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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.
Huh, never thought of that. I always figured in gear it would still still feed the engine gas to keep it idled. In a manual car I guess in gear it wouldn't feed the engine gas because that's the driver's responsibility, if you let the RPMs drop low in gear the engine chokes out. In an automatic the torque converter stops the lock-up and let's it coast and if the RPMs get too low it'll either drop gear for you or let it idle. I've noticed in alot of automatics the torque converter just lets go of lock-up and lets the engine idle low and if you come to start braking or if you accelerate the lock-up comes back on and decides if it needs to downshift, upshift or stay in gear.
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.
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.
Actually there is a neutral gear in SMG & DSG but I still would never switch it over to neutral to coast though. And you're right, the majority of people that buys these 2 great cars will buy it for performance not gas economy.
Actually there is a neutral gear in SMG & DSG but I still would never switch it over to neutral to coast though. And you're right, the majority of people that buys these 2 great cars will buy it for performance not gas economy.
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.
11-01-07, 10:28 AM
But for the streets, I rather save the clutch than to save a few dimes and nickle at the pump.
