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ajb1967

Fans in engine cover

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Guys,

As i mentioned a couple of weeks ago i am fitting double fans into the engine cover to aid cooling the engine compartment.Due to certain other mods the engine compartment is getting a bit warm ;-)

Anyway,i have the fans set up and ready to mount with variable speed motors which will be coupled to a temp. sensor to regulate fan speed.

I was just wondering ( i have a feeling this question is going to sound stupid by the way ) if i should have the fans blowing air into the compartment or sucking it out.My intuition says "suck out" but would appreciate it if anybody can confirm this.

Thanks

Adrian

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had the same thing built in in my renault alpine A 310

they were known for getting warm while standing with the engine running

i think that must be your only goal

cooling the compartement off when your driving slow in the city or standing in a traffic jam

for other reasons you wont need it

when the car is running the cooling (with the undertray and the engine bay lid on) is sufficient whatever mod you have done

heat tends to go up

so if you ant to cool you'll nee a fan to dring in cool air from underneath or the sides

rens


researche is something i do when i don't know what the hell i'm doing

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With regards to the 'suck' or 'push' question. I work with computers, and you always go for air flowing through something, and aid it.

I think as those vents on the tailgate normally are designed to have air going out of them, (possibly by some positive pressue caused by the sill intakes?) then you'd be better having them pushing air out of the engine compartment. Hot air wants to rise too. Server cabinets always have fans at the top sucking the hot air out.

Having said that.. Fans move cold air better than hot air as it's denser, so they won't be as efficient pushing hot air out..

It's swings and roundabouts.. Balancing the flow of air through the engine bay, against efficiency of the fans in warm air.

I think if it was me I'd set them pushing hot air out.

Good luck!

Glyn.

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The standard turbo gets to 1200 degrees as is and is fine with what's there. What have you done, added a bbq to the engine bay? :lol::whistle:


88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

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cant imagine power of vents.................but hot air goes up to the cutouts in dash, if ll be there vents they ll push hot air back to the engine, i cant see in this mod some cooling advantage, mby i ve bad undestand and u mean suck off hot air out, not for cooling.


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HAHAHAHA,Bibs.

Yep,i decided that my Esprit would also be a great mobile BBQ in the summer so have added a hotplate on to the valence ;-)

Nah,seriously though,i have a lot of residual heat in the engine bay.So,maybe this is normal but in the summer it will be worse.Secondly,i reckon that if i take some heat out of the bay then the chargecooler will be more efficient also.I still think the positioning of the chargecololer is wierd on these cars.It is mounted straight on top of a very hot engine !

My Turbo is glowing bright red after a long run so i would agree on the 1200 degrees.I just feel that the cooler the engine bay is,the better

Adrian

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Dermot has added some very effective heat resistant material under his 'huge' chargecooler which is very effective from what I can gather.

http://users.ox.ac.uk/~ohare/engine.htm#h6

You're right, it's not the best place for the chargecooler to keep it cool and 1 degree off the intake temp = 1 extra 1bhp so this could be a good idea, as may be wrapping the exhaust side of your turbo to keep the heat in there with the gases and not in the engine bay.


88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

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Seems a bit excessive :whistle:

Any sort of heat transfer is related to how muhc you can move - it doesn't matter where the fans are (on PC they usually pull air OUT of the case to reduce dust pickup because the air can enter through a large veriety of holes, reducing it's pressure and ability to bring in dust). However it does depend if you want to direct it to a certain sport - ducted fans are much better for this as their total air flow is concerntrated on 1 area.

The best bet is to have a pusher / puller fan system of the same fan rated at the same flow/rpm, although I am really not sure how much it's going to help as air isn't the best heat transfer system.

IMO the best bet is to duct air in from the car like a RAM effect to your hot spots - this is how it's done conventionally becuase it's reliable, cheap and easy to fit.

Look at the race cars for inspiration - they had NACA ducts in the roof coming down into the engine bay, doubtless you could also re-direct the 'ear' intake (opposite to the air filter) and also ducts from the underside.

This would flow similar amount of air (only when moving) weight a lot less and drain naff all from the alternator.

The final thing you might wanna try is water misting, it of a dodgy subject but you can get little fogging systems that inject a tiny amount of water into ducts (indeed into air intakes for the engine itself !) which will drastically increase surface cooling (water is so much better than air). you might have corrosion issues there though, perhaps a paint job 1st might help things ?

Need to know more info really.

FWIW I dont know of many Esprits who's manifold and turbo dont glow hot, mine certainly does.

Also the Chargecooler sheds so much more heat through it's design than what you'd ever hope to achieve through blowing air over it.

1. The chargcooler has no fins to increase it's surface area to take advantage of cool air over it (like a radiator)

2. A working chargecooler should only be about 10 degrees above ambient - as already stated, fitting insulation is by FAR the best bet

You could theoretically improve the system by fitting a larger displacement chargecooler electric pump, but at the end a normal turbo's intake will be at about 100 degrees, my chargecooler pulls that down to 32 on an average day so it's working bloody well.

Thought about fitting a larger chargecooler ? - again check Dermots site, he's done a lot of the donkey work and it all makes perfect sense imo.

Edited by Jonathan

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Hi There,

I did the same mod on my 89 Turbo by using some large computer fans. I had it set so they sucked the air out of the bay and vented it to the atmosphere.

TBH I felt it worked as you could feel the hot air being blown out of the bay!!

I also fitted a fan that blew cold air from the side intake onto the turbo. This also aided the airflow through the bay.

HTH

Cheers


Alan Croft

2000 V8 GT

87 Turbo Esprit HC

2000 Elise Sport 160

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Why not add water injection. I have it fitted on my skyline and it works perfectly, only draw back is you have to keep checking and topping up the tank. It reduces detonation too so you can increase boost safer and advance the timing for more power.

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the water (or methanol) injection does wonder to lower intake temps - I have use it on many car

however - wasn't the need to cool the engine bay - using fans to move the air more? not simply cooling the intake charge.


Lou Senko

Austin, TX

more, more, more....

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Anyway,i have the fans set up and ready to mount with variable speed motors which will be coupled to a temp. sensor to regulate fan speed.

Adrian, speaking to a very knowledgable source I'd say that you only need fans running either when idling in traffic or to cool the engine after a spirited run. When you're all speed there is a huge amount of air circulating in the engine bay area anyway so the fans would be redundant.


88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

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I do not think fans or air to the compartment will really make that much of a difference at idle, cars can overheat in freezing temps if their cooling systems are not working. I would think investing in a larger oil cooler setup or even just adding larger more modern fans to the front radiators would make a much larger difference than air in the compartment. I have raced for years and an engine which runs too hot is not going to benefit from air blowing on it, by that point it is too late. The internal temp of the engine must be lowered, or all you are doing is cooling the outside. Which does not prevent damage. Ask Marcus, I would imagine he could wiegh in on this one. Put the fans on the radiator, or clean your radiator, make sure no air is in the system, even going to a cooler thermostat, not crazy cool, but a few degrees could solve it. Air on the motor may make your temp guage drop 1 degree if the air is blowing right on it. But generally this makes no difference. Electric charge cooler pump may also help in that it runs at a constant speed, independant of the engine. This would cool intake charge. Just my 2 cents from years of racing, when a car is too hot, air will not help, unless it is directed at radiators or in the case of air cooled cars, directly around cylinder heads . . .

And there is always the idea of wrapping the exhaust manifold, increases temps inside, which supposedly moves the air out quicker and decreases the time it takes to spool the turbo. Then encase the turbo in some of those heat sheilds available anywhere, this keeps that heat from spreading over the engine bay. In many race applications they box in the exhaust side of the turbo and then provide some type of outside escape for the air, I would imagine this would lower the temps in the bay quite a bit, as the turbo is a friggin heat beast . . . .

Edited by CBrownstead

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the water (or methanol) injection does wonder to lower intake temps - I have use it on many car

however - wasn't the need to cool the engine bay - using fans to move the air more? not simply cooling the intake charge.

Yeah i know but it is so much better to cool the intake air rather than the air surrounding the engine.

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Often had brief thoughts about this but not having a chargecooled engine haven't tried anything.

My main thought would be what temperature is the watter within the charge cooler when it returns from the radiator?

Could this be cooled further?

Would a colder chargecooler actually cool the intake further and offer benefits?

If so increasing the efficiency of the radiator (extra cores) or adding a further radiator somewhere maybe behind the skirt duct could prove affective.

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Glyn - depends on the boost - on idle the turbo is not compressing so there is next to no heat generated.

It's when you put the mallet down that the heat picks up as the air is compressed it generates heat.

I know mine works tickety boo so on a day like 20 degrees C, and having a little fun the temp will get to about 50-60ish maybe a bit more depending on road speed and RPM (as the pump is RPM dependant) - slow down and you should see it level out at about 30 degrees. So you're looking at peaks and troughs for a normal Lotus drive between 30 normal speeds and 50-60 putting the pedal where it should be.

Leave it long enough and it'll return to ambient (given an hour or so !)

If you can hassle it an electric pump would be a good option because even at low RPM (2000) the pump should be moving water much faster than standard so down hill you could see a significant increase in cool down speed when off the throttle.

Further to that increase the size of the heat exchanger (CC rad -OR- Chargecooler itself) and increase the water flow a bit and you should see cooling benefits. Heat insulation is a plus, larger diameter pipes can store more water and gain a conductive cooling benefit.

As dermots page shows a bigger heat exchanger means the max/min cooling is more evened out which helps control the temperature on sustained levels of high boost. Insulating it is probably the most weight / cost effective.


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Totaly agree with that Jon, my question was more is it better to have the intake air (charge I guess) subjected to cooling for a longer period of time / better heat transfer by having a larger charge cooler. Or is it better to subject it to a colder environment by reducing the temperature of the heat exchnager in this case the water and charge cooler.

Its something that does interest me as I have often thought about in the future upping the boost on mine now having the nikorsil pistons/liners, but wouldnt do it without figuring something out to reduce the intake temp. I am sure Dermot or someone would know as there must be some chemistry going on there to give you an optimum transfer and/or transfer rate. If this is reached obviously making it colder will make no or little difference but subjecting it to cooling for longer would mean that it could loose more heat??

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Fans in the engine lid was a very popular fad in the MR2 community in the late '90's and early '00's, but is rarely done anymore. The debate over push or pull of air was a heated one (excuse the pun), but it was determined that if you really wanted to install fans, pushing air onto the engine at idle was best and the fans should be off when the car is in motion allowing air up and out.

The fans basically just add weight to the car and workload to your alternator. There is no evidence that it is an effective means of cooling your engine. Fans of a sufficient size to aid in cooling are also quite loud.

http://www.mr2.com/TEXT/MkIIEngineFans.html

A properly sorted cooling system is the way to go in my opinion.

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Glyn - not a proven method but when faced with a dilema like this I usually take 1 example and goto the extreme and see what would happen.

In this case take a standard charecooled car and make the turbo heat exchanger really small. You rely on water to absorb the heat - because of the small size you wont get a lot of water in there so the water will heat up very quickly (possibly boil !) once it gets to the rad it'll probably return to near ambient just as quickly as it normally would - so you'll have a large difference between the 2 heat exchanger temps, over time it'll probably hit a higher max and average temp.

Now reverse that - more water in the cooler, takes much longer to heat up - thus it will reduce the maximum and average heat in the intake.

This will require LESS cooling from the rad as the overall temp is not considerably high - in theorey you could get to a point where your chargecooler was so big it doesn't need a rad to cool it significantly - my PC cooling works like that, the reservoir is so big it simply cannot heat all that water to a significant temp - you also wont get spikes in temp when you put the hammer donw on the throttle - Dermots graphs demonstrate this.

Now look at the rad, apply same theorey - smaller rad, less cooling - they work in exactly the same way but in reverse.

So the answer is (imo) to match the 2 coolers best you can because they compliment each other. By unbalancing them you'd get waste in the system where one is working like the clappers and the other is under worked, but again this all depends on flow rate (pump displacement and constant / variable rpm) and road/air speed over the cooling fins and also how conductive the heat exchangers are.

So I personally dont think it matters one way or the other.

For stock boost the regualr chargecooler system (when working propperly) is fine (imo) for normal use - it works really well.

Depending on your budget the steps you take to reduce that can be as easy as adding insulation to adding a larger chargecooler - also keep in mind the closer you get to ambient the less quickly the water will cool down - get a thermometer and put it inside some hot water and then watch it cool - it's not linear - it will lose heat quickly at 1st and then slowly as it reaches room temp. Further more you get restricted by the amount of time the fluid is in the cooling stages, put simply it's not practical to get the temp much lower than 10 degrees above ambient becuase of the efforts needed to get such a little gain once you get that close to ambinet.

Hope that makes sense, just my theory.


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