dprantl

I was on that path for the A/C chargecooler. I even assembled a brand-new double-parallel flow condenser that fits in place of the stock one with receiver-drier attached same as stock and scoured the junkyards for the right size evaporator that would fit in place of the air box. Then plans changed.

Dan
'91 928GT S/C 475hp/460lb.ft

ptuomov

Air-to-air first stage and AC supercooler second stage would be the killer combination.

dr bob

The discussion gets skewed when you start talking about how a particular system helps on the street, vs. which system is more efficient. Most street driving is short bursts of demand with relatively lengthy periods of no demand. For these street situations, the air/water system has the distinct advantage thanks to the total heat that the large mass of water will absorb. So the large mass of water absorbs the heat from the compressed air rather quickly, even though that heat is dissipated slowly but over a longer period of time.

So while the answer to the "Air to air is more efficient than air to liquid? What!?" question is still an unqualified "Yes!", the air-to-air setup is probably not the best choice for a stoplight gran-prix car.

For those thinking that the AC pre-cooling is more "efficient", it's not even close. You are just delaying the movement of heat. Again, for a stoplight GP car, it's a very viable alternative. You are just choosing when you are getting rid of the heat again.

LightStriker

Sorry... But when I hear "efficiency", I think how good the medium is at eating heat off the intake air.

Obviously water absorb heat faster and in larger quantity.

After that, which system heat soak slower or give a better result is something else.

hacker-pschorr

My point of view / opinion is on a different route.

We know for a fact each system can work well if executed correctly (plenty of production cars with both systems proves this point).

Problem is the "executed correctly" portion. Forget all the theories and where the car will be driven and how hard etc....
Install either system properly and it will do what it's designed to do.

When I walk around various paddocks, I see air / air systems hanging out in the breeze, no ducting, no sealing to trap air etc...
I see this a lot with aftermarket 911 coolers on top of the motor. The factory unit is sealed to the ducts on the spoiler. I almost never see this with aftermarket units. How much air is simply going around the core? Sure it's still doing something but nowhere near it's capacity.

With an air/ water these points are not as critical. Sure there can still be mistakes like pump to small, heat exchanger not properly sized / installed etc.. but the margin for error is greater. Like my point with the 928, you really need to start heat soaking all 3 gallons before the critical placement and size of the heat exchanger comes into play. Too small of a pump can easily be rectified since it can be installed almost anywhere in the water line.
Let's assume you have a 20GPH pump (which is huge for an IC system). You have roughly 10 seconds before all 3+ gallons move through the system. So even if you don't have a heat exchanger installed, the IC is still fully functional for 10 seconds. Install even a small heat exchanger this time is extended. Install a properly sized / installed exchanger........and / or mist a little water on it (like many do with air / air).


I will stir the pot (since it's so much fun to do in these threads).

• I'm pretty sure of all companies, McLaren could have figured out a way to use air / air with the SLR if they felt it would have improved performance.
• Not sure I would give that much credit to GM, so I'll leave the Corvette out of this.
• Shelby Series 1, not only air / water but supercharged too
• Bugatti Veyron? No limits, no budget, break all records supercar, but they simply went with air / water because it's easier and not more efficient?
• The current "king of the hill" Shelby SSC uses air / water IC's.
• RUF, who has been making air / air IC's for decades is using air / water IC's with their supercharged kit.

There are a few more........too
I know I know...mid engine, easier etc.... Ferrari figured out how to use air / air with the GTO and F40......

Yea I know, name me a race car with air / water. Well, like I said before: "If I boost my track car it will use an air / air IC". This will be on a car that is stripped to the bone, which makes proper placement of an IC easier.

Bottom line for me is if these very well respected engineering teams say air / water is "good enough" for their supercars and I have a respectable intake air temp with my system, seams like a lot of work for little to no gain to do a 180 and install an air / air system on my car.

If air / air is so superior, why did Porsche dump air cooling for the 911? This started back in the 80s, the 959 has water cooled heads.
An engine / radiator is no different than an Intercooler / heat exchanger.

LightStriker

This started back in the 70s, the 928 has water cooled engine.

Close, but I like how Mr. Million Post think.

dprantl

Well, an air-cooled engine is a little different. The shape is pretty well defined and cannot change much, so you are stuck putting fins on it all over the place (and on the outside only) for air to flow by. When intercooling, since you are cooling air, you can fashion any shape you want to maximize surface area and heat transfer away from the air as long as you keep it contained in the closed system.

Dan
'91 928GT S/C 475hp/460lb.ft

ptuomov

I think "effectiveness" is a bit better here.

ptuomov

My system will have shrouding in a way that the air is forced to flow thru it if it wats to get from high-pressure bumper opening to the low pressure wheelwell. It basically either goes thru the intercooler or it doesn't go there at all.

BC

The issues are the reservoir, and power cycles. With a 3 gallon water tank you are heating the water to above ambient, or even close to hot - within a set time. The extra radiator is there to INCREASE the time the entire system will start to match the outlet temp of the charge air. Eventually, it will. Because more heat it going into the system that can be pulled out with a nominal exchanger. Add more water mass, and that ticking clock can run longer, but you need larger lines, more pumping capacity, a larger radiator, etc. And eventually - you will end up in the same situation.

The argument is: You can't go that fast anyway on the street. You can't keep your foot in it that long. That's probably true. But in that case, why have other systems that will work for WOT for more than a few seconds?

At the end of the line, when you DO run at higher WOT charge air temps for a longer period, you will eventually be heating the charge air and not cooling it, depending on ambient temps.

Todd is doing it the right way for track usage and street usage, with an eye on simplicity, weight, and duty cycle - a very large a/a intercooler, with VERY powerful fans pulling through it whenever you demand, and a sprayer to increase the aluminum's ability to transfer the energy out of the charge air.