porschemikeandnancy

This may sound stupid, but I am a mechanical engineer. It is fact that wear is produced by friction (which is motion). So if you wind up your engine in the higher rev ranges, you must, by defintion, be wearing them faster then if you don't. Look at F1 engines, or even NASCAR engines. They are designed to perform at very high engine speeds - and they do not last very long. I think this year's F1 series allows the manufacturers only 8 engines for the season - and that's it. I know they measure all types of variables so that they even out the wear expecting the engines to require rebuilding. I'm talking normal wear and tear and not catastrophic failure (such as a connecting rod breaking at very high rpm).

I read on these boards often that many rennlisters routinely red line their cars in everyday driving. While the 993 (and any air cooled 911) engine has that special sound - especially in the higher rev ranges (for the most part above 4000 rpm), I can't believe it does them any real long term good. If you take piston travel per mile driven, it defies any engineering data to suggest it will last longer at more piston/feet/mile travelled than less.

Same with tires, brakes - any item in or on a car that "wears" from use. Even windowglass gets pitted and eventually needs replacement - and that's just friction of little particles in the air hitting off the glass as you drive.

While I'm not advocating putting your car in the garage and not driving it, I do see lots of "harry high school" types driving their muscle cars at full throttle all the time and these cars when they get only a few years old look like the walking wounded.

goofballdeluxe

The reason you may feel confused is, there is a vast difference between running a car at "full throttle all the time" and redlining a car for a split second on a spirited run. I'd imagine as an engineer you are aware that these cars are designed to run near redline for much longer than the split second between shifts with no problem.

While it's true that friction begets wear etc., there are some benefits to revving an engine to it's higher rev range from time to time, such as blowing out any carbon deposits.

nile13

Life has a 100% lethal outcome. Remember that. I do, as I wind up the engine.

mongrelcat

http://www.youtube.com/watch?v=guDH-OQqJkQ

sdrake

Those F1 engines are also turning at 18,000 rpms and making 700+ horsepower with 2500 ccs!

I'm sure my car would last longer if babied, I give you that. But that's not why I bought it!

jdistefa

As an engineer, you know there is also a safety factor engineered into every device (especially German ) - in this case a street car rpm limit in regard to oem rods, valve springs, and acceptable wear rates with spirited use.

Change the oil frequently and enjoy the car as it was meant to be driven.

Crimson Nape Racing

I raced my 84 for 5 years and when I sold it we did a leak down test on the engine. The cylinders were all 4-5%; pretty much as it left the factory. That car lived at redline for 5 years and we both loved it. These cars were made to be driven.

race911

Likewise one of the 3.2s I have sitting around. Hank Watts engine out of his '86 Cab (author of the Secrets of Solo Racing). He basically took delivery of the car and ~175K and 15 years later of full seasons of autocross and time trial had Bob Grigsby tear into the engine. Even though the bill was $12K (circa 2002), they didn't replace the P/C set. Amazing what known proper maintenance does for longevity, no matter how "hard" you drive one of these things.

Flip side was my '79 I got as a total one owner POS in '92. 100K, and at most 5 oil changes in its life. Probably never really warmed up ever, as the heart surgeon owner lived only a few miles from his office. But not driven hard at all. When I pulled it down, I could have reused the bearings. P/C set went on another engine (used Euro 3.0s on it since it was a large bore CIS engine), and though I don't really remember I probably just resurfaced the heads and put in new guides, reusing the valves.

Terry Adams

It's ok. Not my car, but this 993TT was only 13 miles from factory delivery. The break-in manual for all 911s does say "Vary RPM up and down".

I see your point about high rpm = more wear, but occasional peak rpm seems to be good for these engines.

black ice

Like Matt said, engineers design lubrication systems into engines to minimize wear within their operating parameters.

You also have to think that some of the highest stresses don't occur at max RPM. Over the nose pressures on the cam occur at idle.



dave

JDS968

To keep your cylinder bores in good condition, it's actually important to spend a little bit of time at maximum RPM, on a fairly regular basis. If you don't do that, you can develop a lip at the top of the bore. When tearing down an engine, you can actually feel this with your fingernail. That lip can break your top piston ring when the engine finally IS revved to redline.

It's pretty much irrelevant anyway because 90% of your engine's wear occurs at startup. If you're really worried about component wear, you can do more by avoiding the middle of the rev range (and, obviously the top of the rev range, that goes without saying) when cold, than by avoiding the redline when warm.

cgfen

is there a question here, or are you just dispensing info prophylacticaly?

cheers

Craig

ps, i'm a ME too

cgfen

?????????????????????
explain this to me please?
are you saying that the stroke varies depending upon RPM or something else?

cheers

Craig

brucec59

This is the first thing that popped into my head. Listen to the first 52 seconds. That will answer the question.

Pickled Piper

I'm also a Mechanical Engineer but a great believer in the "Italian tune up". Once the engine is warmed up thoroughly, then a blast up to the red line does it a world of good. We are not talking about sustained maximum rpm here.

pp