Mitsubishi Thermostat Advice?

[Chuck1986]

My 2001 Mitsubishi Eclipse GT has a 190 degree thermostat. Most other Japanese imports (including very similiar models such as the Mitsubishi 3000GT, Eclipse GTS, Galant, etc) use 180 degree thermostats. Is there a particular reason why my car came outta the factory equipped with a 190 degree thermostat when most others get a cooler, 180 degree thermostat?

My only guess is that it's cuz I have low compression pistons (9:1), which means the engine naturally runs a bit cooler?

And I'm not considering replacing my thermostat cuz I'm having cooling problems or anything, my curiousity just wants to know.

 

[Quest]

In order for the ECU to sense the correct operational temperature of your coolant in order to go into "closed loop" operation, always go with what the factory specified temperature thermostat.

I'm no longer interested in finding out why certain engine calls for 180F thermostats while most Japanese engines are >190F. If it calls for a higher temp thermostat to get the job done right, I'll do so with a heartbeat.

Engine design and management subject is too advanced for me and the subject typically involves academic discipline and lots of knowledge and knowhow. One cannot simply throw you an answer just like that (IMHO)

 

[mechtech2]

Higher temp thermostats keep cruising engine efficiency high.
Ford even has a dual temp thermostat now - about 195 when accelerating, and 210 when cruising.
This is a great idea, but I don't like the added complexity of the system.

 

[dwendt44]

I've read that some car nuts have put 180º in their GM engines with no problems from their ECU computers.
Apparently, the computer goes into 'open loop' at/near 170º or so.(it considers the engine 'warmed up' by then).

 

[The_Jeff]

It's possible your thermostat is closer to the "core" of the engine and its pellet is easily warmed. The 180 thermostat might be way out on a gooseneck and needs to open at 180 to keep the middle of the engine, say, 190 or even 200.

Regardless, stick to stock for reasons others have mentioned.

 

[porcupine73]

I agree it's probably for mileage, with cafe and everyone all mileage happy these days running the engine hotter is an easy way to bump up efficiency. I thought the 'closed loop' was determined right when the ECU started getting a readable signal from the O2 sensor(s) after the exhaust warms up, not based on engine temp. I've only watched it a few times but it seems my car goes closed loop within a couple of minutes of idling when it hasn't reached anywhere near operating coolant temp yet.

 

[Chuck1986]

Hey guys thanks for your opinions. It's obviously not a good idea to try to act 'smarter' than the factory engineers and run a cooler thermostat.

 

[Doc8404]

HOWEVER, if you are running a tuner (like the hypertech power programmer) it will make a difference (or so they claim) because they program the tuner with the lower temp stat....why they don't offer it as a programming option is beyond me.

 

[unDummy]

If factory engineers were so smart, we wouldn't have engine recalls, TSBs, sludge monsters, head gasket eaters, intake manifold gasket eaters,..................

I don't think that 5-10 degrees either way will make a big difference. I think that hotter is better for emissions tuning and efficiency.
I know that my 160F thermostat caused excessive moisture buildup in the oil which is bad. But the 180F solved the oil moisture problem, and prevented pinging that was very common with the stock 195F thermostat.
In another car, I run a 195F thermostat in place of the stock 180F thermostat which gave me a solid 15 mile increased range on the tank. That engine runs in a narrower temp range since fan kicks in @200F. 195-200F vs 180-200F is a narrower more efficient operating range for me.

A cooler OEM thermostat might be the engineers bandaid for the stock cooling systems with the higher perf motor. Its OK for engineers to do this, but the backyard wrench can't? Too funny!

I don't claim to be smarter then OEM engineers. But, with an aftermarket fuel computer, a dyno, and an experienced tuner, just about ANYONE can squeeze more HP and/or MPG then those factory engineers.

Nissan has an engine with 2 thermostats, one for the block and one for the head. Hows that for complexity? A common mod is to washer substitute, or hollow out the unnecessary 2nd thermostat. Offend Nissan engineering!

I believe that a German automaker is using ECU controlled coolant servo valves instead of thermostats in some higher end models. Would I want to trust an ECU if a failed servo motor or simple electrical issue might caused overheating?

You can use the thermostat to make up for factory engineering screwups.
If you vehicle doesn't warm up quick enough and you live at the north pole, find one a little hotter.
If you live in a hot climate and want a little more insurance, run one cooler.
If you have mild pinging or don't care to use recommended highest octane fuel, run one thats a little cooler.
If you're advancing your timing for more power, run one a little cooler.
If you're looking to improve MPG, run one a little hotter.

If I lived in Tempe AZ, I would switch to a cooler thermostat. Since your vehicle is 6 years old, your are due for themostat preventive maintenance if not already replaced. Since I've had too many store bought thermostats fail, stick with OEM sourced parts if possible.