I won't do it justice but you guys should read the guides and information on low temp thermostats and the cooling system for bore scoring from Hartech who are a UK based specialist.

Was that in Phoenix driving thru city streets driving in traffic? My 2001 S and my son's S couldn't stay at that temp with new water pumps, thermostats, fluid and clean radiators. Maybe coasting down hill.

I added low temp thermostat when I replaced the water pump and engine mount. Also added S center radiator and a 996 front bumper. Noticed cooler/more stable temps. Added the 996 bumper not 993 as previously stated at same time as S radiator so cant say which change made more difference. Also plan on adding a GT3 style top bumper vent for added look.

Oh, this is interesting. Is the 993 front bumper a direct plug and play? If so, would you have pictures of your vehicle that can be shared on the forum? I didn't know or think this was possible. Did the temperatures end up being cooler based on the bumper change? Or was this a direct result of the centre radiator?

Hi JFP. OK. You;re one of those go-to guys... and I would appreciate some clarification.

The LTT doesn't cause the engine to run cooler... it just serves to allow coolant to flow sooner than a stock thermostat. The engine is going to get as hot as it would even if there were a stock thermostat installed. So... low temp or stock thermostat the engine is going to hit the same operating temp. No two ways around that fact. Please tell me I'm wrong... and tell me why. I really want to know.

Now... installing the S cooler in a non-S car... more oil cooling ability.. that I'll buy.

In advance, thank you for your consideration.

OK, that's easy, your wrong. The thermostat in the engine functions just like the thermostat in your house; it throttles coolant flow to maintain proximity to its rated temperature. If your cooling system did not have the excess heat transfer capacity in the radiators to shed sufficient heat, it would never cool back down running after getting stuck in traffic; but that is not what happens, it does cool back down until the thermostat takes over flow control again. The internet "old wives tale" about thermostats not controlling steady state temperatures has been needlessly confusing people for millennia. One of the easiest ways to prove my conjecture is to totally leave out the thermostat; if your idea was correct, the engine would still get up to 210-220 F; but that is not what happens. Instead, it struggles to get above 120-140 F under the same operating conditions because coolant is circulating too fast and the radiators are pulling out the heat faster than the engine can produce it.

Thermostats in your engine serve a vital function, just like the one on the wall in your home, without them things would get rather uncomfortable.

So what you're saying is that the cooling system (thermostat open, coolant flowing) has WAAAY more capacity to keep the engine cool than it really needs to. So, in a way, the thermostat is also designed to keep the engine from running TOO cool. Correct?

What I don't understand is how the LTT will (as you say) cause the engine to "actually warm up quicker."

If cars did not have excess heat transfer capacity in the radiators, life would be rather different: You would daily see cars on the side of the road with their hoods open while the driver's waited for them to cool off. The radiators have more heat transfer capacity than is needed to maintain a given "steady state" operating temperature, other wise you could not get the car to cool back down once it got moving after being stuck in traffic, and yes, the thermostat is a throttling device to limit coolant flow to maintain its rated temperature. A common comment among customers who we have installed a third radiator for is that the car seems to take longer to get hot on the track, and cool down quicker once off the track; because the third radiator has added even more heat transfer capacity.

The quicker warm up is a perception more than a reality created by the stat going to full flow sooner (at a lower temperature); many customers comment they get heat quicker in the winter, this is why they see it as warming up quicker. If you actually tracked and graphed the rate of thermal rise of the engine with the LTT and OEM stats, it would actually remain unchanged until the low temp stat opened, after which the LTT stat engine would actually warm up slower to its steady state temperature due to increased coolant flow. But drivers regularly comment about faster warm ups, which is a dominant perception about the LTT.

If I have a LTT in, and it fully is open at ~160 degrees... water will circulate sooner... and will sooner reach operating temperature ~210 degrees. Assuming no city driving... the temperature should remain at ~210 degrees.

If I have in a stock thermostat... and it fully is open at ~210 degrees... water will circulate later... and will later reach operating temperature ~210 degrees. Assuming no city driving... the temperature should remain at ~210 degrees.

By later I mean like around 5 minutes.

Under what conditions would the/either thermostat, while the car is running/driven, open and close according to the temperature? If the car, with either thermo, is at ~210 degrees... the thermo will remain in the open position. Highly it is unlikely, while driving, that the coolant temperature will hit the ~160 degree mark.

Is that correct? Believe me... I want it to "click".

Would it be prudent to install a coolant temperature guage (aftermarket)? If affirmative, which one would YOU recommend?

Thank you, JFP. :)

Here's were your thought train goes off the rails:

When the LTT engine reaches its opening temperature, it begins to open partially and waits to see what the circulating coolant temp is, it does not suddenly pop open or slam closed, it moves in steps controlled by the coolant temps it sees. If it begins to drop (say the outside air temp is 50 F), the stat closes partially to bring it back up to its design temp. This is the throttling action. Eventually the engine will reach what is called "steady state" or some level where it plateaus (lets say you are driving at 40 MPH on an open road on a pleasant spring day). The OEM stat will go steady state on a 68 F outside temp day at around 210-220 F. The LTT under the same conditions will go stead state around 170-175 F.

One of the biggest problems in seeing this is the poor quality of the dash temperature displays in these cars; they are both woefully inaccurate (coolant is actually at 215 F while the display says around 180) and non linear (the gauge sweep is not in even increments). As such, they are little more than idiot lights that move. On vehicles with after market temp gauges, the difference is obvious, with the OEM display, the needle movement difference is tiny, leading people to reach the same conclusion you have: There is no difference, which is not correct.

On fully instrumented engines, we see 170-180 F steady state readings on the coolant, and even more important, drops of 25-35 F (or more) in the oil temps with just the change of the stat. That is huge.

We like the MotoRad aftermarket stat, which is what LN sells as their product; well made and consistent.

I've returned to the rails. Thank you for that revealing narrative!

Inquiring minds want to know

This is keeping me up at night. :D

IRRC, the LTT is 160 and the OET is 180. That's a 20 degree difference.

Why/how would the actual temps be 30-35 degrees different between the two?

Just trying to understand better. Thanks.

You are looking at the OPENING temperatures, not the steady state temp, which is where the car actually settles while running. The OEM thermostat goes steady state at 210-220 F, the lower temp unit at 170-175 F.

LN or Jake Raby have tested teh stock thermostat to not fully open until about 210 degrees, whereas their LT unit is fully open by about 185, so roughly 25 degrees.

OK. Makes sense. Thank you both.

Oh, that's interesting. Is it a direct fit?

That looks like a 996 bumper to me.