Mike Murphy

I don't think the Cats would be affected. Cats temperature is largely a function of exhaust temperature, which is mostly related to throttle position: the more gas you give you engine, the more heat will come out of the headers. Cats gets hot even on cold engines by having a secondary air pump inject air into the exhaust to cause exhaust temps to rise even when the engine is cold, and it only runs for a few mins. Once the engine has run for 5-8 mins, the cats are well hot by then. Driving your car soon after you start your engine is the best way to get the Cats up to temp. I don't see how a low temp tstat would negatively affect cats.

Mike Murphy

Correct. A thermostat's main job is for warmup.

Too many people are overthinking this.

Having a low temp stat is like adding overdraft protection on your bank account. There's nothing you can do if someone withdrawals more money than you have beyond a certain limit, but it does give you better margin of protection, which can often mean more time before temps hit that limit.

Example: if the ideal engine temp is 210F, and you want to perform a mountain climb. You start at 180F off the highway and by the time you reach the mountain top, you're at 230F. Doing the same using a low temp tstat means you might actually only hit 220F because your starting water temps are 170 instead. Keep climbing and you will still hit 230F, but you started off cooler, which gives you better margin.

cvtbenhogan

I'll probably put a low tsat when I do the water pump. Ain't thrilled by the longer warm up time though. It's too long already.

Bruce In Philly

Exactly..... this is why I haven't put in a lower temp thermostat while I like the idea of slow thermal transitions. There are many circumstances over the last few years where I was parking my 2009 C2S outside in the winter..... knocked the snow off.... drove through a few neighborhoods, then have to hit the Interstate. Slower warmup will not work for me.

BTW, my objective is to keep this car until it blows up.... or the economics of repair outweigh another purchase.... so... small things that may improve longevity are appealing to me. I got 197K miles out of my 2000 Boxster S until the 2nd engine blew up...... I still miss that car.... so when I get something I like, I keep it.

Peace
Bruce in Philly

Petza914

Thermostats in the cooling system have absolutely nothing to do with catalytic converter warm up or temperatures. That's completely a function of the combustion process in the cylinders and that hot gas going directly out through the headers to the cats. The reason you want to drive off to warm the car and cats is to actually use the extra fuel the DME is injecting into the motor to warm the cats faster than they otherwise would, solely for pollution compliance with fewer hydrocarbons being released to the atmosphere sooner.

Theoretically, as Wayne profisizes, no thermostat would make for the most gradual of warm ups, but it would take forever to or the car to achieve proper operating temperature, and in the winter, might never get there, so you need a thermostat, and from the hundreds of motors that Flat6 has seen and rebuilt, the 160 degree thermostat provides the right balance of acceptable warm-up time and may help to eliminate bore scoring.

The LTT does not result in any codes from the cooling system or the cats and the 997s do not need to be programmed for which thermostat is in the car. Between my 2 997s, I've been running the LTT for about 5 years without any issues.

mikeson

I don't get this for daily driver.
Isn't it better you run warmed up engine? then isn't it better to warm up faster?

Low temp tsat takes longer warm up the engine, right?

Mike Murphy

It doesn't take longer to warm up to 160. Only to get from 160 to 180 or more. So, when people are noticing longer warmup times, really what they are saying is it takes longer to go from warm to fully hot.

lowbee

True but what you may have overlooked is this

And the above has been observed and confirmed by more than a few people even Hartech (UK) and Flat6 ....

so if you believe your OE 180 Tstat is working right, then you don't need this...

Petza914

Yes, and aside from the points that lowbee and murphyslaw make (which are good ones BTW), in motors that weren't having the occasional occurrence of bore scoring, that would be the case, but with both the 997.1 & 997.2 engines showing bore scoring that looks to be caused by different metals having different coefficients of expansion when exposed to the heat of the combustion process going from a cold motor to a warm one, and in a motor with tight tolerances to begin with, having the motor do a more gradual warm up by the thermostat allowing for earlier coolant flow seems like a good preventative scenario.

If we start seeing scored bores in motors where people are running the LTT and have owned their cars for a year or so and follow proper drive off and warm up procedures, then we'll know the LTT doesn't help with that, but until then, it's a hypothesis that makes sense to me and one I'll stick with for my 2 cars.

mbatarga

The mechanic that did my PPI suggested staying with the stock tstat when I did my water pump/tstat/reservoir tank replacement a few months ago. It delays warm up period and doesn't alter normal operation temperature. Certainly doesn't make the engine/oil run cooler.

Petza914

Yup, the whole point is to delay or prolong the warm-up period.

Bruce In Philly

Not true per the original poster of this thread. Note he did something shocking.... he installed one and reported real results.... maybe we should ban him for such heresy as counting horse's teeth.

Given that our cars are sports cars and should be designed to handle hard, heat generating use, it is no suprise that the cooling system can whisk away large amounts of energy....... it has been supposed here as fact, maybe not so, that when your car is up and running.... the factory thermostat is full open. It may not be.

It is very possible that the cooling system must be restricted (via 180 thermostat) to get the engine up to 180 degrees due to the large cooling capaicty of the system. Therefore, it is no surprise that putting in a 160 stat will lower the car's normal operating tempuatre. Note I said normal..... put the car on a track or drive it hard, and the OP may see higher temps.

BTW, my Ford engineer friend noted that given an engine design, there is an optimal temperature for efficiency.... and now emissions are in that calculation... Target temps may not be set for longevity but other objectives so these lower temp thermostats may actuall be good for your car beyond bore scoring.

Peace
Bruce in Philly

Petza914

Got some new data points from my 1 hour drive home from the airport the other day in my silver supercharged 997.1. This car runs DT40, K&N filter, MantisSport Deep Sump, and has front radiator as part of the SC kit.

Outside temp was 93 degrees with high South Carolina summer humidity. Once warmed up, I was running 85-90 on the highway with some bursts a bit higher (had a modified Challenger come up I had to deal with). Oil temp got up as high as 230 degrees and at anything above 2,000 rpm, oil pressure was at 5 bar. Above idle but below 2,000 RPM it was at 3.5-4 bar and at idle, 2.5 bar. Once I slowed down to around 70 MPH, oil temp started to fall back closer to 215/220 and oil pressure stayed the same as previously mentioned. Direct info from Joe Gibbs Racing told me DT40 is good to 300 degrees and track cars see oil temps above 250 all the time, so I don't worry about oil temps in this range as long as the pressure is still strong.

Iceter

One person's data point does not make a case. A thermostat does not affect the normal operating temperature of an engine, except in exceptionally cold weather, where it affects the low end of the range. Once a correctly-functioning thermostat is open, it is open. It doesn't matter if it is a 180, a 160 or a 100 degree Tstat. Once the Tstat is fully open, the temperature you see on the gauge is dictated only by the thermal efficiency of the car's entire cooling system. The Tstat is out of the equation.

This isn't my opinion. This is fact.

I will not argue the benefits of a 160 Tstat towards eliminating bore scoring. Engine builders on this forum claim the slowed warming effect of the 160 keeps one or two of the cylinders from heating up too fast and scoring. That may or may not be the case. Keep in mind that one of those engine builders recently stated on a thread on this forum that installing a 160 and going with thicker oil will reduce your chances of bore scoring but increase your chances of crank failure and so he recommends a "pre-emptive" engine rebuild at 85k miles. To me, that sounds ridiculous.

But, whether or not the 160 does reduce your chances of bore scoring in this particular engine, it does not, and never will, reduce your normal operating temperature. Thermostats don't work that way. 180 or 160, once they're open, they do exactly the same thing--nothing. They sit there and flow the exact same amount of coolant at the exact same rate.

German888

I agree with most of what is said here but would point out a critical assumption bolded below. A recent test I did with my old 180 and new 160 revealed a poorly functioning unit that was not completely open even after 200 degrees and may have never been fully opening which certainly would affect oil temps regardless of run time. I'm betting the difference people are reporting to oil temps after installing a new properly functioning 160 is tied to the original 180 not working at 100%.