4 ms·

> It's only for coasting, there is a small electric motor that will only help to re-start the engine [but not really pull the vehicle]. Classifying a car as a

by n3k5 6y ago

> It's only for coasting, there is a small electric motor that will only help to re-start the engine [but not really pull the vehicle]. Classifying a car as a mild hybrid electric vehicle on the basis of nothing but a glorified starter motor doesn't sound entirely unlike something Volkswagen Group might try to get away with, but this doesn't seem like a fair assessment. Doesn't conventional coasting mean that the ICE still is driving the wheels — at idle RPM? So if instead the clutch decouples, the electric motor has to make up the difference, right? That's not nothing when you consider that diesels (such as your Audi) output significantly more power at idle RPM (and also use more fuel, I'd guess?) than petrol engines (relative to max power).

Daniel_sk 6y ago
The engine decouples and either shuts down completely (if you don't have Start-Stop switched off) or it just idles on low RPM. Before the Audi I had a BMW that wasn't classified as MHEV and it still would decouple the engine during coasting (in Eco mode), but it would not turn it off because this would add a delay of 1-2 seconds until the engine is ready again (and it didn't have the additional battery + electric motor to start it in these conditions). The small electric motor helps to quickly start the motor in this decoupled mode (which again is not something that only hybrids have) and so it can be turned off for up to 40 seconds of coasting. All of this can be disabled in the Settings menu and the engine will never go into "coasting" mode and this coasting mode will almost never be triggered in the city anyway (you can see that it will shift from a specific gear like 6 to just "D" - and then you know that the engine is decoupled). Anyway, I and many others (most?) turn off the start-stop right when you start the vehicle. I just don't like that the engine turns off on every intersection and then you have a second of delay and slow response + more wear on engine for so many starts and stops. In this case it will still coast with the decoupled - but idling - engine. Also by coasting I mean condition where the car has enough momentum and either goes downhill or there is a slower speed limit ahead (this is detected automatically from map data) and the car knows that it can just decouple the engine. This is evaluated by the car based on some conditions, it's not controlled by the driver.
- Daniel_sk 6y ago
  More information directly from Audi: https://www.audi-mediacenter.com/en/techday-on-combustion-engine-technology-8738/versatile-and-efficient-mild-hybrid-technology-8761 https://www.audi-mediacenter.com/en/techday-on-combustion-en... "The 48-volt-based MHEV technology is particularly more comfortable and efficient. If the driver takes his foot off the accelerator at a speed between 55 and 160 km/h (34.2 to 99.4 mph), the car can coast for up to 40 seconds with the engine off completely. During slow coasting, the start-stop phase already begins at 22 km/h (13.7 mph). Once the driver accelerates again – whether from a stop or while driving – the vehicle restarts quickly and very comfortably: the BAS revs up the internal combustion engine to the target speed, then injection occurs again and, in the case of a gasoline engine, ignition. While the conventional pinion starter remains on board, it practically comes into play only at the initial starting, if the engine oil is still cold and viscous. In such a situation, the belt of the BAS could slip through. "
- n3k5 6y ago
  Thank you! I just quickly looked up some terminology and it turns out the mode I'd been thinking of is more properly called ‘coasting in gear’, which is indeed not at all implied by the more general term ‘coasting‘. Now that I know what's what, I agree that Audi's quarter-assed implementation shouldn't qualify as ‘MHEV‘.

by n3k5 6y ago

Daniel_sk 6y ago

The engine decouples and either shuts down completely (if you don't have Start-Stop switched off) or it just idles on low RPM. Before the Audi I had a BMW that wasn't classified as MHEV and it still would decouple the engine during coasting (in Eco mode), but it would not turn it off because this would add a delay of 1-2 seconds until the engine is ready again (and it didn't have the additional battery + electric motor to start it in these conditions). The small electric motor helps to quickly start the motor in this decoupled mode (which again is not something that only hybrids have) and so it can be turned off for up to 40 seconds of coasting. All of this can be disabled in the Settings menu and the engine will never go into "coasting" mode and this coasting mode will almost never be triggered in the city anyway (you can see that it will shift from a specific gear like 6 to just "D" - and then you know that the engine is decoupled). Anyway, I and many others (most?) turn off the start-stop right when you start the vehicle. I just don't like that the engine turns off on every intersection and then you have a second of delay and slow response + more wear on engine for so many starts and stops. In this case it will still coast with the decoupled - but idling - engine. Also by coasting I mean condition where the car has enough momentum and either goes downhill or there is a slower speed limit ahead (this is detected automatically from map data) and the car knows that it can just decouple the engine. This is evaluated by the car based on some conditions, it's not controlled by the driver.

Daniel_sk 6y ago
More information directly from Audi: https://www.audi-mediacenter.com/en/techday-on-combustion-engine-technology-8738/versatile-and-efficient-mild-hybrid-technology-8761 https://www.audi-mediacenter.com/en/techday-on-combustion-en... "The 48-volt-based MHEV technology is particularly more comfortable and efficient. If the driver takes his foot off the accelerator at a speed between 55 and 160 km/h (34.2 to 99.4 mph), the car can coast for up to 40 seconds with the engine off completely. During slow coasting, the start-stop phase already begins at 22 km/h (13.7 mph). Once the driver accelerates again – whether from a stop or while driving – the vehicle restarts quickly and very comfortably: the BAS revs up the internal combustion engine to the target speed, then injection occurs again and, in the case of a gasoline engine, ignition. While the conventional pinion starter remains on board, it practically comes into play only at the initial starting, if the engine oil is still cold and viscous. In such a situation, the belt of the BAS could slip through. "
n3k5 6y ago
Thank you! I just quickly looked up some terminology and it turns out the mode I'd been thinking of is more properly called ‘coasting in gear’, which is indeed not at all implied by the more general term ‘coasting‘. Now that I know what's what, I agree that Audi's quarter-assed implementation shouldn't qualify as ‘MHEV‘.