A Question on something I read here

As I am pouring through the horror stories about the 996 engine, I read something that bewildered me. One comment on how to slow down the scoring was to NOT let the engine idle right after startup. And as we all know down running it a 5k right after starting it cold. So I'm an old timer and have always thought you were supposed to let a car idle for a minute before taking off...let the oil get through the engine. SO my question is why don't let the engine warm up a minute before taking off....what does it harm? Thanks

I'm not the one to explain this but, I believe it has to due with the fuel mapping. The engine is dumping additional fuel in cold start situations and if you let the engine idle, without a load, it stays in that mapping for a longer duration of time. The additional fuel washes out, dilutes the oil on the pistons/piston rings. If you start the engine and drive conservatively (low rpm, light throttle) for the first several miles and let the engine warm up with a load, it switches the fuel mapping faster, therefore it is better for engine bore lubrication and life of the engine. If I'm incorrect, someone please correct me. Mike

Start the car and begin driving. Keep engine around 3000 rpm until warmed up. Don't lug it..

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Correct. Check out the Rennvision videos on YouTube. Great information.

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This

Had this conversation with my guru indy mechanic. Bottom line, the fuel mapping issue is NOT the case for the 996.1 and 996.2 series. But it IS true for the 997 and newer.

"A minute" is fine - as long as it doesn't turn into 5 or 10 (like if you start the car then connect your seat-belt, check/adjust mirrors - then drive!)... As mentioned above keep your shifts under 3k rpm until it's reached operating temp (180 or more). Obviously if you've got a manual transmission, the rpm's are going to be all over the place through shifts - just average it out. The idea is that when you're cruising, keep the rpms between 2500 & 3k - don't cruise at 2k or 2200 (in other words choose the right gear - 5th or 6th are best used only for the highway - rarely get to 5th around town). In fact, I try to keep the rev's between 2500 & 3k all the time (not just while warming up) - believe it or not, the gas mileage seems to do best this way.

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Are you saying the 996 cars don't have cold start enrichment? Who is this "guru" you speak about?

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Not sure what your "Guru Indy Mechanic" knows or how/why he knows it, but my understanding is that the ECU does push extra fuel when the engine is cold (sort of an electronic "choke"), as well as run the SAI in order to heat up the Catalytic converters. Why does he say this is NOT an issue for the 996 but is for the 997? I'm not trying to be argumentative, but this is the first time I've heard this...

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Exactly my thought! I'm no automotive historian, but cold start enrichment, secondary air injection, etc. are emissions processes implemented on modern cars dating back to the early 70s. It's only big news to us because of the contributing factor with cylinder bore scoring.

I wouldn't worry about 1 minute of idling, but I don't live in a cold climate, so perhaps it is bad if temperatures are really low. I keep my engine under 3500rpm until I've driven about 6 miles. I do run in 6th gear because with the freeway only 2 miles from my house, I get over 80mph very soon. In 6th gear I'm running about 3000rpm. Once I've made it 6 miles, I'll drop down into 3rd, 4th or 5th and speed up a little, if traffic will allow it.

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997.1 has the M97 engine which is similar to the M96. Your guru indy mechanic may be talking about not worrying about it in our area. With average winter temperature in the 50s, it's not nearly as much of a concern to us down here.

I just recently picked up my car...996.2 When I was doing test drives...one owner would get mad at me if I changed the gear and let the car drop below 3000 RPM...he said always keep the car above 3000 RPM I'm the type of person who starts up...belt on, wait about 1 minute and take off...but I just coast and switch below 3000 RPM until it is fully warm.... but even when it is fully warm...i'm always driving so that the RPM are about 2 to 2.5rpm my car had the engine replaced by porsche in 2012...so from what I've been told i have the newest M96 engine from 2005 (even though my car is 2003) - that came with the larger IMS etc. etc. and now I only have 50,000 KM on it

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Letting the car idle stopped being the advice a long time ago, just nobody was paying attention. Even in the 90s BMW started changing its owner's manuals to tell you to idle briefly a cold automatic trans car (to let the torque converter fill back up) but for the same car with a manual trans to drive immediately. The 996 owner's manual tells you to drive right away and so do current Mercedes owner's manuals. Setting aside the mixture issues, letting the engine idle doesn't help it come to temperature because without load the engine doesn't heat thoroughly, and this presents a problem with different rates of thermal expansion. There is nothing gained by waiting a minute, and probably something lost (unnecessarily extending the period of time when the oil will suffer fuel dilution, exacerbating differential expansion, wasting fuel for no reason). As far as the shift point, Raby says keep it above 2500rpm once warmed up. This makes sense, as spinning faster will actually increase the viscosity of the lubricant in the IMS bearing and help it endure the load.

Good luck starting ANY engine without fuel enrichment (aka without the choke on) in the cold. Won't happen.

I bought some used 996 taillights from someone on Craiglist earlier this year. While we were talking about our 996s, he told me he always fires his up and allows it to idle for 30 minutes before he drives it. I started to tell him he shouldn't let it idle before driving and he quickly interrupted me and told me I didn't know what I was talking about, he had been doing that since he was young. Of course I'm much older than he is (as if age=knowledge, NOT!) and I've taken many Many MANY automotive courses, including a few from The Knowledge Gruppe. I told him thanks, and left with my cheap used taillights. It's probably a good idea to have the owner of a car you're interested in to drive it some for you. You'll likely see how it was typically driven, especially on a sports car.

A smart engine guy told me and many others: get in, let the oil checking gauge do it's thing(if first start of day and level), start car, buckle seat belt, drive off keeping revs below 3k until engine temp is at least 160f. Do not stay in 2k to 2.4k rpm for extended times. I trust this guy...

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That's what I do, just add before I head out I gradually increase the revs to 2.2K twice. To answer all the folks questioning my guru indy, when you hear him explain it sounds right. He said that the 997's actually dump more fuel than our 996's do at cold idle. And yes, I do know that all cars are putting more fuel in. The hard part for us is finding that perfect zone of heading off to fast, vs idling for too long. Soooooooo many factors involved! Temp, humidity, wind chill, how flat/hilly your drive is out of the driveway, too name a few.

So how do remote start systems figure into this conversation ? Obviously with a manual transmission they�re not very common but I�ve had them on several of my other vehicles without any issues. When it�s below zero the cars seem to run much better after letting them warm up for a few minutes. At those temps I can hardly switch gears when I start up and go because everything is so stiff.

Fuel injected engines warm up way faster if they are driven rather than idle. The engine only need a few seconds to get the oil pressure up to normal and then the car is good to go. You can really notice this if you drive a diesel. They can idle all night and never reach operating temperature. I know because I had to do this once when my starter died and let the engine run all night so I can go to work in the morning. FI engines are not meant to idle when cold. The factory remote starters probably run a different map than if you just start the engine and let it idle. The aftermarket units are the same as if you started the car with the key. The ECU doesn't know the difference and is not good for the engine BUT it is good for the manual transmission oil. So take your pick of what is more important to you.

If I recall correctly the owners mainly of my e46 M3 said just get in the car and drive. The RPM counter also had lights that displayed as the engine warmed up so you knew when you got to optimal operating temperature.

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Cars are not warrrantied for a length of time that makes remote starters matter, or at least not matter frequently enough that the money won't be made back in higher consumer demand. The companies are not concerned with your cost to repair outside of warranty. Cars do run better when the engine is warmer (this is why you need cold-start enrichment), but that doesn't mean idling them cold is better than running them cold. Porsche, BMW, and Mercedes are all companies telling you to start driving immediately after starting in the owner's manuals. I haven't been around Porsche long enough to know what they used to say, but I know in the case of Mercedes they used to tell you to briefly idle after a cold start and in the case of BMW they specified different treatment for automatic and manual trans cars. Now they all say drive immediately. I can't imagine they would go out of their way to make this change for no reason, and in fact we can surmise reasons founded on sound automotive knowledge to support this change. There are lots of things bad for a car that nobody will notice during their ownership, despite it slowly damaging the car. Modern cars can even completely mask a vacuum leak and won't turn on a check engine light while doing so until the leak is significant.