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Old 08-30-2010, 07:00 PM   #1
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How do I make radiator fans start at a lower temp?

Hello Gents:

I wish my 99 Boxster would start the fans a tiny bit sooner that it does. They actually start a quarter of an inch before the 220 mark. I guesstimate is 200 or so.

It is 85+ all year round here in Puerto Rico and traffic jams are common. I have a lower temp thermostat 160F from LN Engineering and the car takes a while to get to that level. Even then, I wish they would start a little sooner. I know what heat can do to cars in the long run.

What would be the best way to accomplish this?
Does the DME controls this or is it a thermostat switch like other cars?
Does anybody have any suggestions on the suggested temperature?

I think 180-185 should be ideal to me. I use 15w50 M1 oil all year round.

Thanks beforehand for your comments and ideas,
Fred Larracuente
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Old 08-30-2010, 08:41 PM   #2
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the easiest thing to do is to wire in a switch that can be turned on from the cab. Do not disconnect the OEM wires, so that if you forget to turn it on, you wont overheat. Otherwise, the computer will have to be programed to turn on at a lower temp. I dont know if that is even a choice because the special porsche laptop and program to do that is around 3 K-6K$ and only dealers and large shops have it.
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Old 08-30-2010, 08:54 PM   #3
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Quote:
Originally Posted by jhandy
the easiest thing to do is to wire in a switch that can be turned on from the cab. Do not disconnect the OEM wires, so that if you forget to turn it on, you wont overheat. Otherwise, the computer will have to be programed to turn on at a lower temp. I dont know if that is even a choice because the special porsche laptop and program to do that is around 3 K-6K$ and only dealers and large shops have it.
Thanks Jhandy, just what I was thinking. Now that you mention it, instead of a manual switch, I guess I could hook up a separate temperature sensor, (one that just has on/off signal) so when the desired temp is reached (say 180F) and a 50 amp relay to turn it on/of for me.

Any insights on brand/type of the switch or the temperature setting I should be selecting?

Anybody else (maybe at the tracks) have done this?

Thanks!
Fred
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Old 08-30-2010, 10:14 PM   #4
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Unfortunately, unlike the Audi's and VW's, you cannot adjust this setting from within the PST2 (MAYBE the PIWIS has this functionality, but I don't know as I don't have one). I am working with Revo on a custom flash for my 3.8, and I have asked them to write in functionality for turning on the fans at a lower temp, but don't have an exact answer back regarding whether or not they can do this.

I'd be careful about hard wiring the fans, as I can see that pissing off the DME if the fans are on and it didn't they they were.

While the lower temp thermostat certainly helps, the real solution to keeping the temps down is to turn on those fans sooner whenever the car doesn't have enough airflow through the rads.
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Old 08-31-2010, 03:33 AM   #5
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And... cleaning the radiators out on a regular basis!

Cheers!
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Old 08-31-2010, 07:41 AM   #6
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Thanks to all for the comments.

IMHO, i do not think the DME has that much control or temperament as to know whether the fans are on or of. It just turns em on. I suspect this because I forgot to hook one of them one day DME did not turn on the CEL or anything. I had it like that for at least 2 days, plenty of time for the DME to notice I guess. Also, a friend of mine had one of his fans not working and the DME did not tell him nuthin'. He just noticed an increase in operating temp. We checked each side and noticed that one of the sides was not turning on...

For sure, the last thing I need is to 'piss off' the DME (or damage it in the process). Can anybody else give their opinion on this?

Thanks,
Fred
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Old 08-31-2010, 07:58 AM   #7
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The DME doesn't know (or care) if the fan is already running. All it does is monitor temps and energize a fan relay when its logic says coolant temp exceeds a programmed threshold.

You have two ways to attack this:

1) the aforementioned hardwired switch -- although I would suggest you not run the full amperage through the switch and instead have your switch control the fan relay (the same one the DME is energizing), or

2) use an adjustable temperature switch to control the fan relay -- this way it is automatic.

Or an even easier approach is to simply run your AC when it is hot. This keeps both you and your engine cooler, since the AC condenser is mounted in front of the passenger side radiator and that side's cooling fan runs continuously while the AC is on. I find this drops the indicated temp on the dash gauge by about 5-10 degrees on a hot day (from just right of the "0" in 180 to the middle-right of the "8").

Of course, YMMV.
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