Race Car Tech Discuss anything related to road racing and auto X.

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Old 04-01-03, 03:21 AM
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One Q

just wonder any of auto cross fan or TRACK DAY guy runing the cooling system with out fan. MY engine builder told me during the hight speed the fan will just block the air?
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Old 04-01-03, 07:30 AM
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He's pretty much correct. The fan on a roadrace car is generally of the electric type and only used on the grid. I wouldn't take the fan off an autocross car though. You aren't moving fast enough for a sustained length of time to warrant taking it off. The electric fan on an autocross car might be best because you can still run it after you shut the engine down.

Good racing...

db
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Old 04-02-03, 01:24 PM
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you can drain the hydrolic fan fluid so it spins freely. that helps a little
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Old 04-02-03, 07:55 PM
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I concur about autocross. It's a 40-90 second burst of high reving fun but when you get back to the grid, you'll want that fan running. I tend to idle my car between runs in the grid, sometimes with the hood up, to let the engine temp cool down in the Summer months.
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Old 04-02-03, 11:36 PM
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What!!!! somebody has lost their mind. I race Autocross every monthj and my water temp only goes to about 85-90 deg celcius. I also run circuit, road courses like Nikko, Ebisu, Tskuba and Fuji. ON the circuit the water temp is out the roof. At ebisu on Nishi course which is 2,103m long the water temp goes to 115 deg or so. I use the Stock Clutch fan and have a aftermarket thermostat.

I just purchased a 3 core radiator for this season so I can survive without overheating at Fuji. Autocross gives a very small demand on the cooling system but road racing triples it. If you are only drag racing then you could do away with the fan but anything else I would want it there.
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Old 04-03-03, 12:36 PM
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Originally posted by Ranzo
What!!!! somebody has lost their mind. I race Autocross every monthj and my water temp only goes to about 85-90 deg celcius. I also run circuit, road courses like Nikko, Ebisu, Tskuba and Fuji. ON the circuit the water temp is out the roof. At ebisu on Nishi course which is 2,103m long the water temp goes to 115 deg or so. I use the Stock Clutch fan and have a aftermarket thermostat.

I just purchased a 3 core radiator for this season so I can survive without overheating at Fuji. Autocross gives a very small demand on the cooling system but road racing triples it. If you are only drag racing then you could do away with the fan but anything else I would want it there.
just wonder do u have ur under tray ( black plastic cover the radiator) my engine builder telll me that tray is very important it will direct air to radiator and oil cooler without that the air will just past under the radiator. air want to take lease resistance area

Last edited by diyman25; 04-03-03 at 01:00 PM.
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Old 04-03-03, 12:51 PM
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I can only offer my experience with my car here in Atlanta. Remember, in the Summer, it's HOT here.
I'm using my stock temp gauge and we all know how reliable they are.
I did notice that the under-tray did help the cooling by about a needle-width.
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Old 04-03-03, 01:00 PM
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Well, he is right about that. Keep the under tray. There is no advantage to removing it. If helps the airflow through the engine bay. But removing the fan because it impedes airflow? Take the crack pipe away from him. Of course there is air resistance with the fan. How else can a fan move any air if there is no resistance?

Keep the fan and be happy.
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Old 04-04-03, 01:16 AM
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At present I do not have the under tray on my car. I do concur that it is best to have it in place for cooling. I have the closing panel on top of the area where the dryer tank for the AC. Also I have a aero bumper and not a stock bumper this will direct more air into the radiator and intercooler.
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Old 04-04-03, 11:48 AM
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Originally posted by Jerk_Racer
Well, he is right about that. Keep the under tray. There is no advantage to removing it. If helps the airflow through the engine bay. But removing the fan because it impedes airflow? Take the crack pipe away from him. Of course there is air resistance with the fan. How else can a fan move any air if there is no resistance?

Keep the fan and be happy.
what he's saying is impeding air flow at speed. mainly its the shroud that does this as it bottle necks. area initial is greater then area exit. thus a pressure differential. however you still need the fan. the shroud is there to allow the fan to pull air through the entire radiator. if you want a good compromise, get an electric fan and lose the shroud. this will gain you little to nothing at an autox though since the air velocity through the radiator is minimal enough to be affected much by the shroud or fan.
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Old 04-04-03, 11:55 AM
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My road race RX-7 runs without a fan. I don't know that I'd auto-x without one. My temps are fine, but I dont' leave it running on Pregrid of course.

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Old 04-04-03, 04:01 PM
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Yeah, I know what he's saying. Of course a fan is a slight restriction. But it really comes down to if he'll be driving a car without a fan on the streets or not. 100% track use, it'll be fine. AutoX? Then it's not a good idea. Especially if he has to drive the car to and from the events. There's a reason why those fans are there after all.

I have a Black Magic fan on my car and it's great. Even without the shroud it's much better than the stock fan setup. I use an OE thermostat as well. I haven't had it out to a lapping day yet (since it was installed over a month ago) but for autoX and around town it's great. I'm confident that it'll be just fine when I do take it out for a track day.
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