E30 electric fan. Push vs pull

[beemw]

I'm looking to put a Spal 16" 2360 CFM electric fan in my e30 track car. AC aux fan and evaporator is (will be) removed. Clutch fan will also be removed.

Looking through the posts, DIY, Bimmerworld, ... it seems the high volume fans are ~3.5" thick and apparently that is too thick for mounting behind the rad. Is there room to mount a push fan in front? Any downsides to that approach? Anyone done it?

Also, I was thinking of using the Spal basic harness that taps into the Aux fan on/off. Since the Aux fan will be removed, seems like I can just wire up to its switch and call it good. Is there more to it?

[Northern]

I believe a puller fan is ideal, but most people I know with electric fans run pusher fans for clearance. I wouldn't hesitate to run a pusher fan, but make sure you buy a pusher fan as the curved blades will be backwards.

There is definitely enough space in front of the rad with the A/C removed.

See here for wiring http://www.r3vlimited.com/board/showthread.php?t=210783

[jlevie]

A 16" 2300CFM SPAL will fit behind the radiator, but it has to be offset to the driver's side (that is what I have on my race car). But it is better to mount a pusher in front of the radiator. The mount and shroud is much easier to make. I would have mounted my fan in front, but I have a pretty large oil cooler mounted there. Don't even think about using any form of the through the radiator mounts. They can (and will) eat holes in the radiator fin tubes. I leave it as an exercise for the reader to figure out how I know that.

The aux fan switch is not a good solution. The low temp switch is about 10C too hot and it will open when the high temp switches closes. You can work around the either/or operation, but the simplest solution is to get an 82C thermo switch. Bavauto and other places have those. In a similar manner, you don't want to be using either the low or high speed relays in the fuse box. These puppies draw some serious current and are best wired with a direct line from the power point in the engine bay with the SPAL relay kit. Add a switch in the cabin for manual control of the fan.

[beemw]

The aux fan switch is not a good solution. The low temp switch is about 10C too hot and it will open when the high temp switches closes. You can work around the either/or operation, but the simplest solution is to get an 82C thermo switch. Bavauto and other places have those. In a similar manner, you don't want to be using either the low or high speed relays in the fuse box. These puppies draw some serious current and are best wired with a direct line from the power point in the engine bay with the SPAL relay kit. Add a switch in the cabin for manual control of the fan.

Thanks for the detail. Why go for colder than the standard switch? Should I also be going for a colder thermostat?

I like the idea of wiring directly to the power. Bonus that the fan can run independent of the car being on.

[jlevie]

The stock thermostat is an 80C unit. You want the fan to come on just above the thermostat rating to keep from storing heat in the engine, which could result in a temperature spike before the fan can bring the temperature back down. In the stock configuration the aux fan serves as a safety for the engine driven fan and should never come on when AC isn't running.

[beemw]

The stock thermostat is an 80C unit. You want the fan to come on just above the thermostat rating to keep from storing heat in the engine, which could result in a temperature spike before the fan can bring the temperature back down. In the stock configuration the aux fan serves as a safety for the engine driven fan and should never come on when AC isn't running.

Any one know at what temp the stock clutch fan engages (or is it always on)? Since this is mostly a track car, it seems like the thermostat will always be open while underway on the track. Conversely, the fan should always be off. To make that happen there should be a gap between the thermostat temp and the fan switch temp. 2C seems small.

Related but separate, the car has a replacement rad and the fan switch bung is on the top righthand side. This means that the hot coolant will have come across the rad (and cooled some) before hitting the switch. No idea how much of a difference that makes.

[Northern]

From the link I posted above: "STOCK FAN SWITCH IS 90/98C in most instances" this is why you need the 80degree switch. The part number in that link as well.

[beemw]

From the link I posted above: "STOCK FAN SWITCH IS 90/98C in most instances" this is why you need the 80degree switch. The part number in that link as well.

This is what I don't get. If the thermostat is 80C and the switch is 82C then the fan will come on very soon after the thermostat opens. That is just a 2C gap where the cooling system is working without the fan. On the track with hill climbing and heavy acceleration temps will likely rise and fall considerably. A wider range would prevent the fan from coming on while underway on the track.

The link to the official thread is great. Thanks a lot.