The PCM uses coolant temp because it is not a mass air engine (i.e. no mass air sensor), it is a speed density system. In fact, it uses a combination of sensor inputs to determine things like fuel curves and open/closed loop modes among other things. I don't think you will actually get a CEL from too cold of a t-stat, but many people get a stored code.

I do not consider the t-stat change a performance mod. It might help other performance mods you have by reducing the likelyhood of pinging caused by those mods (like advance timing you might have from a PCM performance mod for example). But by itself, it is not a performance mod.

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I was just using the mass air flow sensor as an example. Thanks for the lesson. When it comes to all the electronic bs I have a lot to learn. These trucksbeing my first and only attempt at modifying a computerized vehicle. Pretty much old school-- carb, distributor, and well made internals.

 

FWIW I run a 160 stat here in Georgia and have no problems in the winter. It's especially needed for the summer as it gets 100+ on a regular basis here.

With the stock stat in the summer my truck would reach well over 210 degrees and knock like crazy unless I had 93 octane in the truck. With the 160 stat the truck stays cool in the summer, no knocking with 89 octane and never reaches about 200 degrees.

Also, I have a hypertech power module FWIW

 

I've run a 160 t-stat before and it took forever to warm up and it ended up tossing a code. I recall that the pcm goes into closed loop somewhere around that temp and I wouldnt recommend a 160 in a daily driver. If its a tow vehicle, maybe. you will get your best performance with a 180* IMO

 

I was just using the mass air flow sensor as an example. Thanks for the lesson. When it comes to all the electronic bs I have a lot to learn. These trucksbeing my first and only attempt at modifying a computerized vehicle. Pretty much old school-- carb, distributor, and well made internals.
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I cant chime in on exactly how the pcm is effected by a lower t stat, because I havent seen the fuel maps and the variables that cause the patterns, but I can speek from first hand experience. The 160 has not given me any problems, no cel and no stored codes. IMO theres really nothing to consider other than overheating/underheating. If you are overheating, lower it (try to nail down why its overheating). If your underheating, raise it. If its fine, leave it alone. Just my .02 on that.

 

damn. i should go to electric fans. haha. it looks like the extra room would be nice for when you need to do some serious work inside the engine compartment.