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I just installed a 160 degree thermostat in my 944 turbo/LS1 conversion. The final task before putting it back on the road is the settings for the fans. The previous owner that I bought this swap from was using the stock 944 wiring and relays to control the fans off a thermoswitch.
My stock fan wiring is questionable at best, so I went with the three relay setup. This is a track car (road course) so doing what I can to keep temps down as low as possible. Would like to keep them around 180 - 190 if possible. Still using the stock radiator and fans, so will have to see how that works out this summer. Here are the settings as of today in my PCM.
I have heard the following are the temps recommended by Hypertech for this thermostat.
ON OFF
FAN 1 184 175 FAN 2 194 185
Does anyone have any other set points they would recommend. Is there anything else that should be addressed on the Fans page or elsewhere? This is my first time using HPTuners. My car is non-A/C.
It's so close to being ready the first drive! Thanks in advance for your help.
Your settings look good. It's really going to depend on the radiator and how much cfm the fans put out. You won't really know until it's driven on a fairly warm day how it will do, you said stock radiator and fans is that stock for the 944? If it is you might run a little warmer or cooler, never know until you drive it and get up to temp.
So I wanted to follow up on this. I have been having this issue since I went with the 3 relay setup. I believe I have everything wired correctly, but my symptoms are this. My fans kick on at low speed at the expected temperature (verified through a temperature gauge). Fans step up to high speed at the the expected temperature.
However, once the fans reach high speed, they don't kick back down. Also, the temp will remain steady around 190F. I am using a 160 thermostat.
I have the stock radiator in now, and the stock 2 fan setup from the 944 turbo. But going to put in a higher capacity radiator this winter. Just trying to sort this out before it gets warm out. Planning on tracking it in a few months.
If it's needing both fans just to maintain 190F in the winter time -- when you start tracking in warmer weather, suspect you'll further confirm that a radiator designed for a much less powerful engine is undersized for the LS. Go ahead and upgrade the radiator -- ESPECIALLY on a track rat. If you don't have it - I'd want oil cooler and oil temp gauge as well. Lastly, if you're not boosted and trying to control detonation, there's little reason to try and run the motor down at 160F -- even if you have the bigger radiator needed to reject enough heat to get it down there. I'd put the stock temp t'stat back in it and control around that.
The wiring diagram looks correct. I am running that setup in my GMC.
You mentioned that it's staying around 190F....so, your High fan settings won't turn off until 185, so I'd expect not to turn back to low speed in that case.
My general rule of cooling systems:
To check the fans, I want to see the temps stay where I want them when I'm stopped.
To check the radiator capacity, I Want to see the temps stay where I want them when in motion, no fans.
In my case, My heads/cam LQ4, stock compression, I run the stock (187 degree) T-stat, so its about 190 in real life. My low speed fans I usually turn on I think at 205, and off at 195. If I idle long enough, or in stop and go, I'll get into this range, but as soon as the fans come on, temps go down. So I know my fans are moving enough air to be effective at low speeds. (My fans NEVER get to the high setting of 215 degrees. Burnouts on Woodward ave in August sitting in traffic for 3 hours, never gets past low speed). If I'm driving say 45 mph, it'll sit at 190 degrees, and fans stay off. So I know my radiator capacity is good.
Now, that's just normal car stuff, not HPDE/track car, so you'll need more capacity than that. Sounds like you are not where you want to be just at idle?
Another thing that could be a factor is your ignition timing. It can have a BIG effect on temperature. Sometimes, people tuning are conservative. When timing is too lazy/retarded, then the fuel is burning later, after the piston is going down. When hot gas expends, it cools, so by lighting the charge later, it's missing some of this expansion time (which is why you lose power)... so it's keeping heat in the cylinders.
I've found significant changes in low speed temperature of my engine by moving the timing either way a few degrees. Just something to check.
My stock LS3 has the OEM 187F t’stat on the inlet. If your rad/fan combo is capable of rejecting enough heat, that results in coolant temps at the sensor (driver’s head, front) of 196F-198F. I have my PWM fan controller set to control at 202F. Under cruise with enough air to keep fans off, temps stay pegged right at 196/197F as read through ECU data - which is to say, the t’stat is controlling operating temps. If moving slow enough that fans are on, then temps stay right at 202/203F - which is to say, fan controller is controlling operating temps. You want enough radiator and control over air flow, that things work that way.
Excellent information guys, thanks so much for taking the time to reply. I'll put in a 187 t-stat and adjust accordingly.
Great suggestion on the oil cooler and gauge. I purchased this swap from another guy that had this setup on his 944 turbo which included an oil cooler, so I am set there. I have a gauge as well, but not getting a reading. I think it's a sender issue, just haven't tracked it down yet. That's also on the list of winter projects!
If possible, mount oil cooler heat exchanger so that the rejected heat DOES NOT go back across the rad - but under the car. This keeps you from putting oil heat right back into the coolant (think about it) — allows the oil cooler to truly be an incremental source of heat rejection. I have a separate fan on my oil cooler for use at low speed.
Try using water from a garden hose on the radiator. This should cool (quickly) down to the opening / closing temp of the thermostat and then turn off your fans depending upon programming. If you aren't approaching that temp on your gauge, there is another issue.
I use a cheap infrared temp gun too to verify temps on the gauge. You can use some sort of OBDII device to pull temps from the ECM, too.
+ Remember, heat transfer is driven by temperature difference. You can give off a lot more heat by increasing system temps (1 reason why OEMs use higher thermostat temp vs. 160F).
With a 160F stat, you have less delta T from ambient to radiator, but MORE delta T from engine to coolant...so, more complex than it might appear. More relevant - unless you’re trying to keep detonation at bay (boost) - everything works better at a higher-than-160F operating temp. Amazes me to see the NASCAR boys running around during July/August with coolant temps in the 270F-280F trying to balance “too hot” with having better aero by having the front taped up.
03-05-2019, 07:59 PM
HPTuner Settings for 160 degree thermostat 
