theedge

IIRC it does... At least the one shown on Top Gear did

dualblade

you too, huh? i figured after the ac gasses cool down would be the perfect time to pass them through an air to water intercooler. fortunately, the low pressure side of the ac system is when the gasses are cool so i don't see why this would work. it'd supercool the incoming air more effectively than water would i'd think.

Dark Lightning

There's no such thing as a free lunch.

Matt H

At least SOMEONE got what I was saying. In virtually every setup like that I have seen, anyone wanting real power ditched it and went A-A. I guess I am a dumbass, I want simple. Virtually every problem with the 944 series cars is that someone made something simple overly complex.
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thesmokingman

There's a guy I know who built a custom water IC. His Rex was pushing 500+awhp. Funny, he dropped the water dealio during a full redesign. They are in search of twice the power.




http://cgi.ebay.com/ebaymotors/ws/eB...e=STRK:MESE:IT

Danno

The only catch with using the AC to cool the air is its load on the engine. Cooling 10-20CFM down 20-30 degrees is one thing, but trying to cool 300CFM @ 250-degrees down to 60-degrees is another altogether. You'll most likely increase the load on the AC, therefore the engine, by the same amount of extra power you're getting out.

The trick with water-to-air intercoolers is the water. It's the transfer medium (3x of air-to-air) that stores the heat and moves it to the auxillary radiator where it's dissipated passively. Doesn't require engine power and only uses a little electricy. Basically what you're doing is separating the two heat-transfer processes in an air-to-air intercooler:

turbo outlet air -> aluminium -> outside air

into two separate processes that's more efficient in each step due to the water:

turbo outlet air -> aluminium intercooler -> water
water -> aluminium (or copper) radiator -> outside air

In both cases, the air-to-aluminium transfer is the same, it's that on the opposite side, you have the water which transfer heat 3-5x faster than air.

NZ951

Danno, how is your water injection kit coming along?

theedge

Im not switching over to it definatly, I figure if I can make it fit cheap and easy ill try it out for a few weeks for ****s and giggles to see how it is. His car wont be using it anytime soon, and hes making money on the swtich, selling his spearco for MORE than he paid for it. Looks like he'll make about $500CDN switching over

He says theres MR2 guys pushing 650RWHP through this unit and getting 30-40 degree F intake temps even after extended runs. Sounds like a solid system to me.

Dark Lightning

I guess my issue is that I want a car which doesn't *need* anything besides gasoline. This is why I don't run N2O or water injection. I am an avid fan of both, but I want a car where all I have to do to achieve consistent performance is make sure the gas gauge reads higher than empty. Call me simplistic, I won't mind.

For the stock intercooler to work all you need is a head wind, something easily supplied with a heavy right foot. So long as you're moving and your intercooler is properly sized to match your power levels, you're ok. To realize the full benefits of an air-water intercooler, you honestly need a source of ice cold water prior to every attempt at max-power.

For dyno queens that live in shops, are only good for bragging rights, and are all about one-time peak power production, ABSOLUTELY air-water is the way to go.

For a drag race, I can see air-water working; you're only at wide open throttle for 15 seconds tops. (hopefully less. )

For autocross, eh, it'd probably be ok to drain and refill after each run.

For road racer, well, probably but you're going to be pushing the car for (relatively) long distances. Farther you go, hotter the water gets, the less effective the air-water IC becomes.

For daily driving I just can't see the practicality.

[/preaching]

Dark Lightning

For fun, list for me the production turbocharged cars with air-water intercoolers.

Now list the ones with air-air.

Which list is longer? Might the manufacturers be onto something? If an air-water intercooler could make more reliable horsepower, don't you think there'd be one in a GT2? *shrug* Take that as you will.

Tomas L

Yeah, and that source is head wind just as with a air-air ic. To run a air-water system without a watercooler is not a good idea.

Yeah, they are on to something. Weight, simplicity and most of all cost.
If your car allows you to build an efficient air-air system then you should.
Since our cars are space limited an air-water ic would be easier to fit. For the bigger water to air heatexchanger you have more freedom in placement and it should be possible to fit it in somewhere.
Regarding efficiency, a properly designed air-water unit will be more efficient than an air-air ic and, if the watercooler is large enough, it will not have problems with heat soaking.

Tomas

Dark Lightning

So how and where would you install the heat exchanger? Any heat exchanger would have to be AT LEAST as large as the stock 951 air-air intercooler to be remotely effective and as you said the 951 chassis is already space-limited. Ideally the air-water IC heat exchanger needs to be of a reasonably large size to maintain near-ambient temperatures. Do you go the extra step of adding a secondary radiator as a heat exchanger? Ok, where? In front of the A/C condenser? For cars with the A/C delete, in place of the A/C condenser? Maybe after the radiator?

For those wondering, the way to get sub-ambient temperatures with an air-water intercooler is with already chilled water added into the system immediately prior to the event. A bag of ice laid on top of the intercooler or dry ice placed on the intercooler and/or heat exchanger would work too, but this would work just as well for an air-air intercooler. An extremely efficient air-water system might be able to do see sub-ambient temperatures with enough wind chill, but again it would also be true for air-air as well.

Now what about the high-flow electric water pump to make the system function? Factor a place to mount that as well as the weight it adds.

Speaking of weight... Place the following items on your bathroom scale:

• An empty radiator
• An air-water IC (you can substitute a stock 951 air-air IC since the weight will be similar.)
• Two or three gallons of water/coolant.
• An electric water pump.

Now I know the water alone is a good 8 pounds per gallon; anyone care to add in the approximate weights of the other objects? Most Rennlisters would agree adding this much weight would wreak havoc on your car's diet.

Ok, so forget weight and go the cheap route: use your coolant system. Most air-water Honduh guys go this route to chill their intercooler. While, yes, this WILL work it'll cause two blatant issues:

1. The additional heat transferred to your coolant will tax your engine's ability to maintain proper operating temperature.
2. After a cold start and the vehicle reaches operating temperature, your air-water intercooler will never be any colder than the temperature of your engine. This in turn dictates that the charge air passing the throttle-body can't be any colder than 180*F.

*sigh* My $0.02 yet again. Take it as you will.

theedge

For the weight, it depends on how you do it I guess. Ive been thinking of using the windshield washer tank as the resevoir, since it has such a huge capacity (8 liters or something). So, the only weight there is fluid that is already there, at least on my car.

I have already checked and there is substantial space in front of the A/C condenser, so all that would be required is some creative mounting. Other option is the nose panel cavity, where the stock unit sits... Or both So ultimatly, the weight increase wouldnt too big I think, just the unit itself, a pump, some hose, and the heat exchangers. Easily offset and then some by ditching the A/C later, which I plan to do down the road either way.

Im not saying there arent downsides, of course there are. I have a chance to give it a try, so I figure why not. My long term power goals are easily within the limits of this unit, so that isnt the stumbling block for me. At the end, if it sucks then I swtich back. Spiffy project either way, and ill try to get some temp sensors together and do some sort of datalogging, which I want to do anyway.

Tomas L

It would not be easy finding a place for the heat exchanger but it will be easier than placing an air to air unit. First you can take advantage of the fact that it's water and not air flowing inside. This means that you can optimize the volume and shape in a way that's not possible with an air-air ic. Second, since the water hoses can be very long you are free to use spaces that would not be possible with an air-air unit. Anywhere on the car where there is sufficient air flow can be a potential mounting place. And why not us two or more smaller heat exchangers? It would perhaps be easier to find room for several smaller units.

No, that's not possible in either case.

Using engine coolant water is only practical at very high boost levels with corresponding high charge temperatures. Or maybe in a precooler before the ordinary ic in medium high boost applications (perhaps >20psi).

Matt H

You can mount an IC big enough for a MACK truck behind the stock bumper. Not only does SFR sell a kit to do so but I have seen more than one installed "home" version.
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