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Old 12-01-2012, 10:52 AM
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civdiv99 civdiv99 is offline
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Somehow I wasn't clear about what I was referring to about plastic. I was talking about the radiator and expansion tank, and the increased "psi" when running at 225 vs 195, pressure cycles, etc.

Maybe I was or wasn't clear about BMW's 225 running temps. They did this to support lean burn mixtures under part throttle cruise. The hotter combustion environment is necessary to support a complete burn as lean mixtures are much more difficult to light off. The process is sound and has been around for a long time. The compromise comes about because while the system can alter timing (has to; detonation is an increasing risk) and mixture rapidly, the operating temperature of the engine takes considerably longer to adjust.

It's that compromise.

BMW recognizes that 225 is too warm to apply optimal engine parameters for performance and response, thus we can see the factory system bringing the temps down by tens of degrees if under certain condition. Those same conditions that can promote detonation (whereby timing is pulled back; remember, they also had to go from 2 knock sensors to 4 at the same time).

I decided to take the "lag" out of this, forego the "lean of peak" ops at part throttle for optimal running conditions all the time.

195 is not "cold" or remotely suboptimal for a spark engine on pump gas. It is well within this factory's parameters for normal operating range for this engine.
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