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The one thing that I have noticed time and time again while tuning MR2s with different intercooler setups is that air to water intercoolers tend to have higher average intake temps (by about 20-30F). The only time I see these setups produce good intake temps is when they are cold and the tank is full of ice. The reason for this lies in the nature of intercoolers. Intercoolers and heat exchangers provide the most cooling when the temperature difference between the two mediums is at its highest. When the temperature difference between the two mediums is small, intercoolers and heat exchangers provide very little cooling effect. The main problem with an air to water setup is that it is not one, but two systems. The regular core uses the water as the cooling medium and cools the air heated by the turbo. As it does this, the water takes on the heat and the system then circulates this water through the heat exchanger to release the heat. The problem is that the water must heat up to about 30F degrees above the ambient air temperature before the heat exchanger becomes effective enough to pull heat out of the water so that the water does not heat up any more. If the water is only 15F warmer than ambient, it takes a long time for the heat exchanger to bring it close to ambient again.

So, unlike good aftermarket side mounts or trunk mounts that will keep the intake temperatures fairly low as long as the core does not reach its limit and heat soaks, you can pretty much count on an air to water setup to generally provide intake temps that are about 40-50F above ambient after a few good pulls unless an external cooling source (such as ice) is used. The good news is that these system do not tend to heat soak even under constant prolonged boosting while air to air cores will.
 

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RickyB said:
The problem is that the water must heat up to about 30F degrees above the ambient air temperature before the heat exchanger becomes effective enough to pull heat out of the water so that the water does not heat up any more. If the water is only 15F warmer than ambient, it takes a long time for the heat exchanger to bring it close to ambient again.
Coupled with the fact that many a2w setups that people have built lack an adequate heat exchanger.

Oil coolers and AC condensers are not adequate...

I have a 24" (wide) by 7" (tall) by 3" (thick) heat exchanger mounted up front. And is built specifically for the application of a2w IC heat exchanger.

So if you guys decide to go a2w with a big expensive Spearco core in the back.. make sure you get a large, efficient heat exchanger up front.

smaller car radiators, bike radiators, and specifically built HE's do a great job.

I agree with all that Ricky has said. Just chiming in, with my thoughts on creating an optimum setup for a2w.

Marco
 

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uspspro said:
Coupled with the fact that many a2w setups that people have built lack an adequate heat exchanger.

Oil coolers and AC condensers are not adequate...

I have a 24" (wide) by 7" (tall) by 3" (thick) heat exchanger mounted up front. And is built specifically for the application of a2w IC heat exchanger.

So if you guys decide to go a2w with a big expensive Spearco core in the back.. make sure you get a large, efficient heat exchanger up front.

smaller car radiators, bike radiators, and specifically built HE's do a great job.

I agree with all that Ricky has said. Just chiming in, with my thoughts on creating an optimum setup for a2w.

Marco
I can second this. IF you go A2W IC, then this makes all the difference. I have an ST205 core and by changing from a "large" heater core HE up front to a Mustang Cobra HE, my core water temps dropped by 30 deg F.

-Eric C.
 

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I would be very interested to see precise intake air temperature readings on different set ups (ACTUAL NUMBERS IN DEGREES!). Anyone with an EMS would have this, it would really be great if they would share!

Good topic Ricky.

califcarm: you say your temps dropped a lot with that change. From what temp to what temp???? ;)
 

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anyone ever ran coolant through an AWIC? kinda a dumb question, but running pure water in a cooling system isn't good because it doesn't cool enough...the water takes in the heat. so why not put coolant in the tank?!? just a crazy thought...
 

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RickyB said:
The problem is that the water must heat up to about 30F degrees above the ambient air temperature before the heat exchanger becomes effective enough to pull heat out of the water so that the water does not heat up any more. If the water is only 15F warmer than ambient, it takes a long time for the heat exchanger to bring it close to ambient again.

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Can you explain this again Ricky I'm not sure I get what your saying

This is my setup
spearco 231 single core
3 gallon reservoir with distilled water
Rabbit radiator in front of the ac condenser
single pump
21 liters total

At night here on the island it's like 27 -28 degrees ambient
I logged 28 to 29 while while boosting to 18+psi during 1/4 and *cough* else where
at day time its like 32- 34 degrees and my intake temps are 1-2 degrees higher
If I park the car however the ic core heat soak to say 45 degrees it takes 5 to 10 minutes of driving to bring the temps down again to ambient +1 or 2

Lawrence
 

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flynhighaf23 said:
anyone ever ran coolant through an AWIC? kinda a dumb question, but running pure water in a cooling system isn't good because it doesn't cool enough...the water takes in the heat. so why not put coolant in the tank?!? just a crazy thought...
Coolant has lower cooling efficiency than pure water. It is only there to keep the system from corroding / freezing.

Pure water with a little waterwetter probably nets the most efficiency....unless of course it freezes and cracks your core and exchanger. :thumbdown
 

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chris_dittrick said:
califcarm: you say your temps dropped a lot with that change. From what temp to what temp???? ;)
I can at the moment only measure WATER temps in the IC system (No IAT available). Those water temps used to be (with just a chevy van heater core as a HE) from 100-135 degF. Now, with the addition of the Cobra HE, under approx. the same driving habits and weather conditions, IC water temps range from 80-100 deg F.

I am really waiting for my first track day where I can drive for 1/2 hour or more continuously hard to see what happens.

This is on an MK1.5 with an NA lid. I suspect that my IC water temps now are mostly influenced by the engine compartment temps since the NA lid does not necessarily vent very well. I think an SC lid or otherwise would help my situation greatly (although I am somewhat satisfied with the IC water temps as they are now and like the sleeper look of the NA lid).

-Eric C.
 

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my temps were about 90ish deg F in an 82 deg room at the dyno. at 17 psi GT28RS on my 4agte

st165 core
big ass custom heat exchanger
centripuppy pump
 

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I have a PWR heat exchanger for my setup. The core is 600x200x39mm and it fits nicely in the front of my AW11. It is designed specifically for water to air setups.
 

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You can see it here...

It's from an ebay store called Entopy Tech





 
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RickyB said:
The problem is that the water must heat up to about 30F degrees above the ambient air temperature before the heat exchanger becomes effective enough to pull heat out of the water so that the water does not heat up any more. If the water is only 15F warmer than ambient, it takes a long time for the heat exchanger to bring it close to ambient again.
I do not understand this. Can you explain it.

I have a big heat exchanger and I usually have about 95 to 100% efficency.
 

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i think data logging on the dyno vs on the street your temp will differ. when making over 400 hp on a side mount even after one pull the i.c. will be heat soaked. i see your point as far as the water temp has to be hotter than the outside temp for the heat exchager to be effective but at the same time i dont think you can duplicate the effect of air cooling the heat exchanger on the dyno as on the street.
when tuning the v6 twin charge car at Alamo Autosports we went as far as pulling water from a water hose to run through the i.c. and temps were about even (air temps in and out). when ran through the heat exchanger it took a couple of pulls before we saw a heat soak change. on the street however temps seem to be fine.
i know that when working at ATS with Aarons car the ice seemed to help quite a bit but he has a small pump circulating water. i think that the pump is just as important as the exchanger and getting air flow across the exchanger.
heat soak also is determined by how much air you can draw across the core of the i.c.
ambient air temp would only matter if there was no airflow accross the core and the same goes for drawing air accross a heat exchanger.
thats just a thought. maybe peoples problems are not a2w i.c.'s but not having the whole system work well together. after all thats the hardest thing to do is to have parts that work with others.
 

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mr2 2ner - The temp difference between the intake air and the water in your IC core is very high, so the IC core can quickly pull the heat out of the charge air. The problem is that the temp difference between the water and the ambient air is very small, so the heat exchanger has a hard time cooling the water down, until the water heats up, at which point it is no longer as effective at cooling the charge air.

A big enough heat exchanger will still be able to cool the water sufficiently despite the low temperature differential.
 

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Not the heat difference in the heat exchanger. If the air temp is 72 degrees, your water temp is, say, 80 degrees, and the charge air is 250 degrees, then the temperature difference across the heat exchanger is only 8 degrees, compared to a temperature difference of 170 degrees across the core.

So, at the heat exchanger, the heat transfer will be very low because of the lower change in temp.
 
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