Cooling down the turbo: I still don't get it :(
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Cooling down the turbo: I still don't get it :(
Why do you have to idle before turning off the engine? Is it only after driving hard? Is a couple of minutes of slow driving (parking style) at the end of your drive equivalent to idling? How long do you have to idle? Does a minute of idling really make a difference, considering how hot the turbo becomes and for how long?
I do it every time (ok, almost every time), but I always sit there for a minute asking myself what sense it all makes. One can get pretty existential in an idling car :-)
I do it every time (ok, almost every time), but I always sit there for a minute asking myself what sense it all makes. One can get pretty existential in an idling car :-)
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You're not actually cooling down the turbo...you're letting it spin down while you still have....
...oil flowing through the system. The turbo can theoretically wear out faster if it spins down w/the oil pump turned off.
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I only sit around after a hard drive.
Usually for the last 1/2 mile or so before I get to my destination, I take it slow and easy to let everything cool down...I keep the engine under 4000 RPMs and don't accelerate very hard during that time. If I don't take it slow for the last little bit, I go ahead and just let the car idle for a minute or so.
If you've got a 225, it shouldn't matter since we have some kinda pump that keeps the oil moving long enough to keep it from cooking in the turbo, but I still do it anyways just for peace of mind...Better to waste a minute here and there than to spend a whole bunch of money for a new turbo one of these days, right?
If you've got a 225, it shouldn't matter since we have some kinda pump that keeps the oil moving long enough to keep it from cooking in the turbo, but I still do it anyways just for peace of mind...Better to waste a minute here and there than to spend a whole bunch of money for a new turbo one of these days, right?
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Someone will correct me if I'm wrong, but I don't believe that pump that runs after you switch off..
...is an oil pump. My understanding is that it is an engine coolant pump. If it is an oil pump, I'd like to know that for sure.
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my take on this
the car continues to circulate coolant after you turn off the engine so perhaps this is not as needed as with older turbo cars. The real point for me is this though: the real issue with hard driving causing damage stems from heat soak. If you drive hard you should also cool hard. How? Keep driving. Letting the car sit and idle after a hard run causes heat soak. You should drive for a while afterwards at moderate speed (30-50 mph) to keep the air moving and cool the engine and brakes. Race cars always have a cool down lap to keep the air moving around the engine and brakes.
I welcome comments on my ideas on this topic but I think it makes sense to drive longer rather than idle. The added bonus is that you drive more :-)
I welcome comments on my ideas on this topic but I think it makes sense to drive longer rather than idle. The added bonus is that you drive more :-)
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The reason is...
that the turbo is lubricated by a thin film of oil and when you shut off a car that has just "pitted" (hard drive), the oil residue AND the oil left in the lines gets REALLY hot. In pre-Mobile 1 days that oil could actually coke into an enamel and clog the oil lines and screw up the turbo.
There is STILL some risk of this...letting the car idle (recommendation is for about 2 minutes) significantly cools the entire assembly WHILE it's being lubricated (one of the main functions of lubrication IS cooling, taking the hot oil away and replacing it with cool oil cools the turbo). The turbo temp is much lower and the chance of coking the oil is virtually eliminated.
It's one of those things that CAN'T hurt...but you MAY never need it. Good rule of thumb is that if the last couple of minutes of your drive are mild and gentle, this probably has the same effect. If you have been romping on it through the canyons for the last two hours...you SHOULD be doing a cool-down for 2 minutes. It's actually in the manual.
Hope that helps.
There is STILL some risk of this...letting the car idle (recommendation is for about 2 minutes) significantly cools the entire assembly WHILE it's being lubricated (one of the main functions of lubrication IS cooling, taking the hot oil away and replacing it with cool oil cools the turbo). The turbo temp is much lower and the chance of coking the oil is virtually eliminated.
It's one of those things that CAN'T hurt...but you MAY never need it. Good rule of thumb is that if the last couple of minutes of your drive are mild and gentle, this probably has the same effect. If you have been romping on it through the canyons for the last two hours...you SHOULD be doing a cool-down for 2 minutes. It's actually in the manual.
Hope that helps.
