Spal Fan

I am going to put the 5.2" Spal fans in the rear of the car to aid in heat escape (Allan has done this on his build). So here is the question... do I order the fan as "push" or "pull"? My guess is "push" but it really depends on which way you look at the fan.

Pretend you are mounting the fan to a radiator. If it's mounted behind the radiator, it's "pulling" air through the radiator. If it's in front of the radiator, it's "pushing" air through the radiator. So, assuming you are mounting the fans inside the engine compartment, you want "push" fans.

So confusing....
Mount the fan(s) to blow air out of the compartment.

Molleur and Pete, Sorry, you are both partially wrong. It depends on where you mount the fan, and which way you want the air to flow, or create pressure in relationship to the flat side of the fan. If you mount the body of the fan in the engine bay, and you want the air to go into the engine bay then you have a puller. Just like a radiator fan mounted behind a radiator pulls the air through the radiator. You are pulling the air into the engine bay away from the flat side of the fan. If on the other hand you want to push air out of the engine bay, the air flows toward the mounting surface of the fan(the flat side), and is thus a pusher. So you can have either one in the engine bay. It just depends on where you want to mount your fan, and which side of the fan has pressure. flat side pusher, other side puller.
Micheal, I would suggest you go to Way electrical(I think that is their name) and get an off time relay. This will allow your fan(s) to run on after the engine is stopped for a variable amount of time to cut down on heat soak. The times vary from a few seconds to an hour if you want. I run mine for 3 minutes(stainless exhaust). Seems to be enough. The wiring is a little tricky If you need help let me know.

Bill

wbmusarra said:

Molleur and Pete, Sorry, you are both partially wrong.

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They both sounded right to me :huh:

PeteB said:

Pretend you are mounting the fan to a radiator. If it's mounted behind the radiator, it's "pulling" air through the radiator. If it's in front of the radiator, it's "pushing" air through the radiator. So, assuming you are mounting the fans inside the engine compartment, you want "push" fans.

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This is correct.

I would think you would want a temperature sensing relay to turn the fans on instead of a timed relay. With this configuration you fans would come on in, say, a slow or stalled traffic situation where you don't have the option of pulling over and letting it cool off. They would still operate at shutoff until the engine bay temp dropped to a safe/predetermined level.

This is the part # of the fans I bought: Spal 30103013

I bought a radiator thermo sensor relay kit to control the hatch fans. The probe just measures air temperature in the engine bay and turns the fans on at 160 degrees (the temp is adjustable).

A.J. said:

I would think you would want a temperature sensing relay to turn the fans on instead of a timed relay. With this configuration you fans would come on in, say, a slow or stalled traffic situation where you don't have the option of pulling over and letting it cool off. They would still operate at shutoff until the engine bay temp dropped to a safe/predetermined level.

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To even more specific you want an adjustable Ambient Temperature Sensing Relay Circuit for this application. Since you want to move heat out of the engine bay you want to to use the engine bay's ambient temperature to do so. I am adding one and maybe two for the same purpose. It should be adjustable so that you have options when locating the temperature sensor. A secondary option would be to have them operate with the radiator fans. It would work, but definitely not optimally since the radiator is up front and responding to coolant temperature and AC activation.

The Fan.... I'm not a fan expert but I have noticed that the fans, I am using, exert more cfm when the air flow is pushed through the open side. I have no way to measure the delta, but I would estimate it to be 30% less in the other direction. Your fans may not have this characteristic, but it would be a good idea check this prior to install or to leave the option of reversing the fans mounted position.

Just my $.02. HTHs

VD2021 said:

To even more specific you want an adjustable Ambient Temperature Sensing Relay Circuit for this application. Since you want to move heat out of the engine bay you want to to use the engine bay's ambient temperature to do so. I am adding one and maybe two for the same purpose. It should be adjustable so that you have options when locating the temperature sensor. A secondary option would be to have them operate with the radiator fans. It would work, but definitely not optimally since the radiator is up front and responding to coolant temperature and AC activation.

The Fan.... I'm not a fan expert but I have noticed that the fans, I am using, exert more cfm when the air flow is pushed through the open side. I have no way to measure the delta, but I would estimate it to be 30% less in the other direction. Your fans may not have this characteristic, but it would be a good idea check this prior to install or to leave the option of reversing the fans mounted position.

Just my $.02. HTHs

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Most all the fans in automotive use are running normal DC motors, which are typically reversible. So in theory, you just swap wires to get to fans to move air in the other direction.

However, better fans, like the ones Vidal apparently has, have direction-specific blades that are designed to work best in one direction.

If you select on of those, and since you will likely want to mount the fans on the inside of the bodywork, you'll want to select "pusher" fans.

As with all fan installations, efficiency is increased with shrouding. That may be a little difficult for this application, and experience may show the extra efficiency isn't needed if the selected fans have enough power to move the quantity of air needed to evacuate the engine compartment.

I agree that controlling the fans with a temp sensor is a great idea. Wiring in a switch that allows manual override is also an idea to consider.

If you are using ISIS, you might consider just running this circuit from the battery, or talk to their technical people about changing the programming and using one of the unused outputs from the rear powercell (there are a few open ones on the standard SLC setup).

Al, All I addressed was the turn off. You can use whatever turn on you want, a switch or thermostat or what ever. The timed off relay will not turn your fans on. It only times the amount of time you want them to run once the engine is shut down. This will save your paint job above the engine. Ask me how I know.
Ricardo. Reread what i posted. If you have a puller on the inside of your radiator, as you wrote, then if mounted on the inside of the engine bay it too is a puller. It has do do with which way the air is flowing through the fan.
Toward the surrounding housing is pull. Toward the face of the fan(no housing) is push.

Bill

Haha...Jack's response CAN'T be wrong, unless one wants to argue the appropriateness of the word blow (vs. suck).

The basic and pertinent question is .... what specification fan do I order IF using a fan with a mono directional fan blade design (which negates the efficiency if reversed)

Assuming one would mount the fan on the inside and at the rear of the bodywork (because after all having fans bolted to the outside of the body would be, uh....unique). Then you would need to order "pusher" blade design fans. Since they should not be run backwards they will always be pusher fans. Having said that, IF one wanted to mount fans behind the intake ducts on the sides of the body one would order puller design fan blades if using mono directional fan designs.

Pete, Will and Roberto get gold stars.
Bill gets a gold star too, but gave me a headache and must go sit in the corner

Can anyone help me with locating an adjustable Ambient Temperature Sensing Relay Circuit for use with the fans?

Mr Fling
Please try SUMMIT Part # " FLX-31165 "
I had read good luck using this on another car, it has a temp bulb that senses temp that your slides into the radiator fins, it should work fine for ambient air you can adjust the target temp for the fan and the ramp up function is also nice. I was planning to use this on the SLC but ISIS obsoleted it.

I really like the idea of exhausting hot air from the engine compartment. Has anyone installed a set of Spal Fans in their engine compartment. Not being familiar with these fans; I don't know how large they are and just can't imagine where they would be mounted?:blank:

Could someone please post a picture of these fans installed in an SL-C engine compartment?

Thank you,
Jim

Yes - Allan did. It is on the last page of his build: threadhttp://www.gt40s.com/forum/slc-clubhouse/33536-sl-c-50-allans-build-12.html.
This is where I was wanting to put them... in the rear bay to aid in engine bay cooling. The ISIS system has 4 unused pins or ports that could be used for this. However, I was unclear about the adjustable temp. sensor that would talk to and place nice with the fans and the ISIS.

mcfling said:

Yes - Allan did. It is on the last page of his build: threadhttp://www.gt40s.com/forum/slc-clubhouse/33536-sl-c-50-allans-build-12.html.
This is where I was wanting to put them... in the rear bay to aid in engine bay cooling. The ISIS system has 4 unused pins or ports that could be used for this. However, I was unclear about the adjustable temp. sensor that would talk to and place nice with the fans and the ISIS.

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You could use ISIS to always provide power to a specified output, and use a temperature-sensing circuit to run them, with a manual override switch. That's probably the simplest, safest approach.

You'll likely need to get a software update from ISIS to do this, and have access to a programmer device from them.

The bigger problem is finding the right controller, as most of them are based on radiator systems that have a relatively high lower limit. IOW, they don't typically start turning on until 190 or so, which is already pretty hot. I guess it also depends where you mount the sensor- if you put it just over an exhaust pipe, it would probably start early and run for a long time, if that what you wanted. But two serious fans running for a half hour after the car shut off might start to have an effect on battery life, so a controller with a max run time after ignition is off would be one way to mitigate that risk.

TheJimer said:

I really like the idea of exhausting hot air from the engine compartment. Has anyone installed a set of Spal Fans in their engine compartment. Not being familiar with these fans; I don't know how large they are and just can't imagine where they would be mounted?:blank:

Could someone please post a picture of these fans installed in an SL-C engine compartment?

Thank you,
Jim

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You can get Spal fans in just about any size you want: SPAL Electric Fans- High Performance Racing Fans

Pete

A cooling fan in the engine compartment should be a part of every build. In 2010 I posted details for adding a pair of five inch fans to our GT40. It was one of the most significant upgrades to the car.

On the track there is a lot of air moving through the engine compartment. When driven on the street, however, there is just not enough air. To protect the fiberglass, reduce issues with vapor lock, etc. cooling fans should be a part of the build plan from the outset.

Obviously locating the fans is highly variable. Consider the natural flow of air through the engine compartment, including low pressure and high pressure areas, and try to locate the fans to complement the flow rather than work against it. Consider the primary heat generator, the headers, and try to get air to move directly across them. Typically the air will move from the front of the engine compartment and exit out the rear: a low pressure area.

I used a Waytex relay to control the fans and permit them to run after shut down. Coolant temp would not be a reliable means since it will not necessarily correlate to the temp in the engine compartment. Ambient air temp would be better, but it could result in highly variable run times, so make sure you have a hefty battery. A timer is predictable and experience will quickly reveal that a preset time will provide good results.

Link to details of the relay are attached.

http://www.gt40s.com/forum/396506-post864.html

Further research I found

" Derale Performance Adjustable Fan Controllers 16769 "

this controler has a range of 32 to 220 Degrees and is $34.97 at Summit.
The cons are it's not set up to run for a set time after engine shutoff .