HHR SS thermostat
 

My 06 Colblat SS SC - and My 86 Monte SS are both running 180 degree thermostats, for more performance, but less gas mileage, has anyone gone to the 180 thermostats on the HHR SS's and seen a benefit???

180 is the stock and only t-stat.

Modern cars do not respond well to the wrong temp.

I do believe they are already a 180 degree thermostat from the factory.

How do you figure "more performance, but less gas mileage"?

Used to be ,before OBD2, people would put a higher temp t-stat in to increase performance; Higher temp=more complete combustion. We don't need that with computer controlled motors. The old days were wrong.

The only effect on MPG of a t-stat would be if you had a temperature dependent choke. Cars with EFI don't have chokes.

The way the t-stat works is different now. It opens at 180F then STAYS open until the engine temp gets back down to under 180F. In other words; it is mostly always open, it just makes the engine warm up to the temperature the computer is optimized to faster.

cars that run cooler can have more boost richer air fuel mixtures and more gas means more energy and more bang, they are also able to run more more timing w/o knocking. that is why cold air intakes help. todays cars run much hotter for emissions. my hhr consistently runs about 195, when my cobalt get to 180.

How do you re program the computer for a different t-stat?

Have you experience knock? If you have your computer is very messed up and your cat is in danger.

Sounds like you have a 190F t-stat in your HHR and a 175F t-stat in your Cobalt. Don't know about Cobalt, but 180F is proper for HHR.

What does the coolant temp have to do with the A/F temp? That's the intercooler's job.

Today's cars are controlled by the computer, changing sensors only lies to the computer. If you think something needs tinkering with it is a tune you need not different sensors or t-stats.

Before 1996 you could do physical things to change performance, now if you do physical changes the computer will sense differences and compensate back to what it is programmed for.

The computer calculates the A/F using a lot of data points, including coolant temp and ambient temp. If you change the coolant temp the computer will change something to keep the A/F at the optimum.

From: https://www.turbobygarrett.com/turbo..._rich_vs_lean:
"There are actually three ways to reduce the probability of knock at full load on a turbocharged engine: reduce boost, adjust the AFR to richer mixture, and retard ignition timing. These three parameters need to be optimized together to yield the highest reliable power. "

Note that coolant temp is not mentioned.

Stick to any antiquated ideas you like. It is your time and energy.

i called the parts store and they said it should be a 180 in there...I question if previous owner upped it to a 195, as we are in the north with the cold, and perhaps the previous owner wanted more heat, I had assumed it was running a 195, as that is were it runs.

195 or anywhere around 190 is fine. A 180 t stat doesn't mean it'll be running at 180 all the time it'll just stay above that. Generally about 10 degrees higher.... Or 190

A 180 degree AC Delco! Not the cheap Motorad or Stant but the AC Delco thermostat!

no one " back in the day" installed a hotter t-stat. engine would be prone to detonation. hot rodders always installed a cooler t-stat . cooler densor air means more power. the t-stats from oem went up to 190 - 195 for 1 reason only - emissions.