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      03-15-2011, 09:27 AM   #63
mkoesel
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Drives: 2015 Felt IA2
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Location: Canton, MI

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Quote:
Originally Posted by JIO View Post
Now that everyone is shocked and appalled...I have to say that driving the car to redline all the time as people say "that's the way it was designed" will cause such an increase in engine wear with the internals running at 8400 rpm, as say 5000 rpm.
Well, I can't speak for others, but I never drive the car around at a constant speed at high RPM, or at least not for more than a few moments just to hear the engine note. Cruising at 8400RPM obviously makes no sense since there is no benefit vs. cruising at low RPM instead. So, when people "it is designed that way" they are talking about accelerating - or at they should be if they understand how a car works. The point of using all of the powerband is to extract the best acceleration from the car.

Also, surely the important part as far as wear is average RPM over the life of the engine. After all, the wear is probably going to be roughly proportionate to how much internal friction occurs over the life of the engine, i.e. how much heat is generated, which itself is proportionate to the speed of the moving parts. Even if we assume it is far from linear (wear vs. engine speed), time spent at that speed is still going to be a huge factor. So, for each high RPM shift that happens in our cars, how much time is spent cruising at a constant speed at 2000 RPM? The answer is a lot. I don't know the exact number of course, but if you figure I am at redline for a total of less than three seconds on my morning commute, but am at 2000 RPM for a total of 25 minutes, well you do the math. The average RPM is still very low, and guess what? If I instead made those high RPM shifts at 7000RPM I didn't really change the average RPM much. Another thing, even if you figure that, just for example, the avereage S65 only has 100 hours - or heck maybe its only 50 hours - of life at 8400RPM, it is going to take a long, long time to amass that amount if you are not cruising around at high RPM needlessly.

Back of napkin, off the cuff math, yes. But I would be very surprised if the exact nature of the "wear and tear equation" is far off from how I roughed it out above.

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I show restraint as there really is no need to redline the car to extract power from the M3.
Max power is at 8300RPM so if you want 414hp, then, yes, you really do need to (effectively) redline it.

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Heck, the M3 is faster than 95% of all the cars out there, even if you shifted at 4000 rpms.
That's a stetch, IMHO. I don't have a dyno readout handy - but I'd guess its probably 230hp@4000RPM off the top of my head. Most cars have 200hp or less, sure, but I really doubt it is 95%. And even if it is, so what? If you only want that much power, then a 328i is perfect for you, and it probably even makes max power a couple thousand RPM below redline (though it still may not accelerate at the highest rate unless you hit redline).

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I track my M3 and I never go to redline...no need to go the last 500 rpms.
No need, sure, but if you were in a race or time trial then guy that shifts at redline is going to beat you (assuming he is reasonable driver not grossly overshooting the braking zones and turn in points, etc.)

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Heck for the "racers", you can Dinan software that moves the limiter to 8600. Why not get that?
I could just as easily ask you why stop at 8000RPM? That's pretty arbitrary. How much wear and tear are you really saving?

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You can probably find software to move it to 10k rpms. Given the chance, I'm guessing (hoping) most would say 10K is too much. So why not 8K instead of 8400?
The engine will go nuclear at about 9k from what I'ver read here, so yes, 10000RPM is way too much. Also, the engine is designed specifically with the redline right around when the power would start to fall off. So, yeah, there's no really good reason to make it go that high anyway. Some software tuning will allow it to keep making power at a little higher RPM but 10k RPM would take some head, valvetrain and induction work (assuming the block and bottom end would hold together, which as I say, they would most likely will not).

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Just my views of redlines in cars. Lastly, my home stereo has enough power to generate close to 120 dB of Justin Bieber. Just because it can do it doesn't mean I play Justin Bieber at 120 dB until my ears bleed. Actually I wouldn't play Justin Bieber at any volume...he he.
And my car can do about 160mph or so. I never go that fast, but I do accelerate as quickly as I can to a reasonable speed. Do you play all of your music out of just one speaker? I bet you don't, even though you'd still be able to hear it just fine from that one speaker.
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