Rev Limiter on 6MT

[dynamite]

Hi. I am afraid of over revving the engine when up shifting the gears on my 6mt and because of that I am changing at nearly 8000 RPM didn't go beyond of that RPM since I owned the car.

I know the engine is capable of revving about 8300 RPM (or 8400 not sure) but what about beyond of that ?? Does it possible to over rev the engine during up shifting like stand still launchs ? Or in otherwords does it possible to rev the engine beyond redline ?

Thanks

[SlammedR8]

Originally Posted by dynamite

Does it possible to over rev the engine during up shifting like stand still launchs ? Or in otherwords does it possible to rev the engine beyond redline ?
Thanks

No, the rev limiter will kick in before you do any damage!

[Lemans_Blue_M]

Originally Posted by dynamite

Hi. I am afraid of over revving the engine when up shifting the gears on my 6mt and because of that I am changing at nearly 8000 RPM didn't go beyond of that RPM since I owned the car.

I know the engine is capable of revving about 8300 RPM (or 8400 not sure) but what about beyond of that ?? Does it possible to over rev the engine during up shifting like stand still launchs ? Or in otherwords does it possible to rev the engine beyond redline ?

Thanks

Under normal upshifting even at WOT, the rev limiter will prevent a mechanical over-rev. So there is nothing to worry about in that situation.

But...

Incorrect downshifting however, (grabbing the wrong gear) can potentialy cause a mechanical over-rev to occur.

This may damage to the engine if the over-rev event was much higher than the 8400 redline. You typically damage something in the valve train in these situations. Dropped or bent valves are a common occurrence with severe mechanical over-rev events.

[Jaypod]

Originally Posted by Lemans_Blue_M

Under normal upshifting even at WOT, the rev limiter will prevent a mechanical over-rev. So there is nothing to worry about in that situation.

But...

Incorrect downshifting however, (grabbing the wrong gear) can potentialy cause a mechanical over-rev to occur.

This may damage to the engine if the over-rev event was much higher than the 8400 redline. You typically damage something in the valve train in these situations. Dropped or bent valves are a common occurrence with severe mechanical over-rev events.

Exactly - well said!

[jackolo]

When you're not in M-Mode, does the limiter come on earlier?
It might just have been my imagination but once or twice when I was accelerating hard to redline I notice a drop in power much earlier then there should have been.
Again, maybe my imagination, there could have been other factors at work that day.

[SlammedR8]

Originally Posted by jackolo

When you're not in M-Mode, does the limiter come on earlier?
It might just have been my imagination but once or twice when I was accelerating hard to redline I notice a drop in power much earlier then there should have been.
Again, maybe my imagination, there could have been other factors at work that day.

other factor IS:

Your engine was cold and wouldn't let you run past 6000 or 6500 rpm

[jackolo]

Originally Posted by slammedm3

other factor IS:

Your engine was cold and wouldn't let you run past 6000 or 6500 rpm

Nope, I never run WOT until the motor is fully warmed up. I was getting close to 8K RPM and I had a slowdown immediately.

[dynamite]

I also worried about that for the test runs done by dealer. Those techs don't care about your car while test driving, especially if it is an "M" car.

[John@BMW]

the car has a soft rev limiter- It will not 'bounce' off the rev limiter like a toyota/honda-

If you are sitting still (0 mph) and floor the car, the car will stop at 7k rpm and hang there. Active autowerkes ecu adjusts this number down to 4000 rpm for a launch control feature as seen in my video-

If you are moving with the car in neutral, and floor it, it will go to 8400rpm for a few seconds and then back down to 7000 rpm until you let off- The reduced redline marker will show up at the 7k rpm mark.

the will act just like my video below but at 7000/8400 rpm

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[NFDoms2k1]

Great video reference John!

[lucid]

Originally Posted by jackolo

When you're not in M-Mode, does the limiter come on earlier?
It might just have been my imagination but once or twice when I was accelerating hard to redline I notice a drop in power much earlier then there should have been.
Again, maybe my imagination, there could have been other factors at work that day.

You are not imagining anything. What you observed was that the WOT torque output decreases past 7000rpm all the way to the redline. However, the power output increases until 8300rpm. In other words, although the torque output is decreasing, the power output increases because the engine speed increases. Power is proportional to torque and engine speed, so if engine speed increases faster than the decrease in torque, power will increase.

[Eugene-TAIWAN]

Originally Posted by lucid

You are not imagining anything. What you observed was that the WOT torque output decreases past 7000rpm all the way to the redline. However, the power output increases until 8300rpm. In other words, although the torque output is decreasing, the power output increases because the engine speed increases. Power is proportional to torque and engine speed, so if engine speed increases faster than the decrease in torque, power will increase.

Pretty crazy what you said there!!

But for me I always rev to 8300 RPM

[lucid]

Originally Posted by Eugene-TAIWAN

But for me I always rev to 8300 RPM

If you want to maximize your acceleration, that's what you should do--shift to maximize power.

[Eugene-TAIWAN]

Originally Posted by lucid

If you want to maximize your acceleration, that's what you should do--shift to maximize power.

That is how we do it in Taiwan