I really don’t think I get “testy” with anyone………. That said, after I got my BS degree, I worked for Ford in their R&D operations for several years, developing & testing engine components. Later, I spent several years with one of the major oil companies developing and testing new lubricants. I then went back to school for my MBA and joined an automotive supplier, where I eventually rose (sank) to VP of Sales and Marketing. Eventually, I became tired of the corporate life and went out on my own, setting up my own shop……………

I appreciate the explanation. It's interesting info.

- Are there UOA results for both the standard and low temp t-stat for comparison?

- What your explaining on the t-stat operation is that the engine won't run hotter than the fully opening temperature during cruising, which is essentially steady state at 72-74F. Keeping everything else equal, the water temp should go up linearly with air temp, so at 84F, the water will be 10F hotter, right? What temperature do the fans come on? Does the car run at a temperature independent of the t-stat at non-steady state like at an autocross or mountain road driving?

I definitely am not in this for a p*ssing contest, just to understand what's going on. I was an SAE member as well when I had my papers published there in in-cylinder flow simulation. I'm haven't been working in the auto industry for about 10 years so the membership expired a long time ago.

OK, you went over to the dark side, getting that MBA.

Now, I have no respect for you, or for me, as I have one too! :D

..................................................

Yeah, but you eat better on the "dark side".....................

There is another possible explanation that has been overlooked as to why Porsche chose a 180 T-stat for their cars ... creature comfort.

Germany and most of Europe has long cold winters and a car with a 180 T-stat has a cabin heater that ROCKS. That extra 20F makes a big difference in keeping the cabin toasty on a cold winter evening. I believe many German cars; Porsche, VW, Audi, BMW, MBZ choose a higher Tstat for this reason. One of the many compromises a car company must make when designing cars for the masses. Since a GT3 is primarily designed for motorsport and not winter driving I suspect the 160F T-stat made more sense here.

When choosing a T-stat for your car consider your typical usage. If you do a lot of winter driving the 180 might be the right one for you. If your interest is Summer driving and motorsport than a 160 would be a good choice.

I have no MBA, SAE, just a measly BA in business. I have no documentation or internal memos to support this theory. Just a basic understanding of cooling systems, an observation that most German cars have a higher T-stat, and that their cabin heaters are "the best" when it is cold outside.

Well, as someone that lives where 0F in not unusual, I can assure you that a 160 stat delivers plenty of winter heat.........................

Yes it does. And a 180 T-stat produces 20F more heat on a cold day. As i said, just an observation not absolute Porsche design philosophy.

Somehow, I don't see what that would be an issue in Cucamonga CA :cool:

Likely. On the other hand, I am about to get my doctorate, so I am back to living like a pauper.

:D

If I put in a lower thermostat, am I not just making my cooling fans run more? If so, doesn't the engine have to work just a bit harder to run the cooling fans.

If a tree falls in the forest and no one hears it ..............................

:D

"If you lead a horse to water, he won't drink any; however, if you hold his head under until the bubbles stop coming up............"

It is not an issue in Cucamonga. Although when we spend the weekend in Big Bear (1 hr away) at 7500' elevation and there is 6 ft of snow on the ground with temps in the teens my wife might argue that there is no such thing as "plenty of heat" in the cabin. :)

While you and I may agree that you get plenty of heat with a 160F T-stat and it is probably better for the motor in the long run I am sure all those fine German engineers had a plan when they collectively installed 180-200F T-stats into most modern German cars. My father was an engineer and he didn't tie his shoes in the morning without a plan. Better heater performance is just one plausible explanation. There are many others. Until someone pipes up who was actually in the room when these decisions were made we may never know for sure what they were thinking.

Going way back in this thread; using higher temp thermostats has always been a cheap way to ring a little more emission compliance out of water cooled engines. Literally every car manufacturer out there, European, US and Japanese has used this as a low cost route to compliance. But, as previously noted, it tends to kill volumetric efficiency. Lowering the coolant temp improves the volumetric efficiency and the band width of the DME allows the A/F ratio to correct and still use more timing (with in the DME algorithm limits). Running the engine hotter is not better for the engine, it is worse; but because the OEM has to warranty the emissions system to work for 80,000 miles (Federal mandate), they set it up to make it easier to pass when the engine had a lot of miles on it. But, because the engine warranty lapsed much sooner, if the engine fails, it is not the OEM's problem, it is yours................ So the bean counters over rule the engineers, you get a less efficient engine with a potential for premature breakage. And where the bean counters have less sway, say with the GT2 or the RSR cars, and max performance is the target, you find 160F thermostats as factory parts……..

I'm sure Jake and Charles get a good chuckle when they read these types of posts.

Me, I'm looking for the next controversial engine mod I can do to my Box S. Wish I had more time to drive it (it hasn't been out of the garage since beginning of June; and it's summer!)

Well, I do know (not to “put words in his mouth”) that Jake (in particular) gets agita when he takes his time and money to research and document improvements for the M96, and then posters tell him he is wrong (with little or no support for their position), or that his ideas lack merit because “Porsche knows more than he does”………….. I just hope he and Charles Navarro don’t get fed up with the incredible “backlash” their ideas and products seem to get online and give up. No one else is trying to address some of the issues they have undertaken…………..people should really take the time to listen to what they are saying and at least attempt to understand why they are moving in the direction they have chosen. There aren’t many other proven aftermarket vendors out there for the M96 engine……………

JFP - I agree with you whole heartedly regarding Raby & LN Engineering. While I've only been a Porsche owner for 12 months or so, I appreciate their engineering and commitment to the "cause" of improving the M96 engine.
That's why I'm investing in the low temp thermostat and having it sent out to Australia.
Great tech article though by all participants......

I've seen on this board and others that they're both more than accommodating and forthright with answers to questions of why they make the changes that they do, very professional.

Is there a comparison b/w the UOA of a low and high temp t-stats, in general?

OK, so the cooling system is capable of dropping the water temp below the opening temp of the t-stat. So on average, the car will run cooler when you mix in all driving conditions. Is there any difference b/w 2 and 3 radiator cars?

It was mentioned earlier that there are hot spots in the engine. Do you know how these were identified and monitored? I would imagine they have an instrumented engine out there somewhere?

I personally tested the low temp thermostat in the dead of winter, and I can tell you, there were few days with wind chill at -34 F and the car warmed up very fast AND there was plenty of heat. There is a separate set of lines that go to the heater core and are being fed water regardless of thermostat state, so you will receive heat at the same time regardless of what thermostat you have.

At speed, even on a hot day, a 15 deg F drop in operating temp is normal on a car without a center radiator. That figure can be higher, up to about 20+ deg F with the center radiator.

But, to keep the coolant temperature down airflow is needed across the radiators. So if you're in traffic, coolant temp will creep up to the temperature where and when the radiator fans kick in, so at or around 205-210F. With the A/C running, they kick in harder, faster. Experienced this myself just yesterday at the Chicago PCA Autox.

I run instrumentation on my wife's Boxster and i've seen at times upwards of a 15-20 deg F difference in coolant temperature between the gauge and what the OBDII metrics read. I've also noticed the hotter the engine gets, the larger the variation. Just like the OBDII shows the speedometer is 6 mph off at 60 mph!

If I were to take a stab at why these cars come with such high thermostats is that they are trying to get the oil to run hotter, at or above 210F, to get the moisture out of the oil. By doing so, there is less acid formation and the oil retains its TBN reserve longer, allowing for longer drain intervals (as evidenced by Porsche's desire for initial 24000 mi target drain intervals). My own observations have shown that oil temperature is 10-15F over that of the coolant temperature.

Although I don't think this is the reason behind the high thermostat opening temp, additionally, having the oil hotter also reduces the viscosity, which technically would slightly improve fuel economy. But the flip side to that is by running cooler, you are increasing the volumetric efficiency of the engine, which makes power more efficiently.

Coolant temperature does not go up (or down) linearly with ambient air temperature, unlike cylinder head temperatures on an aircooled Porsche. The best explanation of what increased ambient air temps do on a watercooled Porsche is increase the amount of time it takes to lower the coolant temperature back to its initial point. The colder the day, the faster (and closer) the coolant temp can get to the point where it stabilizes. On a really cold day, that's 172F or when it's bloody hot, around 178F, for the low temp tstat, on one of Jake's 2.5->2.9 engines running 12.8:1 CR on pump 93.

Did I answer everyone's questions?