kevin12973

I have a occasional overheating issue with my SP1 race car. This year I upgraded my oil cooler to the turbo console and that has been awesome, keeping temps 210-220 deg. But for the first time the coolant temp has run past the middle mark all the way to the third mark. LimeRock was fine with outdoor temps 60 deg, Watkins Glen was 80 deg and this is when it started.This happens when I do several laps tucked behind another car waiting to make a pass. I try to pull to the side to get cooler air to the radiator but loose speed not taking advantage of the draft. After getting a pass it takes 10 minutes to cool down to normal temps. My oil cooler is in front of the radiator and is about 12"x8". Radiator looks fairly new and clean. Bleed the cooling system thoroughly. I need to improve cooling somehow, what can I do?

StoogeMoe

That sounds pretty normal to me if you're running in someone's draft. You don't get near the same air flow. Happens in my Spec E30, and we're always running in the draft. You have to poke out every now and again to get some cooling.

Are you running the under tray? That helps the 944 a bit. Are you using water wetter or pure water?

fwb42

Is the oil cooler pre-heating the air through the radiator? From your posting it looks like this problem didn't happen until you up-graded your oil cooler.

V2Rocket

Adding the air-oil cooler will take a lot more load off the cooling system than putting the oil cooler in front of the rad.

BTDT...When I first put a big air/oil cooler on my NA, the water temps dropped 20 degrees consistently (in an area where ambient got over 110F in the summer).

I would pop off the front bumper and nose panel and double check all the ducting is in place...if there is any sort of easy air path that doesn't include the radiator, block it off...since its a racer looks don't matter as much, and you can make easy ducting by taking cereal-box cardboard, spraying it with truck-bedliner and ziptie/taping it in place. Cheap and hackish but it WORKS. Certainly good enough for an experiment, although I ran with a Cheerios-duct for about 6 months on the street...


OP...for your race class do you need to keep the stock rad fan, or can you change to non-stock/aftermarket?
For a few years I ran a HUGE fan off a Volvo S60 (bigger than the radiator) and the only time I ever got to the middle of the temp gauge was sitting in stop and go traffic with the AC on when it was 90-100+ outside. The fan made a breeze behind the car...maybe try that
If you were interested in trying this I have a whole spare such S60 fan I'd sell for super cheap.
https://rennlist.com/forums/924-931-...tallation.html

kevin12973

Thanks for the replies. I am running water wetter, no antifreeze. Also have the aluminum under tray. I have the one fan on the left and cut out the right side fan. That is the side the oil cooler sits in front of the rad. I thought driving would blow more air than fans anyway and they are only needed when sitting in traffic.

kevin12973

This is my oil cooler location

nrider42

So what was it like before you added the oil cooler? It looks like it blocks a third/quarter of the radiator? Doesn't seem like a lot compared to the AC evaporator.

By the way...I think I met you at the Glen...I was the guy working the scales and I was bugging you on saturday afternoon in the stands. Thanks for taking the time to answer my shouting questions!

Nate

kevin12973

LOL, no worries Nate. Engine coolant temp was never an issue before the oil cooler went in. Air condition condenser will throw a lot of heat also,if its running.Just curious what others are doing to get better cooling in racing conditions.
Buy the way, I won 1st sprint race,2nd place sprint race 2 and 1st place on the enduro! 10th overall on the rain soaked enduro. It was a blast to drive Watkins Glen in the rain Sunday.

Van

As you know, I didn't have cooling issues... But I have a little more ducting on the front to get air flow to the radiator.

Another factor for you, Kevin, is the clearance between the water pump impeller and the housing... I assume that's the water pump that came on that engine?

Also nice meeting you, Nate!

car_slave

Question: What is the water flow on a 944? Hot water in low on the radiator or high? Will convection be a factor?

As Van is getting at: make sure that air to radiator intake is sealed to ensure optimal flow to where its needed. You could also cut holes in the bumper and divert air that way too.

Van

Water goes from the bottom of the radiator to the water pump, into the block around all the cylinders, up through the head, to the front of the head, and back to the top of the radiator.

nrider42

Just curious..what were your oil temps before the addition of the oil cooler? Do you have an actual number readout for the water temperature? What does that typically run during a race?

I guess it is a big balancing act....what is the best way to dissipate all of that thermal energy...oil or water?


Nice job on the racing to both you guys! It was fun to watch and glad I was able to talk to you. Hopefully I will be joining you within the next couple years!

Nate

V2Rocket

remember that the oil-water bath the 944 came with stock is as much a warmer as it is a cooler.
the whole point of that type of bath is to make the oil warm up faster (since it is surrounded by coolant which warms up quickly on a cold day) and then to keep the water and oil temps very close to the same.

200* water and 200* oil makes for an engine that is very happy, minimizing emissions and not wasting energy trying to churn thick oil.

but as we know racing puts a lot more heat into both oil and water and so the water-oil bath loses its effectiveness...so separating the systems (air-oil + air-water) is better to keep both cooler. since we are limited (generally) at the radiator space we can get, we may as well maximize the oil cooler surface area.

kevin12973

Ok, I will look at opening up air path to cooler. The stock ducting is in place and tight. So I will try to improve volume of opening. Van, you gave me some insight last month. Have to talk about it more at the picnic.

car_slave

I think by having the oil cooler low on the radiator you might actually be heating up some of the cooled water right before it heads back to the engine.
Hard to say what the thermal math is exactly as far adding heat. I guess ultimately, it would be best to vent the oil cooler air somewhere other than the radiator.
If you can mount the oil cooler on the inside of the radiator it might be even better. NASCAR teams tend to do that with a thin oil cooler which covers the same area as the radiator - on some tracks (speedways) they seem to run a water/oil custom radiator. There may be other reasons for them to do that - I figure those teams know what they're doing.
See if this one will fit http://www.ebay.com/itm/PWR-Radiator...9XMJp-&vxp=mtr