JET THERMOSTAT YES or NO ?

[quicksand]

I have a 97 wrangler with many mods under hood, from air intake, big TB, catback, hot coil and spark and more. My question is will a jet 180 degree thermostat help performance or not. I have heard that by lowering temps affects the air/fuel charge. True or not ? Does anyone have any experience with this and what is the temp on a factory stat ?

[aka-justin]

In short, go with the stock $5 one. Too many systems overlap.

At length, here's why.
Thermostat open and close based on the engines temperature. If you get a thermostat that opens more or sooner at set temperature, the coolant will run cooler along with the motor. That logic backfires on electronically/computer controlled engines that monitor the temperature of the coolant is monitored separately from the thermostat itself. The engine will sense the cooler temperature and compensate by adding more fuel and richening the mix. In the end, you'll waste gas and put pressure on catalytic converter as it's working harder in longer spouts of rich cycles.

A bigger cooler couldn't hurt, as with a stock thermostat, it would close until the water warmed. Other noticeable improvements are converting to an electric cooling fan and other upgrades.

[Jeffy]

Personally I prefer the Robertshaw thermostats.  JET doesn't make their's it's basically a Stant, I think.  Nothing special about it really.  The Robertshaw's are built a lot better and open within 1-2* of the target temp unlike the cheaper thermostats.  I have yet to find one that failed out of the box as they are built to a higher standard.  Better material as well.

The 2.5L likes most MPFI's like to run on the warm side.  I have a 180 as well as two 195's.  I forget why I have an extra.  In any case I run the stock 195* temp as I'd rather not screw with the problem that some with a lower temp thermostat.

[quicksand]

So if I swap to a cooler stat I will burn and waste more fuel and hurt the cat ?

[aka-justin]

So if I swap to a cooler stat I will burn and waste more fuel and hurt the cat ?

Yes, you will burn excess fuel trying to warm the motor and the air/fuel will run in rich cycles longer make the cat work harder. The cat's temperature is regulated by the switching from rich to lean cycles. That's what's the 02 sensor is measuring for to modulate back and forth. If you trick the system to thinking the motors cold, it only knows how to heat it up by dumping more fuel.

As Jeffy mentioned, you could go with the stock rating temp. on a Jet Thermotstat. I think you'd just be better with stock in this one area. Why spend the extra money. If it's broke, replace it. If you need better cooling, service and/or go with a bigger radiator cooler and/or electric fan.

[sharpxmen]

i replaced my 195deg with a 180 last week, there's no change in mpg (was actually slightly better, just did a fillup yesterday, but very little to be significant). the reason i did it was b/c of where my temp probes are located for the e-fan (bottom of the radiator), in the winter or low temps there's really no need to run the 180. On the other hand according to my Autometer temp gauge which is more accurate than the stock one it still opens at 195 (EDIT: 190 actually), so it could be that is mislabelled or faulty (the thermostat), i can't compare with the 195 one as i just replaced the sender for the gauge with the autometer one at the same time i did the thermostat, i used the stock one for the gauge before, they are very close in value but not exactly the same so i can't tell for sure.

[quicksand]

Alot of good info guys, I think I will just leave the stock stat alone. She cools good I just thought maybe I could gain a bit more MPGs. My concerns with going electric fan was its life span or just more stuff to go wrong on the trail. I even thought of a daul fan setup and run them seperate ? Well time and money will tell. We will see what happens. Thanks guys.

[4banged]

The jet 180 degree thermostat is just a normal thermostat and its made by slant as Jeff mentioned. Jet reccomends the 180 degree thermostat and 91 octane if you use their stage 2 chip which has more aggressive timing and fuel curves. I run the stage 2 chip and 180 thermostat on my 2.4l and it definitely added some umph.

[quicksand]

Well that sounds good you got more umph but that is inconjuction with that chip and engine size. I like those 2.4L.