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Intercooler position

Intercooler position

(OP)
I have a Supra 2JZ-GTE factory turbocharged L6 engine in my Lexus, with automatic transmission. I have a wide but short (top to bottom) turbocharger intercooler, with a wide but short ATF fluid cooler behind it, both in front of the (water only) radiator.
This appears to be a common install, but I'm not sure of its efficiency. There is no temperature problem currently, but I'm going to increase power which will raise the load on all three coolers.
Would it be better to stack the ATF cooler above the intercooler (their total height is still less than the radiator core), which would have the following effects:
1. both cores would get air at the same lower (ambient) temperature, rather than the intercooler warming the air before reaching the ATF cooler
2. the extra height would prevent incoming air from passing over these two and reaching the radiator directly, making better use of the air volume, but wouldn't this tend to raise the radiator temperature since it would always receive warmed air?

Any thoughts, comments, links most welcome.

RE: Intercooler position

Hard to know, too many variables. What I would do is instrument each cooler out temp (& in, ideally), and datalog the temps with your current setup under the most severe foreseen conditions. From the results, determine which cooler is most marginal, and configure your new setup to favour that cooler.
What you could do to optimize the trans cooling, if your engine radiator is so equipped, is run the line in series, to the engine radiator first, then to the existing air to ATF cooler.
Other than that, just make sure the external air flow over the coolers is not blocked by anything but the coolers, and has no significant leak paths around the coolers.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Intercooler position

If you plan to increase boost levels, the charge air cooler is probably your primary concern. Keeping intake air temps at acceptable levels is important for controlling detonation.

The engine coolant heat exchanger capability can be improved by increasing its core thickness with the same frontal area.

The transmission fluid cooler in/out temps are probably high enough to allow it to perform satisfactorily behind the intake charge air cooler.

RE: Intercooler position

this setup indeed is very common and for a reason. the lowest out temp you would like in the intercooler, the warmed up air passing through the transmission oil cooler is still low enough to cool down the ATF, which usually is run at quite elevated temperatures anyway. when you would stack both coolers the watercooler would loose capacity, because its whole surface will receive already warmed up air. if you increase the power output of the engine (assuming the automatic transmission is up to it smile ) you might indeed need a more effective watercooling system. be aware though that the loading of cooling systems does vary over the use of the car quite considerably - running at low speed after driving on the highway at high speed will most likely be more critical then driving at high speed continuously because less air is passing through the coolers.

designing a sufficiently capable cooling system under all driving conditions can be very complicated because there are so many variables involved: air temperature, coolant temperature and heat capacity, amount of heat that needs to be taken away, amount of air flowing to the coolers. in your case you start out with a existing system laid out to be able to cope with the requirements of the car in its present state. if you alter that state you should first need to sort out which operating parameters will change , how far and whether those are still ok, or exceed the limits what the engine and transmission can take.

for example, how much rise in coolant temperature and intake air temperature is acceptable before knocking or overheating of the engine occurs, how much of the extra power installed will be lost when the air intake temperature rises, what are the consequences of a raised temperature of the transmission oil in terms of lubrication, oil oxidation and the forming of varnish on critical transmission components etc. all in all that can be quite a daunting task....

RE: Intercooler position

The other turbo issue relates to the intake air and under hood temps. Making sure that you are getting as cool of air as possible to start with and insulate the exhaust so that you pick up as little heat from external sources as possible.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Intercooler position

Yes, lots of variables.
I'd vote for stacking the coolers. I suppose you could analyze the performance of the main cooler with half getting really warm air and half cool, versus each half getting somewhat warm air.
Duty cycle and heat storage are biggies here, I think. Hard to run the engine at serious boost very long without going really fast, right?
Worst case would be going up long grades in the desert in the summer with a full load of people and luggage. Do you tow a trailer with it? If so, add that to the mix.
Make sure the cooling air can be exhausted from the engine compartment, of course. Easy to get cool air to the front of the coolers - harder to get it from behind them.
For short high-power high-speed runs, I doubt the trans would have a heat problem. As long as it's kept reasonably cool normally, it can just heat up a bit during your 20 second blast up to ridiculous speeds.
fwiw
Jay

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Intercooler position

Anther way of looking at the system that might help. If you arrange the coolers so that the average air temp leaving the coolers is a maximum, you will have maximised the heat removed from the coolers.

je suis charlie

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