Low temp thermostats....

[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...................