Start stop systems

[sebhaque]

I was wondering earlier - my BMW has start-stop fitted. While in my mind it seems nice that the engine will cut out for a minute or so at a red light, are there any times when it shouldn't be used? I researched online earlier and all I got was that BMW just use a beefy starter motor for the system.

IIRC fuel is only saved by restarting a car if you're idling for at least 45 seconds - so if this is the case in start-stop traffic all the system is doing is just burning excess fuel needlessly restarting itself?

If someone who's a bit savvy with these systems could let me know if I'm being sensible in disabling the system in light traffic (i.e. 5-10 seconds stopped between moving) or just leave it as it is, that'd be great.




Of course, I do know fuel is best spent by having the tail out, with a dab of oppo, at eleventy.onehundredandtwelve leptons in a remapped MX5d with a red bull dent and a wheelchair, but the best I've got out of the 120d is 59.4 mpg average, would be nice to crack 60.

[eldar]

sebhaque said:

but the best I've got out of the 120d is 59.4 mpg average, would be nice to crack 60.

Fold the wing mirrors in, fold the back seat down and pump the tyres up to the max permitted. It would be more fun to crack 15mpg.

[Liquid Knight]

My Rover 213S has a similar system. I turn the key when I'm stuck in traffic or at a red light and turn it again when I can move.

[Toyless]

Ive always thought these systems are going to increase wear on all the engine components, based on the fact that engine start up is when the least lubrication is available.

Have any of these systems got increased or alternative lube systems ?

[Mr Sparkle]

I would have thought the fuel used to restart an already hot engine would be less than that used during 45 sec. on idle. Seem the remember hearing the break even point was more like 10 seconds since its not going to do it when it is on chock.

[Engineer1]

Toyless said:

Ive always thought these systems are going to increase wear on all the engine components, based on the fact that engine start up is when the least lubrication is available.

Have any of these systems got increased or alternative lube systems ?

Why?

Surely stopped for a minute or two the components will still have a film of oil on them, after all stop start is a youngish technology, normally a car is stopped for long enough for the oil to drain into the sump.

[deveng]

IIRC the VW system doesn't use The starter motor to restart, and it ties in with 'reusing energy normally lost during braking' quoted on the passat advert.

Sorry about not being vague enough, I tried.

[Ozzie Osmond]

sebhaque said:

I researched online earlier and all I got was that BMW just use a beefy starter motor for the system.

Maybe a bigger (higher capacity) battery too as it has to run the A/C etc while you're stationary. Fuel injection system is optimised to use virtually no additional fuel on the restart, cat' will still be hot, hence the easy savings.

[ZeeTacoe]

Ozzie Osmond said:

sebhaque said:

I researched online earlier and all I got was that BMW just use a beefy starter motor for the system.

Maybe a bigger (higher capacity) battery too as it has to run the A/C etc while you're stationary. Fuel injection system is optimised to use virtually no additional fuel on the restart, cat' will still be hot, hence the easy savings.

I fairly certain the systems only work once the car is fairly warm too.

[LukeBird]

ZeeTacoe said:

I fairly certain the systems only work once the car is fairly warm too.

Yeah they do, or at least the one in my dad's A4 does.
It doesn't work when the car is cold or the battery charge is low. I've had it 'not work' at various other times I've been stationary, no idea why, I can't imagine the battery was pretty low but it obviously decided for the best!