Thermostat ?

[04FX4]

Ok so what thermostat are you all running? I am running the stock 195 ,and now with summer and pulling a trailer it seems that the 195 may be to high and was thinking of going to a 180. Any body have any pros or cons to this before I do this. Will it affect my gryphon and custom tunes??

[Sburn]

Keep the stock temperature thermostat. Running too low of a temperature will make the engine computer think that the engine has never warmed up (>170 degrees) and the computer will try to compensate by keeping the mixture on the rich side.

If you really are running too hot, there's another problem beside the thermostat temperature.

Jack may chime in here and proabably has some good advice, since he tows a trailer in Arizona.

[Jackpine]

I'll chime in all right. Yep, it's hot in Arizona and I've kept the stock thermostat in, basically, for the reason Sburn gave you.

The whole point of the thermostat is somewhat misunderstood by many. First, it's there to warm your engine up quickly. Coolant won't circulate until it opens, so the block get warm fast. Then, when it DOES open, it does so near the optimum operating temperature of the engine. It opens part way at first, and becomes fully open a bit later. At this point, your engine's temperature is maintained by the balanced design of radiator area, fan velocity, coolant quantity and chemical properties. The engine will not really overheat if things are designed and maintained properly unless you run the engine at very high rpms, pulling a heavy load, and at a slow driving speed in very hot ambient temperatures. If you get into colder conditions, the thermostat will begin to close to keep the engine in the ideal heat range.

If you use a colder thermostat, it will open too soon. With a good cooling system, the engine will stay between 180 and 200 for too long. However, if it was going to overheat with the stock thermostat, it will do so with the colder one too (and probably just about as fast, once the coolant starts circulating). Once the thermostat is open, regardless of the temperature it opens, the rest of the cooling system controls temperature increase.

So really, what the thermostat is for is to put a "floor" on the operating temperature range. You want that floor to be around 195.

When I'm towing, I monitor the CHT (since there's no coolant temperature sensor). About the highest I've seen it get is 216 (under very heavy load). The failsafe CHT is 258, so you can see there's a lot of headroom. I should add that the 50-50 mix of antifreeze/water and the fact that your cooling system is pressurized, raises the boiling point of the coolant to somewhere close to the failsafe temperature too.

- Jack

[Power Hungry]

Great job, Jack! You got that one nailed perfectly. You too, SBurn.

[88Racing]

Keep it "stock" @ 195 for optimum performance.

Lars

[BlackSTX]

I've recently swapped mine out for a 180 degree stat, so far so good. I know part of the reasoning for the manufacturers going to higher temps is emissions, I just don't like running a vehicle that hot, though I know it's engineered for it. It's possible that in the winter I may want to swap back to a 195 depending on how well it defrosts the windows in winter; but for now I'm happy.
The question I have is this something that may allow me to advance my timing a degree of two since the head temps are now a bit lower and will this help prevent pre-ignition to any usable amount? I guess, from a programming stand point, is there a benefit to having changed this?

[88Racing]

Originally Posted by BlackSTX

I've recently swapped mine out for a 180 degree stat, so far so good. I know part of the reasoning for the manufacturers going to higher temps is emissions, I just don't like running a vehicle that hot, though I know it's engineered for it. It's possible that in the winter I may want to swap back to a 195 depending on how well it defrosts the windows in winter; but for now I'm happy.
The question I have is this something that may allow me to advance my timing a degree of two since the head temps are now a bit lower and will this help prevent pre-ignition to any usable amount? I guess, from a programming stand point, is there a benefit to having changed this?

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

[Jackpine]

Originally Posted by BlackSTX

I've recently swapped mine out for a 180 degree stat, so far so good. I know part of the reasoning for the manufacturers going to higher temps is emissions, I just don't like running a vehicle that hot, though I know it's engineered for it. It's possible that in the winter I may want to swap back to a 195 depending on how well it defrosts the windows in winter; but for now I'm happy.
The question I have is this something that may allow me to advance my timing a degree of two since the head temps are now a bit lower and will this help prevent pre-ignition to any usable amount? I guess, from a programming stand point, is there a benefit to having changed this?

Actually, I doubt there's any benefit at all. If, in fact, you ARE running a couple of degrees cooler, it's because you live where there are only two seasons: Winter and the 4th of July. I cannot see how that small a drop in engine temperature would allow you to advance your timing at all.

But, you now have a longer warm-up period which means you are running richer longer. This can lead to carbon fouling and possibly increased "washing" of lubrication from the cylinder walls.

Once your stat opens, your engine temperature will ultimately rise according to the load and the ambient temperature, so after everything stabilizes, you'll see very little difference from what you had with the 195 degree stat.

(And, I see Lars beat me to the punch - well, he's younger and quicker)!

- Jack

[BlackSTX]

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]

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