air temp sensor

[bloky]

mate has got a top mount intercooler on his cruiser wagon and wants to put a thermofan on for offroading. Being for the intercooler he's not too woried about the engiine temp, but wants it to run on sensor that tells him when the intake air is hot. Has anyone ever done this before? or is the compresssion of the air from the turbo enough to warrant running the fan full time? i think he's keen for it not to run for highway driving.

[thechuckster]

If the engine has an IAT in the plenum and uses an aftermarket ECU, it could be configured to enable an output (to turn on a relay) when air temps are over a certain temp?

Factory thermo fan switches switch at too high a temp.

Adapt a temp switching kit from jaycar to use the IAT from a v6 commode (mounted in the plenum) to drive a fan relay?

[Duk]

Does the engine use a post intercooler temperature sensor? If it does, a variable voltage switch (you can get a build it yourself 1 from Jaycar) would be able to be used to do the job by watching the sensors output voltage and switching a relay at the right temperature.
If it doesn't use a post intercooler sensor, then you/your mate could possibly look at using a variable temperature switch like the Davies Craig radiator fan switch. Whether that can switch on at a low enough temperature I don't know.

[trdee]

aw11s have engine bay temp switches that turn on an extraction fan in the side vent at something like 50-60deg. could use something like that??

[stradlater]

I would have thought that the temperature of intake charge would fluctuate too quickly for it to be used as a switch point for an intercooler fan. It will only really be HOT when the turbo is spinning up, the temp will drop back down off boost. To that end, you'll get high temp for 5~10 seconds, 30 seconds TOPS, and then it will go back down. That's WAY too quick for a switch on an intercooler fan.

Atlernatively you could use an engine bay temp sensor like TRDEE said. That would mean the intercooler would be being cooled when the engine bay ambient temp is up high. This would be far more worthwhile.

Frankly I think a switch in the cabin would be the easiest. You will know when you are off road, and you will know when you are on highway. Then you can just use that internal logic device we were all (or most of us) born with to do the switching.

[Rhyno]

I agree with Stradlater, it would be the best way to go, then you could switch it off when you get to a river crossing or similar when it would not be best to have the fan running.

I have ran heaps of fans this way on rally cars and paddock bashers over the years, just flick the switch when you want to have some fun, then flick it off on the highway. Just be sure to use a relay of course

[Duk]

Turbo Diesels spend a shiet load more time on boost than turbo petrol engines. You can sometimes hear work's 4wd Hilux cruise down the highway on boost (aerodynamics of a house + a head wind, with a VGT turbo, it will do that). So their intercoolers would spend more time being a radiator than just a heat sink.

[SHEPPO3930]

i looked into this for a wrx intercooler but the switching was done a little different.

the plan was to buy a Jaycar adjustable frequency switch and tap into the speedo sensor's wiring loom. then at road speeds lower than 50km/h it would turn on an intercooler fan. at speeds above 50km/h the fan's mass airflow would have been far less than what would have been coming in from the bonnet scoop.... so there's no reason to have the fan on (regardless of inlet temps).

the switch can be set to turn on on a rising or falling signal... in this instance we want a falling signal (car slowing down), and when the car slows to 50km/h the fan turns on. to turn the fan off, use the adjustable hysteresis and set it at 60km/h. this way when you're crusing along in a 50km/h zone the fan isn't switching on/off all the time.

anyway that's my 2 cents

[bloky]

We did discuss going the console switch, however we wondered if there was a more interesting way.
I like trdee's idea of engine bay temp. Having no digital speedo or aftermarket ECU sorta limits our options otherwise.

[bloky]

just found this, so we might start there.

Engine Cooling Fan Controller

[Rhyno]

Looks good,

But I would run it with a 3 position switch that allows it to switch between on, off and auto, then you have the best of both worlds.

[stradlater]

+1 for Ryhno. Very true...

That way you get to override it with your own internal logic switch. Pending you have one.