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Turbo Coking and Temp

EricVonHa

Well-known member
Joined
Feb 18, 2002
Messages
693
Location
Suburbia Phila
Corvette
'93 6-Speed & '87 Callaway
One of the urban legends with turbos is that you're supposed to let the car idle for a few minutes before shutting down the car. This will allow the oil temp to decrease, allow the turbo(s) to cool and thereby not coke the oil within the turbo's oil passage(s). Funny thing is, Callaway literature makes no mention of this in anything that I have. (I've got bulletins and what I think to be all original owner info) It stands to reason that the Callaways should also be idled for a few minutes before shutdown, no?

Mine has the heavy duty cooling and oil cooler and on a night like tonight here in Pa (45 deg), it ran around 160 degrees both oil and water for the cruise home from the 1st car show of the season. Even though it was that cool when I pulled into the driveway. I still let it "idle down". I've never seen anything posted like this regarding Callaways, so please offer your feedback...
 

TAC

Well-known member
Joined
Feb 18, 2002
Messages
252
Location
Bothell, WA
Corvette
1987 Yellow Callaway TT Convertible & 2003 MY Z06
I've read that too and I thought it was in the Callaway manual or their website but am danged if I can find it now. My understanding of this is that you should worry about it only if you've been hitting the turbos pretty good and then come to a quick stop and turn the engine off. This leaves the oil in the lines right next to a very hot turbo and produces the effect you describe. Most likely, you have driven at least several miles after getting into the turbos and you are alread cooled down. My turbo runs are always a ways away from home so I am always cooled down by the time I get home. If on the road, I do let it idle several minutes.
 
9

90Callaway

Guest
I don't think this is any "urban legend" it's fact. You should do this with all turbocharged engines. I looked in my Callaway literature and can't find any specific reference either. But I'd swear that I've seen it somewhere.

I believe what happens is that if you've been driving really hard and the turbos are spooled up they take quite a long time to spool down. They are turning at something like 100,000rpms at full boost or close to it. If you stop quickly and shut the motor down the impeller is still spinning. You now have no oil pressure so oil does not continue to flow through the turbo. The oil that is in the bearing will get fried and "coke" from the friction generated heat of the spinning impeller shaft. That's why you wait a while to let the turbo spool down while it's being cooled by flowing oil before shutdown. You should also not rev the car just before shutdown as that will accelerate the turbo impeller... some people do this as a habit.

I have a Porsche that supposedly has an auxilary electric pump that keeps oil flowing through the turbo after shutdown. I still don't take a chance and leave it idle for a minute or two before shutting it off.
 
S

SurfnSun

Guest
Greddy actually sells what they call a turbo-timer which keeps the motor running for 1-2 minutes after you turn the key off and pull it out.

They only make them for all the common import turbo cars though.
 

EricVonHa

Well-known member
Joined
Feb 18, 2002
Messages
693
Location
Suburbia Phila
Corvette
'93 6-Speed & '87 Callaway
Thanks for chiming in everyone. Turbo physics is turbo physics. Anybody find anything in their Callaway documentation that requests cool down procedures..?
 
T

TurboLuigi

Guest
There is a similar product for Turbo Buicks that keeps the engine running after shutdown for the same reason. I also ease off the turbo's as I reach a destination. If you are interested visit the turbobuick.com or gnttype.org for info about that (and its not for imports).

However I am not as concerned TurboCoking with the Callaway as I am with by Buick GNX because of the fact that the Callaway has coolant flowing through the turbo housing while the Buicks do not. I thought this was an added measure from Callaway to prolong turbo life.

Luigi
:cool
 

mxdout165

Well-known member
Joined
Dec 16, 2000
Messages
109
Location
Soon to be Greeley, CO
Corvette
Not Any More :( - '92 Typhoon #2482
It's interesting that Callaway has no mention of it in their literature. While I'm not a Callaway owner, I do own a Typhoon, and after reading my manual cover to cover, I also find no mention of a cooling period after prolonged turbo use. Of course I might have missed it, and I'll look again later today. To me it's just common sense to let it cool. Is there a reason this info seems to be left out? A turbo is expensive to replace...is it a "we don't tell them so they replace it later to make us money kind of thing?"

As per Turbo timer, the new WRX's come with them stock. I've been thinking of getting one, but I would have the wierdest feeling walking away from my car while it was running.:eyerole

T Jay
 

Tom Bryant

Well-known member
Administrator
Joined
Nov 9, 2000
Messages
7,304
Location
Edgerton, Ohio, United States
Corvette
1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
Turbos are turbos, right? In a big truck you are under boost constantly to some degree, unless you are coasting or decending a hill with the Jake brake off. All truck engine manuals tell you not to use full throttle until oil and water are up to 150 degrees and to idle an engine for 3-5 minutes before shutdown. It is also policy in most trucking companies. If you want an education install a Pyrometer (exhaust temperature guage) on the turbo exhaust outlet. You will be amazed at the temperature increase during boost conditions. you can also tell when it's cool enough to shut down.

Tom
 
S

Stan A

Guest
Turbo Cool Down

Hello To Everyone,

Callaways only note on the cool down process came in the form of a sheet of paper that was surposed to be included with each Callaway manual.

There was no other mention in any of the other materials sent out by them during the five year run.

It would be wise to run your motor for 30 to 45 sec after driving your car in a moderate range. Atleast two minutes after using the turbos in any hard runs. This becomes even more important now because of the difficulty in finding replacements.

Current pricing on a new unit has hit $3,000. We can still get rebuilds done.

Hope everyone has been doing well since my absence...

Stan
 

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