cooling down a turbo

cupra14

Active Member
Aug 31, 2017
332
63
England
I understand a turbo should be cooled down after use... but how do you know when a turbo kicks in?

I suppose a subsidiary question is: why no dash light to show that enough cooling has not yet been done?

Is Start/Stop disabled if the turbo is still too hot and if not why the **** not?
 

TheLuckys

Active Member
Nov 26, 2018
162
168
AFAIK the turbo doesn't need cooling down after a drive. Also, it's not something you "kick in", it's always on when the car is running.

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Deleted member 103408

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I am no mechanic but i thought the turbo was spinning all the time it just works harder (spins more) the more you push it.

Re dash light, when would it come on, it does not know you are nearing the end of your journey or it would only come on when the car came to a stop (so at every traffic light) and there are temp parameters in the stop start process but what you are doing is hopefully increasing the life span of the Turbo

This thread sums up why

Your turbo heats up to around 900 degrees Celsius under hard driving conditions. When you shut off the car, You suddenly take away the heat source and the ambient temperature falls to around 95 degrees Celsius (the normal operating temperature for a Subaru that has been driven hard). This causes the turbine housing to experience thermal shock. Now granted, it would take a long time for this thermal shock to actually cause damage, but you're probably reducing the turbo's life by putting it under stress unnecessarily. If you let the car idle for a minute or so, you allow the exhaust gas temperatures to gradually go down to 700, 600, 500, etc.

An example to support what I said: 1. When a cast iron manifold is welded (turbine housing is cast iron too), it is recommended to toss the whole thing into a fire and let it burn out overnight so that the manifold cools down gradually to prevent stress points from forming.

From experience, it's not necessary to let the car idle if you simply drive normally for the last 2 or 3 miles before you shut off the engine. Just never shut the car off immediately after doing a hard pull. E.g. when the cops pull you over on the highway.
 

Brimfull

Active Member
Nov 7, 2018
1,385
418
Wrexham
From owning many a turbo engined car the only advice I would give is,not to thrash the car before it's up to temp and never switch the engine off whilst the engine is reving (only shut down when the engine is idling)

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BoomerBoom

Active Member
Jun 1, 2018
690
249
Correct me if I'm wrong, but I thought they'd solved this in modern cars with overrun systems that keeps the coolant flowing around the turbo bearing after you've switched the engine off.
 

Brimfull

Active Member
Nov 7, 2018
1,385
418
Wrexham
Correct me if I'm wrong, but I thought they'd solved this in modern cars with overrun systems that keeps the coolant flowing around the turbo bearing after you've switched the engine off.
If you shut down the engine whilst the engine is being rev'd the turbo keeps spinning until it winds down but the oil is stopped being pumped as soon as the engine is shut down, starving the turbo of oil.

Not familiar with the notion of coolant being pumped around the turbo


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Damo H

Remind me, what's an indicator?
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Oct 3, 2012
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Car Length In Front
Correct me if I'm wrong, but I thought they'd solved this in modern cars with overrun systems that keeps the coolant flowing around the turbo bearing after you've switched the engine off.
Yeah both my 280 and 300 you can hear a pump wearing away for a few minutes after switch off. Longer on hot days.

Agree with @theoldboy if you’ve thrashed your car, always let it cool down a little first before switch off. For me that’s more than just sitting at idle but making sure the car has chance to cool off on the last bit of the journey too.
 
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Deleted member 103408

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All I will say is that the latest maps (stage 1 as well as other) have specific software in place to stop max boosting when everything is not at the right temp (both cold and hot). My Garage who tuned mine to Stage 3 and all the guys I meet on the Track with Turbos have always advised to always cool it down on the last lap and or let the engine cool a little before turning off.

But we also make sure we don't apply the brakes after a hard track session to protect the disk's

I also change my oil much more frequently than most people, again to protect the engine (because it gets used hard) and give me a few more years fun.

Normal driving is fine but if you push your car and you want to keep some longevity of components then allow it to cool down.
 

BigJase88

Jase
Apr 20, 2008
3,767
1,069
In all seriousness

Take it easy until at least water temp is at 90 (i know oil takes a bit longer) just be sympathetic

On cool down nobodys coming off an autobahn and slamming it straight in a garage so generally you will of slowed down for the last couple of minutes of a journey. 30mph residential area, which will be enough to cool it down
 

LouG

Active Member
Dec 1, 2017
1,319
481
Nelson, New Zealand
Turbo cooling was an issue in the old days of air cooled turbos and less advanced oils, hence the market for turbo timers. (and alarms to protect the still running car)
Now just a short time of normal use after a thrash cools the turbo sufficiently. I seem to remember that the manual does refer to this. Something along the lines of not killing the engine immediately after a record setting lap of the Nordschliefe.
 

Legojon

I only wanted a remap
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Jul 7, 2015
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My Garage who tuned mine to Stage 3 and all the guys I meet on the Track with Turbos have always advised to always cool it down on the last lap and or let the engine cool a little before turning off.

I recall from the olden days, cars coming off the track, parking up and opening the bonnets to let the heat escape. Does anyone still do that?
 

Deleted member 103408

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yep still do

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