine and then the same one rebuilt with a new block running 10 degs hotter!! James, maybe you could post a dia of your cooling system, what rad do you run?? Cheers Mark |
| Mark Turner |
| I would not for a moment assert that ours is the only answer to the problem - there are miriad ways of arriving at the solution, however the way David (Shannon) and I have always plumbed in the cooling system of Spridget racecars is to run the hoses as standard (or on Metro Rads the top hose to the top of the rad and the water pump hose to the bottom). Bypass hoses have frequently been blanked altogether (although as it happens on my present car it does run a working bypass). Then we run a hose from the heater take off at the rear of the head to a decent sized header tank which is positioned so the water 'head' is above the engine and the top of the tank. Why does it work? Don't know - it does though - 1 Class A Midget Challenge championship, 1 Class B Midget Championship, 3 FISC Championships and no overheating issues even on the hottest days... On the A car we had a Metro turbo rad - on the B/FISC cars a thick core Midget crossflow rad. All cars ran a level of radiator ducting though not much on the A You might think that there would be no water movement in the header tank - but there clearly is... the only issue is you have to ensure that the system is properly bled to start with - just requires keeping the top hose off until the water starts to pour out... Please feel free to adopt or not - as I say it works - but if you feel your way is better then I won't argue... :) I have adapted Bill's diagram (clumsily) to explain...  |
| James Bilsland |
| James can you amplify this bit please? How does a blind alley allow through traffic... |
| David Smith |
| Dave I have to admit that whilst it doesn't make sense, Dave S changed my cooling system to that set up and I never ever had heat problems since and that was the six years with my first 1380 one, the two years it ran my 1293 which it worked far better with and since we put the new 1380 in it. Sometimes things just do work. And that is why I asked the question in the first place. A. |
| Andrew McGee |
| David The world is whizzing round at 700+mph and yet we don't all go spinning off into space... why? I don't know, but we don't... I can't honestly remember how we came to this solution - we may even have robbed the idea from someone else. All I do know is that it truly works... As I say if you don't like the idea, don't adopt it. :) Cheers James |
| James Bilsland |
| It's not that I don't like the idea, as a relative nube to racing I'm always looking to improve the car, and always studying others to see if I can learn better ways of doing things. However to evaluate a solution I need to understand how it works (I'm a techie at heart) hence my request. |
| David Smith |
| James & all - Lovely diagram, thanks! The header tank is functioning to allow air/vapour bubbles to get out of the back of the head, and it lets the system "breathe" water as it expands and contracts with temp changes. There is movement but no water through-flow with this. The tank also provides a separator to allow steam bubbles from overheating or combustion gases from incipient HG failures to get out of the system without blowing the water out, which is sometimes a good thing! If you added a small line (1/4" up to 1/2") from the bottom of the tank to the highest point on the rad or tstat housing - whichever is higher - then there would be flow through that circle, and additional free cooling would result from the added radiation area of the components. Fins on the tank, spare heater cores in line, or fans on these would add cooling if needed. All that water would finally get cooled in the rad. Best of all, this totally eliminates all possibility of airlocks, either in filling or operation. The tank opening must be the highest point in the system for best operation, though it will work if it's not quite at the top. All this would totally render the bypass redundant, so that hose can be eliminated, great for race cars or anything without heater requirements. Also recall that the bypass water is always recirculating but not being cooled, except on some systems that have a bypass blocking valve built in to the tstat. Old British things (Healey, MGA) and Volvo B series engines are examples. I would suggest a 1/4" tank to rad return for tstat/heater equipped cars. and a 1/2" for non heater, and I'd be using a high temp 195F stat race car or no. FRM |
| FR Millmore |
| Thank you all. Now I feel that I know what to do in as much a we'll take out the ali fabrication and replace it with a standard catch tank for the crankcase and rocker box and install the original expansion/header tank from the grey car with the addition of a small bore return pipe to the original radiator expansion tank take off. Think we'll start on stripping it all out tomorrow. Happy Christmas to all. A. |
| Andrew McGee |
| Fletcher, how would one retain the heater along with a header tank? |
| Tarquin |
| Tarquers. Think we are combining two different scenarios here, my specific requirement is for a set up without a heater as it's for the race car. Not saying that I don't want any discussion on the requirement for a heater of course. Although it never dawned on me that an additional "mini-rad" could be installed using the heater take off, so that's one to bank for future. A. |
| Andrew McGee |
| I've just endured, sorry, enjoyed an hour long discourse on the intricacies of cooling systems design, compliments of my engineer neighbour. It costs me two hours every time I stop to say G'day. He does actually have a great depth of experience in this area, albeit relative to mining equipment, and for some years was race engineer for one of the off shore power boat teams. I'm left with the conclusion that if it works, leave it alone, and if it breaks just follow what someone else has done, for redesigning cooling systems can get very expensive very quickly. He was talking of testing with 12 thermocouples on just the cylinder head, and of calculating/measuring flow, temp, pressure, cavitation, ambient temps, fan designs etc etc. Asleep yet? |
| Mike Allen |
| Andrew Let me know how you get on with the header tank return if you try it - only thing I disagree with FRM about is the use of the blanking sleeve on race engines, - to my way of thinking they cost too much to rebuild/replace to take the risk on running a thermostat - blanking sleeves were the order of the day with Special Tuning on race and rally engines and cannot go wrong... If your engine runs cooler than you want it to (and usually its the opposite problem) you can mask radiator fins if you want. However I take the view that running slightly cooler than optimum is a good thing when you have to replace your race engines out of your own salary... Happy Christmas all James |
| James Bilsland |
| So it becomes an issue of avoiding a potential disaster vs. optimum HP? When was the last time a thermostat failed on you? Two years ago for me. They are cheap and easy to test, so replace it every year. The thermostat CONTROLS the temperature of the engine; this is important for optimum HP as well as for bearing longevity due to cold oil. Your cooling system has to compensate for hot days and cold days, idling and WOT, without a thermostat, how can you delude yourself into thinking it is possible? David "drill an extra hole or two?" Lieb |
| David Lieb |
| David I have never had a failed thermostat.... :) James |
| James Bilsland |
| Incidentally everything I say in this thread relates solely to racing engines - I would run thermostats on road or sprint/hillclimb cars for instance. J |
| James Bilsland |
| Tarq - One way is to just use a dead end header as in James' diagram. It should come off the high point where the head water goes to the heater. Best to also have a bleed to the rad top direct. All small lines. General principle for dead end headers is they are the high point of the system, and other local high points also get vented to the tank bottom. If the header tank must be mounted low, the use of small bore lines lets the system suck water back as the engine cools, preventing air bubbles in the water jackets, but you have to bleed it when filling. This was the Volvo design C 1966. or late MGB - but they didn't bleed all the local highs, notably the high point of the heater circuit. To include the header in the flow path: You would run the water Head>Heater>Header> lower hose for quick max heat = arctic. Stock plumbing with heater return feeding header then continuing to lower hose + a small bleed line from header bottom to rad top. This might call for reversing the flow through the heater core. Retain bypass for quickest warm up of engine. No bypass needed IF you cannot completely shut off the flow; car heats up with engine. Head>Heater>Header> upper hose for some slower heat but better cooling once hot; call that spring/fall demist mode. As above but Replace normal return with 1/2" from bottom of tank to top of rad or stat housing; it's both return and bleed. The heater circuit is bypassing the stat, so warm up is slow and temps may be low in low ambient. Stat cannot completely shut off flow from engine through rad. Head>Header>Heater> upper hose = race, with the heater core mounted in airflow someplace. Best gas separation, best self bleed on fill, best cooling. Or just leave it as demist, turn the heater blower on, and you may want to provide an exit point for the heater air output! The general rule is always avoid local highs in pipes or components if possible. Provide bleeds from local highs to header if necessary, but remember that they do reduce flow through the normal path, so use small lines for bleeds. Mike's observations are true, but we are already out of range of factory design by making these things produce 4 or 5 times the power they were originally designed for! Failing all the lab work, the things I'm pointing out keep you more or less within known practice, but might explain such as Andrew's mysterious distinctions between different engines/systems and their effectiveness. Stats: Stat failure sucks, but the general idea is that the engine wants constant temps and the stat is better at that than the driver is - cars used to have manual blinds, just like manual spark & mixture controls. The half inch circuits described will prevent total instant meltdown if the stat fails closed, which is quite rare. There are millions of high dollar power installations running stats that successfully keep temps within a couple of degrees of optimum. For my part, I've found that stat quality is variable, but once you find one that works keep it. They rarely wear out, and changing a good one for a new unknown one is silly. Stat manufacturers tell you to change them because they get to sell them. I have cars around here with 30 year old stats, that in more than one case were changed out but put back when the new ones failed. Lots of new ones fail, after about 6 months you can usually rely on them! I never change a good one, and I never throw a good one out. Bad ones get beat to death with a hammer. As far as power vs optimum temps, if you can spare a few percent power, you either have a really good car that could be better, or you are following somebody who does! You can just as well say you will give up the top thousand rpm because the crank might break, but you have a temp gauge - no crank fatigue gauges I know of. For long distance stuff, the fuel mileage gets very important, nobody can stand an extra pit stop. FRM |
| FR Millmore |
| FRM.... my "distinctions between different engines/systems and their effectiveness" are only cos I haven't a clue about the science of these kinds of things. I can only relate what I see as being there and the resultant reaction to it. For clarification purposes then, however there is no data to relate here, the 1293 engine was in at first before the original 1380 engine that Davis S and James built was installed. Therefore the only benchmark that I can offer is the comparison of the 1293 with my set up for the cooling system, against the cooling system that Davis S and James applied to my car when they put the "big" engine in. Nothing else changed on the car (well cooling wise anyhow) same ducting, same radiator, however I noted that on reinstalling the smaller engine that it subsequently ran cooler to the order of instead of sitting just under the N (at 6 o'clock) it ran at around a third of the dial (around 7 o'clock), if that makes sense. I think to aid the science a bit more, we may now install the old unit in the same configuration as we had it in the grey car and make some temperature notes and then run the small pipe between the header tank and the radiator and let you know the results then. However that is likely to be a couple of months away as we have to strip it all beforehand (and the engine is back down at David S's being fettled after it got battered about the rolling car!). I didn't actually think my simple lack of knowledge would create such a healthy response and as usual I thank you for enlightening this slightly ignorant driver..... .... as Max will tell you I know how to make things look well and I was constantly told how pretty the grey one looked (least I can get something right!) so hopefully the new one will also be well presented. Tomorrow we pull the engine and box out, so if anyone wants me to take specific photo's of it's current configuration then shout out now. A. |
| Andrew McGee |
| There are many answers to the question of what coolant system to employ depending on how you 'cycle' the engine, i.e. full race,or, high torque/low rpm set up, etc, etc. What we all need to understand are the basic requirements of a cooling system. Firstly, the water pump needs to have a solid head of water to push round the system. The suction of the water pump will draw air from the system into the eye of the impeller if it gets half a chance. It is possible for it to become "air bound", in severe cases, resulting in zero circulation. Excessive impeller tip speed can also create unwanted (air)cavitation, hence the different pulley sizes available for the 'A' series engines in order to keep impeller speeds down on high rpm engines. Any air 'entrainment' must be capable of being dissipated via the radiator top tank design, or, failing that it should have a 'header tank' with a deaeration capability. There are suggestions that the rear 'A' series cylinder/head cooling can be marginal on higher powered units, if so using an original heater matrix system can he benefitial. Alternatively a take off line, with restrictor ( N.B. a heater matrix automatically 'restricts' flow) can be substituted to good effect, it thus retains a positive block pressure in the cooling system and theoretically purges any air out of any 'nooks and crannies' in the castings. If you are not sure if water is going in the direction you think it is, and/or, you are having trouble with air in the system/overheating,then fitting clear sight tubes into the system is the best way forward to check on what's happening. Due to the multiplicity of head/block casting types and cooling system set ups that have ended up in spridgets you just have to suck it and see with what you have. The watchword is, keep it simple,and,only make one change at a time. Peter |
| PJ HOBSON |
| Andrew = The observations of the unlearned are very often the most valuable input to those who have a good idea of what is going on. Experience totally free of expectations gets around preconceived ideas. I love to pick up info from the unlearned, much easier to sort through than that from those who can explain (and confuse) everything except the discrepancy they either asked about or didn't realize they had! Random or idiosyncratic effects can drive anybody nuts. They confuse those who don't know much, leading to erroneous conclusions that get perpetuated, but they really mess with your mind if you have a good understanding of how things work. Some approaches usually work, some have their best effect only if there is something borderline that you don't see. Example: the degassing effect of a good header tank setup will only be useful if there IS gas. So, a leaking gasket, or local boiling under load can be "fixed" by the tank, otherwise it seems to do little except eliminate bleeding whilst filling. But local boiling might be caused by pump inefficiency - too fast, too slow, bad impeller, slipping belt - or it might be caused by casting flash in a block or head passage. I've encountered castings with a lot of internal flash, to the point I went in through every hole available with long bent chisels and broke or ground out everything I could find. Bill Young's offering of the old idea "there are circumstances where you can get too much flow through a block or radiator and not allow the coolant time enough to either absorb or release heat, that's when a restrictor disc or experimenting with different diameter water pump pulleys may help" is an old misconception; I first heard it c1951 when my father was racing flathead Ford V8s. We used to put big flatwashers in the twin rad top hoses, and it does work, but what's really going on with the restrictor is that it maintains high positive pressure in the water pump and jackets, reducing cavitation and local boiling on hot surfaces. One good point of view is that race cars should always be "on the edge" in every respect. If not, then it is too heavy, too big, etc. Never gets hot = not enough power, or too much cooling system weight and power loss, or too much airflow hence drag. That said, the fine points I'm trying to get at are all meant to give you "cushion" on cooling, and ease of servicing. If it all works well enough, you could maybe make a rad or an airduct or pump impeller smaller, lighter, and so gain on it all. Not bad to keep from cooking the motor either! The famous dirt sprint car driver Doug Wolfgang told a local driver I know "If you don't get upside down a few times a year, you're not going fast enough" - same for race cars that don't break. As you & Nev proved, "too strong" is not a fault in safety gear, but anything else should break or reach its limits at some point. Paul van Valkenburgh observed that the only part of a race car that is irreplaceable is the driver. I want to say that you do indeed make it look good, and it is my belief that this usually gives good function as well - art and science are bedmates. The grey car was beautiful, and I was sad at the demise; best of luck with the new one! FRM |
| FR Millmore |
| OK as Andrew mentioned my name and FR called me up (he spoke about the "unlearned"), can I add my OBSERVATIONS to this thead? All I know is these worked... 1. When I started racing my "standard" 1275 was a vertical flow rad, which constantly pushed out at least half its water during a race. After half a season I ran the water level a little lower, fitted an expansion tank in the standard place, put a non-pressured cap on yhe rad and pressured the tank, and the water loss problem went away. 2. My modsports 1399 had the heater matrix mounted at the front of the car plumbed back into the bottom hose, it never overheated 3. When I re-started racing with a 1301, it never overheated once we sorted out an airflow problem 4. On my "Zandvoort" 1380 FISC car I had the heater hose plumbed into the top of the vertical flow rad, it never overheated. Alas the rad was wrecked so my next car was: 5. My latest FISC car with horizontal flow rad. With the 1301 engine temps were always marginal, frequently 200 deg +, I think there were myriad problems. Tried a triple core rad, no difference. When the engine went pop, I stuck in a road-going 1380 for Monza and it ran *25* degrees cooler with the same set up so there was a mechanical problem somewhere What does it prove? That every solution is right *if it works for you*! Doubt this has added anything to general knowledge on the subject, but IMHO there is a danger of over-complicating things, and trying to fathom it out may send you up a blind alley. The quickest car I raced was my Sports 2000 racer and that had a really simple water system using standard Ford Pinto water pump, and we constantly had to blank off the rads! |
| Max max-at-midgetmax-dot-com |
| This thread has inspired a whole new level of thought with in my own mind. Let me ask you guys about my set-up for your personal opinions and thoughts Im going to be running a HOT 1330 fast road engine, So I know over heating is going to be an issue esp. during the july/aug dog days of summer here in missouri. I had a custom made alumiun rad made from Afco racing with 1.25 inch vains compared to the 3/8ths inch vians in brass orginal , its a double pass, meaning it goes thur the rad twice before going to the engine (Dont ask how, I havnt figured that out yet) but i ran the hose from the heater tap straight into the top portion of the radiator instead of going back into the lower hose before the water pump as original. Ive also drilled 2) 1/8th inch holes into the stat face...(that is a huge must do modifation for any engine, My truck loves the extra hole in its stat face) Im currently running a fan off the pulley but will convert to an electric fan down the road. and will do a oil cooler as well at another time. So is running the heater hose dirctly to the rad a good idea instead of the hose just before the water pump, Ive been running the heater tap By-PASSing the heater core matrix for several years and found the engine always ran a bit cooler |
| Prop |
| Prop, my first 1380 (David smith's race engine) had the heater offtake going straight into the rad matrix and it worked well enough. Electric fan's a bit of a sideshow IMO. It prevents some power loss, but it also prevents some airflow. It only cools the motor at low or zero road speed. |
| Max max-at-midgetmax-dot-com |
| But Max, the only time that you NEED any cooling from a fan is at "low or zero road speed", so the electric fan does EXACTLY what is needed. The mechanical fan is at its least effective at "low or zero road speed" whhen most needed and it is at its most effective at higher rpm when its net effect is to rob power. What's to like? Electric fans, properly installed AFTER the radiator, do very little to prevent airflow. David "guess what fans I use ;-)" Lieb |
| David Lieb |
| David, I meant that the electric fan doesn't affect the cooling of the engine per se, just avoids toasting it in traffic. If you've got a high speed/high temps problem, installing an electric fan doesn't help. I'll concede the airflow point ;-) |
| Max max-at-midgetmax-dot-com |
| Max, I agree 100 percent. You cannot correct an overheating engine with a cooling fan. David "not for lack of trying..." Lieb |
| David Lieb |
| I'll stay out of the cooling system debate. I would like to know how the car will pass scrutineering with what looks to have a standard plastic air ducting hose that looks to feed into a heater case that assumedly vents to the cockpit and thus compromises the regulations on bulkheads. |
| Daniel Thirteen-Twelve |
| Daniel You've nailed it, I've wondered about that since I saw it the very first time!!!!! Suffice to say that the aluminium (note our Atlantic bretheren Aluminium!!!!) thing has been removed and will not be going back in either. btw, there is no heather matrix in there, just a marine spec fan that assisted the blowing of cold air onto the screen. As we won't be having a screen, it's all superfluous. Another thing that I thought was not the done thing, is the glass bowled "filterking", we removed an Aluminium one from the grey one which will be finding it's way back into the new car. And all the rubber fuel lines will get swapped for my braided hose ones too..... lots of things to change in the coming months. Andrew |
| Andrew McGee |
| That's a can of worms Daniel. Seal up the air intake and fail the demisting rule, or comply with the demisting rule and fail the sealed bulkhead rule. Is there a single car out there that complies with both? I know when mine was closed, there was no screen demisting. |
| Max max-at-midgetmax-dot-com |
| We managed it on the grey one! 1. Cut away part of the rubber seal twixt screen surround and scuttle. 2. Take a strip of 1mm clear plastic sheet and cut a strip out the same length as the opening in the rubber seal. 3. Place said strip into big pan of boiling water, simmer gently for a minute. 4. Remove from pan and form against roll-edge kitchen worktop. 5. Hold in place until cool. 6. Then fit to scuttle top inside the cockpit area. A small amount of air flows through the gap and is then directed onto screen and it works. Unfortunately once whilst wearing an open face helmet to stop my specs from misting up, I saw a stone get kicked up by a car in front. I actually managed to watch it come towards me, miss the bonnet, then saw it slot itself perfectly through the gap, it then bounced off the plastic deflector and the screen and then stung me right in the middle of the forehead.... OUCH! It was a full face helmet very soon after that for me! :-) Seriously tho, I'm sure you can have the set up that was in the car, providing it's something more appropriate than a flexible plastic pipe. We've been busy over Christmas..... A.  |
| Andrew McGee |
| Hi Max, It's not really a can of worms at all. If the car is upside down, on fire, driver unconcious and the marshalls running to the other car on fire first you really want a decent bulkhead between you and the engine bay (even with your overalls and underwear). That's why (I guess) there is a requirement for the bulkhead. How to demist the car without compromising the bulkhead? Lots of options. The simplest but not one I recall seeing on a Spridget is to replace all of that plastic pipe with aluminium pipe end to end and voila you have a legal bulkhead using the standard heater core and fan. It's rare to see any racing Spridget that retains the heater core and those that do have the inlet into the car blanked off so how do 99% of all racing Spridgets acheive de-misting? I don't know but I'll be asking in 2010 De-misting doesn't have to be warm air blown from the engine bay. Probably the simplest option and one I keep meaning to sort for my road car (which has no heater) is to buy one of those small electric plug into the cigarette lighter socket (that I do have in my Sprite)heaters that sit under the screen. Or RainX de-mist and an open quarterlight gets the job done most of the time. |
| Daniel Thirteen-Twelve |
| Hi Daniel, I agree with the reasons for the bulkhead! Mine's sealed as much as practicably possible, (passing through steering column, cable etc) but then again I don't run a screen. With one two-race exception, I haven't done since 1982. Andrew - chapeau, mon ami. that's a lot of work done |
| Max max-at-midgetmax-dot-com |
| Demisting is acheived by a polycarbonate screen, Rain-x and an open (absent) door window with a window net on my car... Polycarbonate screens don't seem to have the same misting issues as laminated glass screens. |
| James Bilsland |
This thread was discussed between 21/12/2009 and 30/12/2009
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