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In a turbocharged engine, the fan of the turbo can spin at speeds of up to 100,000rpm. This means that the bearings must be adequately lubricated at all times.
If you spin the turbo up too soon after starting the engine, the cool oil may be slightly sluggish getting along the oilways and the fan will
be spinning without proper lubrication. Similarly, if you drive hard, park and turn the engine off immediately the oil pump will stop pumping oil around the engine (and turbo) although the fan will be spinning for quite a while as it slows down from 100,000rpm. Ideally, you need to start a turbocharged car up and let it idle (or drive off-boost) for a few minutes, before using the turbo - and then idle (or drive off-boost) for a few minutes before switching off the ignition.
Owners of high-performance sports cars tend to obey this rule, but in my experience users of family turbo-diesel saloons (or tiny (600cc turbo) smart cars) don't.
Available as either a factory-fit optional extra or an aftermarket modification, the Turbo Saver disables the turbo for 5 minutes after ignition and keeps the engine running for 5 minutes after ignition is turned off and the car is locked.
The 5 minute delay after ignition could be cancelled automatically if you only stopped the car a few minutes before (to buy a packet of cigarettes for instance).
The worrying aspect of walking away from your car and leaving the engine running is tempered by the fact that the car is locked/alarmed - and will be immobilised in 5 minutes - therefore even if someone breaks in they can't drive away.
(?) Turbo timer
http://www.machv.com/turbotimers.html
And many more like this.. [Ling, Dec 29 2004]
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Would you just mechanically bypass the turbo? How about an electric auxiliary oil pump? |
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I understand that the factors you state may contribute to turbo failure. How common are such failures? |
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I've only owned one turbocharged car, a diesel. The only measures I take to protect my turbo is to change the engine oil every 5000 miles and not race the engine then immediately shut it down. 240,000+ miles - 23 years and still going seems like a pretty good service life to me. |
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I was thinking of a rev limiter rather than a mechanical bypass... |
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Not sure how common, tbh. My wife drives a turbo-diesel and that's never caused any problems (far lower mileage than yours though!!) |
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On a similar note: my non-turbocharged car has a lower rev limiter until the engine's warmed up and oil's got to all the nooks and crannies. |
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[half] - I'm interested as to what car you have. There can't have been many turbo diesels around that long ago. Impressive figures though. |
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This is definately half baked. Turbo Timers being baked and on the fly re-programming of engine management systems also already done... |
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Why limit yourself to a turbo application? A rev limiter would work for a normally aspirated car as well. If this is an after market modification it will be about as difficult to implement as any ECU re-map. |
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[kmlabs]: The implementation is perfectly correct. Unfortunately, this is really baked. I had one on my Scooby.
By the way, the turbo slows down really quickly. The damage is caused by the burning of the oil by the (red) hot impeller and casing on the exhaust side, which is why you should slow down a little earlier before you want to pull over and switch off. |
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Turbo Diesel farm tractors state in the owners manual that you should idle 5 minutes before shut down. A farmer I know had friends who were all having turbo bearing failures while he was getting good service. He was the only one who read the manual. Perhaps the basic design of the turbine is at fault. If a less compact design were used more heat might be kept away from the bearing on the turbo side. Sometimes a design that works fine on aircraft, boat or tractor, (if you read the manual), has problems in a car because of the way it is used. |
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Saab water cools the bearings on their turbochargers. Don't know how much it helps with bearing oil coking after shutdown, though. Their smaller Garret turbos spin at about 280,000 rpm. |
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Disabling the turbo for 5 mins after startup sounds a good idea. Leaving the engine running for 5 minutes after you turn it off sounds downright dangerous in case of an accident. Guess a manual override could be fitted, but I'm much happier with the first part than the second. Idling for five minutes a la [hangingchad]'s anno would solve the problem neatly. |
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What about refueling? You're supposed to turn off the engine. |
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"Wow this turbo saver is a really neat thing" (shuts garage door, notices car still idling because of turbo saver). "Oh wait, Carbon Mono... (trails off, passes out)" [-] |
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This sounds like a real loser to me [-]! |
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I have a smart car, and disabling the turbocharger on startup would be detrimental to my sanity. That car is slow like a tortoise when it is off-boost. |
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Besides, I don't think five minutes is necessary on startup - the oil doesn't have to be warm to lubricate bearings, it just has to be flowing. Perhaps 10 seconds would be good, but not 5 minutes. |
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Alternative solution: include a brushless electric motor on the shaft of the turbo (small ones can hit 200,000 rpm). The motor could accelerate the turbo, reducing lag, or brake the turbo when the engine is switched off. I have no idea whether a motor capable of such speed would be powerful enough for this application. |
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