A quick question about turbodiesels

You're supposed to let them idle for 30 seconds or so before turning them off, right? (Obviously combined with gentle off-boost driving the minute or two before).

But if you've literally started the engine and simply moved the van about

20-30 metres, not going above, say around 1500rpm at the most, am I right in thinking that the turbo will barely have spun up at all, and you'd be fairly safe just to leave it 2-3 seconds and turn it off almost straight away?

What about if you've just started it and literally let it run, idling, for about 5 seconds or so? The revs won't have even changed from tickover - would it be ok to just turn it straight off? As surely it won't have spun up at all beyond the amount it spins at idle speed, and the potential problem of oil supply being cut short won't be a problem as that's only really an issue when the oil is nice and hot, and/or when the turbo's spun up to full boost (around 20-30k rpm or whatever it is they spin at), won't it?

Stupid questions maybe, but please no stupid answers :-)

Peter

-- "The truth is working in television is not very glamorous at all. I just go home on my own at night and sit alone and eat crisps."

Reply to
AstraVanMan
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AstraVanMan was seen penning the following ode to ... whatever:

Yep, although IMHO you can skip that if you were driving off-boost for the last mile or so.

I'd say so, but you'd have to check at what kind of rpm the turbo starts to spin up properly.

Turbos can spin at up to 100k...

Right, the problem with turbos and cutting their oil supply is that turbos tend to heat up pretty nicely. Now if you drive the car hard for a while and turn it off immediately afterwards, the worst case scenario is that the turbo is still spinning at eeek rpm and you cut its oil supply. Due to the heat generated by the turbo and especially the heat generated by the internal bearing friction, it can burn the oil in the bearings (and there's no supply of fresh oil). Oops. You've just lost your lubrication...

This is more of a problem with non-watercooled turbos, as they tend to generate more heat, but generally the best thing to do is to drive the car gently for the last mile(s) and leave it idling for a short amount of time so the turbo has a chance to both spin down and cool down a bit.

Reply to
Timo Geusch

Yes.

Yes.

It is more of a cooling down thing really. A full boost turbo on a hot engine can get very hot indeed, working hard they will even glow red. If you turn it off while it's like this the metal will continue to expand for a few minutes after turning off, and heat will still build up. Of course at this time there is no oil flowing in the bearings, and the oil that is there simply gets burnt.

Actually, this applies to all engines to a small extent, it's always a good idea to bring down the power on an engine a few minutes prior to stopping, as they get *hotter* for about 10 minutes after stopping.

You have to be kidding! :-)

Reply to
Andy Hewitt

On cars, letting the turbo spin down isn't too big a problem, provided you've been driving gently for the past mile or so. As has been said in previous posts, excess heat buildup can damage the turbos, but i've never seen this on any modern turbo diesel. Car turbos are generally small enough, that they spin down pretty fast.

Letting turbos spin down applied more to large lorry turbos, that could quite happily take several minutes to spin down from full revs (could easily be in excess of 200k rpm).

Given the number of turbo diesel vehicles around now, I've only seen 2 failures on cars in the past 5 years, and both were caused by lack of engine oil. Have seen plenty more failures on vans, but these were caused by Ford's high quality turbos.

Reply to
Moray Cuthill

The reason for the slow run after high speed use is to keep cooling oil flowing round the turbo bearings. If you stop a red hot turbo the oil can literally catch fire inside the turbo, next start there is no oil in the turbo and some ash in the bearings.

There is usually no problem with ordinarily used road vehicles.

Some vehicles have an electric pump which continues to run after switch of so that the oil can cool and lubricate the turbo without the engine running (such as renault 21 turbo)

However, unless you come to a very quick stop after blasting up an alpine pass then I don't believe you need to worry about it.

mrcheerful

Reply to
mrcheerful

I was told a while ago that it was turbo petrol engines that suffered more than turbo diesels, because they run at higher temperatures. I've never had a turbo problem with 8 TD's. But they were all run on Millers fully synthetic with regular changes, and sympathetic treatment.

An ex neighbour used to let his son drive his T5. The little dear used to scream up the hill towards the house, then up the drive, and switch off the engine before the car came to a halt. The son lost his licence after smashing up his own car, and we moved away before I could judge the outcome for the T5.

Reply to
Doctor D

I wonder if their son was called Hugo. :-)

Peter

-- "The truth is working in television is not very glamorous at all. I just go home on my own at night and sit alone and eat crisps."

Reply to
AstraVanMan

"Moray Cuthill"

Have seen plenty more failures on vans, but these were caused by Ford's

Aren't they made by Air Research, Shwizer, KKK, Holset or Mitsubishi? If not, who supplies Ford with turbo's?

Huw

Reply to
Huw

"mrcheerful ." wrote

Almost all current production car turbo's and most van ones are water cooled. It is water that is pumped through the turbo after engine shut-down. Don't know specifically about renault 21 though.

Long term damage leading to faulty turbo's and even cracked heads is fairly common and attributed directly to poor shut-down procedure. This is the case even when a manufacturer does not specifically mention the nead for a shut-down sequence, such as in modern BMW 3.0 as used also in Range Rover.

Huw

Reply to
Huw

Garrett. Made to ford's standards.....just like the high *cough* quality bosch fuel pumps.

Reply to
Moray Cuthill

Although Garrett was part of the CAV group :-) & come to think of it Ford actually used to pay extra for an extra grading process on fuel pumps.

Reply to
DuncanWood

the TD mondeo hire car the other had no warning sticker, i used to cut the engine after the turbo had kicked it.

Never OWNED a diesel do dont know from personal exp

Reply to
JULIAN HALES

Garrett Airesearch, now part of Allied Signal, do tailor their products to the manufacturers requirements of course, but the actual working parts of the turbo will be to the same high standard as all their other products. The occasional one does come through with a manufacturing fault though. I've not long supplied a vehicle which blew oil out the exhaust from the second day.

Huw

Reply to
Huw

In news: snipped-for-privacy@uni-berlin.de, Huw decided to enlighten our sheltered souls with a rant as follows

strangely enough, my brothers' 530d has just needed a new turbo. ('53 plate

30k miles).
Reply to
Pete M

When the first of the 2.0L diesel transits came out, there was a major recall to change the turbos, after several turbo failures. Some of the failures even led to major engine damage. Even after the modified turbos were fitted, we still got the occasional turbo failing..

As for the fuel pumps, rumour has it ford reduced the price they were willing to pay Bosch for them. So Bosch reduced the quality to cut the price. This resulted in pumps that either broke up internally, or started leaking externally. Another costly lesson for Ford, as bosch denied responsiblity. At the peak of this problem, we were fitting a new injection pump every 2 weeks on average.

Reply to
Moray Cuthill

Are you talking about the modern Transits? That's one thing I've never been quite sure about - first I heard they were using the 2 litre TDCI engines, then a lot of the DuraTorq (a synonym for TDCI if I'm not mistaken) Transits have a 2.4 litre engine? What's what, and what sort of economy do they give?

Peter

-- "The truth is working in television is not very glamorous at all. I just go home on my own at night and sit alone and eat crisps."

Reply to
AstraVanMan

If he continues to be a naughty boy then he should worry about a new head at some point ahead. To be fair, all turbo car handbooks should warn of the correct procedure, but they increasingly don't, both because turbo's are more resilient due to water cooling and superior oils and because they think it will frighten the punters. They are correct in both cases but I feel it is best to have the information even though some anally retentative types will worry unnecessarily and take over-the-top preventative measures, even to the extent of shouting for 3000 mile oil changes perhaps LOL

Huw

Reply to
Huw

In news: snipped-for-privacy@uni-berlin.de, Huw decided to enlighten our sheltered souls with a rant as follows

Heh, it's had two heads already. Long story...

Heh.... but BMWs never break. Diesels are better than petrols, etc. ;-)

Reply to
Pete M

Some engines have two heads already. Some even have four.

Peter

-- "The truth is working in television is not very glamorous at all. I just go home on my own at night and sit alone and eat crisps."

Reply to
AstraVanMan

Since you mention it, I have a six cylinder engine with two heads and it is brand new. I also have another with six separate heads and cylinder pots. Totally irrelevant to the bloke who has had several heads fail, but he should realise that he would have the same problem with a petrol turbo engine and, if he was a real animal, even with any naturally aspirated engine eventually.

Huw

Reply to
Huw

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