Will the M3 have the 7 speed SMG transmission?
#46
When you're in gear above a certain RPM with no throttle, the engine has a fuel cut-off to engine brake. If you're in neutral and you coast to a stop, fuel will be supplied to the engine to keep it idling. So technically you save gas if you put it in gear and let off the accelerator But for the streets, I rather save the clutch than to save a few dimes and nickle at the pump.
So basically if you have an automatic, no need to really put it in neutral to save gas, the fuel is already cut to the engine when you let go of the throttle. If it goes below a certain rpm it'll let the engine idle or drop gear.
In a manual you'll save gas because the fuel is cut off when you let off the accelerator, and no fuel is sent to keep it idle because manuals don't idle unless you're in neutral.
The only reason you'd ever really coast to a stop to save gas is if you knew a full stop was unavoidable and you knew that the gas you had already given the engine wasn't enough to get you to the stop with engine-brake. But even than you're probably not saving anything worth while if you you're gonna put your torque converter or clutch in stress.
#47
I don't know too much about the DSG and SMG trannies but they don't have a clutch pedal either so there's no way to let it coast with no tranny hooked, unless you of course drive it in full auto and drop it in neutral when you want to coast. You wouldn't be able to do that in the SMG though, there's no neutral gear in that transmission.
#48
I was looking at older SMG shifters and they didn't have the neutral position. The newest does though. Thanks for the correction. In any case, it definitely doesn't seem worth it to put the car in neutral as a gas saving measure.
#50
#51
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03-28-08 02:47 PM