Why is it that with a turbocharged engine you're supposed to 'cool down' every time before you shut down the engine? Is it even necessary every time? If the oil is so hot, why does the temp gauge not reflect that? Is it that the temp gauge is showing the coolant temp, not oil?

Please enlighten a newbie. I know nothing.

 

Technically, on the stock WRX turbo it's not required.

I don't have a good enough explanation on the exact reasons for the cool down though, so I'll let one of the other guys explain it.

 

This is not as necesary on the Subaru as it may be on other cars as the coolant design is intended to push fresh coolant through the turbo as the vehicle cools down after the engine shuts off. You don't need to "cool off" your WRX or use a turbo timer but if you really get on it for a bit most agree you should drive nicely for a bit before you shut down. Hope that helps.

 

Yeah, basically, the oil and coolant circulate through the turbo via convection when you shut off the motor. The turbo heats up the coolant and oil in it, which causes it to expand, and the pressure from that expansion forces cooler oil back up into the turbo. Lather, rinse, repeat until cool.

Also, yes, the temp gauge reflects coolant temp. However, oil temp is usually not much warmer than coolant temp unless something's broken.

 

The reason, though, why many people may think they need to cool off their WRX is because in older turbo cars, the turbo wasn't designed to cool itself after shutdown, so you would get oil trapped in the turbo, which would cook it, and cause the bearings and other bits to get all nasty with burnt oil crud.

Its not really necessary with the stock WRX turbo, but it doesn't hurt either.

 

You think it makes a difference if I'm talking about an STi?

 

no... same deal for all turbos the thing that u wanna take care of when ur cooling down the turbo is to cool off the bearings and when u cool off the bearings u cool of the oil and keep it from crusting up

 

it never hurts to take precaution

 

Nope. The only downside to getting a turbo timer is that they aren't free, and a REALLY neurotic dealer could give you crap about it if you took the car in for warranty (although their claim would be baseless. SOA doesn't mind if they're installed properly and your issue isn't electrical related).

 

Now what exactly does a turbo timer do? It's not just a timer is it? I'm assuming it measures the temp inside the turbo?!?

 

No, it's just a little electronic box that lets the engine continue to run for a given amount of time afer you remove the key. Many come with voltmeters or boost gauges built in.

 

^^ and some even have lap timers, g meters

whoring at its best

 

Production turbocharged cars have not always had water-cooled turbo housings. This led to a coking effect of the hot turbo literally frying the lubricating oil in the bearings when the engine was shut down.

I don't bother with a turbo timer after I read about that one member's mishap at a track day. He crashed out and his WRX caught fire. Fire crew or volunteers put the fire out, only to have it restart. They put it out, then the fire came back again. The turbo timer in the car kept the fuel pump energized and it was fueling the engine compartment fire! I don't want that to happen to me if I'm trapped in the car. You can always use a turbo timer and just turn it off if there's an accident, I guess. But what if you forget...

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0==WW==0
"…axles of evil…" - george w. bush

 

ive noticed that my coolant reserve is low after i havent check it for awhile.... maybe the turbo has consuming my coolant? and my oil runs low....

 

Everyone's car has a different rate of consumption. Do you notice oil dilution on your oil dipstick or at oil change time? Is there visible white smoke (steam) coming out of the exhaust even after the engine is fully warmed up? Unless you are adding more than one quart of oil between recommended changes, or topping off coolant often, I wouldn't worry about it. If in doubt, have a dealer check it out.

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0==WW==0
"…axles of evil…" - george w. bush