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YOUR RESEARCHRev limiter Hit
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Clean off better
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Believe it or not the higher rpms do make the pistons reach a little higher in the cylinder walls getting the pistons and rings to keep things cleaned off better.
Leading evidence: 'Clean off better' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'best in my opinion' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check by the rev limiter' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
I didn't want to upshift into 4th for 1 second and have to downshift for Turn 9, so I would just let the engine speed be checked by the rev limiter.
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Suggestion
chopperzzz, the piston travel changes by tiny amounts due to some stretch in the rods at those piston speeds.
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Suggestion
Is it true that it actually changes the piston travel??
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Believe it or not the higher rpms do make the pistons reach a little higher in the cylinder walls getting the pistons and rings to keep things cleaned off better.
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Suggestion
Thinking about the harmonic issues alone caused by cylinders essentially misfiring at max rpm for 20 seconds at a time makes me not want to do it, but use whatever common sense you want.
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Last night on my way home I hit the rev limiter, had never done that before.
Was in first and thought I was in second, (can you tell I drive an automatic alot).
How worried should I be?
That you've presumably owned this Porsche for several months and this is the first time you've hit the rev limiter? I'd be very worried. Go do it again. Right now.
Thanks guys I feel much better already!
Who said I know how to shift anyway. I have to say the longer I have this car and the more I drive it the more I love it. I'm sorry winter is coming. Not that I dont drive it every couple weeks but not as much. The longest it sat last winter was alost 4 weeks because we had so much snow.
DOH! sell the car, QUICK!
as said before, just dont do it downshifting.
LOL +1
I love to hit 3rd then 4th....thats fast enough for me - this morning was a redline commute for the 86' She loved it !!
Multiple the rpms attained by 10 then devide by the gear in when hitting the rev limiter. Then multiply by the number of infractions given in a ticket.
[(rpmX10)/G]T+=Concern
Actually as long as your bearings are doing good and things are spinning balanced and good it is a good thing to check out the higher rpms once in a while. Believe it or not the higher rpms do make the pistons reach a little higher in the cylinder walls getting the pistons and rings to keep things cleaned off better. Bad thing to not be winding it out as a habit which allows laquers and carbon to build up and start screwing with your rings and peformance having the stuff there.
There is nothing wrong with hitting the limiter, and there is a good engine health-based argument for getting the revs up that high on a regular basis. Exceeding it, now that would be a problem. But that's why there's a limiter.
Whiles its not bad to hit it on occasion, I certainly would not make a habit of banging the car off the limiter regularly.
chopperzzz, the piston travel changes by tiny amounts due to some stretch in the rods at those piston speeds.
The idea is that if you take it too easy, it builds up a carbon ridge in the cylinder, and then when you get on it, the ring catches that ridge and can be damaged.
Not a hugely valid concern in my opinion.
Maybe somebody can jog my memory, but I think there was a piece written about this quite recently, maybe in Excellence's series on the M96 engine. There was some kind of metallurgical phenomenon or something... anyway, it didn't argue for bouncing off the limiter per se, but it did argue persuasively for giving the car some serious spur on a regular basis. I've read similar advice in the past. The fact is that the engine's maximum output isn't far south of the redline, so I'm going to assume it's happy there.
Of course, as Sneaky Pete points out, the mechanical overrev or 'type 2' overrev is a whole 'nother story.
I didn't believe it when I first read about it in a car magazine in the 60's. Try figuring this. The compression cycle has the pressure keeping the cylinder and rings pressed as low as possible. Also figure in the piston is not and exact fit which the rings make up for. So the there is a slight wobble available in piston travel. Anyway when you are hitting the higher revs the travel of the piston is faster thus getting more momentum to get higher in the cylinder fighting the compression cycle.
For a real good one if you want higher revs out of an engine go for a looser fitting piston and make up for it with the rings. Trick is the lower tolerence pistons have the piston travel sticking to a more straight up and down force which eats power slamming the tdc and bottom. Looser pistons allow a slight arc. Yah believe it or not I'm not BSing you on this stuff above.
This one is secret.
I put a Kailua Kona turtle decal on my back winshield for more power
Busted a motor mount when I got back last summer and put it on. You can feel the real power gain
http://www.tikitoes.com/html/4inchstickers.html
The "shift indicator" is in place so you don't damage the engine. If you hit it and the light comes on and revs go no higher then it is doing its job. They wouldn't set it to where you would do damage and then the indicator would come on.
My '84 911 with a higher numerical rear-end ratio would get to the redline in 3rd gear between Turns 8 and 9 at Watkins Glen each lap. I didn't want to upshift into 4th for 1 second and have to downshift for Turn 9, so I would just let the engine speed be checked by the rev limiter.
I did this for YEARS. The car now has 130+K miles on it, of which probably 40K at least are track miles.
The engine has never been out of the car. No valve jobs, rings, zip.
Bumping into the rev limiter didn't hurt the car at all.
Cool story!!!
A good friend of mine has an '84 911(Turbo look) and I absolutely love that car. In fact it was the first P-car I have ever driven and I will never forget that experience.
So how do you know it hasn't hurt the car at all? What are your compression and leakdown numbers? have you test the valve springs (they love it when you bounce it off the rev limiter).
Furthermore, your anecdotal evidence, plus the fact that your only proof its not harmful is that the engine hasn't blown up yet doesn't amount to much.
Follow-up to Quadcammer:
I did have a leakdown test done. The results (at the 120,000 mile mark) were within factory spec for a brand new engine.
So, yes, this is just one data point from one guy, but it implies that hitting the rev limiter does not harm the engine. I sure did it a lot, and so far at least the engine does not seem to have suffered.
I'm not sure where all this heat is coming from, Quadcammer. The rev limiter is an ECU function, not a physical barrier. These engines are made for high rpms; they suffer much more from the opposite kind of use, it seems to me. And I have trouble imagining that Porsche would go to the trouble of programming the engine to cut fuel at a certain rpm, and then choose an rpm that produces engine damage.
This runs the risk of becoming one of those debates in which the absence of evidence just serves to dial up the rhetoric. Me, in the absence of evidence, I just default to common sense...
Of course its an electronic barrier. Just like getting the correct a/f ratio in a 996 is an electronic function. Electronics have a very serious effect on engine longevity. The engines can tolerate high rpm, they aren't built for high rpm. Furthermore, its not the rpm that causes the damage.
Obviously tapping this thing on occasion is not a big deal. Thats why its there. Holding the car on the limiter is simply not a good idea. Thinking about the harmonic issues alone caused by cylinders essentially misfiring at max rpm for 20 seconds at a time makes me not want to do it, but use whatever common sense you want.
drive your car in 1st gear banging off the rev limiter for the next 20 years if it makes you happy...but I sure won't.
Um, not really what I had in mind. I just sometimes want to upshift so that the revs drop into the meat of the power band. With this motor, that's sometimes going to mean the redline.
I think you may be misunderstanding what I'm getting at. Let me try to clarify.
Scenario 1:
You are an enthusiast. You regularly accelerate briskly and hit the rev limiter for a millisecond before shifting (i.e. you do not hold the car on the limiter)
Scenario 2:
You are on the track. Your gearing is not optimized for the track. You decide to let the car bang against the rev limiter for 10 seconds/lap (i.e. literally keeping your foot to the floor while the rev limiter limits the rpm for 10 seconds).
The first scenario is absolutely fine and will not cause any damage. hit the thing momentarily as often as you want.
The 2nd scenario, while probably not resulting in immediate damage, is not doing your engine ANY favors.
