To flywheel or not to flywheel!?

[Skylude]

My question...I've got a r33 rb25 and will be changing the clutch. I'm debating between keeping the oem or to put a lightweight flywheel. Faster rev's is nice but drivability is decreased. What's your input on this...and what are you using/feedback...

thanks

[99_SI]

I had a lightweight flywheel before on R33 RB25 with a six puck clutch. Xtd was the name ...I know , it's crap....but it did do the job. Faster revs, brutal bite. Reason I went back to stock is lightweight was almost impossible to creep with....traffic became a brutal bounce. Machined the stocker and Spec'd the clutch. Bites hard , smooth engagement when you want. Someone else might chime in....it all depends what u want it for-track, drift, street?



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[Skylude]

For street at 99%!

[amnash]

Doesn't a lightweight flywheel sacrifice torque? Torque is based on rotational mass momentum so stock flywheel should be better for torque.. I might be wrong though but that's how I've thought it was

[Skylude]

I'm really leaning on keeping the oem. I know you get a better top end with a light flywheel also...

[Special_K]

it also kinda depends on how you're shifting. If you like faster rpm climb and drop(free revving) then you go with a lighter flywheel. Feels better toe-and-healing with a light flywheel imo. More racecar

[Cuami]

Doesn't a lightweight flywheel sacrifice torque? Torque is based on rotational mass momentum so stock flywheel should be better for torque.. I might be wrong though but that's how I've thought it was

An automotive engineer buddy of mine basically told me that as well... Lighter Flywheel means faster deceleration and faster acceleration from a stop but you lose on top end torque and flywheel momentum due to the decreased rotational mass.

So... Whether or not you want to go with one would really depend on your driving style. I personally like having one somewhere between the 'super' lightweight Flywheels (around 7lbs) and the stockers... Which sometimes takes some trial and error to pick the right weight (disclaimer: I haven't done this on my gtr yet).

How light were you thinking about going?

[Dragon Humper]

The lighter the flywhell the less parasitic losses while accelerating or decelerating. The only thing you give up is having more stored energy in the flywheel to add to the motor for stop and go traffic. It can add torque to the motor but onky when you have spent torque to wind it up. With the clutch engaged you will only gain....everywhere. Low end, top end and everywhere inbetween.



Jon.

[MarusGTR]

An automotive engineer buddy of mine basically told me that as well...

*scratches head* Engineer or tech? Us engineers can't be right all the time, but this is a strange interpretation of physics. As Jon said, its simply an energy storage to maintain momentum during shifting so, paired with the synchromesh, don't have to double clutch.

I.E.: The more weight, the more the motor will want to maintain its current momentum until acted upon (or through parasitic losses).

[Cuami]

Engineer. All I said was that I was told something and gave an extremely basic interpretation of my recollection of said conversation. However... since my integrity is being called into question, I figured I might as well give him a call to get a better, in depth explanation (I'll be paraphrasing).

Note: I liked Jon's post because it was a much better breakdown and covered what I should have taken more time to explain (admittedly... my wording did suck lol).


Anyway, here are the cliff notes of our conversation (minus the swearing and bad "that's what she said" puns)...

Less mass results in more vibration which leads to a rougher engagement of the sychros/speed gears (however, he mentioned that any increase in wear would be negligible -- just that it causes a very slight delay). The tradeoff being less parasitic loss which means you'll be able to rev through the RPM range faster. A heavier flywheel requires more force to continue its rotation which results in slower acceleration. Having less rotating mass results in less stored kinetic energy to keep the engine turning when the clutch is engaged. This causes the engine RPM to dip as the stored energy is spent, more than a heavier flywheel would, until the clutch is disengaged. He also mentioned that the inertia of a heavier flywheel will help smooth the pulses during combustion but didn't go into much detail on that.

He corrected me in saying that it's not the top end torque that decreases but the all around torque. The tradeoff being an increase in horsepower.

[Dragon Humper]

He's wrong about the torque...

You won't lose any torque anywhere at all, in fact you will gain torque (figuratively speaking) as you are changing engine speed...also known as horsepower. The torque remains constant, the only thing that changes is the work done over time...horsepower. If you did a power pull with just the engine alone on a stand, the torque curve will remain constant from pull to pull but the horsepower will go up when you remove mass from the rotating assembly due to the fact that the same effort is being expelled in a shorter amount of time. That's all horsepower is, a math equation where the result is torque vs time.

You are right about the added mass smoothing out power pulses though...but more so in a high compression na motor. A low comp. turbo motor is pretty tame putting around, idling and such.



Jon.

[nickisonfire]

Wait for skym to respond and you will have your best answer