Please confirm - ECUs treatment of off-throtle decel

[sunshineFC]

Im looking for confirmation on how the ECU behaves during off-throttle decel (engine braking). I was under the impression that the ECU cuts fuel during engine braking...is this accurate?

I'm asking so that I can adjust my driving style to maximize my fuel milage. I have the fortune of sitting in 10 miles of traffic in each direction to/from work, and I got thinking whether I would save more gas by coasting to the stopped car infront of me before stopping myself, or if I should stay in gear, off-throttle untill the last moment, and then stop. In neutral, your using the little fuel required for idle, but if the ECU cuts fuel during decel, then you would be using 0 fuel in that same situation. Im sure that little bit would add up after a while.

Anyone have insights?
-a

 

[VRMS6]

In neutral your car does indeed cut fuel to maximize fuel economy. Keep in mind it still needs to burn some gas to keep the engine running. If your after max fuel savings then yes going int neutral and coasting is your best bet...

 

[8.5MS3]

Engine braking will maximize fuel mileage. dropping into neutral and coasting actually consumes more fuel. Over roughly 3000rpm the injector duty cycle drops to 0 which means no fuel is being injected into the engine. once you fall below 3000rpm it injects a minimal amount of fuel to keep the engine turning in case you push in the clutch.

 

[FORZDA 1]

Im looking for confirmation on how the ECU behaves during off-throttle decel (engine braking). I was under the impression that the ECU cuts fuel during engine braking...is this accurate?

I'm asking so that I can adjust my driving style to maximize my fuel milage. I have the fortune of sitting in 10 miles of traffic in each direction to/from work, and I got thinking whether I would save more gas by coasting to the stopped car infront of me before stopping myself, or if I should stay in gear, off-throttle untill the last moment, and then stop. In neutral, your using the little fuel required for idle, but if the ECU cuts fuel during decel, then you would be using 0 fuel in that same situation. Im sure that little bit would add up after a while.

Anyone have insights?
-a

If you're over 2k rpm and shut the throttle, the ECU cuts fuel until the rpms drop to 1800.

 

[8.5MS3]

thanks for the clarification, wasnt sure of the correct rpm levels.

 

[FORZDA 1]

thanks for the clarification, wasnt sure of the correct rpm levels.

(yes)

 

[zinger002]

thanks for the clarification, wasnt sure of the correct rpm levels.

my cobb ap tells me i am still getting 99.9 mpg, which is infinite because the injectors shut off and the momentum of the car keeps the motor turning, untill 1500 rpm during decel. even then under 1500 all the way to 900rpm i see a minimum of 70 mpg.

this all is taking place in 6th gear btw so... thats just what i have found.

neutral is not the way to go in terms of economic savings.