968Forums.com

With all of the discussion around increasing HP in the 944/968 platform, what's the conversation and consensus on aftermarket vs stock cooling systems? What's your opinion? (based upon HP ranges up to 300 HP or beyond)

Gene,
I had a special 3 core radiator made for my 968 RS. It used a large single fan. It held 3 gallons vs 2 stock
On dyno car would get hot quickly without fan. With fan it would cool quickly.
At track, the same. On infield car would heat up quickly and cool quickly on straights.
I made some mods to cooling system and installed stock radiator and dual speed fans.
Cars runs almost too cold???
MY Firehawk with same setup runs a bit hot!!!
I think large radiator flowed too quickly and actually didn't let air remove temperature.e
Still working on cooling issue
Pete

Pete, Griffin in SC has a custom unit that they can make from drawings on file and it has been sold via group buys in the past. Wizard cooling has one that has been said to handle 600 hp from 951s. I'm still looking for the best solution for my LS1 conversion. I have a griffin dual pass that they tell me should be working. I have a large oil cooler in front of the rad at this point that I will try relocating.
http://www.youtube.com/watch?v=s_0bq6mgea0...e=youtube_gdata

My big rad didn't seem to be the answer. It seems flow and fans make a huge diff

not sure where exactly your cooler is located, but anything like that wants to be very close to the radiator, and not away from it - this promotes through flow, whereas having it too far away inhibits flow by creating a turbulence zone - you don't want it touching, as that could induce conduction, but 1/2" is about right

as for size of radiator, there is a formula for that, but it's been at least 25 years since i used it - the V8 will need more volume than the 3.0, but it won't be much, and more than anything, it will be more rows needed to increase the surface area

the shroud will be the key - it needs to fully encapsulate the rear of the radiator, and then having a fan that can move the appropriate cfm, and not get in the way of the flow (i.e. terminal velocity of a propeller) - while not likely to be a problem in any 968, high speed cars need very high cfm fans, or they can actually create a high pressure zone behind the radiator - i've seen systems that actually cut off the fans at certain speeds, and others that had a relief flap that opened up at certain speeds or was controlled in the cockpit

also cutting off extraneous entry of air into the engine bay, and forcing all air to pass through the radiator first, will provide the best negative pressure zone and the best flow and therefore cooling - the 3 factory belly pans to a pretty good job of this - the V8 won't let you use those, but you can create something similar

"others that had a relief flap that opened up at certain speeds or was controlled in the cockpit"

Sounds like the McClaren f-duct

BTW, on 968's a large oil cooler located in front of radiator is less effective than stock single oil cooler. We tested a few variations and ended up with dual Sertrab coolers located in stock locations with larger ducting into coolers.

I spoke with Griffin and the suggestion was to move the oil cooler. It is large and blocks what might be considered the sweet spot. The fan is as large as the core and flows a significant CFM. Flow is 100% directed through the radiator at this time.

Another thought (and this should really spark a few comments), I am using an Autometer temp gauge. It is very accurate and responsive leading me to believe that I may have more information (and more quickly) than a 968 gauge would report. By more accurate I mean that it reports 200 vs 210 vs 215 etc. Where as a stock gauge isn't as particular.

I'll move the cooler and we'll see. Thanks for the comments.