Which Turbo timer do you use?

[911cabby]

Hi guys,
Soon I will be converting my 1987 carrera 3.2 to a turbo set up...
What turbo timer are you useing and why did you choose it over another?
Thanks for your feedback-

[MT930]

what's a turbo timer ?

Do you mean boost pressure gauge ?

[spuggy]

Originally Posted by MT930

what's a turbo timer ?

Do you mean boost pressure gauge ?

Turbo timer is an aftermarket device that keeps the motor running for some programmable time after you switch the ignition off.

The factory does this via one of the extra relays in the back of the 930 engine bay - makes the car run on for 10-30 seconds after the ignition is switched off. This is because turbos spin up to 100,000 RPM - they don't stop turning immediately when you turn the ignition off.

KKK's are plain bearing and oil-cooled, they rely on the motor for their oil supply. If your 930 doesn't run-on, you're likely missing the relay, or it doesn't work correctly.

Read a test drive of the 935K3 where the guy cut the motor on the pit road, coasted in, stopped, unstrapped and got out and could hear the turbos still turning... Then the pit boss asked him not to do that...

On the other hand, I don't have this relay or the associated wiring and my turbos last just fine. Just drive a mile or two off-boost or let the car fast-idle for a few minutes before turning off the ignition. All you're looking to do is avoid killing the oil supply to a red-hot turbo spinning unreasonably fast.

If not been hitting boost, I switch it off just like an N/A car.

The thing you should probably be more concerned about with a really, really, hot turbo (e.g. one that was 1450 degrees and glowing cherry-red a few seconds ago), is just switching off and having the heat-soak turn the oil to coke. Do a search on the 930 forum.

The factory timer is intended so that non-gearheads can drive a production car, but I wouldn't rely on it to protect from extreme scenarios like that - it doesn't run on long enough

So you might as well take charge of the cooldown procedure yourself. But then, I like manual heat, too

[911cabby]

thanks for the reply!

[javadog]

Factory timer? Runs for 10 to 30 seconds? Don't think so...

Having owned a couple 930's for the last 25 years, let me say that a turbo timer isn't needed. I have never has an issue with a turbo. I don't run the car hard for the last few miles when returning home, to cool the turbo down a little. Low load, lower rpms, nothing unusual.

The delay in the engine cutting off is this; the fuel pumps are cut off when you turn the key and the ignition is left on for a couple seconds, to ensure any fuel remaining in the engine, as it winds down, gets combusted.


JR

[spuggy]

Originally Posted by javadog

Factory timer? Runs for 10 to 30 seconds? Don't think so...

I stand corrected - as I don't have one myself and heard folks complaining about the car running on (and wasn't dieseling), figured it was longer - comparable to the shorter periods on the aftermarket devices.

Just out of interest/comparison, the 944 turbo (951) has a factory-fitted separate electric pump that continues to pump coolant through the water jacket after the ignition is off to ensure bearing temps are below 340 degrees. For as long as it takes...

Having owned a couple 930's for the last 25 years, let me say that a turbo timer isn't needed. I have never has an issue with a turbo. I don't run the car hard for the last few miles when returning home, to cool the turbo down a little. Low load, lower rpms, nothing unusual.

Exactly. If this was a bad practice, I think I'd have killed a turbo by now in 30,000 miles.

The delay in the engine cutting off is this; the fuel pumps are cut off when you turn the key and the ignition is left on for a couple seconds, to ensure any fuel remaining in the engine, as it winds down, gets combusted.

Interesting. Might have to look at adding that.

[MT930]

Thanks for the explanation

Mine runs for couple seconds after turning off.

Makes sense

I never turn it off quickly after hard running.