Road Course & AutocrossAutocross, Road Race, and Open Track Event discussions. Preparation, technique, tips, and stories from the events. Tell us about your last event.
So I brought my stripped down Talon to it's long due virgin shakedown last Wednesday to Cayuga's road course and it ran amazing...for a maximum of 5 laps at a time.
Everything about the car ran amazing except for the cooling system. After about 5 laps it would overheat rapidly and I'd have to let her cool down for 10 minutes. I have a roughly 70/30 mix of water/coolant and a bottle of Water Wetter in the system.
Problems/diagnostics:
1. I noticed the water temperature gauge would get all wonky and go from really hot (far right) to normal or really cold (far left) occasionally. Could this be air lock or a faulty temperature sensor?
2. I still had the thermostat in, I was told that I should remove it since I'll ONLY be racing this car and it's not a street vehicle.
3. I have an FMIC which blocks the rad which has no shrouding around it. Yes I'm dumb.
4. I have one 12" slimline fan without a shroud (do I really need a fan shroud or a second fan?)
My plans to fix these will be:
1. Install an 18X10 RRE hood vent on the hood to extract the heat.
2. Remove the thermostat and run without one.
3. Make some kind of shroud for the radiator behind the fmic, to guide air through it.
4. Cut some holes in the front bumper cover to let air enter the top of the rad.
Am I on the right track or is there something else I should try?
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Leave the thermostat in, the computer wants to see a minimum tempurature. Vent the hood and do the ducting in front of the radiator, focusing on making sure the airflow HAS to go through the radiator, allowing it to flow around the IC if need be. Get a radiator cap for a '91 Nissan 300ZX TT. It has a higher psi rating, so as to keep the coolant that is trying to turn 90* after the thermostat, from pushing the cap open. I'm not convinced that more fans will help when the airspeed is faster than the fans can pull/push.
The hood vent is the most important one IMHO. The air seems to just stop due to having no place to go, all the front facing openings in the world won't help if the flow backs up.
The hood vent is the most important one IMHO. The air seems to just stop due to having no place to go, all the front facing openings in the world won't help if the flow backs up.
I thought the same too until I spoke with my suspension specialist (his dad is a NASA engineer). Even though the air in front of the radiator is traveling faster than what the fans can move, this does make a difference. Instead of pulling the air through, what the fans do is create a low pressure zone behind the radiator, thus allowing the incoming air in front to flow through faster. Think pusher/puller fan combinations. This was backed up with some runs on the highway with the fans off and on. Pretty dramatic difference, ~15 degree. Food for thought.
what the fans do is create a low pressure zone behind the radiator.
If the fans are pushing into a high pressure area, and underhood is just that, a well placed/designed hood vent gives that air somewhere to go.
My unsubstantiated theory is that at racetrack speeds, production aerodynamics weren't concerned with the blob of dead air that has to squeeze out from behind the radiator, under the front floor. I believe at this stage the fans are cavitating. Venting the hood uses the speeding air above the hood to draw some of that air out, above the car (which coincidentally reduces front lift too). I know this works for 2 reasons:
1) ALL road race cars use them, lots of 'em, if it's allowed.
2) I tied some strings to the louvers on my hood vent and the string stands straight up, even/especially at high speeds, about 1.5"-2". It's definately relieving pressure. Funny thing too, the string doesn't move at all at standstill when the fans are on.
Am I really counter-pointing a NASA engineer? Hmmm...
2) I tied some strings to the louvers on my hood vent and the string stands straight up, even/especially at high speeds, about 1.5"-2". It's definitely relieving pressure.
90% water mix with WW
Remove the thermostat
Mishimoto aluminum radiator
Hood Carbontrix vent
Fans always on (I'ts a small track)
Cutting the front bumper for more airflow
Put all back the stock heat shields (the most important)
Put a DEI blanket between the DP and the alternator (was going through 2-3 per year) after that still going strong after 3 years with that simple mod.
When 30C +++ removing the front headlight to channel air to the radiator
With all that NEVER an issue with hot temperature.
Hope it helps.
____________________________
Paul M. stock TB-head-cams 11.98 @ 117mph (BR20G)
If the fans are pushing into a high pressure area, and underhood is just that, a well placed/designed hood vent gives that air somewhere to go.
My unsubstantiated theory is that at racetrack speeds, production aerodynamics weren't concerned with the blob of dead air that has to squeeze out from behind the radiator, under the front floor. I believe at this stage the fans are cavitating. Venting the hood uses the speeding air above the hood to draw some of that air out, above the car (which coincidentally reduces front lift too). I know this works for 2 reasons:
1) ALL road race cars use them, lots of 'em, if it's allowed.
2) I tied some strings to the louvers on my hood vent and the string stands straight up, even/especially at high speeds, about 1.5"-2". It's definately relieving pressure. Funny thing too, the string doesn't move at all at standstill when the fans are on.
Am I really counter-pointing a NASA engineer? Hmmm...
Anyhoo, let those fans breathe man!
No doubt a vented hood is a deal breaker, and with proper ducting to direct air flow I believe there's a point where that type of setup will yeild those results. But with a FMIC in front of the rad, there's a huge difference on my car with the fans on and off. TWS is a fairly high speed track with mph averages in the 80s on a stockish DSM.
Overheating at track
