2002M3Drew

Hi all,

I have a 911SC that I have been using for track days since late last year. This winter/spring, I added a Carerra Tail to the car, and oil temperatures rose a little bit to 200-210 or so, even on the street.

Two weekends ago at Lime Rock, temperatures outside were running over 90 degress, and with no breeze whatsoever. My car would get up to close to 250 degrees in 12-15 minutes of track or so. I would immediately do a "cool down" lap and then bring it in. My car had the "trombone" oil loop in the front, which apparently wan't doing much for oil cooling.

Last week, I added a B & B front fender oil cooler with fan, as well as one of those fender scoops that everyone sells. I also added SSI's and a Monty 2/1 muffler this week, which should also help reduce temperatures. I then did a two day DE at Pocono this past weekend.

My temps, again, were getting high if I really pushed t in the infield sections. It got up to approximately 240-245 degrees under heavy flogging. The main difference was that it would cool down very quickly, dropping as much as 35 degrees indicated between checkers on the backstretch and the pits.

Mid event, I unscrewed the front turn signal and gave the oil cooler even more air to work with, and temps did drop. With the blinker removed, max temps were 230-235, and with a little less 2nd gear through the infield, 225 or so.

Here are my questions:

- Will synthetic oil help keep temperatures down?

- Is there a simpler solutiion to removing my turn signal to get more air to the cooler? Any common devices or tricks to get more air?

- Did I go with the right cooler? I didn't want to modify the front facia, so I thought a fender mount would be the best option.

Is the fan on the cooler a hinderance to air flow? It supposedly comes with a built in thermostat that turns the fan on at 180 degrees, though my mechanic wired it up to be on all of the time. If air comes in at a slower speed than the fan is running at, will it actually reduce the amount f air getting to the cooler?

- Is it normal for the engine to be able to drop temps so quickly while coming of the track? Think sender might be bad, or perhaps thermostat?

Any ideas welcome!

Drew

Peter Zimmermann

Drew: In my PCA Club Race SC coupe (no A/C, large rear wing) I used an '87-89 Carrera cooler with fan, wired the fan to a dash-mounted switch and never saw 210 after that (even on a couple of 100 degree days). I machined the front bumper as the Carrera (they have a relief under the turn signal), and took the light out also, but only in extreme temps. It sounds like you've done your homework, are you sure your gauge and sender are compatible? In my opinion, the cooler fan should be on the thermostat (no oil goes through the cooler until after 180 anyway) or on a dash switch, why have the draw on the alternator when it's not necessary? I did switch from Kendall GT-1 to Mobil 1, but I did not notice a change in temp that was caused by that change. Sorry I can't comment on the cooler that you chose, I've never used one.
Pete

Edward

Sorry I've got nothing to add here except a restatement of one of Drew's questions:

Does a fan help or hinder a track-only car (not worried about traffic on the street, but DO play on some tight short tracks like Streets of Willow). For reference, I've got a stock SC with OE valance and rubber lip, but planning to cut a "carrera foglight" hole into it and add a plastic scoop dealie. I'm doing this in tandem with replacing my 28-row with a Carrera oil cooler, but was wondering if I should put a fan in or not? Opinions?? ...especially from those "in the know" ??
TIA

Edward

Steve Weiner-Rennsport Systems

Drew:

Super advice from Pete,....

Remember,..oil coolers are simply heat exchangers and they need LOTS of airflow to dissipate the heat you are making. I'd suggest either a Carrera front valance with the fog light openings left clear for cooling air (remove the lamp mounting bar) or making the same size opening in your existing one. Airflow is Everything,....

Cooler fans do nothing above 30 MPH so as Pete said, put a switch on that so you can turn it off when the car is moving fast enough to ensure proper airflow. Above 60 MPH, the moving fan will impede airflow,...........

Use the fan on cool down laps and when idling to control temperatures.

2002M3Drew

You know, my good buddy at the track said the same thing about that fan...that it actually was impeding air flow, and I told him he was full of crap! Shows what I know!

I'll wire up a switch and that should take care of that issue. W/r/t the cutouts, the "Carerra holes" are those notched cutouts under the front bumper, right (like the ones Anderson illustrates in his book)? I can just Dremel those out, I guess?

I am also wondering about that gauge and sender, especially since they were on the car when I bought them. Let's say that the gauge was changed but the sender was not...would the reading be off to the high or low side, or would there be no readings at all? I see that most of the kits include both gauge and sender, but I've noticed that PO's of my car have taken shortcuts on other upgrades they have performed!

JackOlsen

Just as a data point, I get improved track cooling with the fan going. This is a Carrera cooler with shroud and ducting. I know the fan should be impeding airflow at those speeds (average speed of a lap at Willow Springs is close to 100 mph), but I've been able to test it repeatedly, and the fan helps.

2002M3Drew

Jack,

what do you use as a shroud underneath the car...is it a standard Porsche Carerra cooler part that helps divert air up the cooler?

Peter Zimmermann

Drew: Like Jack, my SC was Turbo-bodied, and I frequently ran at Willow Springs in very hot weather. I also used a factory Carrera cooler, with a fan and all shrouding in place. Therein might lie an answer to your higher temps. The factory shroud seals the cooler's perimeter, which forces almost all incoming air through the cooler. If your cooler is mounted in the opening and has free space around it incoming air might be taking the path of least resistance, and going past, rather than through, your cooler. As Steve W. said, airflow is everything! I wish that I had thought, at the time, to test the car with the fan on, then off, but I never did. Also, as Steve said, the fan really helps on your cool-down laps, and at idle following a run (or when you're stuck on the freeway!). The factory thermostat kicks in at 220 F, I figured that turning the switch on manually would give the cooler a head start. 220 indicates that the factory might have recognized the need for the fan was more in heavy traffic situations, than for high speed. I do know that temperature management depends on a lot of factors; air flow, heat exchanger surface area, exit air flow, dead areas produced by body shape, oil flow through the cooler, etc., so Steve's comment's probably apply in the vast majority of cases. However, Jack's car might be interesting to review more closely, because he has done the testing, and might have a unique set of circumstances that allow the fan to aid air flow. Jack, what front valance do you use (RSR?), and is it open in the center?

About your gauge/sender - everytime that I updated from a sweep style gauge to a gauge with numbers I always put in a matching sender. If there is any doubt that you have a proper setup you should buy a new gauge with sender. Let us know if your cooler is perimeter-sealed, or if it is mounted in an open area.
Pete

JackOlsen

My car has coolers in each front fender. in addition to the horn grilles, I've cut openings in the fog light area -- they're larger than the standard fog light cut-outs. I've got ducting around the coolers, and also underneath them. Any incoming air has to go through the coolers.

Still, the temps are lower with the fan running.

On really hot days, I take out the headlights so that air can go through holes cut in the back of the buckets. I think at that point the effect of the fan becomes negligible.

Noel

You have received a lot of great advice here. The only thing I have to add is on the aesthetics of the fan switch installation. If you don't have a rear wiper on your car, you can buy a rear wiper switch from Porsche/Pelican and install it on the dash in the factory location. You just hook it up to your cooling fan instead. The cutout in the dash is already there, it is just covered in leather/vinyl. In fact, you can feel the cutout under the vinyl if you feel around to the left of your Tach.

BTW, I also notice my temps coming down if I turn my fan on while on the track. Maybe this is due to me not having the factory foam surrounding my Carrera cooler.

red911 Targa

Hi Drew,

One of the items to check your guages might be a hand held laser temperature guage. Point and read. I used this to see when my thermostat opened on my 1988.

Good luck, Tom

Peter Zimmermann

Jack: Ah, ha! Unusual configuration, but it sounds efficient. Did you car used to be a short wheelbase model?
Pete

JackOlsen

No, I used to have an RS-flared 73, but I put it into the wall at Laguna Seca (ouch, that hurt). The drivetrain got moved over to a 1972 tub that's flared like an RSR 2.8.

I don't like the look of the center bumper cooler, and my 3.6 doesn't have an engine-mounted unit, so a cooler in each fender was my solution. I rarely get above 210-215 now, even on hot track days (and that's with the AC running).

Noel

I guess it does get hot in CA if you have to run at the track with your A/C on.

Peter Zimmermann

Jack: The reason I asked about SWB is your right park wipers... I ran the A/C at Willow a couple of times in my 944. I was on pre-grid one sweltering afternoon and the grid marshall saw my window up. She wagged her finger at me, I waved her over and let a blast of cold air out of the car. You should have seen the look on her face! Needless to say, she let me keep the window up until they waved us out...
Pete