Subaru Turbo Cool Down Procedure

[m sprank]

It is not necessary to perform a “cool down/idling” procedure on Subaru WRX/STi/LGT turbo models, as was recommended with past turbo models. The current 2.0/2.5 liter turbo engine has a far greater cooling capacity and, coupled with technology advances, makes this practice no longer necessary. This explains why information about a cool down is not included in the Owner’s Manuals. The heat contained in the turbocharger begins to vaporize the coolant at the turbocharger after the engine is stopped. This hot vapor then enters the coolant reservoir tank, which is the highest point of the coolant system. At the same time the vapor exits the turbocharger, coolant supplied from the right bank cylinder head flows into the turbo. This action reduces the turbocharger temperature. This process will continue until the vaporizing action in the turbocharger has stopped or cooled down.

[MoleMan]

On 7/7/2023 at 3:14 PM, m sprank said:

It is not necessary to perform a “cool down/idling” procedure on Subaru WRX/STi/LGT turbo models, as was recommended with past turbo models. The current 2.0/2.5 liter turbo engine has a far greater cooling capacity and, coupled with technology advances, makes this practice no longer necessary. This explains why information about a cool down is not included in the Owner’s Manuals. The heat contained in the turbocharger begins to vaporize the coolant at the turbocharger after the engine is stopped. This hot vapor then enters the coolant reservoir tank, which is the highest point of the coolant system. At the same time the vapor exits the turbocharger, coolant supplied from the right bank cylinder head flows into the turbo. This action reduces the turbocharger temperature. This process will continue until the vaporizing action in the turbocharger has stopped or cooled down.

Maybe.  However when I drive my 1998 3/4 Dodge with the Cummins I always cool off the turbo after driving.  I just let the engine idle for about 3-5 mins.  I would prob use the same method with a car that was driven hard.  That truck always surprises me.  Manual shift and a Banks controller and exhaust.  1400 LBS of Torque at 2k.  Problem is I hate parking it but I live in wide open country land so I can take 8 spots at the Wally World like everyone else lol.

[blackobxt]

Maybe? Lol

[Max Capacity]

On 7/10/2023 at 10:21 PM, MoleMan said:

Maybe.  However when I drive my 1998 3/4 Dodge with the Cummins I always cool off the turbo after driving.  I just let the engine idle for about 3-5 mins.  I would prob use the same method with a car that was driven hard.  That truck always surprises me.  Manual shift and a Banks controller and exhaust.  1400 LBS of Torque at 2k.  Problem is I hate parking it but I live in wide open country land so I can take 8 spots at the Wally World like everyone else lol.

I'm sorry, did you not understand, he's talking about a turbocharged Subaru for those models he referenced.

I'll add, since buying the GT wagon in late June 2004, I would always tend to coast in neutral when I could before stopping or shutting the car off. I found during my normal driving, it was easy to do. I understand with the 5eat, that might not be as easy to do.

 

That and using a good quality oil.

[Pleides]

I have never been in a situation where I could romp on the car right up to my parking place in my car. I can't imagine driving normally for 30 seconds wouldn't be enough to "fix" any hot oil or coolant temps.

[Code]

MoleMan has some interesting takes in several different threads, approach his comments as satire or just plain old bad advice. 

[m sprank]

13 hours ago, Pleides said:

I have never been in a situation where I could romp on the car right up to my parking place in my car. I can't imagine driving normally for 30 seconds wouldn't be enough to "fix" any hot oil or coolant temps.

The reasoning for cooling down a turbo is 3 fold.  The heat generated from high demand driving without a cool down could cause oil coking, causing the oil to lose viscosity (thermal break down).  If the turbine housing is not adequately cooled this leads to premature cracking around the turbine wheel.   The heat generated could also roast the bearings which are no longer being cooled by oil or coolant flow. 

The explanation is the original post details why this is no longer necessary with a  Subaru WRX/STi/LGT turbo model vehicle.  Subarus engineers designed a system that cools the turbo even after the engine is shut down.  No turbo timers necessary. 

[All_talk]

On 7/7/2023 at 2:14 PM, m sprank said:

It is not necessary to perform a “cool down/idling” procedure on Subaru WRX/STi/LGT turbo models, as was recommended with past turbo models. The current 2.0/2.5 liter turbo engine has a far greater cooling capacity and, coupled with technology advances, makes this practice no longer necessary. This explains why information about a cool down is not included in the Owner’s Manuals. The heat contained in the turbocharger begins to vaporize the coolant at the turbocharger after the engine is stopped. This hot vapor then enters the coolant reservoir tank, which is the highest point of the coolant system. At the same time the vapor exits the turbocharger, coolant supplied from the right bank cylinder head flows into the turbo. This action reduces the turbocharger temperature. This process will continue until the vaporizing action in the turbocharger has stopped or cooled down.

Yes, this recirculating coolant feature has been part of the EJ turbo design since the start. My 1991 Legacy SS had it.