modifry

Does it make that much difference?

I assume you only get the "stay in VTEC" effect if you release the clutch in the higher gear while the engine is revved above the "rev-matched point? How much of a difference does this make? Does it pull the revs up 100rpm, 200 rpm? I can't imagine it would be more than that unless you left it at WOT during the shift, which on an AP2 with the delay valve doesn't seem like much of an advantage.

If this was the only reason for a heavier flywheel, wouldn't it have been easier to lower VTEC by 100-200 rpm?

Billman250

I can tell you this.....I've put a Toda flywheel in an AP2.

If you don't rev it to redline and shift as fast as possible, it will fall below 6k.

It makes a dramatic difference.

Billman250

The engine dynamics are not designed to make power on big cam lobe under 6k. It would take a few supporting mods, or an engine re-design, to make up for the flat spot in the powerband.

Dan05S2K

light flywheels on s2000's arent good anyways they make you lose horsepower. more on ap1 then ap2...........

Billman250

That is the dumbest comment I've heard this year on all of s2ki

modifry

^ You need to get around more. (good idea for a thread though)


I think maybe I'll have to measure the VTEC "clutch jump" when I get my '08 (base, not CR). The hardest part will be re-training my right foot to not lift.

There are only 2 shifts where you miss VTEC - 1-2 and 2-3. If you run to 8,000 you only miss VTEC in third by 200 rpm, and less than 100 rpm if you push it to 8200 in second. I could see the flywheel yanking the car up 100 rpm with a harsh up shift from 2nd to 3rd (it's only about 1 mph)

But the 1-2 shift is out of the ball park. You've got either 800 or 650 rpm to make up, depending on 1st gear shift point, and I can't imagine the flywheel storing enough energy to jerk the car 7-8 mph faster just by releasing the clutch.

.

jguerdat

I'm no mechanical engineer but I was corrected a few years ago in the R&C forum about energy application. Remove your foot from the gas pedal and the engine stops increasing speed immediately, no overshoot/inertia. That is obviously an exact case since we can't speculate as to how fast the foot is removed and how the mechanical/electrical linkages move in response. However, a heavy flywheel wouldn't make a difference since the energy needed to cause it to continue to increase in speed has been removed - it simply takes more time for it to slow down.

Now if a REAL mechanical engineer would step forward...

Billman250

Anyone who doesn't understand just drive an AP2 and you'll see what a heavy flywheel does. The RPMs hang up before coming down.

modifry

Agreed.

And, while it might keep you from dropping below VTEC on a 2-3 upshift I'm not sure how much of an overall performance advantage it really provides. You have to consider that the energy stored in the heavier flywheel came from the engine and could have been used to accelerate the car if the flywheel were lighter. A lighter flywheel gives you faster acceleration in the lower gear followed by less "yank", whereas the heavier flywheel gives slower acceleration in the lower gear followed by more "yank" when you upshift. But only if you take advantage of it, if you're slow to react you can lose the advantage of the heavier wheel.

modifry

But if you rev-match you don't get yanked into VTEC by the flywheel, you have to lug your way back up to 6,000 rpm.