Dr. G

Is it necessary to let the engine run for a few minutes after all my driving, or just after driving the car hard? Basically, if I'm not in a boost situation and driving around town should I still wait a bit before shutting down?

PorschePhD

You should always allow the car to idle for 2 minutes prior to shut down. Any time you can give it without a quick shut off is a bonus.

hatchy

I usually just take it easy for the last few miles of the drive to give the oil and the turbo a chance to cool down a little, never had any problems. I also change the oil very often as well (3-5K miles), some people say it is an overkill, but it is cheap insurance.

Jeff 993TT

You may also want to install an aux oil cooler to keep the temps low.

Or go the cheap route and install an oil fan switch. This forces air though the exisiting cooler to cool down the oil temps.

kingleh

not sure if you guys like jap parts but invest in a turbo timer.

non boost situations 30sec is fine.

if you have been driving for a while and boosting some. prob about 1 1/2 minutes

on the track for 25minutes, well your looking at about 7 minutes


2min is a little bit over kill imo, just for normal driving.


i have a exhaust temp gauge and judge by that

Kevin

Turbo timers won't work for our car system alarm. You aren't going to exit a 70k car with the engine running and no alarm set... Unless someone makes the timer to lock the doors, set the alarm, shut engine off. That would be a system.

You guys HAVE to cool the engine down, 2 minutes! Or you will be posting, smoke at startup...

kingleh

We don't have the luxury of a watercooled engine to lower the head temps and thus exhaust outlet temps.. And no watercooled bearing housings to stabilze the heat transfered from the turbine housings to the turbine wheels.

911/Q45

Kevin,
How does the ceramic coating on the turbo effect cool down? It seems like it would retain heat that would be transfered to the bearings, shaft and seals.

Kevin

The ceramic coating prevents the radiant tranfer from the housing to the bearing housing. It is a physical barrier that keeps the heat in one place..

FineProperty

Ok. Not owning a turbo air cooled, I have a few questions. Wouldn't the engine be better off driving 'off boost' for 2 minutes (like a short cruise through your neighborhood) letting the air cool the engine, rather than letting it idle at a standstill? And, the reason behind letting them cool is so the oil doesn't bake onto the turbo shaft and seals, does a good synthetic (Mobil1) keep this from happening except in extreme heat?

I do drive a dual intercooled turbo Volvo, and after a hard run I still let it idle for a minute before shutting down, just so the turbine isn't still spinning.

Kevin

Rich your Volvo was watercooled.. The idle circuit AFR is higher thus the added fuel cools the surfaces of the head and turbine housing, this is what is needed. Now if you let you car idle for 10 minutes you will start having heat soak.. Not good, so we want a happy medium... 2 minutes

hatchy

Even when you let your car idle, the turbines are still spinning. Not very fast, but still spinning.

Kevin

Hatchy;

That's not the problem, the problem is that the temps in the turbine housing are to high, you need to idle down the car to allow the fuel to cool the headers and turbine housing. If you shut the car off, Nothing is going to cool the turbine wheel/housing and the heat will wick through to the bearing housing.

FineProperty

Is it bearings boiling the oil and baking them black that occurs next? Just a little confused on where the damage is occuring. I have seen my turbo at night after a fast run, it actually glows.

Do 993TT's have a fan that cools the engine in traffic and when stopped (sorry, I have not yet had the pleasure of a 911, and my 914 got so hot it cooked an ECU).

Anir

This has always been my gut feeling, as well, and is generally my approach. I do try to also wait about 30 seconds before shutting it off. At the track, I let it idle for 5-8 minutes after a hard run, but I simply don't have the patience to wait 2 minutes every day on every short jaunt.

I've also installed the GT auxiliary oil cooler, which helped lower oil temps. I've also noticed a further significant drop in oil temps since removing both mufflers. I would think that this greatly improves airflow to and cooling of the turbos.

Ruf-Dan-Ruf

I have had plenty of Turbos with alarms and with Turbo timers.

The Alarm is set with the timer counting down and engine running.

If the handbreak is taken off in this count down state the engine stops immediately and the alarm is still set.

If someone breaks the window / opens the door the alarm triggers and the engine stops immediatly.

The biggest danger is people chasing you in carparks saying "hey mister ... your car is still running" .... which is quite funny.

The other funny was my wife forgetting to remove the keys from ignition leaving the car running and locking the door.

The good ones know how hard you were driving leading up to turining off ..... light driving the timer autoruns for 10 seconds .... hard out .... 50 seconds etc.

It is very safe and secure in my opinion.... I might put on the RUf and let you know how it goes .... The RUF has the porsche factory alarm system so a good test if it can be done.