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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N20 and N26 Turbo Engine / Drivetrain / Exhaust Modifications > Start Stop Query & Turbo cooling.
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      02-27-2013, 04:48 AM   #1
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Start Stop Query & Turbo cooling.

I see the start stop doesnt work when the engine is cool & starts to operate after reaching a minimum engine heat level.

But what after a high revving run if i approach the traffic light (or on a track) & the engine shuts down to save fuel wouldn't it harm the turbo ?

Ideally turbo engine would require an idle time of 30-60 secs to cool off the TURBO (Practice for longer Turbo life)

Does the engine shut down ? Or is there a higher limit temperature specified ? after which the start-stop disables itself.

What are your observations on the start stop tech after a high revving run ?
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Last edited by 7 4 7; 02-27-2013 at 04:58 AM.
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      02-27-2013, 11:49 AM   #2
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Start-stop will not trigger even if one of the dozen parameters are not met. I am sure that ASS also checks for engine/turbo temp and if it's too hot for it to shut down it wouldn't kick in.

Also modern turbos don't need "idle off" to cool. Correction, I should say modern turbo designs don't need cool off. Even if the car is shut off after boosting into your parking spot, fan will remain on in order to cool it down to a safe level before everything shuts off. So by the same standard, it is safe to deduce that even under engine off with ASS the fan will continue to cool it down at stoplights.
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      02-27-2013, 12:07 PM   #3
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Quote:
Originally Posted by kppanic View Post
Also modern turbos don't need "idle off" to cool. Correction, I should say modern turbo designs don't need cool off. Even if the car is shut off after boosting into your parking spot, fan will remain on in order to cool it down to a safe level before everything shuts off.
There is no fan to cool a turbo. Modern turbos are oil & water cooled. After the car is shut off, the hot fluids still flow through the turbo, and force them through bringing in cooler fluids, basically siphoning oil & coolant through the turbo after the car is off.

OP, let the car shut off, you don't need to worry about it.
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      02-27-2013, 01:06 PM   #4
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Quote:
Originally Posted by smohr33 View Post
There is no fan to cool a turbo. Modern turbos are oil & water cooled. After the car is shut off, the hot fluids still flow through the turbo, and force them through bringing in cooler fluids, basically siphoning oil & coolant through the turbo after the car is off.

OP, let the car shut off, you don't need to worry about it.
Absolutely correct! The big silver heatsink does the job!

Just wondering what keeps the oil/water circulating. Is it the pressure or is there an active pump?

Thanks.
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      02-27-2013, 01:28 PM   #5
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On most cars, its basically a gravity feed like I said. It works like a siphon, the way the oil/water flows, the hot water gets forced though and keeps pulling cooler fluid behind it till it reaches a certain temp.
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      02-27-2013, 01:32 PM   #6
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In addition, the coolant pump is electric, so it is possible that the ecu will continue to pump coolant through the engine/turbo/etc. while the vehicle is off/standby if it detects that there is a need. I do not know that it does this, but merely highlighting the possibility.

Also, apparently the oil pump is electric too, so same logic applies here as well.
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      02-27-2013, 02:33 PM   #7
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N20 has a water cooled turbo right ?
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      02-27-2013, 02:37 PM   #8
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Quote:
Originally Posted by 7 4 7 View Post
N20 has a water cooled turbo right ?
This entire topic has been discussed HERE. Summary: N20 turbocharger is oil and water cooled, and so is the N55.
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      02-27-2013, 05:38 PM   #9
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After a hard run, shut the engine off and pop the hood. You'll here the gurgling of fluids flowing through the turbo and the faint hum of an electric pump. You may also note a glowing red color from the turbo housing

Either way drive hard and don't worry about it. She'll take care of herself. If you have any doubt, before you park take a slow cruise around the block.
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      03-07-2013, 01:23 AM   #10
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Quote:
Originally Posted by Jeff_in_Oviedo View Post
In addition, the coolant pump is electric, so it is possible that the ecu will continue to pump coolant through the engine/turbo/etc. while the vehicle is off/standby if it detects that there is a need. I do not know that it does this, but merely highlighting the possibility.

Also, apparently the oil pump is electric too, so same logic applies here as well.
No, the oil pump in the N20 isnt electric, its driven by the counterbalance shaft, its only a variable output pump, but its Map controled.
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