Thermostat ?

BlackSTX · #1 Wed, May 27th, 2009, 10:23 AM

Quote:

Originally Posted by 88Racing

No, you may confuse the pcm and it may make the truck run richer. Thinking it is in a warm up mode all the time until it reaches the switch over to run temp.

Lars

That was a concern I had, the old GM-OBD systems had a set temp before going into normal operating mode, if I recall correctly, it may have been around 165 degrees. I have been monitoring mileage, and so far it seems like it's consistent, though I'm sure temps doesn't have to be significant for the PCM to enrich the a/f mix. My only real concern is going too rich for the cats, since no one wants to have to replace a set of cats.

***Jackpine*** · #2 Wed, May 27th, 2009, 10:35 AM

Quote:

Originally Posted by BlackSTX

That was a concern I had, the old GM-OBD systems had a set temp before going into normal operating mode, if I recall correctly, it may have been around 165 degrees. I have been monitoring mileage, and so far it seems like it's consistent, though I'm sure temps doesn't have to be significant for the PCM to enrich the a/f mix. My only real concern is going too rich for the cats, since no one wants to have to replace a set of cats.

Yup - I forgot about the cats. They suffer too. You'll probably be operating open loop longer after a cold start. But again, once the thermostat is open and the coolant temperature stabilizes, you're really just about back where you started, except that if it's really cool out and you don't put much load on the engine, you might be running colder than you really want, since the "floor" is lower.

- Jack

BlackSTX · #3 Wed, May 27th, 2009, 11:22 AM

Either way, I can swap a 195 back in, it's simple enough. I guess some reasoning to this is that you used to be able to buy chips years ago designed for use with 180 stats. I believe they allowed for more aggressive timing, and hence, better performance. Of course, they also were programmed for such a change and I imagine made all other required adjustments accordingly.

I guess the other question that I now have is how does the temp. change affect under hood temps, and A/F ratios vs. the increased efficiency of the engine with CAI and exhaust mods. Does the lower temps, and possible richer mixture offset the possible leaning effects of the other mods? Also, how are the spark plugs (heat range) now effected by operating temperature changes? How much does the PCM compensate for the CAI alone; obviously, it does compensate for it some, at least enough to not burn up the engine or trip a SES light..... These are the questions some of the master techs I asked couldn't answer, though they aren't tuners/programmers so I didn't expect them to have an exact answer, they could only say that the PCM will compensate for an increased airflow, but didn't have know as to how much.

BlackSTX · #4 Wed, May 27th, 2009, 01:58 PM

Well, I did a little reading online, Looks like I may be changing back to the 195. According to what I read, it appears that the 195 may be better over all for performance and efficiency. Though I will admit, it seems kinda strange cause we always used cooler stats years ago; but that was long before they were putting computers in cars too.

***88Racing*** · #5 Wed, May 27th, 2009, 02:09 PM

Some of these changes on these newer vehicles really effect the outcome of the end product. Don't they?

Not old school anymore!

Lars

BlackSTX · #6 Wed, May 27th, 2009, 02:15 PM

Not at all like they used to be! I miss the good old days when parts were cheaper, and most of the work you could do with little knowledge or specialty tools.