Auto Start stop and turbo's

[JimsZ]

So... I'm under the impression from my experience of turbo charged engines that it is good practice to let a turbo spool down for a minute or two before stopping the engine on a turbo powered engine. That leads me to the question, how can you run start stop on turbo'd engines without potentially compromising the life of the turbo.

Am I too old school and out of touch or has turbo technology really moved on and is no longer is an issue to worry about.

Reason I ask is.. I keep disabling the start stop button because of my old school ways

Any one care t share their wisdom on this subject

 

[Smartbear]

It's only an issue if you've just been giving it beans/running high boost for a while, turning the engine off immediately afterwards isn't very good practice-if you've only been driving normally without elevated temperatures then it's not nessessary to let the engine idle before switching off.
It's probably more important to treat the car gently in the first place to let it warm properly before giving it some stick.
Imho
Regards

 

[JimsZ]

Thanks for commenting.

I get that but what i don't see is how the start stop function determines if you have just come off the motorway for example and hit some traffic. If enabled it will still shut down the engine and therefore not allow the turbo time to spool down.

I guess for "town driving" a high speed spool up of the turbine is unlikely and its down to the driver to manually intervene and use the override button until such time it's spooled down.

I would have expected timer delays to have been built in for automatic control by now though unless it's not an issue as such any more?

Note, I'm referring about the auto star stop feature not normal on/off by driver

 

[srhutch]

I think turbo designs have changed to include water cooling. Guessing it's not the problem it used to be. Often thought about it myself after driving nearly 200 miles without stopping and the last 100+ at 70mph then pulling of the slip road and coming to a stop. My E87 is 4.5 years old with 74k on the clock. No issues, and tbf not heard of any anywhere else.

 

[JimsZ]

Good to know they last a while, my old one lasted 50k (Non BMW)and that was running plus 60 Bhp over standard, I just took care of it and when it did expire replaced it with an upgraded one.

 

[GuidoK]

my old one lasted 50k (Non BMW)and that was running plus 60 Bhp over standard,

chiptuning turbo engines always limits turbo life as the turbo runs much hotter.


But start stop is carefully managed by the ecu, so it knows exactly how you've been driving. It monitors all kinds of parameters before it decides to start-stop. It is not a 'dumb' system.

Also motorway driving is not at all stressful for the engine. lots of cooling and it generally only uses 30HP or so.
Heavy acceleration is the most intense for an engine.

 

[JimsZ]

my old one lasted 50k (Non BMW)and that was running plus 60 Bhp over standard,

But start stop is carefully managed by the ecu, so it knows exactly how you've been driving. It monitors all kinds of parameters before it decides to start-stop. It is not a 'dumb' system.

Heavy acceleration is the most intense for an engine.

Interesting, if this is the case I guess I should just trust the system to do its thing, thanks for explaining.

 

[techathy]

As others have said, the turbo is water cooled & an E89 BMWs that's an electrical water pump so can run independently of the engine.

 

[JimsZ]

Turbine bearings/seals will be lubricated by oil though so I would have thought this is unchanged and normally this is the part of concern for the wear and tear, the turbine is spooling still when the oil pressure drops as the engine is switched off and no or reduced lubricant present hence increased mechanical wear if the turbine is still spooling down when the engine has stopped. Perhaps the oil pump is designed to run on still?

Well, observed it today and found the auto start stop working after only a few minutes of driving, the engine was not even up to normal operating temperature either, it was only town driving so if this is the case my instinct is still to override particularly on short journeys and or until the engine is operating at normal temperature until I have more reassurance this technology is protecting the turbo, which I'm sure it is... just would like to know for sure...

 

[GuidoK]

It is not the turbine spooling that is the reason that you have to gradually slow your drive. (like a turbo timer)
The turbine stops spooling in an instant (few seconds) so that's no problem.
In fact, if you you're below 2krpm and don't have your foot on the pedal, the turbo doesnt spin at all.

The reason is heat. The idea behind it is that when you really strain your engine, the turbine housing, turbine wheel and manifold get really hot (red hot). When you stop driving, all that heat has to go somewhere. And a lot of it goes to the cool turbo side (the inlet side), via the turbine shaft. That heats up and burns the oil seals.

So what you normally do is drive slowly for the last mile or so, so both the oil and the exhaust gasses (exhaust gasses when driven slowly are also less hot and therefore cool the turbo, even more than the oil) cool the turbo down a bit.
Especially on a gasoline turbo car (exhaust gas in a turbo diesel is less hot than gasoline exhaust gas and thus diesel turbo's are mostly not watercooled)

The start- stop system also monitors coolant temp, oil temp, outside temp etc etc.
It won't work when it's really cold and the engine is still cold (oil is still thick so too heavy load on the alternator). But the engine doesnt have to be up to normal temp.
The oil has to be a specific temp, and probably the cats also have to be a specific temperature (but that is probably reached in a minute or so, as there are systems in the car that speed up that temperature)

 

[jamesbond]

well

When you buy a 35is .. the start/stop function is not included ! so no worries with this model of Z4

And when I shut mine off (sorry ours ) I can hear the electric water pump running on for some time ..

regards

 

[JimsZ]

I knew I should have bought a 35 ...

That makes a lot of sense, thanks for explaining in detail

 

[dr_john]

well

When you buy a 35is .. the start/stop function is not included ! so no worries with this model of Z4

And when I shut mine off (sorry ours ) I can hear the electric water pump running on for some time ..

regards

When you buy any E89 with auto gearbox start/stop is not included.....

 

[Mister T]

It is not the turbine spooling that is the reason that you have to gradually slow your drive. (like a turbo timer)
The turbine stops spooling in an instant (few seconds) so that's no problem.
In fact, if you you're below 2krpm and don't have your foot on the pedal, the turbo doesnt spin at all.

The reason is heat. The idea behind it is that when you really strain your engine, the turbine housing, turbine wheel and manifold get really hot (red hot). When you stop driving, all that heat has to go somewhere. And a lot of it goes to the cool turbo side (the inlet side), via the turbine shaft. That heats up and burns the oil seals.

So what you normally do is drive slowly for the last mile or so, so both the oil and the exhaust gasses (exhaust gasses when driven slowly are also less hot and therefore cool the turbo, even more than the oil) cool the turbo down a bit.
Especially on a gasoline turbo car (exhaust gas in a turbo diesel is less hot than gasoline exhaust gas and thus diesel turbo's are mostly not watercooled)

The start- stop system also monitors coolant temp, oil temp, outside temp etc etc.
It won't work when it's really cold and the engine is still cold (oil is still thick so too heavy load on the alternator). But the engine doesnt have to be up to normal temp.
The oil has to be a specific temp, and probably the cats also have to be a specific temperature (but that is probably reached in a minute or so, as there are systems in the car that speed up that temperature)

Yes the reason is heat, but modern roller bearing turbo can spin for considerably longer than that on shutdown and the turbo always spins when the engine is running.

 

[GuidoK]

yes you're right. What I ment to say is spinning on high revs. It only can do that with the wastegate closed and obviously lots of exhaust gas flow (it requires a lot of energy as it also is compressing air). If your foot is off the pedal, the TB is closed, so there isnt any/hardly any airflow. That means that the turbo can only do some very low efficiency low revs, the air also has nowhere to go (so any rotating that yealds efficiency on the compressor side is immediately counteracted). The low speed rotating on ideling/ run out is not very critical for lubrication.