How often do you hit the rev limiter?

[PorscheBound]

Originally Posted by The Radium King

dr. science says ...

torque at wheels = flywheel torque * gear ratio
using the torque curve for a 987 that I found online, torque peaks at 4500 rpm (360 NM) stays flat to 5500 rpm, then drops to redline at 7000 rpm (280 NM).

here is a chart that shows gear, ratio (taken from california motorsports website for a 986S 6-speed transmission) wheel torque at max rpm, and wheel torque at max torque:

1 3.818 1069 1274
2 2.200 616 792
3 1.516 424 546
4 1.216 340 438
5 1.024 287 369
6 0.841 235 303

so, if you compare wheel torque at max rpm to wheel torque at max torque in the next higher gear (ie, an upshift at 7000 vs an upshift at 5500 with rpm drop to 4500 to 'stay in the power band') you'll see that this produces less power in 1st and 2nd gear than staying to redline. the upshifts from 3rd, 4th and 5th are a wash and most likely eclipsed by the loss in power to the ground during this shifting process.

dr. science says hit the rev limiter.

Dr science doesnt say HIT the rev limiter. That would cause a loss in power. Dr science says take it to red line. I think there is a big misunderstanding in this thread about what red line is and what a rev limiter is. Will run side by side. Ill hit red line, you hit your rev limiter, will see who walks away.

[epapp]

YES, rev limiter is slower than a perfect shift.

I'm not racing anyone

[epapp]

AND since my redline is 6500, and the engine rev limits somewhere VERY near that value, I'm calling them the same.

In reality, they are some hundred RPMs away from eachother, but, like I said one million times, I spend 0.09 seconds at the rev limiter, whats the impact on the 'longevity' of the engine compared to 0.09 seconds at 6,200RPM??? Not quantifiable says me.

Fun factor @ 6,6xxRPM limiter > 'serious race' factor @ 6200RPM...I'm only getting on the freeway

[PorscheBound]

Originally Posted by epapp

YES, rev limiter is slower than a perfect shift.

I'm not racing anyone

Never stated anything in regards to racing to you...

Calling the rev limiter and redline the same is ignorance.

The rev limiter is in place for a reason. To think it has no effect on the car is again ignorance. It's not a big deal if it happens every now and again. But deliberately going out and bouncing the rev limiter time and time again is not healthy.

[The Radium King]

well, the redline on my car is 7200 rpm and the rev limiter is at 7200 rpm, and arguing semantics on the internet never ends well so i'll leave it there. regarding the word 'ignorance' which seems to be getting thrown around a bit here, 'ignorance' is defined as 'lacking knowledge or information'. you state that he is ignorant to assume that hitting the limiter has no affect on the car. let's ask Porsche - do type 1 overrevs (hitting the rev limiter) affect warranty? no. that is information which you seem to have been lacking.

[Giller]

It's amazing how such a harmless topic can spiral.....

[PorscheBound]

Originally Posted by The Radium King

well, the redline on my car is 7200 rpm and the rev limiter is at 7200 rpm, and arguing semantics on the internet never ends well so i'll leave it there. regarding the word 'ignorance' which seems to be getting thrown around a bit here, 'ignorance' is defined as 'lacking knowledge or information'. you state that he is ignorant to assume that hitting the limiter has no affect on the car. let's ask Porsche - do type 1 overrevs (hitting the rev limiter) affect warranty? no. that is information which you seem to have been lacking.

So you are saying warranty equals no harm to a car? Just because it's still covered under warranty doesn't mean it's okay. You take a boxster and bounce the limiter on every shift vs driving it the way it was intended to drive and will see which one has a longer life.

[Pdwight]

This is a vague question, but I was thinking and wondering how much conservative tolerance do you think is engineered into our engines ?. Do you suppose the theoretical red line is actually say 500 RPM past what is programmed in our ECU and painted on our tachometers ??

Certainly an engine redlined multiple times a day will have a shorter mechanical life than one that is rarely if ever run to redline....but at what RPM does the engine (in good working order)significantly start to self destruct ?

[Ckrikos]

I had red lined and hit the rev limiter many times in my boxster that had 12 years of use and 50k miles. I had 12k type 1 revs and also think that so long as you stay compliant with the warranty requirements you should be good to go. I'm not telling you how to drive your car, but after 50k miles my car was driving great and there was very little play on my ims. From my 14 years around the boxster forums the cars that have had an easy life have been the ones with the problems.

[epapp]

Dwight, thank you. After all the discussion, that has been my continued question, and something interesting that has come from this poll.

Driving your engine at <2K RPM its whole life will certainly increase its longevity, absolutely no question. BUT, then the problem gets more complicated when you realize you want more than 2k RPM.

I could argue by driving more than 1500RPM, you are prematurely wearing out your engine, to which you would probably respond, 'every RPM up to redline is safe'.

To which I will leave it at, does anyone know the exact wear pattern for the plot of load vs. RPM vs time (many years/lifetime of engine)??? I dont think so...maybe the extreme m96 racing buffs.

I guess I'll always wonder, you guys saying that you 'redline' but would NEVER intentionally 'rev limit' aren't really thinking about the absolute difference to the engine.

6500 is redline in my car, or 108 revolutions of the crank a second. I think I remember the manual says rev limit is at 6750 or something. A 250 RPM difference accounts for only 4 more revolutions of the crank per second. Whats the difference in wear? What changes in those extra 4 revolutions per second that some people are getting crazy about?

All cool sounds, bad shifts, and immaturity of shifting gears aside, I would argue there is no noticeable INCREASE of wear from 6500 redline to 6750 rev limit. You'll just be a bit slower to the finish line of the 'freeway on-ramp' race.

Of course if you never hit redline either, then just think of the PPM of cylinder liner material you're saving!

[JayG]

IMHO, if you push a mechanical device to its limits often, it will have an adverse effect to its longevity. This goes for other things as well like tires, brakes, water pumps, anything that with a bearing in it, etc

In plain words...
Redline your engine a lot and it will have a shorter life than if you don't redline it a lot

I'm not saying you should not drive a Porsche engine hard, just that ANY engine pushed to its limits will not last as long. Lots of things that can and will break or wear out faster. Nor am I saying your should drive it like the little Old Lady from Pasadena going to church every Sunday.

Driving hard and driving at the limit are very different. Engines specifically built for racing have lots of components changed internally as well as ancillary items that hang on the engine that were specifically designed for harder use.

Porsche put in a rev limiter for good reason, it was not for grins

[Pdwight]

All my life I have worked around things mechanical, I love working on them and understanding what makes them tick. Early in life I discovered the cold hard facts about MTBF

everything has a MTBF....everything

[epapp]

So the ultimate message of this thread: YOLO

?

[Giller]

Originally Posted by epapp

Dwight, thank you. After all the discussion, that has been my continued question, and something interesting that has come from this poll.

Driving your engine at <2K RPM its whole life will certainly increase its longevity, absolutely no question. BUT, then the problem gets more complicated when you realize you want more than 2k RPM.

I could argue by driving more than 1500RPM, you are prematurely wearing out your engine, to which you would probably respond, 'every RPM up to redline is safe'.

To which I will leave it at, does anyone know the exact wear pattern for the plot of load vs. RPM vs time (many years/lifetime of engine)??? I dont think so...maybe the extreme m96 racing buffs.

I guess I'll always wonder, you guys saying that you 'redline' but would NEVER intentionally 'rev limit' aren't really thinking about the absolute difference to the engine.

6500 is redline in my car, or 108 revolutions of the crank a second. I think I remember the manual says rev limit is at 6750 or something. A 250 RPM difference accounts for only 4 more revolutions of the crank per second. Whats the difference in wear? What changes in those extra 4 revolutions per second that some people are getting crazy about?

All cool sounds, bad shifts, and immaturity of shifting gears aside, I would argue there is no noticeable INCREASE of wear from 6500 redline to 6750 rev limit. You'll just be a bit slower to the finish line of the 'freeway on-ramp' race.

Of course if you never hit redline either, then just think of the PPM of cylinder liner material you're saving!

And one could easily argue there IS a noticeable increase of wear. Using your logic - then what's the difference of going to 7000? It's only another 4 revolutions...or even 7500 - that's only 8 more revolutions. Where do you draw the line?
And those 4 more revolutions - well, then you have to break it down to how often you are doing it. Once and a while, yes 4 revolutions is nothing, but over a 10 year or more span - that's a lot of extra wear and tear.

Hey - at the end of the day it's your car and you can do with it as you see fit. We do buy these things to have fun, and if redlining it is part of your fun, then go for it! Enjoy it! Just don't expect me to buy it from you when you are done with it!

[epapp]

I understand your logic, but it doesn't make logical sense.

I'm only talking about the 4 more revolutions per second that my car can possibly 'wear more' because of. That is the difference between my redline and rev limit. This is the highest cap on the RPM that the engine can 'wear' so there is no argument of 'what about 7500 its only 8 more revvs'.

Plus, Im talking absolutely with respect to the engine from 0 RPM. Which means 7000 is 2x more 'extra wear' than 6750 rev limit. 7500 is 4x more. So, my logic only works for the absolute difference between your cars redline and your cars rev limit.

Over the span of 10 years, my 60 mile round trip would put my crank revolutions right around:

60 miles, going 75mph at a total average door to door of about 3kRPM =

144,000 crank revolutions a DAY

525,600,000 crank revolutions in 10 years

Say I hit the limiter instead of the redline 5 times a day (upper end, worst case):

20 extra revolutions of wear a day due to rev limiting

73,000 extra crank revs over 10 years due to rev limiting instead of red lining 5 times a day

The extra revvs account for 0.013% of the cars total revvs over a 10 years period.

If you take into account the non-linearity of wear at the higher RPM due to hundreds of other phenomena, probably still fine, and this is at 5 times a day.

[JayG]

It's your car, drive it how you like

Bottom one is you are more likely to have something fail or break at the limits than below

If I makes you happy to rev limit, go for it.
Just please disclose it when you sell it if you
have not blown the engine

[epapp]

'Hello potential buyer, I have driven this car like a sports car and not harmed it in any way'.

Potential buyer: 'Oh, nice, look at the number of type 1 overrevvs, that IMSB must be in perfect shape!'

[woodsman]

Do you do burnouts for your friends?

[Paul]

Perhaps the real reason for a rev limiter is to avoid stretching rod bolts and floating valves....