shaaark89

that is true, however air to air is always going to be more efficient since the water in the air to water coolers will never be at ambient air temp (it's always a bit hotter) whereas the cooling air in the air to air cooler is always at ambient.
the advantage of the air to water cooler lies in the greater heat transfer coefficient from water to aluminum vs. air to aluminum which allows for a more compact core.
quote from corky bells book "supercharged!";
"when space permits an adequately sized air to air intercooler to be fitted and given access to decent airflow, it will always prove superior."
and yes it can be done, but not for the faint of heart

Imo000

WOW.... That's a nice setup. Looks like it's 3 cores welded together with cast end tanks.

BC

OKay Tom. You got me. Without all the heaping holes in the front of big bird, a normal S4 or 2V 928 has very little space for a proper Air to Air without sacrificing the all important area for regular radiator and oil cooler stuff. I've been staring at the front of my 78 for a while now.

TAREK

I think the air/water is superior, to air/air, for about 4 seconds....and then it becomes a large mass of hot water that HEATS the charge air...unfortunately space is limited, and as long as it's meant for street use (short bursts of boost), it seems like the more practical way to go....but I'll keep looking for installing an air/air without seriously compromising engine cooling....we all know the 928 is air flow sensitive in the street

FeedNfrenZ

I'm obviously not as well versed on intercoolers as you guys so pardon the stupid question but why couldn't you use the rear A/C cooling coil just like you would any water cooled intercooler? Simply build it into an Aluminum housing, plumb it into the air intake like the watercooled verions do, have the soleniod open at a certain boost levels and simply let the air pull through the cooling coil just like it does in your A/C system? Hell my A/C runs all the time here in South Louisiana anyway! It wouldn't be any more load on the engine than if it were still plumbed into the rear A/C? I also think that I could build enough safety mechanisms into the system to stop it from letting the boost get to high if the temps aren't low enough.
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heinrich

Brent, I believe the tubes are too small to allow enough air flow. Remember we have to cool the air

Jim_H

Meltdown...

FlyingDog

The issue is that you can't 'store' the coldness. If you're just loafing around at or near idle, you have extremely cold air when you don't need it. When you step on it you'll quickly outpace the A/C's ability to cool the intake air. If you're cooling your intercooler liquid, you are in effect storing the cooling capacity. When you are not using power, you're cooling a large volume of liquid to extremely cold temps. When you step on it, you have a huge reserve of cold in addition to the A/C still adding cooling.

Another issue is that you'll get condensation in your intake which could pool when you park. Sucking up a lot of water on startup is not good for your engine. Letting the car sit for a while with a pool in the intake is also not good.

shaaark89

what you can do is use the a/c to cool the water for the heat exchanger so that you are running water that is below ambient air temp. in order to do this you would need to run the a/c coils around or through the storage container for the water. you would still only have a short effect because the water would heat up fairly quickly once the boost is on, but it would be more effective than noncooled water. again, i would not rely on this system to tune the car with since the a/c can lose freon or break.
as tarek pointed out, air to water coolers are best for short bursts and low speeds whereas air to air coolers will work best at higher speeds but will maintain effectiveness over longer periods.

EB338

I would be concerned about coming up with an A/C core that could handle the boost pressure. If you felt you had to use it directly as the core, under boost you could end up over charging the A/C system and causing damage and then at low RPM possibly sucking the while system down through the motor with even a pin sized hole. Then there is the formation of frost or condensation that always happens and is drained away outside the vehicle in a climate control system that couldn't be drained without bleeding off boost and now would be ingested into your engine. It would seem to me that use of the A/C system would be far less problematic if used to indirectly cool the intake air through fluid or some other way. Then there is the calculation of how much power you would really gain after the A/C compressor robbed the not insignificant amout of power required to run it.

Jim R.

As far as air-air vs water-air for a track car with unlimited space in the nose air to air would be my choice.

For a street car, I have had the water-air for close to a year. The intercooler remains cool to the touch with "spirited" driving and after 4 dyno pulls in a row as well. I do not have any actual temp data to share, but with 3 gallons in the system between the intercooler, heat exchanger, hoses, and tank it seems to work very well. I don't know how it would do for long track sessions.

The only thing I may do in the future is have a radiator shop build me a larger heat exchanger custom sized to fit in the nose and hold a larger volume of liquid in the system. I would rather not link to the AC system unless there was no other option. Keep it as simple as possible.

As a side note, the car runs quite well without the intercooler circulating any water when I tested it out. Vortech recommends not even using an intercooler until above 8 psi for a street car due the relatively low discharge temps at that level of air compression. The intercooler is a nice safety and power adder to have, but at least if the system fails, there is a nice safety margin.

Jim

Fabio421

What are you using to cool you intercooler fluid? An electric water pump? Do you have any temp switches in line or is it wired so that its always on when the car is running?

Jim R.

I have a small heat exchanger (10"x12"x1" or so) in front of the radiator to cool the fluid, electric water pump, and I have mine set up to be always on with the car running. The blowoff valve for boost runs on vacuum, so the intercooler and engine really only see a significant volume of compressed (warm) air under load. Standard Murf setup, works very well.

Jim

Imo000

Jim,

I totally agree with you. There are a lot of SC and even turbo system for other cars that don’t have intercooler at all. IC is more important in a turbo application cause the air get heated more due to the turbo being so hot. If the SC is set up for low boost applications, an IC is not necessary. It sure will give you a little bit more HP but the engine will run safely without it too.

I have no problems running 6~7 psi without an IC. Haven’t yet heard any detonation during even the warmest/humidest days of last summer.

Tony

Problem is , detonation can already be occuring BEFORE it gets to an audible level. Audible detonation is on the extreme end of the spectrum.
Be careful. Chuck on a simple small I/C just for some margin.