Good day to all:
Was thinking about a cooler thermostat for my car ( 1999 xk8 convert )
My code reader had her running about 200 deg F
Which may be the design temperature ?? but it is awful hot under the hood. Was thinking about a 180 deg stat
Anyone out there do this ???
Howard

 

That is a normal temperature. The thermostat rating is just when the thermostat begins to open...cars generally run 10-25 degrees hotter than the rating. As long as the temperature stabilizes and does not continue to climb it is working as it should.

If you go too low, the ECM will get mighty unhappy, and you will run open loop and generate engine faults.

That said, Eurotoys sells a low temp thermostat which (if memory serves) is 170 degrees vs the 182 degree stock thermostat. It is a thermostat that they notch out on one side to fit, since no thermostat maker has a low temp thermostat that fits. I have run it with no issues. The 12 degrees is not going to make a huge difference, however. My car typically runs in the low 190s now.

 

My car runs around 210f

 

There is no benefit in second guessing the OEM design engineers and assuming that cooler is better.

 

+1

 

The main reason to go to a lower temp is to squeeze out a couple of more horses, but it is not enough to really be felt.

 

This is a popular misconception, the only difference is that the 160 opens sooner than a 180, which slows down the process of the engine heating up. Which inturn means that your engine runs rich longer and you waste gas, today's engines are meant to run hot, which is why you do not see 160 thermostats, the only practical use of them is for 1/4 or 1/8 racing.

They DO NOT make your car run cooler, because think about it, once the thermostat opens it's job is done, so how is it going to make a engine run cooler and not they do not open wider to let more coolant through (you can just drill a small hole in your t-stat for the same effect of a 160 t-stat), so save your money and keep the right parts on the car.

 

This is is an old 'Bubba' myth that assumes that lower coolant temps always in lower air intake temps. Not born out in reality.

 

I do not think it is total myth, but I do agree the improvement is so miniscule as not to be worth the trouble.

 

Depending on the outside temperature and efficiency of the cooling system, the thermostat may not always be fully open...there could be some regulating effect under some conditions.

 

According to my OBDII scanner connected to the Torque app on my phone, my coolant is almost always right at 194 degrees. It might get a couple of degrees warmer when sitting in the driveway idling, or right after a hard acceleration on a hot day, but the thermostat and electrically switched fan do a remarkable job of holding the temperature within a few degrees of 194. I assume the designers picked that temp for a reason.

 

The rule of thumb is that power will increase by 1% for every 10 degrees reduction of intake air temperature. A 20 degree decrease in coolant temp might see a 1-2 degree decrease in intake air temp- on a good day.

 

It is not so much cooler air intake since the air in a jaguar v8 doesnt come close to the coolant except the throttle body of which in a hot climate i would bypass. Its as simple a using a vacuum fitting to couple the 2 hoses. I wouldnt do this in when cold or cold climates since its helps to prevent throttle icing. But I dont have an issue on my Nissan throttle in Texas during the winter
The biggest benefit is a reduction in engine temp that reduces a engines detonation tendancies. Ie safer with more boost or crappy gas, or a performance tune. Yes the engine may nnot go into closed loop and run richer(also reduces detonation) but with an increase in emmissions.
A thrmally efficient engine is one that keeps more heat in the cylinders to produce more power and less emmissions. This is why racers and many manufacturers too use piston coatings and coatings in other areas. Keep heat in and reduce friction. This is another reason there is a plastic intake, easier to mold the shapes needed, lighter and cheaper to manufacture, and is thermally inert compared to metal. (doesnt transfere heat like metal does)

 

Hang on a sec, Brutal. Can you explain that thing about bypassing something? I'm a pilot, and on airplanes we have a little knob for "carb heat". At certain times we pull out the knob to allow some engine heat into the carburetor to prevent icing. The ice could clog the carb and cause the engine to die, which is obviously a bad think in an airplane. However, when carb heat is applied the airplane's engine has noticeably less power. Are you saying that there's a connection somewhere in the engine that is applying heat to the throttle body, and that we can disconnect it?

 

Yes, Rev. there is a coolant flow through the throttle body housing which you can bypass pretty safely in your climate.

 

Well heck! I didn't know that. I need to go look. Although with the airplane carbs the knob is actually allowing warm air from around the engine to go straight into the carb. I would guess that the air passing through a warmed throttle body wouldn't have time to gain a significant amount of heat.

 

Correct- it's a matter of physics. Compare the huge volume of air (measurable as mass flow in lbs per sec) versus the BTUs of differential heat available in walls of the throttle body. I bet it would be hard to even measure the increase.

Pre-emissions carbureted small block GM engines had a hot air passage that ran through the inside of the intake manifold to promote anti icing properties, later engines pre-heated the air entering the air filter assembly. Neither increased the air temp enough to affect performance.

 

+1 on that.

In previous generations the effect was twofold. Cooler intake charge because the intake was in the engine compartment, cooler fuel because the carburetor bowl was subject to less heat soak, and cooler combustion chamber because the coolant was cooler.

In current designs, the intake air comes from outside of the engine bay, but it remains true that the combustion chamber is cooler and the fuel is less subject to heat soak.

Hoses, particularly the dreaded under supercharger hoses will live longer when subjected to less heat.

Bubba wasn't so stupid after all.

 

But we're talking about lower thermostat settings here............

 

As so often happens, the thread has diverged.