Pelican Parts Forums - proper warmup

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- - proper warmup (http://forums.pelicanparts.com/porsche-911-technical-forum/297030-proper-warmup.html)

I have to wait about 2-3 minutes before taking off, otherwise the car will stall. Is that normal?

And after a cold start, my oil level gauge is always in the red until it warms up. After running it for about 5 minutes, the needle rises to normal readings. I assumed this was normal until the oil warmed up. Please tell me if this is not normal. Perhaps need more oil?

Thanks,
Darrell

The mixture is extremely rich on a cold start. This extra gas tends to wash the oil off the cylinder walls and accelerate wear. The idea is to get the engine up to temp as quickly as possible to avoid this, so drive off right after startup, but keep the load on the engine and the RPM's down until you've warmed up. The owner's manual advises of the correct procedure to accomplish this. Idling for an extended period is a no no.

ianc

Edited to say: Nashvillecab, with a Motronic or CIS car, you should not have to wait 2-3 minutes to drive off without stalling. You have a problem.

I've done both - the car has idled for a few minutes, and I've also taken of as soon as the key was turned. Neither process has shown an effect on the engine, other than smogging out the neighbor with a putrid rich mixture.

I do think keeping the engine rather conservative at low temps is prudent.

However, I've also been in cars with skilled Porsche mechanics who could care less if the car's been sitting awhile; they stomped on it the moment they were in second gear.

Quote:

I've also been in cars with skilled Porsche mechanics who could care less if the car's been sitting awhile; they stomped on it the moment they were in second gear.

Sure, particularly if they get cheap parts, or the car's not their's! ;)

ianc

Kemo provided an interesting link in an earlier thread shown below:

http://forums.pelicanparts.com/porsche-911-technical-forum/294171-slick-50-a.html?highlight=acid

A portion of the link from The Engine Oil Bible that Kemo included in his reply:

Quote:

The current trend is the "90% of your engine wear happens at startup" advertising ploy. This fact is absolutely true, but as it happens, it's less to to with "grinding engine parts" and more to do with combustion. When the combustion gases burn, they form acids which are highly corrosive when their vapours condense. These acids collect in the upper cylinder areas where their temperature is raised above their dew point. The acids condense and etch the cylinder walls and piston rings. In reality, this accounts for over 85% of engine wear, the other 15% being down to abrasion. So the adverts are nearly right - most of the engine wear does happen at startup, and it is because of a lack of oil, but it isn't because the oil isn't coating moving parts - it's because it's not transporting these acidic gases away. Having said that, if you start the engine and let it idle for 15 seconds or so before moving off, you can probably add another 100,000 miles to your engine's life without one bottle of additive. This warms the oil up a tad and makes sure it's in all the most vital areas before you start putting a strain on the engine. Most handbooks tell you not to let the engine warm up before driving off (they're referring to the acid corrosion mentioned above), but they mean don't let it reach working temperature. If, however, you insist on starting up and belting off down the road, think of this next time: it takes an average engine around 3 minutes of average driving for the exhaust manifold to reach 300°C. If you blast off and run around at full throttle, right from the word go, that process takes a little under a minute. Think about it - from outside air temperature to 300°C in a minute - what exactly is that doing to the metal in your manifold? Ask anyone who's ever owned an original Audi Quattro - they'll tell you exactly what happens.

My methodology is and always has been to use a 30 second time interval between starting and driving the car. Even then I keep the rpm's in check (below 3,000) until I see movement on the temperature gauge. I also give this 30 second warmup to all of my gasoline powered pieces of equipment (lawn mowers, garden tillers, etc...).