[chrisbalich]

Originally Posted by fanaudical

By "stack", do you mean one on top of the other so that the air flow from the first goes through the second? If so, then I suppose you can do that, but it may be that using just one is just as effective. The reason I say that:

Air-to-fluid heat exchanger effectiveness changes with air flow and temperature differential. The amount of heat can can be removed is proportional to the mass flow rate of air and the temperature difference of the air entering/exiting the cooler. Stacking the coolers reduces the air flow through both (air resistance increases) coolers. Stacking also changes the temperature differential; you're effectively feeding warmer air to the second cooler.

Do you have any technical data on the coolers? I may be able to do the math for you...

I do mean stacked on top of each other...with the sides sealed so's to make one thick cooler.
I don't have any technical data, but I'm sure I could get some numbers out of CSF if I ask nicely.

Originally Posted by MFX

Great to catch up with all of you guys in person. Being on the other side of the world most of the time makes it more difficult, which is on of the great things about a global event like Rennsport.

As for the oil cooler. I agree with Evan above. Just fit the one for now. I have a similar sized cheap front mounted one (with no fans) that was designed for an RX7 from memory and even thrashing it on the track on a hot day it only gets up to about 230 oil temp.

It was great to meet you in person.

Originally Posted by Garen

My $0.02: technically nothing "wrong" from a function perspective, however: The front cooler will get fresh cool air, and dump its spent, hotter, and slower air into the cooler on row two. Residual heat from both would have a soaking effect as well on each other.

However, if you look at the stack-up of coolers on modern cars, sometimes you have a radiator, with a trans or power steering cooler in front of it, and there is usually an air conditioning condenser in the middle of all of that. These are usually package-driven decisions, no doubt having them separate with good airflow would allow the engineering team to shrink the size of each cooler due to more efficient performance.

If you do it, make sure you feed the stack with a decent, sealed, dedicated fresh air ductwork so at least you get some velocity at speed, where the fan will generally be useless and in fact, in the way. Anything over 30-40mph. Same goes for an efficient fan to help pull enough air through at idle / city traffic speeds. If you buy lightweight plumbing like the Starlight hose from Aeroquip the weight hit won't be huge, if you use hard plumbing that you yourself fab-up and small hose lengths as connectors your cost will be lower. Then there's the center-mount option for one of the coolers but that would add an aesthetic change to your car that I'm not sure would be a positive.

Basically, the more efficient the flow to and through the heat exchanger, the smaller it can be. 956/962s had really thick intercoolers, but the trend has moved on from there in modern race cars, as has the tube/fin/basic design of intercoolers themselves. In a nutshell it's about efficiency in getting cooling air to go through the exchanger, with "bad" air, the coolers will have to grow to do their job through surface area, heat rejection.

Why not run just one of them to start, and maybe with good ducting it's enough, due to the perceived higher efficiency of the CSF core.

Originally Posted by Garen

Ha! I think fanaudical and I hit "post" at the same time! he basically says what I'm saying, in less words. Like a more efficient cooler...

Originally Posted by Evan Fullerton

Do you need more cooler than 1 fender cooler? Most street cars get by just fine with a good fender cooler and fan setup.

Even 993 that didn’t have an on engine cooler only have 1 fender cooler stock and that’s fine for most people.

Originally Posted by nospiners

Stay with one cooler , sell the other for the "slippery slope" of things !!

Originally Posted by shoooo32

With a carrera cooler and fan, I can't get Pablo's 3.2ss over 220F. That's mobbing uphill mountain passes at elevation where it's tough to shed heat. And Ravi's new coolers are better than the stock ones I'm running.

Thank you all for your replies. It now occurs to me that I've left out one important factor.
At some point in the future, the engine-mounted cooler is going away and I'll relocate the oil tank from RR corner to smuggler's box. I expect this will add stability to oil temps because of the additional volume, but decrease heat-shedding due to the loss of one cooler.
After reading your replies and considering all factors, I think the plan is to replace my Turbotrol with one CSF cooler. Then when the tank gets relocated, add the second CSF to the LF fender to ensure I have sufficient cooling capacity.