I searched this forum before asking and this a small detail. I saw a 20 degree cooler thermostat for the XKR somewhere online. Went to buy it - and can't remember where.
Ideas? Thermostats tend to be universal sizes. Suggesting on finding a cooler thermostat? Thanks.

 

If you have a Car Quest in your area have them search it out for you thru Worldpac. They can tell you what they have available. Or do a search for Ken@britishparts.com

 

There's one at Eurotoysltd.com but it's 13 degrees cooler.

 

Why would you want to make your engine run at the wrong temperature?

 

A motor will run more efficiently, make more power and have less wear and tear at a lower temperature. In a water/air intercooled car this also will lower then intake air temperature via a cooler water going through the Intercooler - with the intake air already is extremely elevated (generally over 100 degrees higher and that causes denotation or engine knock unless the fuel/air ratio is adjusted by the ECU in ways that really cut power.)

The reason they use higher temperature thermostats is NOT for the motor, it is for your interior heater. You can't go TOO cold in a naturally aspired car (all boosted cars have very hot air through the turbo or supercharger - bad) - but for most 140 degrees is the ideal in terms of the motor. 180 thermostats are so your heater can blow hot on super cold days.

A 140 degree thermostat makes it extremely difficult to heat the inside of a car when it's zero degrees outside. At best the air coming out of the heater might be not-cold - but also not hot because the transfer from the little heater radiator is very low.

People up North would hate it. You wouldn't freeze, but you'd really be cold and driving inside a cold car is no fun indeed.

Of course, this doesn't really apply to Florida. So the reason is efficiency, power, lower wear and tear, and the ability to slightly raise boost with the ECU not having to adjust for the higher intake heat as the intercooler then also would be cooler.

 

When in the army, a good few years ago, the armoured vehicled we were driving we were not allowed to move them until the temp. gauge reached 185 deg. f. ...and there were no heater's in them !!!!!
More than that I can't say.

 

Frighteningly incorrect on all counts. Good luck.

 

The Engine Thermostat has nothing to do with the temperature of the coolant flowing through the Intercooler. There is a crossover hose between the 2 loops but there is normally no coolant flow through the hose. The only function of the crossover hose is to make it easier to fill or drain the entire coolant charge.

 

1. If you're right about the Intercooler then you're right. I haven't gotten that much into this XKR, can't find a service manual etc. In the past many turbo cars with water/air intercoolers used the engine coolant water also for the intercooler.

2. Thermostats have to match oil thickness. Speed performance isn't a military vehicle priority. It is the ability to operate in all conditions - from sub freezing to extreme heat. I doubt they were supercharged/turbocharged. And in an odd way might make the point too. Aren't Jaguar thermostats set to not open until 212 degrees, not 185?

Otherwise what I wrote was both accurate and well known for decades - particularly for a boosted motor due to already too high intake air temperature.

 

"Higher coolant temperatures can increase thermal efficiency and reduce emissions, sacrificing performance and longevity. The principle behind lowering coolant temperatures (regardless of application) is that a cooler engine will have higher volumetric efficiency. Lower temperatures will also allow for more timing without detonation since the ECU is capable of changing timing based off of fuel quality and temperature."
http://www.flat6innovations.com/shop...cat=377&page=1




http://www.rpmoutlet.com/mach1stat.htm

* Choose From 160, 180, Or 190 Degree Models

* Stock And Modified Engines Often Show Up To 5 Horsepower Gains From A Cooler Thermostat For Denser Air/Fuel Mixtures

SLP Performance Parts offers these 160 degree C6 Corvette thermostats because these thermostats dramatically reduce operating temperatures, while increasing thermal efficiency and your engine's performance in the process. Racers know that a cooler running engine is a better performing engine. These new C6 Corvette thermostats replace the factory unit, allowing coolant to circulate at lower engine temperatures, keeping the engine cooler.

Install a 160 Degree Corvette Thermostat from LingenfelterPerformance Engineering and your C6 Corvette will perform better. The 160 degree thermostat opens sooner to keep the engine cooler. And a cooler engine produces more power. This thermostat is a direct replacement for the OEM unit, there is no modification required to your engine. Comes complete with rubber sealing ring.

Hot running late model engines often respond to a cooler thermostat by producing more horsepower. Modified engines sometimes run hotter and require more cooling. Mr. Gasket has produced this choice of three temperature level High Performance Thermostats, so that you can dial in just the cooling that is best for your application. Tests on GM engines have shown up a 5 horsepower gain is possible with the 180 degree thermostat. Fits late LS1 engines with separate water neck and thermostat housing. Will fit all LS2, LS6, and LS7 engines."
http://www.mamotorworks.com/corvette...-428-9288.html

From this forum

"Yes the 340.4whp reading was from my XJR.

I actually just installed the low temp thermostat and the results are very good. I am running a 50/50 mix of coolant and distilled water plus a full bottle of water wetter.

Cruising temperature for my coolant prior to the thermostat and coolant change + water wetter was about 200F. Now cruising temperature has gone as low as 182F. Before the change, my car would overheat under extreme load(I assume due to a sticking thermostat) and now, the coolant peaked at 221F under extreme load. This may sound warm, however, the factory thermostat opens at 212F.

I am pleased with the thermostat...installation was a snap!"
https://www.jaguarforums.com/forum/s...d.php?p=168681

From cool-cans to intercoolers, water injectors to cold air induction kits, the value of lowering intake air has been known for decades. Where I'm at with typical 100+ degree days plus having a supercharged motor - increasing intake air temperature over 100 degrees more - anything that lowers intake temperature is a plus. A lower engine temperature is less wear on the motor and allows running thinner oil - also meaning faster oil pressure on starting (over 50% of bearing wear is from motor starting and is why diesel trucks would idle all night long as their high compression particularly takes a toll on bearings when starting). It also takes less oil pump power to pump thinner oil.

There are some folks on this forum that believe any alteration to a Jaguar is mechanically wrong and some militantly so. The percentage seems much higher than for other brands of cars.

 

I'm sorry, but you've been given a tremendous amount of incorrect information regarding the basic functions of internal combustion engines. It is indeed 'well known' but as a multitude of myths or legends and the source for many ill founded inventions that will supposedly extract all the hidden horsepower left on the table by the OEMs.

The false belief that 'cooler is better' gets thrashed constantly over on one of the other non Jag boards I belong to, so this is 'deja vu' all over again. You can beleive what you want and disregard that it defies all laws of physics but I'm sure nothing I can say will sway you one bit. I'll rely on my 31 years of working for an engine OEM to guide me.

 

Mikey--now you've opened the Pandora's box. Follow the circle-jerk that is going on at another thread about how to turn these cars into some Mustang Shelby Cobra for a laugh.

Doug

 

You could reroute your air filter intake opening down to your exhaust manifold and the intercooler could be eliminated and replaced with a straight pipe if you really believe that hotter is better.

 

Check and mate.

I knew you were mixing 'cold air inlet' with 'cold running engine' as soon as you posted the doubletalk from SLP and Lingerfelter.

cold air good, cold engine bad.

 

In the vehicles I'm familiar with, if the engine coolant temp doesn't get above 170F the ECU doesn't register a full warm-up. It stays on a mixture map that is normally rich for cold start and warm-up. If it doesn't make the warm temperature mark it doesn't switch to closed loop mixture control using the O2 sensor. Running "cold" and thereby "rich" and timing advanced you should see a little more power.

OTOH, if you need to get your car smog checked for licensing, too many run cycles without warm-up should set a malfunction code in the ECU that could be troublesome the next time you're at the auto DEQ station for emissions check.

I don't know if the Jag ECU is programmed exactly to this number but likely close. Food for thought, your mileage may vary.

Mike

 

every 10* drop in inlet temp = 1% increase in power and yes does indeed lower the risk of detonation along with being able to use more timing safely.
BMW's new hybrid will run higher temps for cruise, efficiency (MPG) increase while reducing emmissions. it then for more power when needed switches to a lower coolant temp to increase power

 

Higher temperature (in addition to a hot heater for winter) is used for emissions control and fuel economy - not performance or durability.

In old days, if TOO cold the fuel wouldn't atomize - the reason OEM intakes manifolds put a hot-spot in the center for quicker warm up. Performance intakes either shielded the bottom of the intake or raised the center entirely off the motor. Polimer spacers under carbs and even as intake gaskets were/are used specifically to reduce heating of the intake air anyway possible.

A hotter motor also raises under-hood temperatures overall, meaning heating the intake ducting even if a "cold air" setup.

Air temperature too cold is not a factor in a boosted car. Heat is the enemy of a supercharged/turbocharged motor. Engine temperature does affect intake air and combustion chamber temperature - obviously - because that is what the air/fuel mixture is passing through.

There are other minor factors that lead to minor power and life-span benefits. A hotter motor has to run a heavier weight oil - meaning more of a lag getting it into the bearings on start up as an example = particularly if extremely cold out. Oil that functions well at 212 degrees (it will be hotter than that then in the motor itself) is like trying to oil up your bearings with tar at -20. So you go to "winter weight" oil - meaning then too thin at operating temperature as once a motor warms up it doesn't matter how cold the outside air is.

If the oil has to be heavier because of higher operating heat then there also is a larger range of temperature it has to operate in for a hotter motor - meaning thicker when cold or too thin when the motor warms up. The majority of engine bearing wear occurs when starting your motor - the reason you should never fast rev it up when starting particularly if it is very cold outside.

Among the "wish list" of components I'd like to put on (whether I get there or not another matter) is an automatic pre-oiler (accusump) so the motor is never started dry nor oil starved on a long, hard corner. They are not expensive and worth their price in the long run. But there isn't much spare room for extras under the hood nor in ground clearance in an XKR.

Granted the horsepower gain of a lower temperature is nominal - but then so is the cost of a thermostat. Even if it only gained 1 horspower, that still is about the cheapest horsepower you can get. $30 per 1 horsepower? Wish it all was that easy! $6000 = 200 more horsepower? Only in your dreams.

If it reduces any wear on start up, it pays for itself many times over in the long run life of the motor - particularly it's ability to still redline without blowing the motor when past the 100,000 mile mark.

(There are NO emissions or any other kind of inspections where I'm at. No inspection stickers either. Eat your hearts out SoCal guys. That is one reason so many car rental company cars show Florida license plates. A lot of other people figure that out too. Do the police REALLY know you've been in your state for more than 30 days? If your car can't pass and you know someone in Florida, transfer title there. The only maybe inspection is a clerk checking to make sure the VIN is accurate - and usually they don't even need to look at the car unless it's costly or of a questionable nature. It's like classics without a title. Get one from Alabama.)

 

Best share your 'knowledge' of engine thermodynamics with the NASCAR guys. They run their cars at 220+, some run them at 235.

 

nascar engines do not have an issue producing power, they have to have restrictor plates to reduce their power output. they use hotter engines cause they need to have them thermally efficient in regards to fuel consumption. Races can be won or lost with great fuel management. It can be the difference between staying on the track a few more laps instead of pitting for fuel.
DFWX you will have issues kicking on a P0128(coolant temp below threashold) but will only be an issue when it gets cold outside as a colder temp t stat will only open sooner and in most cases will not make the engine run at the temp of the t stat. The engine will only run as hot and cold as the car cooling system will allow. I still believe in a cooler running engine from lower t stat cause it allows for more boost and timing while reducing the the threashold of detonation. When you start tuning you will move away from factory safty margins that are in place for the MASS PUBLIC USE, emmission and economy. You will bump timing up to more agressive values, and lean the engine to power producing level air to fuel ratios. Factory AFRs are notoriously fat since it provides a margin of safty under full power/boost levels.
11.7-12.3afr's are pretty ideal for best power under full throttle. Factory on many cars runs fatter at 10-11.5. this provides fuel cooling and reduced detonation. but not best power. the factory has to tune for emmissions, fuel economy, warranty cost index, insurance concerns, and the public perception of proper driveabilty. Trans shifting is a primary 1. the public wants a smooth almost not perceptive shift. This meens slow, slipping, and torque reduction during shifts(does this by actually shutting of the injecotrs at shift point, if you have an afr gauge hooked up you will see this at shifts cause the afr maxes lean) all this to give the public what they percieve to be a great shifting transmssion.
Problem is for a auto enthusiast looking to the performance end. It meens a slower car and a trans that wont last as long as it could if there was less slipping going on during shifts.....
ok Im done time to go to church, bye

 

It's 10 degree F reduction in air inlet temp. = 1% power increase, not 100.