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I agree that letting it run a little if you just had the turbo spinning is cheap 'insurance'. I also agree that with newer cars, if you drive moderately for the last few minutes before shutoff, it is probably good enough.
As far as how long they last, it not only depends on vehicle mileage/kilometer-age, but also how much the turbo is spun, especially long and hard. Moderate use should extend useful life. Constant pushing/abuse should have the opposite effect. Even the outside temp probably has some effect.
My Mazda MX-6 Turbo (1990 something) was over 150k miles and ran just fine when it was sold. My 2005 Saab Aero over 100k and going well too. 5000 mile oil changes in both cases, the Mazda was just Castrol GTX 10-30 and the Saab Mobil 1 0-40.
The turbocharger is lubricated and cooled by the engine oil, and when the engine is turned off, that oil supply is cut off. If a turbocharger is still spinning at a high RPM when the oil supply is cut off, the internal bearings will utilize what remaining oil is around them then start to heat up - essentially cooking the oil, which causes premature bearing failure. By allowing the turbocharger to slow down to a safe RPM, this bearing failure can be prevented.
A very efficient means of gauging a safe time to turn the engine off is by the exhaust temperature. The suggested temperature range to go by is below 400°F
The real concern is the temperature of the turbo housing, not the oil, because the oil coking takes place when the turbo housing is hot enough that the oil left within the bearing surface cannot escape before the turbo housing temperature can drop to where a specific oil isn't subject to coking. That temp is roughly 300*-400* but you can add about 50* with synthetics since "true" synthetics will coke at higher temps then conventional oils
a rule of thumb.
under slow and go circumstances, 30mph, 1- minute to 30 sec.
medium load or flat highway driving, 2-4 minutes
heavy load and or mountainous driving, 5+ minutes.
Do not rev the engine or accelerate past half throttle immediately after start-up. Oil requires time to heat up for full flow, and high-rpm driving with a cold engine can damage the turbocharger.
After highway driving or high-load driving, allow the engine to cool by idling for at least 30 seconds before turning off the ignition
The turbocharger is lubricated and cooled by the engine oil, and when the engine is turned off, that oil supply is cut off. If a turbocharger is still spinning at a high RPM when the oil supply is cut off, the internal bearings will utilize what remaining oil is around them then start to heat up - essentially cooking the oil, which causes premature bearing failure. By allowing the turbocharger to slow down to a safe RPM, this bearing failure can be prevented.
A very efficient means of gauging a safe time to turn the engine off is by the exhaust temperature. The suggested temperature range to go by is below 400°F
The real concern is the temperature of the turbo housing, not the oil, because the oil coking takes place when the turbo housing is hot enough that the oil left within the bearing surface cannot escape before the turbo housing temperature can drop to where a specific oil isn't subject to coking. That temp is roughly 300*-400* but you can add about 50* with synthetics since "true" synthetics will coke at higher temps then conventional oils
a rule of thumb.
under slow and go circumstances, 30mph, 1- minute to 30 sec.
medium load or flat highway driving, 2-4 minutes
heavy load and or mountainous driving, 5+ minutes.
Or you can do the really simple solution, and then not care. Have been using a quart turbo oil reservoir on cars since the early 80's (granted, an oversize oil pan is required). When the car is running, the oil pump fills up a quart-sized container on the firewall, and when you turn the engine off, it slowly drains through the turbo bearings. Simple, effective.
Not to digress, but I don't see why people even use turbos anymore (other than for high-altitude applications), as driven blowers (centrifugal, roots, Lysholm etc) can be relatively efficient (though granted not like a turbo), there is no back-pressure, and no throttle lag.
Having built a number of custom turbo cars over the years I'm going to say yes it is required. With the small turbos installed on today's cars you can easily spin the turbo to 50-60K rpm just driving around normally.
Synthetic oils don't coke up as quickly as standard oils do so running synthetic is a bit safer. I don't think there is a need for a turbo timer any longer but letting the car idle for a minute after parking is a good policy.
come on people.. When do you EVER have the opportunity to be at full boost and *immediately* shut down the engine a few seconds later? Never.. You are always are going to slow down first and come to a stop. The turbo will spool down in a few seconds.. Don't worry about it.. Its a non issue.. I feel this whole 'condition' was perpetuated by turbo timer manufactures in the early 80's and is never a real issue
Or you can do the really simple solution, and then not care. Have been using a quart turbo oil reservoir on cars since the early 80's (granted, an oversize oil pan is required). When the car is running, the oil pump fills up a quart-sized container on the firewall, and when you turn the engine off, it slowly drains through the turbo bearings. Simple, effective.
Not to digress, but I don't see why people even use turbos anymore (other than for high-altitude applications), as driven blowers (centrifugal, roots, Lysholm etc) can be relatively efficient (though granted not like a turbo), there is no back-pressure, and no throttle lag.
You said it-less efficient. Small turbos can be used to make up a displacement deficit and still reach a useful level of HP.
As you put your foot on the accelerator the wheel starts spinning faster. Small Turbos (e.g. Holset H1C's or HX35's) can spin at up to 140,000 rpm, that's 2333 revs per second or over 2000 km per hour.
From VW,
The owner manual says if you are hard on it or driving long distance to let your car idle for 2 mins before you shut it off.
This is from the Ram Service Manual
Stop & Go, Load - Empty, Turbocharger temp - Cool, Idle Time...Less than 1 min.
Stop & Go, Load - Medium, Turbocharger temp - Warm, Idle Time - 1 min
Highway Spds., Load - Medium, Turbocharger temp - Warm, Idle Time - 2 min.
City Traffic, Load - Max GCWR, Turbocharger temp - Warm, Idle Time - 3 min
Highway Spds., Load - Max GCWR, Turbocharger temp - Warm, Idle Time - 4 min.
Uphill Grade, Load - Max GCWR, Turbocharger temp - Hot!!, Idle Time - 5 min
Actually the engines that this person is speaking of have been used in VW/Audi models here in the U.S. for years.
Volkswagen/Audi Group has had a lawsuit filed against them some time ago concerning sludge build up in the 1.4 turbo.
The way to keep this sludge issue down to a minimum is to use synthetic oil.
My 2003 VW Passat has the 1.4 turbo engine.
I have been using synthetic oil in it since 90,000 miles.
I'm now just over 180,000 miles with no sludge issue whatsoever.
I would say restrict your search to those vehicles utilizing the 1.4 turbo with a proven history of synthetic oil changes if the mileage on them has exceeded 90,000 miles.
My car runs very very well and would not hesitate to drive it across the country.
It's all about maintenance.
Quote:
Originally Posted by NJGOAT
We don't have the engines you are talking about here in the US, so no direct experience with them. You said 40,000km and that would work out to about 24,000 miles. At that kind of mileage (honestly not sure what they call it when they use kilometers, kilometerage???, anyway) the car is really just getting broken in. If you were talking about 400,000km, or 240,000 miles, then yeah, I'd be really concerned about it unless the engines been rebuilt.
One of the key things on any turbo car is performing regular maintenance and using the correct parts/fluids to do it. As long as the used car you were looking at was well maintained, I wouldn't worry about it.
Of course, turbos do wear out eventually even with proper maintenance and normal use. When that happens is very engine dependent. In general, but around 100,000 miles or 160,000km I would start to be concerned about the health of the turbo. As long as everything has been well maintained, it should be fine, but that is the age when you might start seeing small leaks and maybe a little bit of power loss.
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