2.5GT Are you supposed to cool down before turning off?

[2fast4u]

Why would you want to get out of your car at a set of lights?

[Boxer]

I'm a bit puzzled how operation of the wastegate helps cool the turbo down in a controlled manner (rather than the relative shock of turning the engine off immediately after a hard drive)? Any idea?

You'd be puzzled cos its a load of horsesh1t

"äutomatic wastegate cooling turbo"- ...........really

[Sentinel]

I generally drive the last few km's easy to 'cool' down like others have said.

[fatcat67]

Don't listen to Subaru Tech's. Not many know much.
Turbo timers are pointless these days.
The turbo is self cooling after engine shutdown by way of the water flowing through it by capillary action. Just follow the water pipes in and out of the turbo(hot side/cold side) and it should start making sense
It is however advisable to not flog the car then park it of course.

[Zaphod]

I'm new to turbo cars so I'm not pretending to know anything, but my understanding is that's about wear on the bearings, not cooling. The turbo's bearing is lubricated (and cooled too I guess) by engine oil from the engine - when you turn off the engine after a spirited run, the turbo is still spinning at a high rate with no lubrication, resulting in undue wear on the bearing.

Edit: oops, sorry for the threadmining.

</$0.02>

[Ric]

when you turn off the engine after a spirited run, the turbo is still spinning at a high rate with no lubrication, resulting in undue wear on the bearing.
..

No, it's temperature that is the concern.
The turbine spins up and down in only a second or so. If you turned off straight after coming off boost, it would already have slowed down to the point at which wear isn't a concern, and come to a full stop within seconds.

What was a concern in older turbos was that the cooling oil flow would stop, and cook the bit of oil that was left inside the turbocharger housing.

[teK--]

Just like with anything it's important to adequately warm up and warm down. I do this when I go to the gym and I do this when I drive the car. Turbo timers are nothing but an annoyance nowadays (and makes it easy to bypass your immobilisers).

Just go easy on the car for the first and last 1-2kms

[teK--]

I've always made sure the last few kms are quiet.

Track days are harder and brakes need cooling as well, so I do a quiet few kms again before shut down. Mallala track here in SA is easy, you can just do a quiet loop into the town itself and back does the trick.

Yeah that's the only situation where I would idle for a good 2-3mins prior to shutting the engine off, especially if it's a track where you do your run then have to go straight to the back of a queue (no warm down lap)

[tangcla]

The theory is that the turbo is watercooled and even when the car is off, the water will continue to circulate - hence we have a second radiator cap at the top of the engine bay. This makes a turbotimer a double-up of an existing factory design.

[Golf Tango - Bravo]

I was under the impression that it's to do with different components cooling at different rates, therefore expanding/contracting at different speeds. Bearings warp and seize, oil gets squeezed and blows seals, and the wallet comes out.

I blew an engine on the highway and the core temperature increased for the first couple of minutes; apparently it was caused by heat soaking from the exhaust manifold/turbo. The rapid cool-down on the turbo seized it so I had to replace that too, I'm told if the engine dies slowyly they can be saved.

I know I'd be shot if I didn't idle my bus for the first and last 3 minutes...

GT-B.

[chadza]

I know Im dredging up an old thread, but Im bored and cant find the real thread I am looking for!!

Fatcat has it right, on watercooled turbo's there is no need for a turbo-timer if the water pipes going into and out of the turbo are positioned correctly. Once the engine has been shutdown the water will continue to circulate through the turbo shaft housing due to the thermal difference between the now cooling water external to the turbo, and the water in the housing which is heat soaking from the residual heat left in the turbo core.

Turbo shaft wear on non-water cooled turbo's occurs when the core temp is still very high at engine shutdown, so the oil around the shaft essentially 'cooks' and attaches itself to the shaft in such a way that it degrades proper lubrication. Leaving your engine idling with non-water cooled turbo's ensures the oil is still circulated through the core to remove the excess heat until the temperature stabilises.

Hence, a turbo-timer on a Gen2 and up turbo liberty is rice.

[parso_rex]

Rice and quite illegal