Quote:
Originally Posted by TommyW
I remember when I bought my 911 Twin Turbo the salesman said to keep it below 150 on the test drive.
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By any chance do you recall Porsche’s break-in procedure? I ask because of this story:
https://pcaucr.org/12409/
Quotes:
Perhaps it comes better from a Porsche engineer…I asked “why does Porsche feel it is safe for a new engine to run at nearly full throttle in the factory, while the customer must keep the engine speed to no more than 4,000 RPM for a 2,000 mile (3,200 km) break-in period?”
The engineer replied, “Herr Koop, you do not understand (that I already knew). When we do our engine test, the metals inside the engine never reach the temperatures they would when driven on the street since the test session is fairly short. In other words, the bearings, pistons and cylinders never get a chance to thermally expand to their maximum. Therefore, there is little wear on the moving components.
But when you drive a car on the street, the engine parts expand considerably more because of the heat being generated from the engine running for an extended period of time. No matter how tight the tolerances are, there is always a slight amount of expansion in the material. The moving parts can wear quickly if exposed to excessive heat and not always in a uniform way. We also constantly vary the speed and allow the engine to run at both high and low RPM’s”.
“Porsche wants the engine to break-in slowly, which means it needs to maintain a lower operating temperature (below 4,000 RPM) and to allow all parts to adjust (wear in) within their own thermal expansion parameters. This is also the reason Porsche wants the owner to vary the RPM throughout the break-in period; therefore the engine doesn’t get used to one operating temperature range”.
The take away for me regards heat cycles. During break-in, it seems each heat cycle should be a little more than the last to maximize how the metal parts form fit to each other. Does this pass a reasonable scrutiny test?