Hold On

Has anyone built an air to air intercooler setup for a centrifical S/C? Either a front mount or a wheel well type with air intake?

BC

Todd did. He is not on here, other than to read - no posting. What did you need to know? Pictures?

Hold On

What type of flow pattern, size of unit, plumbing, location etc. Pictures are also great.

ptuomov

Here's the one fender mount system that I know of, it's by John Kuhn. He's selling these cold side components separately. I think one could adapt it to a supercharger setup with some effort. I prefer the fender mounted intercoolers, I'll be running his set.

Some photos

BC

Well, one version is here:

http://www.erik27.com/todd/turbo/index.htm

Its quite thick. Same basic idea as the first one.

LightStriker

That video hurts my brain bad...

Air to air is more efficient than air to liquid? What!?

dr bob

Yes. Think of the air-to-water-to-air setup as "100 percent times the product of two heat transfer inefficiencies" and you'll get the idea. The air-to-air has only one transfer inefficiency.

The air-to-water-to-air has the advantage of relatively small liquid piping connecting the two exchangers, so the two parts can be mounted where it makes the most sense. If it weren't for that darm water bridge on the front of the motor, and an intake with a forward inlet would support a pretty decent air-to-air unit in front of the existing radiator with relatively short and simple connections from the kompressor and back to the intake.

hacker-pschorr

It's all theory until you install and make it fit.

I've seen some horrific air / air cores that couldn't cool an Eskimo in winter and equally bad air / water setups.
Long story short, it's very hard to compare apples to apples. Most people are testing their intake air temp with sensors that are not fast enough for a proper reading, giving huge false positives. A sender designed for oil / water is not going to work for a proper intake air temp reading.

Air / air IC's are great, if you can get them good airflow, ducting etc....and make them fit. You can "get away with" more, especially with a street car, going air / water.

Why?

IMO it's much easier to build an efficient air/ water system. They also package up better / easier which is what has made them so popular in kits.
With 928's that use the windshield tank, you have 3+ gallons of water sitting at close to ambient temperature waiting for you to drop the hammer. Unless you have a cop free zone, you are never going to be on boost long enough to heat soak all three gallons.

IMO the amount of extra fabricating, cutting etc... to even equal my air / water setup, much less surpass it, just isn't worth it.
I could have an air / air if I wanted, just drop my car off at Todd's house for a weekend. After seeing the performance of my new IC on Shane Elliot's car a few years ago, it hardly seams worth the effort for possibly zero or little gain.

The Bugatti Veyron, McLaren SLR and even the ZR1 Corvette have air / water inter-coolers.

The SLR is an interesting example. Testers were experiencing heat soak situations in high temp conditions while doing top speed runs.
The solution?
Higher output water pump for the IC system, that was all it took to further increase the efficiency of that system.
I'm sure if the "better" solution were air/ air inter-coolers, a team of engineers like McLaren could have figured it out and gone that route. Much less the team behind the Veyron.
Sure a properly sized air / air might have been superior, the design worked out better going air / water.

I'm not saying one system is always better or always worse, each has it's own set of compromises. If I ever boost my track car I'll probably go with an air / air system.
On my street 81? Not necessary and I'm pushing over 17psi with room to increase that once my new intake is installed.


As for which medium cools better, try this experiment. Stand naked in a freezer set to 35 degrees, see how long you can stand it. Now warm up, and go jump in 35 degree water. I think we all know the answer to this.

If you have a hot piece of metal to cool down, few people go for the air compressor, most use a bucket of water.

As for Todd's air / air IC's, he has a 3 gallon custom tank full of water ready to spray down the IC to increase it's efficiency (pics coming soon). So in a way, even with that massive air / air core up front, he's still relying on water to further enhance the system.......

ptuomov

I agree with this. The only case where air-to-water intercooler is clearly superior is in a boat that can waste the water coolant.

hacker-pschorr

I've personally seen cars "upgraded" from air/water to air/air only to see intake air temps rise.
Why? The first system as a whole was superior. There is more to it than simply the type of IC.

It all depends on the application, installation and design of each system.

ptuomov

This is true. The Laminova coolers and air-to-water-to-air will package well and is almost as effective as air-to-air.

Air to air is hard to get right in terms of air flow, but once you get it right it's probably the best solution for extended periods of high boost.

If you can figure out clean air flow, air-to-air is actually a simpler system than water-to-air-to-water.

Renault F1s used both, I recall. First the air-to-water-to-air is the first-stage pre-cooling and then air-to-air after that.

That's very true. This is not an exclusive privilege of air-to-water-to-air, though. You can get the same effect with the heavy bar-and-plate intercoolers. The metal works as a heat sink almost as well.

Air to air is better solution if you have access to a lot of clean air flow and if you can cut big openings to the bodywork. The Veyron had a stupid 1001 hp marketing constraint, which makes it a cooling nightmare. They didn't have enough surface area in the car for all the openings they need! So air-to-water-to-air is the best solution for that car.

I personally think that the "best" solution for something like a 928 built for ORR is two fender-mounted air-to-air intercoolers. The fender mounting takes advantage of the natural pressure differential between the bumper face and the wheelwell, so you get a ton of flow. It's pretty close to perfect for long boost stints -- with the caveat that you can't ever do that on a public road with regular traffic, these cars are too fast.

For a drag car or a dyno queen or anything that lasts less than a minute, ice water filled air-to-water intercooler is unbeatable.

Horses for the courses.

ptuomov

I completely agree with you. You need good flow for an air-to-air to be better than air-to-water-to-air. I think the fender mounting is near ideal for air-to-air IC on 928, if you are willing to cut those holes to the bumper. I am! ;-)

The other thing that is often ignored is the pressure drop due to the intercooler size.

blown 87

The Procharger setups for the C4 Corvettes use air to air, the early models like mine use a very large single unit infront of the radiator and it works well, the latter C4's use twin smaller units that are mounted in front of the wheels, they work like they were not there and are very restrictive.

This has zero bearing on a 928 set up, but I have over 80,000 miles on it, so you can take that for what ever it is worth. (12 PSI)

blown 87

I will also say this about my Vette, when the new engine goes in it is getting a meth injection setup from here

http://www.blowerworks.net/

Some of the C4 guys have reported huge boost increases by removing the intercooler, one guy with the same head unit I have, but with far better heads is running almost 30 PSI, and friends, that is one VERY fast Corvette.

ptuomov

Some water-to-air-to-water intercoolers are better designed than some air-to-air intercoolers. Some center mounted intercoolers are better than side/fender mounted intercoolers. Some obstruct the radiator and oil cooler less, some more. I guess what I am saying is that there are good designs and bad designs of all kinds.

The intercooler causes pressure loss and power loss. The only reason to run one is that it will allow higher boost without knock. If you can cool the charge in some less cumbersome way (from the air flow perspective), you'll make more power.

One day, someone will build a 928 that moves the rear AC unit to where the stock air box is and will run it as an intercooler. First, an air to air precooler and then AC-based supercooler. I did the simple version of the math a year ago, and this would let one run stupid boost levels on an otherwise stock '87 928 S4 engine.