My buddy and I got into an argument a few days ago about proper turbo cool down procedures. We're in a Stryker brigade and the vehicles are turbo-dieseled CAT engines. Frankly, it's just two sergeants butting heads here.

Assuming all the same aspects apply to all turbo systems and cool down procedures... I can't imagine what would make the turbo on a Stryker so different, but I digress. Would someone explicitly explain why you let a turbo cool down after operation and what happens to the turbo if don't properly let it cool down. GDLS (the company that makes the Stryker) recommends a 5 minute cool down grace period after operation. We're not debating this, we're debating the why.

For the record, I say its because the oil will cook and leave deposits on the inside of the turbo. He says it's to let the oil drain out of the turbo, because if not, oil will stay inside the turbo and over pressurize it, thus blowing it.

Who wants to take a bite outta this one?

It is to let the tubo and mainly the CHRA cool down so the oil won't "coke". Now regarding the overpressurizing, some lower mount turbos run scavenging pumps to pump the return oil from the turbo back to the motor (not sure of the specific design were talking about). Some applications run timers that keep the scavenging pump running for a period after shutdown to pump any residual oil back to the motor preventing this "over pressure" condition which can leak past seals.

Hope this helps a bit

 

what he said ^^^

 

to add..... my understanding is that the older journal bearing turbos had this issue much more than the BB turbos of today. when i get out of mine at home for instance, i just turn it off cause my street is 20mph so thats 3rd gear at like no rpm so it gets all the hot oil out by the time i get home. i think thats why turbo timers are not sold as much also, because of the newer technology of BB and water/oil cooled turbos not needing the same cool down times.


but heck, i could be way off also.

 

So what specific harm does this "coked" oil cause?

 

"coked" = burnt oil.. clogging up the flow.. hot spots..
If the turbo is glowing hot and you just shut down the engine, the oil thats in the
turbo is going to cook like a mf'er.. Burnt oil doesn't like to flow very efficiently
this is why you let the engine run and circulate after running hard..

This holds true for oil AND oil/water cooled turbo's..
cartridge or ball bearing..

 

And hey, Tommy... when you move to Austin, we gotta ride together. I gots a 08' Kawi ZX-10r.

 

And hey, Tommy... when you move to Austin, we gotta ride together. I gots a 08' Kawi ZX-10r.

i'll be there by the new year for sure. got a house in round rock.

 

think of what sludge does to your motor

http://jalopnik.com/5415431/what-happens-when-you-dont-change-your-oil-for-60000-miles

no think your turbo is smaller than your motor

if there is constant coking in the turbo there would be issues

is the turbo getting limited/no oil????

which would shorten the life of the turbo it self severely so just like i did with my MRAP when i was in Baghdad let your stryker run for a minute or two to prevent any coking

 

think of what sludge does to your motor

http://jalopnik.com/5415431/what-happens-when-you-dont-change-your-oil-for-60000-miles

no think your turbo is smaller than your motor

if there is constant coking in the turbo there would be issues

is the turbo getting limited/no oil????

which would shorten the life of the turbo it self severely so just like i did with my MRAP when i was in Baghdad let your stryker run for a minute or two to prevent any coking

Yeah, I saw that post a few days ago. There's no issue with the Stryker, like I said.. I'm just satisfying our egos here. Heh.. I'm not driving the thing.

i'll be there by the new year for sure. got a house in round rock.

Heh, no ****. We might be neighbors. I'm down Old Settlers, if you know where that is :waytogo:. I won't be on R+R until April though. Hope you found a job or have one lined up. And if you do, hook me up! :lol:

 

I am no turbo professional but here is my understanding. Indeed with water cooled CHRA (Center Housing Rotating Assemblies), you can pretty much shut the car off with little to no cool down. The way I see it these are more for the soccer mom's volvo, anyone who is conscious about not shutting there turbo'd vehicle off immediatley doesn't really benefit much from a water cooled housing (I don't think, maybe super high performance applications can benfit from it). As far as "coked" oil, it's my understanding that this is basically when oil vaporizes. When this happens deposits from the oil are essentially cooked to the already thin passages the oil flows through, restricting the flow of oil and leaving rough journal surfaces. With restricted oil flow and rough surface finishes on the journals, I would assume this would lead to high drag and limited oil flow causing early failure. Once again I'm not a pro I just reason through things. Maybe someone else will chime in that has a little more experience.

 

with a water cooled center section its all but elimited the "coking" problems that turbo's had in the past:waytogo:

 

It helps, but wont eliminate it unless you have the water circulating for a little bit if the turbo is still piping hot.

But your mainly right, it is far more difficult to COKE the oil if it has a water cooled CHRA..and synthetic oil

 

I could hear the turbo still spinning after i park, (whirring sound from exhaust). So i put 40 seconds on the timer.

I think the cool down procedure is to let the oil drain, and also to make the blades/turbine of the turbo to slow down. If the turbo is still spinning and you shut the engine off, now theres no oil flowing or the oil inside will "coke" then the turbo is gonna get damaged.



:shrug:

oh yeah, I'm in the Army too. I gave a class about Turbos in military vehicles, Pumps, and Generators. Microsoft powerpoint slideshows and an actual turbo from a humvee. Looked like a T3/T4 i think.

 

My thoughts was to let the turbo cool down and stop spinning at high speeds. basically, you just want it to be cool and at low rpm before you stop the oil/water flow through it (by turning off the motor)

 

Only book worth owning in reguards to Turbocharging..
[ame]http://www.amazon.com/Maximum-Boost-Turbocharger-Engineering-Performance/dp/0837601606[/ame]

 

Only book worth owning in reguards to Turbocharging..

http://www.amazon.com/Maximum-Boost-Turbocharger-Engineering-Performance/dp/0837601606

x2, that book stretches my mind on boost:lol:

 

I haul arse and shut her down!!

 

Also the bearings depending on what type needs a cool down cycle. Other wise the bearings wear out quick. :waytogo: