Turbo timer in new cars

If old Turbocharged cars used to have turbo timer to make sure that the engine idles for a little bit before it shuts down so that the turbocharger and the engine are properly lubricated, how come new turbo cars are not equipped with turbo timer no more?

I am just curious since it seems like more and more manufacturers, from Ford (EcoBoost) to BMW, are going the turbocharging route to produce the same level of power more efficiently. I DD an '08 GTI and always idle the engine for about 10 seconds before shutting it down, is it not needed no more?

Because of a couple reasons.

The old cars didn't come with them from factory, and new turbos aren't just oil cooled typically.

I think that bearing coking from heat was a bigger issue with the sleeve bearings used 'in the day'.
Nowdays, ball bearings are used, not so much of an issue.
Also synthetic oils handle the temps better, don't coke up.

from a subie site....

The Subaru WRX engines have their water catch tank high on the engine above the turbocharger. When the engine is shut off the water continues to circulate via a physical property of water called a thermal siphon. Simply put, hot water rises up to the catch tank, being drawn from the relatively cool cylinder head water jacket up through the turbo housing. One still needs to take a cool down lap at the track and perhaps should not stop at the top of a mountain pass to enjoy the view if you have been on the boost all the way up, but for the other 99% of the time there is no need to let the engine idle for a minute before shutting off ignition. Even when the engine is off, the cooling water will circulate past the turbine bearing housing.

Yep, old turbos weren't water cooled leading to coked bearings and plugged drains.

Thermal siphon are the most important 2 words posted in this thread so far.

Most water cooled OEM turbo setups are built so that the heat from the turbo will cause coolant to circulate through it after the car is shut down. The FWD turbo dodges i am into had this as far back as 1984.

Turbochargers generally fail for one reason more than any other; oil starvation.

I spent a few years diagnosing turbocharger failures for a large diesel engine companies turbocharger division, think Holvest.. <-- actually a name of a chinese knock off of the turbos..

Oil starvation, in my experience was caused by a few items:

1. Miss machining of the shaft or thrust collar piston ring type seals. This failure is very rare and generally caught by production line testing.
2. miss-assembly of various o-rings on the oil seal plate on the bearing housing. Generally rare, sometimes caught at test. Viton o-rings are generally forgiving.
3. Casting defect or machining defect of bearing housing casting internal. Rare, caught at any oil flow testing in line. Turbo will also not balance well as a core assembly with incorrect internal oil flow.
4. Oil starvation due to either insuffcient flow (owner neglect and letting the vehicle run low for a while) or even better a hot shutdown..

Hot shutdowns will and can cause catastrophic oil coking inside a turbocharger. Modern oils are quite good at resisting hot shutdown but specific and repeated abuse will cause the problem. Think about an excavator run flat out for hours on end and then shut down abrutly at lunch time or shift end day after day....

So long story short; Most people won't need a turbo timer, but idling the engine for 5-10 seconds before shutting down wont hurt and will mostly help. For daily driving, it is probably belt and suspenders, but for any type of racing or hard work a quick spot of idling can help add thousands of miles of life to the turbo. Water cooled turbo's can help.

A bigger danger to turbo life is letting the vehicle run low on oil. Low oil can cause flow issues to a turbo and lock the bearings tight fast. That's what I'd be worried about rather than turbo oil temp.

irish44j wrote: from a subie site.... The Subaru WRX engines have their water catch tank high on the engine above the turbocharger. When the engine is shut off the water continues to circulate via a physical property of water called a thermal siphon. Simply put, hot water rises up to the catch tank, being drawn from the relatively cool cylinder head water jacket up through the turbo housing. One still needs to take a cool down lap at the track and perhaps should not stop at the top of a mountain pass to enjoy the view if you have been on the boost all the way up, but for the other 99% of the time there is no need to let the engine idle for a minute before shutting off ignition. Even when the engine is off, the cooling water will circulate past the turbine bearing housing. __________________

I'm correcting a Subaru site - guess I should know better than to even try, but the term is actually "thermosiphon". It's also a device, not a property of water, but yeah.

It was 90% BS to begin with. Oil standards are much higher now than 30 years ago, synthetics aside.

Plenty of solely oil cooled turbos on the road already are running, parking and surviving without hoodoo timers being needed.

Knuckle-dragging mechanics from the 80s loved to blame turbos for all problems because it didn't fit in their carbureted v8 mentality.

Two things to remember:
1) The thermosiphon effect works (the underlying technology of coffe makers), but it kind of sucks for cooling. It's the reason all cars with radiators use water pumps.
2) Any water cooled center section will be limited to the boiling point of the coolant, (unless all the coolant has boiled away).
Boiling point of coolant <<< Coking point of oil

I read once that letting the engine idle while you unbuckle your seat belt is sufficient ..

erohslc wrote: Two things to remember: 1) The thermosiphon effect works (the underlying technology of coffe makers), but it kind of sucks for cooling. It's the reason all cars with radiators use water pumps. 2) Any water cooled center section will be limited to the boiling point of the coolant, (unless all the coolant has boiled away). Boiling point of coolant <<< Coking point of oil

Not trying to nitpick, but it doesnt have to boil water to get it to move, it just has to expand it some so gravity will push denser liquid up to it.. Granted, its not like theres a rushing flow through there at ANY point, boiling or not. Water only expands 4% between room temperature and boiling.

Also, the turbo (and the oil in it) will not stop cooling once the water stops boiling. It will stop cooling (cooling quickly anyway) when the temperatures of all the parts equalize. The center section of the turbo should come down to the low 200s F pretty quickly, a good bit below the boiling point of a proper water/coolant mix.

Most modern cars (n/a and turbo) have after-run water pumps too.

Cone_Junky wrote: Most modern cars (n/a and turbo) have after-run water pumps too.

??? Which ones?

I'm not aware of any.

Even in water cooled centre bearings, the bearing itself can get hot enough if you shut down after a full throttle run to vapourize and coolant and ash the oil in the bearing itself and the latter is what causes the bearing damage.

The main reason modern turbos don't have anything to prevent this is the use of synthetic oil which resists ashing to a great degree. I haven't seen any studies as to whether abusing the car - many shut downs after getting the turbo as hot as possible, without idling down a bit to allow coolong, can overcome the synthetics natural resistance to ashing. It may still be a theoretical issue even with synthetic, yet not a common practical problem.

It was always the ones with no water cooling that had short (sometimes very short) lives - ask anyone that owned an early Volvo turbo!

Turbos have been very reliable in OEM applications (other than some VAG stuff...) and plenty reliable in properly done performance applications for 20 years or so. Turbo timers seem to cause many cars they are installed in to not start, or turn off, or drain the battery, or run till the car is out of gas, or short circuit everything, or light the car on fire, thusly making the car less reliable. I guess that could lengthen the life of the turbo.

bdutro wrote: It was 90% BS to begin with. Oil standards are much higher now than 30 years ago, synthetics aside.

Sorry. But it is not 90% bs. I have seen wheelbarrow loads of dead turbos to prove that oil cokes even modern oil.

iceracer wrote: I read once that letting the engine idle while you unbuckle your seat belt is sufficient ..

Great advice. About 5-10 seconds is all that is needed. Any more is wasting fuel unless you were running the ever living snot out of the thing.

Same thing could be applied to a track car. Cool down lap and into the pits. Then the seat belt. QED

Don't forget, spinning turbos have inertia. It takes a bit to spin down from 80,000rpm. If you blast through an autocross course and then shut down right away, that turbo could spin for a short time with no oil pressure.

Vigo wrote:

erohslc wrote: Two things to remember: 1) The thermosiphon effect works (the underlying technology of coffe makers), but it kind of sucks for cooling. It's the reason all cars with radiators use water pumps. 2) Any water cooled center section will be limited to the boiling point of the coolant, (unless all the coolant has boiled away). Boiling point of coolant <<< Coking point of oil

Not trying to nitpick, but it doesnt have to boil water to get it to move, it just has to expand it some so gravity will push denser liquid up to it.. Granted, its not like theres a rushing flow through there at ANY point, boiling or not. Water only expands 4% between room temperature and boiling. Also, the turbo (and the oil in it) will not stop cooling once the water stops boiling. It will stop cooling (cooling quickly anyway) when the temperatures of all the parts equalize. The center section of the turbo should come down to the low 200s F pretty quickly, a good bit below the boiling point of a proper water/coolant mix.

Counter nit-picks: If the center section temperature is below the boiling point of coolant, then it's well below the coking temp of oil, and so not really hot enough to be a concern.
Heat of vaporization per gram of water >>>> latent heat per gram for liquid water.
Boiling by the way is an isothermal process, you can't raise the temperature of a fluid beyond it's boiling temperature at a given pressure.
And any configuration that will support non-boiling thermosiphon behavior will certainly also support boiling thermosiphon behavior, since they both depend on denser fluid rising to a heated zone, which transforms that fluid into a something less dense (hot fluid, or vapor), that rises and flows away.

alfadriver wrote:

Cone_Junky wrote: Most modern cars (n/a and turbo) have after-run water pumps too.

??? Which ones? I'm not aware of any.

The Abarth does, not sure what other ones do.

Counter nit-picks: If the center section temperature is below the boiling point of coolant, then it's well below the coking temp of oil, and so not really hot enough to be a concern.

I agree. I think i mis-took your use of the word 'limited' to mean that the system would stop cooling once coolant was below the boiling point (and im not even sure coolant ever boils in the center section to begin with), which to be honest was an assumption of a misunderstanding you clearly dont suffer from, so my apologies.

Just my quick $.02.

I used to work at a Nissan dealership's service department as a lot attendant where a 300ZX twin turbo came in with "sticking throttle issues".

No one told me. So while driving it from the back of the lot to the service department the throttle stuck part way open! I reached for the keys and turned off the ignition which is when I discovered the turbo timer.

I was pressing pretty hard on the brakes which is where I discovered the limited slip differential (lots of white smoke from both tires).

Since the car wouldn't shut off I pulled the gear shift to neutral and let the screaming engine bounce off it's rev limiter for what seemed like an eternity. It was a pretty scary experience, all things considered (tight parking lot, possessed car accelerating and not shutting off... etc.). The service manager thought I was out there hooning in a customers vehicle.

Anyhoo: I wonder if vehicle manufacturers tend to omit turbo timers from their cars (partially) because of safety reasons?

Personally I like my cars to shut off when I tell them to. You know, in case I'm shutting it off because of an emergency.

^Good point

And yeah on the street, just letting it idle while you take off your seat belt is good enough.