Who sells a colder thermostat for the 07/08 STR? I guess it's different than the 03/06. Eurotoys sells them for 03/06 but say 07/08 are different design...

 

Attempting to reduce coolant temps will not increase performance- old myth.

 

Not necessarily looking for increase in performance, just not happy with where the car runs with OEM t-stat. But cooler is always better in summer months which is the only time I drive the car.

 

Contrary to another myth- cooler is not better.

If your car is not running at the OEM design temps, a thermostat of a different rating will not fix the root problem.

 

Well maybe that's the case! Car is running about 200 - 205.... Also gauge is slightly above halfway point. Perhaps just a new OEM stat will be the cure!

 

The gauges don't seem accurate apart from cold/overheat. PCM will report errors if out of range. Colder is not better but it's your car so fit whatever you like.

 

The only time a car overheats WRT coolant is if the system pukes water. The hotter the motor , the more power it produces.
Where you will find big gains is decreasing the air/fuel intake charge temp , the lower you can get this , the more fuel you can add and thus make more power.
So the rule is motor hot , intake charge chilled...

 

Quite.

Which is why there are existing threads offering detailed ideas of what & how.

 

Just as a matter of interest the Jaguar EPC shows that the 2003-2006 part number for the thermostat supercedes to the 2007-08 part number.

 

I believe that's about what Jag designed the engine to run at.

 

Also interesting---my Service Manual says the t/stat for the SC engine begins opening at
84C(183F)and should be fully open at 98C(208F).


For the NA 4.2 t/stat begins opening at 86C-92C(190F-198F) and fully open at 102C(216F).

 

Thermostats open at the degree that is specified on the type, so a 165* thermostat will open at 165* and a 180* thermostat will open at 180*. Therefore this does nothing for performance but let the thermostat open earlier but does not sustain that temperature while operating (I don't know how it could?).

If you want cooler temps and more performance, experiment with a high flow intercoolers pump instead. Search my thread from about a month ago on the topic. I haven't installed mine yet but others have with good luck.

 

It could lower the coolant temp to the setting of thermostat IF (big if) the heat rejection capabilities of the rad were there.

No idea why someone would want to do that............

 

A 80*C thermostat is supposed to be fully open at 92*C given the 12*C differential between closed and fully open in standard designs.

Reported results using a 80*C thermostat in Jaguar 4.0L SC engines are that in stop and go driving the engine hovers at 195*F and a few degrees lower for highway cruising.

The ecu turns the fans on a 196*F and turns them off at 191*F. That hysteresis avoids constantly cycling the fan.

That being the case, staying just below 196*F avoids running the fan all the time.

The ecu still goes into closed loop because that transition is made at approximately 170*F.

The cooler temps are also make life easier on the hoses ... especially after turning the key off after a good run.

Who says so? Gates ... the hose manufacturer.

It also lessens the severity of dexcool gel. When dexcool is overheated it's precipitates form a gel. The overheating happens at hot spots where the coolant is superheated and vaporises.

As a matter of fact, most of the plastic materials under the hood ought to be a bit happier.

BTW, from the Jaguar engine course manual as opposed to any other source, the following passage appears in the technical theory portion:

Notice that the anticipated operational range of the thermostat fully includes a 80 *C thermostat in that statement.

And no, the sky isn't going to fall down if the operating temperature is lowered those few degrees.

In fact, if the statement from the manual is parsed correctly, using a 80 *C thermostat still falls within the published parameters.

++

 

Wow! Finally someone not being NEGATIVE, thanks Plums!!!

 

It's neither negative nor positive. It's a bunch of info that doesn't directly apply to the type R.

There are no known issues with the cooling system hoses on S-types so an effort to lower the coolant temps will be an attempt to fix something that's not broken.

There are also no known issues with coolant turning to gel on these cars.

Some people like to predict that the sky is always on the verge of falling.

 

It's all personal preference and people base things on experience! Things they have seen, done, tried, etc... One person says yay and another says nay! To each his own!

 

That's a blatant falsehood.

1) the numbers apply equally to a type R as to a XJR

2) the Jaguar engine manual applies to all models ... including the type R

3) rubber is rubber and Gates did not issue a special exemption for Jaguar in their document

4) dexcool is dexcool and Jaguar does not escape the laws of physics or chemistry

In general, general knowledge applies to all vehicles ... Jaguar is not a special little world where known behaviour is suddenly suspended.

However, if someone has no experience with the supercharged variant, nor an interest in improvements, it would be best if they stood aside.

 

The hottest appears to be after turning engine off. Will it help at all with that?

I've not found the R to run the engine fan at all after engine off, so no help there.

 

To certain degree yes. But bad advice is bad advice. Do your cooling fans run contentiously?