Low temp thermostats....

[JFP in PA]

Originally Posted by blue2000s

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.

Well, we've been running the LN stat in six different customer's cars for over a year now, regularly checking a variety of parameters, including running full UOA's, and the oils (2,500 to 10,000 miles between changes) continue to look very good. And, by-the-by, the normal oil operational temps on these cars, even with the LN stat, are typically well over 200F.............the major difference being that with the low temp stat, they are staying 20-25F cooler than they were with the OEM stat………………


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

[Brucelee]

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.

[JFP in PA]

Originally Posted by Brucelee

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.

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

[Brucelee]

Originally Posted by JFP in PA

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

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

Just asking, don't get testy on me.

[JFP in PA]

Originally Posted by Brucelee

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……………

[Brucelee]

Originally Posted by JFP in PA

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……………

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!

[JFP in PA]

Originally Posted by Brucelee

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!

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

[blue2000s]

Originally Posted by JFP in PA

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 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.

[JFP in PA]

Originally Posted by blue2000s

I appreciate the explanation. It's interesting info.

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

Yes, we have installed several of these stats, including one in my own car, and run UOA's before and after. The actual test results are the property of the car owner's (they paid for them) so I can only provide summary info without their permission. We did not any see evidence of acid formation related issues, and we also did not see increased fuel dilution (another "old wife's tale" about lower the stat temp). In general, the oil looked like it had seen a lot less mileage that it really had, particularly in the cars that get the Hell beat out of them on a regular basis....

- 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?

At any ambient temperature, the "steady state cruise" temp is a function of the ambient temp, air flow, radiator condition, air flow obstruction, etc. etc......as well as the full flow open temp of the stat. As you are an engineer, none of this should be news to you. On a hotter day, in bumper to bumper traffic, or under hard use, a car with the LN stat will still get warm and will eventually cause the fans to kick on (the function of which is controlled by the DME). But, when the increased airflow (either from the fans or movement of the car), the temps drop back down; the major difference is to where they go. In fact, one customer comment is that they notice that their fans do not seem to cycle as much as they did before the change. On my personal car, I saw the coolant temps rise yesterday (while stuck in traffic) to over 215F when the fans kicked in. As soon as I clear the traffic and was back to 65 MPH, the temps dropped back down into the high 170's low 180's range (ambient temps were in the 85F range). Note that I monitor the oil and water temps via a display from an aftermarket data logging system connected to the OBD II port rather than the dash displays, which are notoriously inaccurate and non linear on just about all Porsche models. To address your questions, yes higher ambient temps will result in higher coolant and oil temps, not necessarily in a linear fashion, but they will both be lower than when the OEM stat was used in the same vehicle under the same or similar conditions. When a car equipped with the low temp stat enters an adverse environment (traffic, track usage, etc.), it will start from a lower coolant temp and tend to take longer for the fans to come on, and will cool back down to the lower operating temp once the load condition returns to normal.

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.

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

[blue2000s]

Originally Posted by JFP in PA

Yes, we have installed several of these stats, including one in my own car, and run UOA's before and after. The actual test results are the property of the car owner's (they paid for them) so I can only provide summary info without their permission. We did not any see evidence of acid formation related issues, and we also did not see increased fuel dilution (another "old wife's tale" about lower the stat temp). In general, the oil looked like it had seen a lot less mileage that it really had, particularly in the cars that get the Hell beat out of them on a regular basis....

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

Originally Posted by JFP in PA

At any ambient temperature, the "steady state cruise" temp is a function of the ambient temp, air flow, radiator condition, air flow obstruction, etc. etc......as well as the full flow open temp of the stat. As you are an engineer, none of this should be news to you. On a hotter day, in bumper to bumper traffic, or under hard use, a car with the LN stat will still get warm and will eventually cause the fans to kick on (the function of which is controlled by the DME). But, when the increased airflow (either from the fans or movement of the car), the temps drop back down; the major difference is to where they go. In fact, one customer comment is that they notice that their fans do not seem to cycle as much as they did before the change. On my personal car, I saw the coolant temps rise yesterday (while stuck in traffic) to over 215F when the fans kicked in. As soon as I clear the traffic and was back to 65 MPH, the temps dropped back down into the high 170's low 180's range (ambient temps were in the 85F range). Note that I monitor the oil and water temps via a display from an aftermarket data logging system connected to the OBD II port rather than the dash displays, which are notoriously inaccurate and non linear on just about all Porsche models. To address your questions, yes higher ambient temps will result in higher coolant and oil temps, not necessarily in a linear fashion, but they will both be lower than when the OEM stat was used in the same vehicle under the same or similar conditions. When a car equipped with the low temp stat enters an adverse environment (traffic, track usage, etc.), it will start from a lower coolant temp and tend to take longer for the fans to come on, and will cool back down to the lower operating temp once the load condition returns to normal.

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?

[cnavarro]

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?

[jmatta]

Thanks, Charles. I appreciate all the effort you and Jake have put forth and show it by purchasing your products. Let the sceptics be sceptics; like I really trust what the factory did to butcher these engines, when for minimal dollars, they could have produced them correctly.

Keep up the great work and we'll keep reading and upgrading.

[Topless]

Thank you Charles. Running higher oil temps to eliminate water and then offering long oil drain intervals as a marketing tool is the best explanation I have heard yet for Porsche running 180 T-Stats. Thanks to your research we know this was misguided. Running lower engine temps and changing oil more often has two benefits: The motor runs better and lasts longer. Makes sense to me.

[JFP in PA]

Originally Posted by blue2000s

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?

The only real difference we've seen, and it is a totally subjective observation, is the three radiator cars tend to return to "steady state cruise" temp levels slightly quicker after warming up in traffic. We have seen that on 2.7L equipped with three radiators and the "S" oil cooler as well as on factory "S" cars. The assumption is this comes from the larger amount of surface area from the 3rd radiator adds.

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 first heard about the localized "hot spots" from a Rolex GT team engineer several years back, who attributed them to poor coolant circulation resulting from how the coolant passageways are cast in the M96 style components. As they are capable of running the engines on dyno stands (out of the car), they can measure or use additional instrumentation that is not possible with it in the car. That said, we have used two methods to look at this issue out of curiosity, the first being a hand held non contact infrared pyrometer to measure surface temperatures while the car was being run stationary but with fans blowing cool air over the radiators (to simulate “cruise” conditions), the second was to attach temperature recording strips to various areas of the engine and take the car out for a run, after which the strips are examined. In both cases, multiple areas were noted as reaching higher temps than the coolant had indicated. So it seems real.

This issue, by the by, is not limited to Porsche M96 engines, and is more common than you might imagine. Back when I raced, it was not uncommon to see some really creative "north west passage" external coolant plumbing systems on some domestic engines to get more coolant flow to problem areas. Might not look very pretty, but if it kept you in the race, it was worth it...................

[Topless]

Originally Posted by JFP in PA

This issue, by the by, is not limited to Porsche M96 engines, and is more common than you might imagine. Back when I raced, it was not uncommon to see some really creative "north west passage" external coolant plumbing systems on some domestic engines to get more coolant flow to problem areas. Might not look very pretty, but if it kept you in the race, it was worth it...................

Yep. The Chevy 454 is world renowned for lousy cooling and engine hot spots. Lots of creative engineering is required to keep it cool when building the engine.

[Sputter]

Out of curiosity. Did you find that oil consumption increased with the lower t-stat?