Turbo Coking and Temp: What are your thoughts?

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Turbo Coking and Temp: What are your thoughts?

Post by Callaway Chris »

From the archives:
Turbo Coking and Temp
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...
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Re: Turbo Coking and Temp: What are your thoughts?

Post by undercover »

Probably not an issue with synthetic oil, but can't hurt nonetheless. Some turbo cars, like the Porsche 944T, have an electric pump on a timer that continues to circulate coolant to the turbos for 30 sec after shutdown.
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Re: Turbo Coking and Temp: What are your thoughts?

Post by jonstr »

Out of curiosity, what kind of oil temps are we talking about here under normal operation? Neither of my cars ever get very high - it's hard to tell on the gauge, but I don't think the oil temp on either car ever gets much above 180-200 (needle never moves more than 3/8s of an inch). I used to assume there was just something wrong with the gauge or sensor in the Speedster, but since both cars act the same way, and because of how the oil is routed out of the turbos, I decided not to worry about it.
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Re: Turbo Coking and Temp: What are your thoughts?

Post by Callaway Chris »

Jon, use the digital readout function on your dash and compare to the needle. I do not think the needle is as accurate. :conf
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Re: Turbo Coking and Temp: What are your thoughts?

Post by SurfnSun »

Water cooled turbos really don't have a worry of coking after shut down. Turbo timers are for turbos that don't have a cooling provision. The coolant + synth oil keeps the turbo cool enough to protect it. Thats why its not talked about w/ regard to B2ks. That being said, I wouldn't personally go run multiple full boost runs and them shut down the motor immediately. Hope this helps.
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Re: Turbo Coking and Temp: What are your thoughts?

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Callaway Chris wrote:Jon, use the digital readout function on your dash and compare to the needle. I do not think the needle is as accurate. :conf
I don't believe I have that option on the '91 like you could on the old dash - unless there is a function I'm not aware of. I'll have to get my ALDL cable and software working to get a reading off the computer, I guess.
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Re: Turbo Coking and Temp: What are your thoughts?

Post by Luigi »

Consider that Turbos are spinning at some 10,000+ RPM's with very hot exhaust hast pushing the fins, they will heat up. Though I agree with Surf, the Callaway design uses both coolant and oil to cool the turbos and it is one of the best designs I've seen. Back when I had my GNXs, I had purchased one of the Turbo Timer systems referenced earlier which would maintain oil pressure for up to 2 minutes after shutting off the engine to prevent turbo coking.

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Re: Turbo Coking and Temp: What are your thoughts?

Post by Callaway Chris »

jonstr wrote:
Callaway Chris wrote:Jon, use the digital readout function on your dash and compare to the needle. I do not think the needle is as accurate. :conf
I don't believe I have that option on the '91 like you could on the old dash - unless there is a function I'm not aware of. I'll have to get my ALDL cable and software working to get a reading off the computer, I guess.
Is there a way to "page through" the dash functions?

Instead of showig mileage, etc. it would show the oil temp. etc.
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Re: Turbo Coking and Temp: What are your thoughts?

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Callaway Chris wrote: Is there a way to "page through" the dash functions?

Instead of showig mileage, etc. it would show the oil temp. etc.
No, not on the later C4 dash panels. The digital portion is limited to speed and 'trip meter' stuff - fuel mileage, odometer, range, etc. And, to make matters worse, the numbers on the analog engine gauges are limited to the low and high only, so the oil temp gauge only shows '100' at the bottom and '320' at the top. No numeric indications or hash marks in between. Even if they're acurate, you can't really tell what the reading is.
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Re: Turbo Coking and Temp: What are your thoughts?

Post by SurfnSun »

No, not on the later C4 dash panels. The digital portion is limited to speed and 'trip meter' stuff - fuel mileage, odometer, range, etc. And, to make matters worse, the numbers on the analog engine gauges are limited to the low and high only, so the oil temp gauge only shows '100' at the bottom and '320' at the top. No numeric indications or hash marks in between. Even if they're acurate, you can't really tell what the reading is.

Wow thats really weird. My 96 allows me to scroll thru actual temps, oil pressure, etc. I looked at the dash of a 90 and it does have different buttons. Mine has a "gauges" button so scroll thru them.
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Re: Turbo Coking and Temp: What are your thoughts?

Post by BIGJOHN »

Wow thats really weird. My 96 allows me to scroll thru actual temps, oil pressure, etc. I looked at the dash of a 90 and it does have different buttons. Mine has a "gauges" button so scroll thru them.
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Re: Turbo Coking and Temp: What are your thoughts?

Post by Callaway Chris »

John, that was what I had thought about my 1993. Jonstr, are you saying the 1991 dash cannot do this? :wtf
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Re: Turbo Coking and Temp: What are your thoughts?

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Callaway Chris wrote:John, that was what I had thought about my 1993. Jonstr, are you saying the 1991 dash cannot do this? :wtf
Nope, no 'gauges' button on either of my '91s. I looked in the owners manual also, and no mention of a way to do this. I was going to say the same about my '93 ZR1, but it's been several years since I sold that, so I must be remembering that one wrong. I didn't realizet the dash options changed. The dash bezel color was the same in '90-'91 (gray), then changed in '92 (black). Maybe that's when the 'gauges' function was added. :wtf
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Re: Turbo Coking and Temp: What are your thoughts?

Post by Luigi »

I've never seen a Digital Readout of the temps on my '91 either, perhaps I never tried though.

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