Turbo cooling after engine shutdown?

[jchasp59]

Towards the end of this explaination of the 1.4L turbo engine, he mentions that cooling of the turbocharger continues even after the engine is shut off.

On the 1.4L Fiat 500 Abarth turbo it's done with a small, dedicated electric coolant pump that can circulate coolant to the turbocharger for up to 10 minutes after the engine is shut down.
I can't find any further or more specific information anywhere that tells me how GM does this on the 1.4L Sonic/Cruze turbo? Anyone have the knowledge, or can point me in the right direction?
Hope it's true. Would/Could extend the life of the turbocharger.

GM 1.4-liter I4 Engine @ NAIAS 2010 - YouTube

 

[sonic hotness]

Its coolant cooled so coolant run threw the turbo after shut of too cool it down

 

[CoHPhasor]

Its coolant cooled so coolant run threw the turbo after shut of too cool it down

That doesn't follow.
If there were an electric pump that continues to pump coolant after shutdown, that would be true.
Otherwise, inherently, water gets hotter after shutdown. (An effect known as "Heat Soak")
Basically, the engine is still hot, but the water is no longer being circulated so the water heats and expands.
Nothing about that process says "Makes things cooler after shutdown".

It would be cool to know if GM has done something to help cool the turbo after shutdown, please let us know if you find it!

 

[Screamer4]

Modern turbos are cooled by oil AND water. There's virtually no need for a turbo timer of any sort when it's cooled in this manner.

For reference, my WRX has no turbo timer or electric coolant circulator; 160k hard miles later it has no turbo or engine issues. And I'm running higher than stock boost.

 

[JimmyBuckets]

The WRX does the same thing except it is a passive system that draws the coolant through the line based on heat and the shape of the coolant line. Drive the care hard then park. Pop the Hood and then listen...you can hear the coolant being slerped through the lines after the car is completely off.

 

[SSpeckerwood]

Great video. Thanks for the find.

 

[Machine]

coolant actually circulates through the entire engine even after shutdown. Convective heat transfer in the cooling system causes it to move. If the engine is hot, it is transferring heat to the coolant, the coolant is expanding and as such, loosing density. Less dense float about more dense, and it rises. Vise verse, hot expanded coolant is pushed to the radiator, and the reverse happens, it cools, contracts and flows down.

The turbo actually gets pretty good flow as it temperature differential is high compared to the rest of the system.

The first cars usually had no water pump and were cooled entirely by convection.

 

[laborsmith]

I believe the Corvair turbos were cooled by convection also.

I am thinking the electric fan runs for a while after the engine is turned off, although I can not hear it, the air is definitely forced out of the engine bay through the hood extractors for several minutes, after which I can feel hot air coming ot but not under pressure.

Maybe one of the member engineers knows something about this.

Laborsmith

 

[Machine]

I believe the Corvair turbos were cooled by convection also.

I am thinking the electric fan runs for a while after the engine is turned off, although I can not hear it, the air is definitely forced out of the engine bay through the hood extractors for several minutes, after which I can feel hot air coming ot but not under pressure.

Maybe one of the member engineers knows something about this.

Laborsmith

same thing as the coolant, the engine is heating the air in the engine bay and it is rising up out of the vents. It causes a lower pressure in the engine bay so it sucks fresh cool air from the ground and the cycle continues.

 

[Opticon]

Coolant actually circulates through the entire engine even after shutdown. Convective heat transfer in the cooling system causes it to move.

In all the decades that the water-cooled turbo has been in mass production there has been no reason to circulate coolant with a pump after shutdown... unless the Fiat's cooling system is designed in such a way that the turbo is not filled with coolant in a resting state.

 

[Machine]

im not saying a coolant pump is not better, im saying that there is coolant flow after the motor is shut down.

it all depends on how the system operates and how its set up.

 

[theenico]

My 1986 Audi 5000 turbo had an auxilliary electric water pump. It would circulate coolant through the turbo and cylinder head after you shut the car off. When it got down to a certain temperature the pump would shut off.

Did it actually make a difference to longevity of the turbo? I have no idea, but that car still had the original turbo at 300,000 mi when I sold it.

Have I added anything more than an anecdotal account to this topic? Not really.

 

[CoHPhasor]

^ Bingo

 

[jchasp59]

Modern turbos are cooled by oil AND water. There's virtually no need for a turbo timer of any sort when it's cooled in this manner.

For reference, my WRX has no turbo timer or electric coolant circulator; 160k hard miles later it has no turbo or engine issues. And I'm running higher than stock boost.

I'm wondering if this, or something similar, is what was mentioned regarding the Sonic turbo in the video:
Fiat Abarth After-Run Coolant Pump:
One such feature of the Fiat 500 Abarth that helps guarantee reliability is an after-run coolant pump (ARCP) that circulates coolant through the turbocharger's housing to cool down the turbo when you turn the car off.

http://www.fiat500usa.com/2012/04/fiat-500-abarth-after-run-coolant-pump.html

 

[Alan]

im not saying a coolant pump is not better, im saying that there is coolant flow after the motor is shut down.

Yes. For anyone in doubt, pop the hood after you shut the car off. You can hear water circulating.

 

[SSpeckerwood]

all i hear is the squirrel taking deep breaths from running in the cage.... lmao!!

 

[JimmyBuckets]

See post #5 or read this....
http://en.wikipedia.org/wiki/Thermosiphon

 

[CoHPhasor]

See post #5 or read this....
http://en.wikipedia.org/wiki/Thermosiphon

To be fair, lifting the hood introduces convection that isn't normally there.
It's the same as saying:
"Your car is hot for an hour after sitting out in the sun all day? The car cools very quickly, you can feel the heat escaping when you open (all) the door(s)"


The concept of convection, and of water being able to cool an engine/turbo isn't in question.
The amount of cooling necessary and the amount of cooling without forced circulation is (to a degree) though.

How quickly a (freshly nailed) turbo needs to cool down and the amount of heat a heat-soaked coolant system can transfer is important.

Have you ever done some work on coolant lines and had "no leaks" while running it in the garage, or even while test driving only to have a river under your car shortly after shutting it off?
That's part of the reason the (other model) car mentioned earlier has a post-drive electric circulation pump in place to extend the life of its turbo.

Honestly, if convection was enough to cool the engine and its components, my car's engine wouldn't be hot to the touch hours after I parked it.
(And just imagine how well convection's working in nice cool places like Arizona when it's 110F)

For argument's sake, I imagine it's possible that in the case of the WRX Subaru took great care to ensure that just the turbo's coolant lines are manipulated in a way to make coolant flow faster through that section?

 

[Opticon]

Honestly, if convection was enough to cool the engine and its components, my car's engine wouldn't be hot to the touch hours after I parked it.

Even the most heat soaked intercooler will prevenk oil coking in a hot turbocharger by convection. 200* fluid cools 500* turbos.

After the temps stabilize in the system (say 350*) the coolant stops flowing and the entire system is left to radiative cooling (a much slower process). Even though you won't be able to touch the engine for hours... the turbo is considered to be "cool".

 

[RichieRocket]

Like many things in nature, convection heat transfer is non-linear. The heat transfer rate at 250F may be 5 times faster than at 150F, even though the temperature difference (compared to ambient air) is roughly 2 times larger.
Don't quote me on the actual number, we can pull out the heat transfer text books if need be.

For me, I don't worry about turbo cooling. I don't need to go full boost thru my neighborhood and into my driveway. A couple miles from home, I'll just stay off the boost...