Mild hybrid braking noise - normal or fault?

[neilgorin]

Not sure if this is a fault or they all do it.

B3 Mild Hybrid V60.

Engine goes off on long coasting sessions, like a long gentle down hill locally at approx 40mph or leaving a motorway.

If engine comes back on before touching the brakes, silence.

If engine still off I hear what can be best described as something spinning up or on occasions a rapid "burp" noise from the engine compartment as the charge kicks in.

I assumed it's a fault but googling seems that a lot of hybrid and mild hybrids of different brands do similar, so before I waste a day at the dealer thought I'd ask.

It doesn't do it if the engine is only off for a couple of hundred yards, it's got to be 1/3 a mile or more, example lifting off before exiting a motorway and then rolling the length of the sliproad before touching the brakes.

[sandys]

Hard to know really but probably a vacuum pump/booster for the brakes as and when required.

[Sergeant Grumpy]

Mild hybrid shutting down engine when driving?
Didn’t realise they did that…. My B90 B4 never has…..

[Fibrous]

Originally Posted by neilgorin

Not sure if this is a fault or they all do it.

B3 Mild Hybrid V60.

Engine goes off on long coasting sessions, like a long gentle down hill locally at approx 40mph or leaving a motorway.

If engine comes back on before touching the brakes, silence.

If engine still off I hear what can be best described as something spinning up or on occasions a rapid "burp" noise from the engine compartment as the charge kicks in.

I assumed it's a fault but googling seems that a lot of hybrid and mild hybrids of different brands do similar, so before I waste a day at the dealer thought I'd ask.

It doesn't do it if the engine is only off for a couple of hundred yards, it's got to be 1/3 a mile or more, example lifting off before exiting a motorway and then rolling the length of the sliproad before touching the brakes.

The engine shouldn't cut out at all while driving in motion only when you come to a stop for example in traffic or at lights etc. Something not right if the engine is cutting out while you are driving and or going downhill...get Volvo to check it asap.

[neilgorin]

It's definitely designed to do that. That's the only thing I've been able to confirm so far. The engine goes off when you're off throttle and coasting then seamlessly comes back on when you touch the throttle.

It's just the noise when the regen kicks in with engine off that I've not been able to confirm.

[sandys]

Originally Posted by Fibrous

The engine shouldn't cut out at all while driving in motion only when you come to a stop for example in traffic or at lights etc. Something not right if the engine is cutting out while you are driving and or going downhill...get Volvo to check it asap.

freewheel function is a thing

https://www.volvocars.com/uk/support...a80151784f6f86

[Sergeant Grumpy]

Blimey…..freewheeling……not something I want my car to be doing to be honest..
As said before, can’t say I’ve ever noticed it on my V90, but there is no mention of freewheeling in the manual for late MY22……
I know the engine sometimes stops just before actually coming to a stop at lights etc…..but have never noticed this on the move when lifting off the accelerator at speed.

[neilgorin]

I think this is something they can only do on the v60 due to the DCT gearbox, on the conventional torque converter box on the 22 year v60 and the current xc60 and above it wouldn't work as there wouldn't be a way to totally disengage the gear.

[Sergeant Grumpy]

Originally Posted by neilgorin

I think this is something they can only do on the v60 due to the DCT gearbox, on the conventional torque converter box on the 22 year v60 and the current xc60 and above it wouldn't work as there wouldn't be a way to totally disengage the gear.

Makes sense……but wonder how much fuel that feature actually saves in the long run…..especially as these GPF’s work on deceleration, that’s when you want the exhaust doing it’s thing to prevent any issues….. I’m sure they’ve put something in place to sort that though.

[neilgorin]

No particles to filter if the engine isn't burning any fuel I imagine.

Not sure about how it affects consumption other than that it's only maybe 10% at maximum lower than the D4 manual I replaced, which I think is ok for a 2.0 petrol. I've not had a journey below 42mpg at all so far.