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anecdotal, my z4 28i has start/stop and it functions quite well. the 2.0l engine is very efficient overall and while I have not tested the mileage with start/st

anecdotal, my z4 28i has start/stop and it functions quite well. the 2.0l engine is very efficient overall and while I have not tested the mileage with start/stop off I am pretty sure it contributes to the good mileage I get from this sporty car. The start/stop works with the car in neutral and the clutch pedal not depressed; this is a six speed manual from 2012. US numbers, I track mine on fueleconomy.gov and I do about 32-34mpg commuting and a recent 1800 mile round trip averaged 38-40 at 65-80mph freeway. I could see electric motors taking the place of the drive shaft and trans axel arrangement. You could easily add "awd" to many cars by electrically powering the previously non drive wheels. The best use is launching as that is where my mileage dives. I am not a fan of the i3 because of the compromises made to the iRex for CARB regulations. A slightly larger engine and fuel capacity are warranted. Ideally what I would like to see for a car the size of mine; small 1 to 1.5l engine capable of driving the wheels direct after speed is reached with electric responsible for getting the car off from stop. Chevy does a great job with the Volt but I think batteries still have a long way to go considering the weight required for so little range most offerings have

nawitus 11y ago
Is the engine stopped while the car is moving? That would save even more fuel compared to only stopping the engine while stationary. A further improvement would involve starting the engine without using the starter motor when possible. I could do all that with my old car "manually", but I only tried it a few times.
- smileysteve 11y ago
  With most fuel injected engines, the injectors turn 'off' on deceleration until ~1000 rpm where they kick back on.
  - nawitus 11y ago
    Do you mean they turn off while rolling in neutral or with the gear in? Sure, the injectors turn off when you're decelerating in gear, but that's true even if the car doesn't have a start-stop system. However, I was talking about the case of decelerating in neutral with a car having a start-stop-type system. Rolling in neutral is always more efficient if the fuel is also cut off, but often even with the car running on idle.

nawitus 11y ago

Is the engine stopped while the car is moving? That would save even more fuel compared to only stopping the engine while stationary. A further improvement would involve starting the engine without using the starter motor when possible. I could do all that with my old car "manually", but I only tried it a few times.

smileysteve 11y ago
With most fuel injected engines, the injectors turn 'off' on deceleration until ~1000 rpm where they kick back on.
- nawitus 11y ago
  Do you mean they turn off while rolling in neutral or with the gear in? Sure, the injectors turn off when you're decelerating in gear, but that's true even if the car doesn't have a start-stop system. However, I was talking about the case of decelerating in neutral with a car having a start-stop-type system. Rolling in neutral is always more efficient if the fuel is also cut off, but often even with the car running on idle.