is turbo always running at all speeds?
does turbo start at a certain speed?
Does driving in Sport or Economy mode make a difference if on turbo?

I'm trying to figuire out when i need to let the car idle to let the turbo cool down. I do alot of highway miles and had in Sport Mode on the way home from work, which is 28 miles each way on the highway. Also, should Sport mode be used in cities?

 

You know the turbo is working when you start the car, put it in gear, and press the gas and the car doesn't bog down.

Yes the turbo turns all the time. The turbo experiences boost and vacuum. Most of the time it's in vacuum. When you have a load of over 15 or so, you'll be going into boost. Like when picking up speed. Your car can boost to something like 9.5 psi. When cruising on the freeway, you are likely not boosting at all unless going up hill. In a normal uphill freeway drive, you are likely boosting around 3 or 4 psi. You are boosting most when racing from light to light but usually not over 7 psi unless you are at WOT (WIDE OPEN THROTTLE).

As for taking car of the turbo, don't drive hard (boost on purpose) until the car reaches it's normal temp of 180 degrees F. You also want to let the turbo cool down properly which means your last 2 miles of driving or last couple of minutes, don't boost on purpose before you turn the car off. So, normal driving, you should be able to turn the car off at anytime without causing thermo boiling of the oil in the turbo.

 

Here is a copy of the owners manual if you don't have one.

1998 S70 & V70

 

once again. thank you rspi for your knowledge of the turbos.

I've been playing around with the S more. Really takes off on the highway and cruises past all sorts of cars. weeeeeeeeeeeeeee

Also, some good posts about the Sport and Economy modes:
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