Quote:
Originally Posted by tricky
I think its pretty normal on the M3 (and apologies for the following nerd content).
Going back longer than I care to remember when learning about engines, I seem to remember that its also dependent on the compression ratio of the engine (as well as gearing etc) - when you lift off it typically cuts fuel (but the engine still goes through the suck/squeeze/(without the bang)/expel process of a 4 stroke engine) so the usual process of compressing air etc goes on but without the combustion to add power (granted less air than normal as the throttle is closed).
Given a compression ratio of 12:1 of the E9x M3 which is pretty high compared to most normally aspirated engines - and much higher than most forced induction engines - it takes more energy to turn the engine over if its not generating power. The higher the compression ratio - the quicker the car will slow down if your not adding power as compressing the air highly during each cycle is taking more energy from the car.
That plus low gearing means quick deceleration when you lift off. Certainly mine seems to slow down pretty quickly when you lift off compared to anything other than a diesel :-)
Cheers,
Tricky
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Nice explanation, I appreciate the 'nerd content'.