TOV 2006 TSX review

Uh... you can crack your driveshaft and still be able to drive your car. But I consider that as damage eventhough your car still moves.

I don't get what's your beef? My point is that flat shifting can damage drivetrain components. That's it. I'm not making a distinction between a bearing being damaged, a driveshaft cracking or the whole transmission turning into mush. I'm just saying, flat shifting can damage the drivetrain. My example was the Corolla Sportive that after 3 passes with flatshiting, the car had sustained some damage to the drivetrain. I'm not saying that some part of the drivetrain would fail catastrophically if you flatshifted.

The technical difference between a normal shift and a flatshift is that when you flatshift, the flywheel is exerting torque because your foot is on the accelerator. When you release the clutch fast, all that torque is transmitted through the transmission and into the drivetrain. That quick transfer of torque is what causes the damage/wear. That's it. If you want to nitpick, the torque at the flywheel at that instant is the amount of torque at 7200rpm. So it doesn't matter if you have a car with a linear (example) 200Nm @ 7200rpm or a non-linear (turbo) 200Nm @ 7200rpm. It's still that same 200Nm going through the transmission and to the drive train.

If you are not flatshifting and changing at redline normally, when you release the clutch fast the engine speed is reduced instead as there is an instant where your foot is not yet on the accelerator. Even if you shift so fast that your RPM is still at that 7000rpm that you stated, the moment you release the clutch, the revs will drop because your foot is not on the accelerator.

And if you involve high torque V8s, the difference is in the component that is damaged. V8's higher torque damage the transmission first, while lower torque vehicles like the Euro and Corolla will damage the drivetrain after the transmission.

Quote:

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Originally Posted by aaronng

If you are not flatshifting and changing at redline normally, when you release the clutch fast the engine speed is reduced instead as there is an instant where your foot is not yet on the accelerator. Even if you shift so fast that your RPM is still at that 7000rpm that you stated, the moment you release the clutch, the revs will drop because your foot is not on the accelerator.

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You are making a very big and may I say slightly false assumption there.

1stly whether you flatshift or normal shift, 'the revs will drop' back into the correct rpm (say 5000rpm) at that vehicle speed (say 65kph) for that gear (say 2nd) anyway > EITHER METHOD OF SHIFTING. I hope you agree with me on that.

I put 'the revs will drop' in brackets because it is not due to the foot NOT being on the accelerator, but due to the whole drivetrain being connected to the engine again at that vehicle speed, bringing back everything into reality... so to speak. The shaft(s) in the transmission/drivetrain are still spinning at the same vehicle speed, but due to the higher gear and lesser torque multiplier effect, the engine is ALLOWED to fall back into a lower rpm.
It has little to do with the foot being on the accelerator as you said.

But the important thing to realise is that when you are normal shifting but fast at say 7000pm, and when you let go of the depressed clutch, you WILL step on the accelerator because that is how everyone driving a manual car accelerates, no matter whether it is shifting at 2000rpm or 5000 or 7300rpm. Otherwise the whole damn thing will be shaking like a horse and DECELERATING quickly.

A person trying to shift 'fast' to accelerate up the gears will naturally have this overlap happening, not only that but they will put their accelerator down all the way again during this 'overlapping period'.

Quote:

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Originally Posted by aaronng

And if you involve high torque V8s, the difference is in the component that is damaged. V8's higher torque damage the transmission first, while lower torque vehicles like the Euro and Corolla will damage the drivetrain after the transmission.

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I don't understand how you came into that conclusion at all. I completely disagree. The Engine's Flywheel is separated from the Transmission by the clutch. If there is any shock to the drivetrain after clutch is release again, the first component which bears it first is the clutch. That is the reason why the clutch is the weak link in most powerful cars, because it is suppose to be that way, to save other more expensive parts. If the clutch did bite properly, then it is whichever weaker part (either the transmission or part of the drive shaft or other drivetrain components) which will fail first.

What does this have to do with higher torque or lower torque vehicles? The weak part fails first in both cases.



The thing I'm trying to put across is that - you keep saying you think a flatshift 'relative' to a normal shift will damage the drivetrain somewhat. But that was never my point, as everyone in the world already knows that.


The thing being mentioned by me is that the 'sudden difference of torque' and also 'peak torque figure' are what damages a drivetrain, and on a car with a Linear Torque delivery (less likelyhood of sudden difference of torque during accelerating) and also a Lowish Peak Torque figure, would mean the damage by flat-shifting in such a configurated car isn't as great as one might think. Compared to an All Wheel Drive launch, or the torque of a V8 car flat shifting. Also the fact that Flat shifting isn't even as exaggerated as you think it is, because a fast shift that we all do has nearly equally damaging effects.

The most important thing is that since torque change is what damages the drivetrain, but with a lowish peak torque figure even when one is flat shifting the torque change during that action isn't that big an issue. A 223Nm peark torque figure isn't that high at all and usually drivetrains and transmissions can handle that, even if flat shifting.

Quote:

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Originally Posted by Omotesando

1stly whether you flatshift or normal shift, 'the revs will drop' back into the correct rpm (say 5000rpm) at that vehicle speed (say 65kph) for that gear (say 2nd) anyway

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Unless the wheels are able to spin freely due to crappy tires or a poor road, or because the engine has heaps of torque :cool:

Well at least thats what ive done in my Civic once, the car nearly kept its flat-shift rpm but the wheels spun and the car jolted forward.

Edit: I realised this thread is going way off topic. I've removed my reply and I'll PM it to you, omotesando. :)

I think you will find that in flat shifting the syncro's and to lesser extent gearsets will bear the brunt of the damage - as was said the clutch is designed to be the weak point and if the speeds are not equal there is a high chance the clutch will slip before the gearbox gets its turn if the clutch is used... (Always a good idea to slip the clutch in a new car for this reason)

Flat shifting causes hardly any wear on the clutch, but causes gearbox wear as the syncros get a pounding trying to even up the speed between gears... this shock is also transfer to gears.... helical gears are especially suseptable to breaking due to shock since the initial contact between gears is concentrated at a point.. on racing gearboxes the teeth are straight cut so the load is distributed along the entire width of the gear tooth... this design however is very noisy and not OEM friendly

Bearings and whatnot also undergo stresses which are generated through shafts into their respective housings... The sportivo gearbox would probably feel new agin with a new set of synchro's :)

Driveshafts will not get too damaged - spinning the wheels and whatnot will kill these