Yesterday I removed the radiator fan from our Challenge Q45. I also removed the evaporator core if that helps in this debate. I say that as long as we're conscientious about shutting down instead of idling then we're ok for the Challenge. My teammates range from OMG why would you remove a factory part to well it might be ok. What says GRM?
I managed to drive a turbocharged Talon for 3 or 4 weeks without a radiator fan, did just fine unless I was stuck in stopped traffic. Around town and stop n go was no issue.
At speed, the fan does nothing. If you don't mind shutting it off if you are or are planning to idle for more than 30 seconds, it should be fine. Remember though, a hot (very hot, but not explodie hot) engine will run, but performance will degrade.
I like fans, and will sacrifice a wee bit of speed for peace of mind.
I think I've decided to run no fan but y'all made me think of something else. Is there a problem running to cool in a race like this? Meaning could I remove the thermostat for max cooling? I seem to recall that operating temp is better for emissions but how about performance?
How long do you have between autox runs at the challenge? Not sure how fast challenge autoxes are, but you don't get a lot of cooling at low speeds. The average speed may only be like 30mph.
Is there a reason to remove it? To sell it and recoup $? Or to make room for something else? If there isn't a strong driving reason, I would definitely keep it.
Stampie said:I think I've decided to run no fan but y'all made me think of something else. Is there a problem running to cool in a race like this? Meaning could I remove the thermostat for max cooling? I seem to recall that operating temp is better for emissions but how about performance?
Every car I have had on a dyno made significantly more power at 190°+ than it did at 150°.
My turbo fiat picked up something like 12% more power between 160° & 190°.
In reply to ProDarwin :
It depends on what time you're running. It may be hot laps or it may be 10 minutes between runs. Main reason it's to remove weight up front. Last year we removed a lot off rear axle but didn't get much off the front.
In reply to Jumper K. Balls :
Thanks that's exactly the precise answer I needed. I'll leave the thermostat in.
I overheated the RX8 several times sitting in grid waiting at the Challenge autoX.
Shutting down isn't good enough. Once the engine is up to temperature (which you need for power), the temp will continue to climb with the engine off and no water or air circulation.
If I'm wrong, no big deal. If I'm right, you'll be upset if you DNF.
Switch to a plastic electric fan to save weight. They are only a couple of pounds.
Or, more sawzall. 
The fan weighs very little, and if you throw it on a switch you can shut it off for max power runs at the drags. (Or even take it off quickly for the drags).
Engine mounted fan however, I'd get rid of in favor of electric.
I think you are looking at the single least effective component of the cooling system to accomplish your goals.
Your goals: reduce weight in the front, increase power.
You should be thinking about:
- Relocating the radiator to the rear
- Confirming adequate airflow and shrouding through the radiator
- Increasing the internal pressure
- Increasing total water volume
- Adding contrable fans (electric, with good switches and gauges so the driver has good info to increase or decrease fan airflow)
- Water flow (flush and clean)
- Water pump capacity and flow
- Electric driven water pump if you can
- Pure distilled water in the system- no coolant
The higher the temp, the more power, until you overhear (Ok, that's an over simplification). 212*F is your limit before water vaporizes, until you pressurized the system. 265*F is quite normal with a 30 lb radiator cap.
If you really want to get weight off the nose, move the radiator to the rear. That will shift the weight of the radiator, fan, related piping, AND the water in the system.
Here's a pretty good article:
I want to reduce overall weight but paying particular attention to the front while also being budget neutral. For example I can relocate the battery to the trunk and transfer more weight than relocating the radiator. But I'd take about a $30 budget hit for that and actually add to the overall weight. Shrouding is being taken care of with Irma debris. Remember the true cheap SoBs run at half budget.
When I was crewing on a dirt track modified I had a hard time convincing my driver to get rid of that huge engine driven fan and go electric. So I said , for the fast warm ups, we removed the fan and put it back on for the race. He was convinced after that. Not huge but noticeable.
Power-wise, in theory, hotter is better provided it's not causing parts to fail. But that doesn't hold true in practice, as you start to become knock limited at high temps and you start to heat the intake charge up too. If you could keep the intake charge cold, cylinder head and piston temps reasonable enough to maintain knock margin and let the block run pretty hot, you'd be in great shape.
Fan-wise, I'd keep a fan of some form on the car. A small electric on a switch is fine, but on a longer autocross run you might have issues without the fan, as you're not going all that fast at times. And who knows how good the natural (non-fan) airflow through the rad is on that car...
On street driven cars, there is a backup system. The heater.
In reply to iceracer :
We were talking tonight about deleting the heater hoses. Because a picture is worth a thousand words:
Pretty straight shot to the radiator. The opening is where the grill goes.
Back side of the radiator.
It would probably help your fanless running if you cut the hood right behind the radiator so the air would have somewhere to go while not moving. Heck-you could get a taurus fan and some alligator clips and drop it in the hole between runs to keep the car cool. Not on the car during runs is no budget hit. 
In reply to MrJoshua :
We're already ahead of you but way more redneck.
SVreX said:The higher the temp, the more power, until you overhear (Ok, that's an over simplification). 212*F is your limit before water vaporizes, until you pressurized the system. 265*F is quite normal with a 30 lb radiator cap.
there is truth to that. Years and years ago my Father had an '88 Mercury Grand Marquis with the wheezy 5.0 that made all of 200ish hp. Unknown to us, when I borrowed it to go get paint for my fiat, it had a pinhole in the elbow next to the distributer. When I pulled away from the tollbooth, I floored it (I was 18) and for the first and probably last time in it's life, it left rubber on the ground.
5 miles down the road it overheated. No damage, but the increase in power before that point was noticble.
I am probably going to ditch the mechanical fan on my Rover this spring and go with an OEM Volvo S/V70 fan setup. Trying to get it up over 15mpg
Stampie said:In reply to MrJoshua :
We're already ahead of you but way more redneck.
2 stroke leaf blower in grid?
Stampie said:In reply to MrJoshua :
We're already ahead of you but way more redneck.
Box fan running on an inverter?
Damn you guys are good but yes both are being considered.
BrokenYugo said:Stampie said:In reply to MrJoshua :
We're already ahead of you but way more redneck.
Box fan running on an inverter?
2 stroke leaf blower engine running a box fan?
Bonus points if it involves a chainsaw!
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