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quote:Originally posted by hyracer
Dalite, I've been reading the SRT4 thread with interest and my intereptation of what's being said is leaning in favor of the 160 T-stat install. It looks like a manual switch would be needed though to run the cooling fan (bypass the PCM). Maybe a 180 T-stat would be better to keep the PCM from going to the cold-start loop.
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Well, here is another consideration... The high and low speed fan relays were eliminated on the GT in favor of a PCM controlled fan. The diagrams look like it has a "sense" wire going to the fan from the PCM. I haven't looked any deeper, but I would guess that any change to this circuit may make the PCM mad. I would take a good look at the wiring diagrams in the 2003 Factory Service Manual and make a decision from there on the manual switch.
At least an 180 degree one would let the PCM give better control of the engine variables; especially A/F mixture.
I had made a half-hearted suggestion to TurboG to include a slightly lower t-stat in the Stage I package and re-calibrate the PCM for it.
I made this suggestion when I found out that the only way to replace the "Oring" in the t-stat housing was to buy a new thermostat.
Luckily, the one that is on the stock t-stat is fairly durable, and allows you to reuse it. However, if you don't line up the notch, or if you let it slip while negotiating the bracket obstacle on the front t-stat housing bolt - it may not seal properly.
One thing to keep in mind about the discussions on the forums. It is easy to confuse the performance of a colder engine in summer time with enhanced performance.
Unfortunately, at those temps, the thermostat has't opened. As soon as it opens, the fans will take over and maintain the temp at the stock setting. At highway temps, the fans are off, the temp may slip below the 172 degree mark, and you will have an open-loop system.
This may ultimately cause the OBDII system to do it's job and store emissions-related errors that could cause a smog-check failure (in shops that are using a scan tool to check for errors before continuing a smog test.
From what I see, it may be the wrong thing to do. A lot of folks that have much more experience than I do seem to also be against it.
I would go with the 180 if I felt compelled to experiment, and see what happens from there. Even with it in place, in traffic, below 35 MPH, the engine will still run around 215 degrees.
Let us know...