PCA Forums

when you power down, you can keep some of the fans running for up to 10 minutes

http://www.systemcooling.com/modules.ph ... le&sid=145


interestingly enough, my 1989 ford econoline has the same feature

Almost all vehicles with electric cooling fans (which means almost all vehicles) will have the fan run after the engine is shut down. Because of the mass of the engine and the huge amount of heat energy that this mass can store most cars will experience the highest coolant and engine block temperatures after they shut down unless the cooling system does something to alleviate it. Since an electric fan can run after everything else is shut off, vehicle mfrs decided to thermostatically control the fan and let it run to alleviate "hot soak" conditions.

In the really ancient days before fuel injection, some cars would experience hard starting or no starting on hot days after being shut down because the residual heat would vaporize fuel in the fuel lines and carbueretor.

I wonder if a CPU has enough mass to store significant amounts of heat after shutdown. I would expect post shutdown CPU temps to quickly spike at a couple of degrees higher than operating temperature and then quickly go down to ambient...

Well guys I found this very interesting and since I have a dual digital temp display that runs off of its own battery power I decided to test it and see what happens to CPU temps after shut down. I am running an XP 1700+ @ 1540Mhz. SETI had been running on the system for about 5 hours and CPU temp was 40.3c at time of shut down. Within 2 seconds of shutting the box down the temp immediately started to drop. No spikes at all the temp started a fairly quick fall and within about a minute I would guess it was sitting equal with case temp. My CPU probe is attached directly to the underside of the CPU core so I am very confident that the readings are accurate. I am using an Alpha 8045 heatsink which is pretty big so maybe the shut down tool would be useful for a smaller less efficient heatsink, but I see no need for it on my system.

I agree with Randy, I really don't believe a device like this is necessary as system temps almost immediately start to drop. But some do want a device like this regardless.

We'll be reviewing this one soon. And it's from a company we have a better relationship with.

One of thoes units would be usefull for water cooling. but thats about all i see it fit for. And yes, Heat Soak will cause a hard start for the exact reason you stated. I have that problem with both my cars. A CPU is not going to have a problem with heat soak because its so small. that and as soon as you cut the power it stops making heat. In a car engine, you have hot spots. namely around the pistin walls. what happens it the coolant is moving and removes the heat form the walls. but when the car stops, the heat has a chance to heat all the coolant in the block. if the actual temp sensor was on the pistion wall, you wouldn't notice heat soak cause it would be at the hottest temp allready.

I hope that somewhat explains it all.