Low temp thermostats....
 

Has anyone fitted a Raby Flat6 low temperature thermostat?
I've just ordered one and will replace my 8 year old original thermostat when I change the coolant.
Any thoughts on how your engine now operates (quicker warm up) or any apparent differences to the original 'stat.....

I recenty replaced mine with the LN part on my '02 S. Haven't drivin it enough to give feedback, but I trust what Charles and Jake state (plus the turbos and GT3s all came with low temp stats)...certainly appears to run cooler from the gauge.

I needed a coolant flush anyway; replaced with Porsche OEM coolant....car has 16k miles.

I once did this on my 87 Camaro. I went from a 220 thermostat to a 180 thermostat and it cardoned up the heads/valves really bad. What temp is stock on the Boxstrer and what temp are you wanting to go to?

-Steve

According to Charles and the LN website, the stock t-stat starts to open at 186* and doesn't fully open until 210 or so. This creates some real hot pockets within the engine itself. The low temp t-stat starts to open around 166* and is fully open by 184*, IIRC. Lower coolant temp equates to lower oil temp, which in the long run, could save your engine.

I live in the sub tropics - something like Florida I suspect - where it rarely drops below 5 deg C on a winter night while summer temps are around the mid to high 30 deg C. Considering the M96 engine runs hot out of the box, I will try the low temp thermostat and report any change (if any) to the daily running characteristics.
But I am looking more to the long term reliability more than anything - new coolant & thermostat coupled with 5000 mile oil & filter changes (5W40 Shell Ultra synthetic) hopefully will do the trick.....
I've a lot of money tied up in my Boxster S (they cost about 2 to 2.5 times more here than the US) so I'm hoping the Raby/LN Engineering boys know their stuff.

Engines are designed with specific running tolerances in mind. These tolerances are dependent on certain material temperatures. If the temperatures are different, clearances and pressures in the nominal running state are not the same as what the designers had in mind. This will influence things like friction, oil consumption, combustion efficiency, fuel consumption, and oil pressure.

This is why a thermostat that works for one engine, like the GT3, may not be the best answer for another.

I don't know if lowering the water operating temp in the M96 is beneficial or not, but I do know that it's not what Porsche considered optimal when designing the engine.

It's been my experience that a cooler thermostat does nothing once it's past it's opening point. If your stuck in 110f traffic your going to heat up to the same point regardless off when your thermostat starts to open.

Regards, PK

A good point, the thermostat controls when the water starts to flow through the radiator, but the fans come on at the same temp as always and the radiators haven't changed.

"I don't know if lowering the water operating temp in the M96 is beneficial or not, but I do know that it's not what Porsche considered optimal when designing the engine."

I'm sure Porsche took all optimal points into consideration when designing the M96 engine...like all the other weak points designed into it. I trust the "real world" experience of Charles and Jake over the factory hype and coverup. I wish for my engine to last and will do everything I can to make it do so.

Don't you think Porsche tests their cars on the road extensively before releasing them? I saw a row of 996 Turbos outside of Vail about 6 months before the car was released.

I appreciate what Jake and Charles doing too. And I'm not saying the thermostat is a bad thing, but I do know it's a change from the way the design was intended.

OK, let's put this one to bed: The LN thermostat will lower the point at which the coolant flow starts by about ~25 F. Considering that the dash gauge is inaccurate as Hell (when it reads between the "8" and "0" on the "180", the car is actually at about 205-210F), dropping the full flow point allows the engine to run (steady state cruise speeds) in the mid to high 170's. Considering that the M96 engine has a significant number of "hot spots" (places with the cooling system where flow restrictions cause much higher than average coolant temps), and that these engines use a laminar flow oil to water oil cooler to keep the oil temp under control, reducing the coolant temps by this amount significantly lowers average oil operational temps, usually by 20F or more. That alone is huge in protecting the engine, regardless of what oil you run.

So (from practical testing and longer term running experience) here's what you get:

• Significantly lower average coolant temps.

• Significantly lower oil temps and longer oil life.

Here's what you don't get:

• Problems.......You still have plenty of heat in cold (0F) ambient temps, no impact on the emissions system (no codes, no inspection rejects, etc.)

I really fail to understand why so many people balk at this concept..........

I dont' see how this puts anything to bed.

Lower oil temperatures aren't always a good thing and the lower temperature alters expected operating tolerances. The designers didn't care what the gauge read when they were designing the engine. They didn't use that gauge so it's really not relevant.

But like was stated above, it's really just changing when the radiators start to see flow, extending the warm-up time. The engine will run to the same temperature it would have anyway eventually.

Actually, you are wrong about lowering oil temps; it is one of the most critical things you can do to extend engine life. And in this case, more than likely the designers were overruled by the accountants in the OEM configuration; both the coolant and oil run very hot the way the cars are delivered………….



It doesn't, but feel free to believe whatever you wish..................

Actually, I've read a study that found low temperature operation can form acids in motor oils, and high temperatures can cause oxidation. There is an optimal temperature where both effects are minimized at about 90C, or 194F. So there seems to be a "too low" range and a "too high" range for optimum oil longevity. I don't believe I'm wrong at all, but I'd be happy to be educated on the subject.

I'd also like to understand from you how an engine that runs the coolant in the 200F range under steady state would notice the difference between a thermostat that opens at 160 vs one that opens at 180F.

Simple, actually, the stat controls the minimum engine temp as well as at what temp the cooling system has full flow (stats open gradually in response to temp, not all at once). The LN stat is at full flow in the low 170’s, while the OEM unit does not see full flow until nearly 210 in most cars. As the result, a car with the OEM stat will run (steady state cruise on a 72-74F ambient day) about 210-215. The same car (and day) with the LN stat, the car cruises at 177-179F coolant, and the oil temp dropped over 20F as well. Tiptronic equipped cars also saw a concomitant drop in their ATF temps as well. Because higher engine operating temps are focused on emissions, not performance; lowering the operational temps improves volumetric efficiencies, not unlike using a cold air intake to improve charge density. A cooler engine also allows the DME to use more timing advance without detonation issues; which is an additional benefit to those running remapped DME’s. On Charles Navarro’s otherwise stock base (Tiptronic) Boxster, changing the thermostat from the OEM to the 160 netted an increase of 5 HP and about 4 Lb Ft. of torque at the wheels during back to back dyno runs using 93 octane fuel………volumetric efficiency does matter

I doubt you two will get into agreement so be careful not to escalate.

If there is an engine engineer around, he MIGHT be able to address this.

For what it is worth, unless the engine is showing signs of overheating, personally, I would stick with the stock thermo temp.

Invest the time and money in Red Line oil.

Which of course, starts another argument.

:D

I am a life-long SAE member, does that count?

I'm not sure
 

I'd want to be citing the Porsche engine designers intent/knowledge as the reason for not changing the thermostat's characteristics.

After all these are the same people who brought you slipped sleeves, d-chunks, IMS and RMS problems, not to mention filler caps that went through how many revisions, AOSs that went through how many...I could go on and on.

Mike, while you are talking to them, also ask them what kind of thermostat they put in the GT2/GT3 and RSR cars.......................you might be surprised!

Don't know. What is your specialty???? Engines design, etc.

Just asking, don't get testy on me.

:)

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?