Swacer

And the engine had to be designed for people like yourself that don't do it. By doing the cooldown, you are most likely extending the life of your turbo. If you don't, you are most likely caking oil deposits onto the drive bearings.

Why does it matter what BMW, Audi and Mercedes do? Does everyone have to design their engines the same? With a Toyota, I at least know that after 5 years, my engine will still be running as compared to the germans.

We are honestly talking 1-2 minute here people. It will take you longer to stop, put your sunglasses away, and wait for the garage door to open. Keep in mind also, the car coasting, while keeping negative 7.5psi boost and your foot off the gas (all going out the wastegate) is contributing to cooldown.

99SC42

iTrader: (44)

^^^ Nice post buddy!!

LexBob2

BMW and Audi don't mention a cool down period for their turbos, but it certainly is not a bad idea to do it. As mentioned, most drivers do an inadvertent cool down many times before shutting the engine down.

rVague

One thing to keep in mind is that the intercooler is liquid cooled unlike many other turbocharged cars. Unless you are doing really hard driving the cool down may not be an issue. But I always let it idle for 20 seconds anyway because I'm OCD.

Tom59

Usually water cooled turbo's don't need it. It's done to prevent oil coking my Supra has a timer the car keeps running then it shuts off.
Also with new synthetic oils coking is much less an issue.

What is a water-cooled turbo ?

The central part of the turbo, housing the bearings, is surrounded by a water jacket through which the engine’s water coolant is passed. This water continues to circulate after the engine is turned off, cooling the turbo, and preventing heat soak.
According to a major manufacturer of turbochargers

Following a hot shutdown of a turbocharger, heat soak begins. This means that the heat in the head, exhaust manifold, and turbine housing finds it way to the turbo’s center housing, raising its temperature. These extreme temperatures in the center housing can result in oil coking.
To minimize the effects of heat soak-back, water-cooled center housings were introduced. These use coolant from the engine to act as a heat sink after engine shutdown, preventing the oil from coking. The water lines utilize a thermal siphon effect to reduce the peak heat soak-back temperature after key-off
Conclusion

No, there is no need to run a turbocharged engine after stopping the vehicle - unless you have an older vehicle with an early type of turbocharger and have been pushing the engine to it's limits for an extended time. Check the owner-manual for your car to see if the manufacturer recommends any special procedure, if it doesn't you can assume none is needed.

crankshaft

Tom59.....have you read page 168?

typocl

AndyL

Question arises when reading the guideline for cooling the turbo down.

--a normal driving activity usually is a mix of highway and normal city driving.

Say, you leave house, drive the car in the city for some time before heading the highways. Then exit the highway and continue some city driving before your destination. Before the destination, you wait for making a left turn into the office/mall where you find the parking lot.

Should you simply assume this situation falls under "normal city driving" and so you only need to wait 20 secs before you shut the engine off?

Rdcrow

I try to give it a few seconds to cool down after city driving. I always let it run for a minute or two after continuous highway driving (60mph+ for an hour or more).

Tom59

Did you read the last sentence of that post. "Check the owner-manual for your car to see if the manufacturer recommends any special procedure, if it doesn't you can assume none is needed"

No , I don't own an NX , not yet anyway.

I probably will allow it to idle down in summer months , winter months not as long. I know Lexus used a very new turbo setup so water cooled turbo's aren't all the same.

CanadianRX

Had a 1.8t Vw, did the idle thing for the first 5 k then decided not to worry. 250k km later engine and turbos ran like day one, my brother did the same and no problems, maybe because I'm further north. I would not let it idle unless I was racing.

dnguyen_GS430

Tom59,
There is no such this is a water cooled turbo. If it is, then I would not buy the NX or any car with water cooled turbo. Can you imagine what catastrophic failure will it be if the water leak in to the combustion/exhaust chambers of the engine? Water cool in a turbo engine is typically an air-to-water inter-cooler. Your Supra has what it called an Air-to-Air inter cooler mounted just before the air conditioning condenser and radiator. This is a more efficient way to cooled the charged air before it enters the combustion chamber. The cooler the inlet air, the better it fires. In this setup, it's very similar to the Air-Water inter-cooler as on the early 1990's Toyota Celica ALL-TRAC. On the Celica, inter-cooler sits on top of the engine and the inter-cooler acts like a radiator. it helped cooled the hot charged air. This setup is not as efficient as the Air-to-air that is mounted in the front of the car. This is due to heat from the engine itself can add addition heat to the inter-cooler. This is due to heat convection.
With this set up, the water cooled only cool the charged air and has nothing to do with the cooling of the turbo itself.

I also have an 1998 twin turbo Supra. I'm not a fan of leaving the engine running to circulate the oil to help cool the turbo so I designed my own external DC electric motor to circulate the motor oil to cooled the turbos. A typical temp of the oil in a turbo charged engine is about 200-225 degree F. I used a programmable thermal switch/relay to set the on/off temperature. Not only heat will kill the turbo but also friction. When you shut down the engine over night, all your oil will drained to the bottom of the pan. you should turn the key to leave it on the "ON" position for 30 seconds or so so the pump can pump the oil to the turbo bearings before starting up the engine.

Fast Forward to 2015/16 and with a push button start, I'm not sure how to leave the ignition to the "ON" position before starting the engine. As I'm considering the NX, I did not see where the intercooler is mounted so I cannot make sense on how efficient the charged air will be. If it is true that the NX uses the water cooled intercooller, I'm very disappointed,.

kchnew

From the manual on switching the ignition to "ON" mode:

Modes can be changed by pressing the engine switch with brake pedal released. (The mode changes each time the switch is pressed.)
Off*
ACCESSORY mode
IGNITION ON mode

computerwi

Interestingly...the Canadian manual that came with my NX begs to differ, at least for normal city driving. I guess that begs the questions, what is "normal city driving" ?

15RC350F

I'd say that "normal city driving" is anything less vigorous than the category below it in the manual.