brian1

If a lightened flywheel can noticably improve performance, wouldn't lightening the wheels do the same thing? Pleople are spending more than just a few bucks to shave 8-12 pounds from their flywheels, what avout shaving 20-30 pounds from you're wheels (40 pounds if you have S4 wheels)? Seems to me that they are both similar in that they are rotating masses that need to be accelerated and therefore pass resistance to the motor. Yet lightened wheels don't result in some of the downsides noted with a lightened flywheel (vibration, stalling etc.). Or am I just missing the point, are the people that are lightening their flywheels already riding on 18 pound wheels?

Please don't fry me on this, I'm just thinking out loud... I guess there is no doubt that the engine would rev faster (with the clutch pressed)which would be helpful in some situations. But it seems pretty limited.

Stratocaster1422

Your lightened wheels reduce the amt of unsprung weight on the car in general. Dynamically your car will perform better with the least amt of rotating mass. Your flywheel will be able to jump to different revs faster and therefore be able to get into peak powerband areas faster with the lighter flywheel. The vibration from this stems from the fact that your harmonic balancer on the front of the crankshaft is now not optimized for the OEM flywheel weight

birdsong

Also, the flywheel is pre-transmission, so it's the "raw" power. The faster you can manipulate the raw power, the more this effect is transmitted down the drivetrain. The wheels are at the bidding of the transmission, while everything is at the bidding of the flywheel.

brian1

If the clutch is not pressed, I would think there are two things controlling the engine reving:

1. Rotating mass - engine, flywheel, clutch, transmission, drive shafts, brake discs, wheels, tires.

2. "Rolling resistance" (not sure what to call this) - wind resistance, driveline friction (barrings) and road slope (up, down or flat).

To me it looks like the flywheel mass is a small part of the picture. However, when the clutch is pressed, it is a much larger part of the picture. But, when the clutch is pressed, the only thing that moves is the tach - not the wheels. I'm sure there are some advantages to quickly moving through the rpm range but once you let go of the clutch, you are immediately adjusted to the drivetrain speed.

I don't mean to knock what people are doing. I'm just trying to focus on the overall picture. I'm sure that if you lighten the flywheel, main pully, clutch, discs (ceramic), and wheels, it would have an impact. But like everything else in this world, there are tradeoffs to everything. Wheels just seem the best place to start.

xr4tic

your flywheel spins up to 7000 RPM

BIG difference.

I love my lightweight flywheel, and would NEVER go back.

Besides, shaving 20-30 pounds from a rim is not easy, unless of course, you don't mind replacing them every day after they bend, or spending a lot of money for the rims.

Stratocaster1422

you are correct in that with clutch engaged, it is a small part of the picture. But with a lighter flywheel you get the following:

1.) clutch disengaged - revs drop/rise much faster, allowing for better shifting and better power band manipulation, getting you better track times.

2.) clutch engaged - Less rotating mass attached to the crank causing less stress on the entire system and lowering drivetrain losses a little bit. You have ~25% losses after the flywheel (AWD drivetrain). But elminating a percentage before the drivetrain, your crank power output will increase because the crank will spin easier.

Optimally you want a light flywheel, light wheels, lighter pullies, and carbon fiber driveshafts Reduce the weight of rotating anything in any system.

brian1

Energy = Mass X Velocity ...or something like that. Now I remember my 10th grade math, thanks.

brian1

Agreed, thanks

BrandonLive

KE = mv^2 actually :P

zszabo

Reading over past articles, I get the impression that a lightened flywheel is a big no-no on DBW cars - presumably because they help balance engine vibration (?).

Can anyone substantiate this?