Stop / Start - Here's a question for you all??????

As the new A4 will becoming with the stop / start option it got me thinking....

How will the stop / Start feature affect the life of the Turbo??

Turbo's need the oil circulating to carry the tremendous heat away. After a hard or not so hard run your EGT (exhaust gas temps) should be reduced before shutdown. Of course no one specs their apparatus/cars with EGT gauges.


Glad the below text from another forum to save me re-writing something similar.)

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The main reason is to allow the turbo to spin down from the very high RPM (100k rpm isn't unusual) that it spins at while it's still being fed oil by the mechanical oil pump in the engine. Shut the engine off before it's had a chance to spin down and you cut the oil feed - that's what ruins the bearings.

It's the same for petrol turbo cars, although they typically have the turbo begin working at higher RPM than a diesel (my Tdi hit's peak boost at around 1,800 RPM whereas my old MR2 turbo it was closer to 4,000 RPM) you can avoid prolonged idling (also bad for the engine btw) by simply driving it nicely for the last few miles of your journey and avoid heavy turbo usage.

Some turbos (no LR ones to my knowledge) are liquid cooled by the engine coolant although the second generation MR2 turbo certainly was and heat soak from the turbo could, potentially, boil the coolant in the turbo if the engine was shut down without allowing the engine to idle and cool the turbo off first. This coupled with the oil stavation could ruin the turbo, or in extreme cases blow the turbo coolant piping which leads to a total coolant loss - if you don't notice before driving it again (I know... but you'd be amazed at what some people don't notice) you could kiss goodbye to the head gasket, the head or even the whole engine.

TD, Tdi and TD5 (sorry, don't know about the TDV6 and 8's) Land Rover engines do not feed coolant to the turbo and spin down will take less than 30 seconds. If you've been using the engine and turbo very hard (long uphill for example) immediately before shutting off, give it the full 30 seconds before you
shut it down

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i expect that many TDI or "T" owners dont allow the turbo to cool down after a hard or long drive but with the option of the car stopping and starting when you stop surely this is going to allow the turbo not to displace heat if you let it idle.


I would be interested on peoples thoughts with this.....

Rick

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Originally Posted by RickT

As the new A4 will becoming with the stop / start option it got me thinking....

How will the stop / Start feature affect the life of the Turbo??

Turbo's need the oil circulating to carry the tremendous heat away. After a hard or not so hard run your EGT (exhaust gas temps) should be reduced before shutdown. Of course no one specs their apparatus/cars with EGT gauges.


Glad the below text from another forum to save me re-writing something similar.)



i expect that many TDI or "T" owners dont allow the turbo to cool down after a hard or long drive but with the option of the car stopping and starting when you stop surely this is going to allow the turbo not to displace heat if you let it idle.


I would be interested on peoples thoughts with this.....

Rick

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I've heard, but may be wrong, that as long as you spend the last 30 secs to a minute of your journey 'off boost', you should be ok.

The problem is going to be with people who have no mechanical knowledge/sympathy who will just switch off anyway, in which case there's no difference to before.

My TT used to pump it around to cool the tubro for a couple of mins after turning if off.

Apparently the A4 doesn't need to but I shame the concern.

Like Hex, I totally back of for the last part of the journey, sometimes just coasting if the road is empty.

Other times though, I put the car on the drive, which is low revs for more than 30 secs. I am sure this is the cooling down period criteria met.

I nag my dad all the time about his megane 1.5 dci. He drives all the way from manchester to dunmow (over 3hrs every friday, then back up on monday nights) and pulls in the drive and switches off straight away. I keep tellng him he'll need a new turbo one of these days.

Still taking no notice though... :banghead:

Interesting subject but no-one directly answered Rick's question.

I guess Audi must know the car, Don't these systems usually wait about a minute before switching the engine off? I guess as the guys say providing you have not been using the turbo prior to switch off it is OK. Is one minute enough?

With regards to how it affects the life of the turbo...

The oil is very, very hot in the turbo. Switching off the engine after heavy driving would cut the oil pump out, leaving hot oil in the turbo with nowhere to go. The hot oil in the turbo can cook the bearings. The other extreme is if the oil burns it can choke the oil supply to the turbo.

All explained under "reliability" here. ;)

What is this stop/start option that you speak of?:confused:

hello lads,
i feel the turbo should be ok because,as i understand it,the stop/start
feature would function whilst in traffic,bumper to bumper,or standing at lights?
the turbo wouldn't be being used in most of that time.
i can't see it just simply switching off after a heavy burst,or long run.
my tuppence worth,
regards,
stewy.

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Originally Posted by Black Phantom

What is this stop/start option that you speak of?:confused:

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It's not an option. If you buy a MY2010 2.0 A4 then you'll get it.

Automatic start/stop function for greater fuel and C02 efficiency. Comprising;
– Recuperation for optimal energy utilisation
– Energy saving tips feature in Driver’s Information System;
including gearshift indicator

(Only available on the 2.0 TDI/2.0 TFSI manual engines)