[ds968]

I heard that high RPM levels ( let's say 5500 just for the sake of argument ) are riskier to an engine if the car is in neutral / park , as opposed to the same level of rpm while being driven. So if that's true , 1) why is that ? RPM is RPM is RPM no matter what the transmission is doing , or is it ? 2) what particularly in the engine is being adversely affected by high RPM when the engine is either cold, or the car is not being driven ? Just curious to learn what dynamics are at play in those scenarios ..

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[flash]

well...............

 

in neutral, because the load on the engine is not there, combustion temps are lower (until the lower radiator efficiency, due to the lack of forced air, comes into play).  this can lead to lesser combustion of the fuel, which can result in fuel wash of the cylinders.  then, when the lower radiator efficiency comes into play, other things get REALLY hot, due to the lack of air flowing over them and cooling them.

 

so, you could be fuel washing the cylinders, and then frying components.

 

this all comes down to how long you are running that rpm though.  a few seconds is no big deal.  but, if you let it sit there like that for a few minutes, you could really mess up some things.

 

this would be exacerbated if the engine is cold.

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[ds968]

Got it, thanks . I was reading through the Maserati manual and it noted that there is a factory limiter ( not a fuel cutoff ) at 5 K rpm when the car is neutral or park so you can't take it past that level no matter what . But in gear you can go to the 7500 redline right away, although they do "recommend" against that Andrew that you should not pass 5 k rpm on a stone cold engine until tne temp comes up sufficiently, after a few minutes . So I think pretty much the same concept applies to our 968s, as a good precaution measure...

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