Don't cook your turbo!

2.1td · Unread post by **2.1td** » 08 Aug 2006, 12:52

Owners of cars with a turbo, including diesels, may or may not know that it is considered wise to allow the engine to idle for a while after a long, fast run. This allows the turbo to cool down a little (with oil still circulating) and not "cook" after the engine is turned off. The following quote is from Wikipedia:
"After high speed operation of the engine it is important to let the engine run at idle speed for around one to three minutes before turning off the engine. This lets the turbo rotating assembly cool from the lower exhaust gas temperatures. Not doing this will also result in the critical oil supply to the turbocharger being severed when the engine stops while the turbine housing and exhaust manifold are still very hot, leading to coking of the lubricating oil trapped in the unit when the heat soaks into the bearings and later, failure of the supply of oil when the engine is next started causing rapid bearing wear and failure. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. Oil coking is completely eliminated by foil bearings. This problem is less pronounced with turbochargers used in diesel engines, due to the lower exhaust temperatures and generally slower engine speeds. It is usual for the manufacturer to specify a 10-second period of idling before switching off to ensure the turbocharger is running at its idle speed to prevent damage to the bearings when the oil supply is cut off."

So, if you didn't know already, now you do!

micitroen · Unread post by **micitroen** » 30 Sep 2006, 09:42

That is one of the (many) reasons that the police didn't have cars with Turbos as we didn't have the time to sit there idling them having arrived at the 'crime' as it were. Can you imagine the scene...'Officer, Officer thats the man that killed him over there, look he's just walking away! 'Sorry madam I've just got to let my cars turbo cool down but I'll be there in a minute or two.....
Don't know how they've got round it now though as they use the BMW 5 series turbo diesels here......word of warning don't buy any 2nd hand police turbo diesels as the first thing to go will be the turbo!

Unread post by **lolingram** » 11 Dec 2008, 18:19

Owners of cars with a turbo, including diesels, may or may not know that it is considered wise to allow the engine to idle for a while after a long, fast run. This allows the turbo to cool down a little (with oil still circulating) and not "cook" after the engine is turned off. The following quote is from Wikipedia:

I would wager that any real risk is confined to:

1) 'Hot' petrol turbocharged cars

2) And in any case, the rule only applies after prolonged full boost conditions, which are so unlikely on public roads as to be insignificant.

3) Run on full synth oil if are stopping at the pub after 10 minutes Harry Flatters....

Homer · Unread post by **Homer** » 14 Dec 2008, 13:44

In most normal conditions you won't go from a flat out blat to switching off that quickly. We don't all live on a racetrack. By the time you've pulled onto your estate and parked up a regular diesel turbo will have cooled enough.

uncle buck · Unread post by **uncle buck** » 29 Dec 2008, 23:59

Worth bearing in mind if you pull into the motorway services after a decent run !

Unread post by **lolingram** » 30 Dec 2008, 09:10

Worth bearing in mind if you pull into the motorway services after a decent run !

Cruising along at 70-80 fixed throttle is NOT going to render a turbo red hot... short of running flat-out, I can think of no road-going situation that will IMHO.

Tourist · Unread post by **Tourist** » 31 Jan 2009, 00:49

Good advice, I wasn't aware of such problems. However I think that as others have said, for most situations you'll not need to do this.

HDI · Unread post by **HDI** » 22 Sep 2009, 23:43

Just a few more points. Most petrol turbo cars have watercooled turbo's and are less susceptable to heat soak damage. Diesel turbo's run at a lower temperature than petrol and are normally not water cooled.
Unless the car comes to a stop after running any serious boost for a good 30 seconds or so , which is unlikely on a public road , then 30 seconds is more than adequate to allow the internals to slow and cool down enough.

Good quality modern oils are much more resistant to this problem than 10 - 15 years ago when this was a real issue.

Another tip is to allow turbo cars to fully warm up before using any serious boost. Turbo's last longer if treated with care.

Unread post by **lolingram** » 23 Sep 2009, 08:39

Good quality modern oils are much more resistant to this problem than 10 - 15 years ago when this was a real issue.

Absolutely... a good (but not necessarily expensive) 10-40 Semi Synth will look after a turbo no sweat - advantage being that it will not burn up easily, leaving coke in the bearings.

Another tip is to allow turbo cars to fully warm up before using any serious boost. Turbo's last longer if treated with care.

So will the engine......!

citrov6 · Unread post by **citrov6** » 23 Sep 2009, 09:02

out of the many discussions about this, the best advice was to use your last 2 minutes of journey cruising at a low speed, the air passing through the engine bay cooled the turbo down a lot, where as standing idling became like an oven so that when the motor was switched off it was the same as if it was just parked up.

a big issue was that it baked the oil lines, if the car was using mineral oils it would build up and block the lines.

the water cooling is nice and does help if you forget IF it runs on an after running pump when the motor is switched off

running synthetic oil saved the oil lines on a lot of cars, as did a turbo timer

trev0006 · Unread post by **trev0006** » 23 Feb 2010, 05:33

I just drive the car off boost 2 miles before I get home, that should be good to cool the turbo.

2.1td wrote:Owners of cars with a turbo, including diesels, may or may not know that it is considered wise to allow the engine to idle for a while after a long, fast run. This allows the turbo to cool down a little (with oil still circulating) and not "cook" after the engine is turned off. The following quote is from Wikipedia:
"After high speed operation of the engine it is important to let the engine run at idle speed for around one to three minutes before turning off the engine. This lets the turbo rotating assembly cool from the lower exhaust gas temperatures. Not doing this will also result in the critical oil supply to the turbocharger being severed when the engine stops while the turbine housing and exhaust manifold are still very hot, leading to coking of the lubricating oil trapped in the unit when the heat soaks into the bearings and later, failure of the supply of oil when the engine is next started causing rapid bearing wear and failure. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. Oil coking is completely eliminated by foil bearings. This problem is less pronounced with turbochargers used in diesel engines, due to the lower exhaust temperatures and generally slower engine tires speeds. It is usual for the manufacturer to specify a 10-second period of idling before switching off to ensure the turbocharger is cars running at its idle speed to prevent damage to the bearings when the oil supply is cut off."

So, if you didn't know already, now you do!

TopDonkey · Unread post by **TopDonkey** » 23 Feb 2010, 07:43

micitroen wrote:That is one of the (many) reasons that the police didn't have cars with Turbos as we didn't have the time to sit there idling them having arrived at the 'crime' as it were. Can you imagine the scene...'Officer, Officer thats the man that killed him over there, look he's just walking away! 'Sorry madam I've just got to let my cars turbo cool down but I'll be there in a minute or two.....
Don't know how they've got round it now though as they use the BMW 5 series turbo diesels here......word of warning don't buy any 2nd hand police turbo diesels as the first thing to go will be the turbo!

They use petrol turbos in Wiltshire, I've been stopped twice by a skoda octavia 1.8 turbo

Brigsygtt · Unread post by **Brigsygtt** » 23 Feb 2010, 14:56

And the t5/evo's/scoobys

Couple of mins cool down driving is adequate after a heavy right foot, or one cooldown lap on track will keep your turbo right.

HDI · Unread post by **HDI** » 01 Mar 2010, 15:56

Just to give an idea of how quickly things can heat up on a turbo motor !!

Dippy · Unread post by **Dippy** » 04 Aug 2011, 19:56

TopDonkey wrote:
micitroen wrote:That is one of the (many) reasons that the police didn't have cars with Turbos as we didn't have the time to sit there idling them having arrived at the 'crime' as it were. Can you imagine the scene...'Officer, Officer thats the man that killed him over there, look he's just walking away! 'Sorry madam I've just got to let my cars turbo cool down but I'll be there in a minute or two.....
Don't know how they've got round it now though as they use the BMW 5 series turbo diesels here......word of warning don't buy any 2nd hand police turbo diesels as the first thing to go will be the turbo!
They use petrol turbos in Wiltshire, I've been stopped twice by a skoda octavia 1.8 turbo

Not to mention Scoobies + Mitsubishi evo's

In the 80's A local ford dealer used to fit uprated twin - turbo conversions to the 2.9 V6 police granada's - watched them doing one. . Seriously quick car at the time.

I don't know if they did the same to the 24v Cossie Headed V6's though ? that was already a missile.

might explain why I failed to outrun one in my 2.8i Capri

I wonder how many turbo's have succumbed to lack of oil changes , I would never trust Long - life oils either - 6K and change fer me guys - period. Never had a turbo let go yet - petrol or diesel, and Iv'e had a few .

Most trucks have a seperate Turbo - Filter , it's not there for show.

The most reliable/repairable Turbo's used to be KKK or Garret/Airresearch - but Ive' been out of the game for a while .

The worst ( on cars ) used to be anything made in Japan ! with the possible exception of the water cooled ones on Isuzu 2.8 diesels . - China was a none entity then .......

Although things have moved on apace - is there a link to (supposedly) long life oils + Turbo Failures ?

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Don't cook your turbo!

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