I have a 3rd gen that is used pretty much exclusively for autox and track days.

While the engine is out for rebuild, I'm contemplating replacing the stock flywheel with a lightweight flywheel.

While I expect this to help acceleration, I've also been told that when the rear tires break loose under power with a lightened flywheel, it is harder to regain control than it is with the stock flywheel.

Any experiences here to corroborate that?

Or dispute it?

What other pros/cons should I consider before replacing the flywheel?

The car has other mods already:

Single Turbo T04S
Power FC
Greddy FMIC
Ground Control Coilover w/Konis
Wilwood Brakes
ACT 6 Puck Clutch (sprung hub)
Koyo Rad
Straight Exhaust

 

I highly recommend going with a lightened flywheel. The only pro I've ever heard of is more difficulty launching the car. You will love the acceleration increase in the lower gears, I have had mine since 2001 without one regret

 

Dont you mean con not pro? Anyways im with goodfellas on this, its a great mod and gives a totally different feel to your car.

 

That's a load of crap. Car control doesn't really have much to do with the flywheel.

A lightweight flywheel will help you recover revs faster on a road course. However, just as fast as they recover, they also drop just as fast.

 

I dunno, it seems reasonable to me.

A lightened flywheel increases acceleration.

If you are doing and an autox and have your foot in it a little
too much in a corner and break the tires loose, the car with the
lightened flywheel is going to require faster reactions than
the car with the stock flywheel.

Why? For the same reason everyone likes the lighter flywheel:
it accelerates faster.

Even so, everyone seems to like it so much better I will likely
go for it.

Thanks for the input.

 

A car losing grip in a corner has nothing to do with whether the flywheel is 8lbs or 20lbs. It just has to do with too much speed for the angle of approach (or on the gas too soon out of a corner).

I suppose someone can say that the quicker acceleration cause them to spin out due to access acceleration coming out of a corner, but that's still driver error.

 

I didn't explain what I meant clearly enough.

True, the flywheel has nothing to do with losing grip.

After the point at which grip is lost, the lightened flywheel requires the driver to get the throttle under control a little quicker than with the stock flywheel, for the same reasons that everyone likes it, it accelerates quicker.

If the lighter flywheel allows the car to accelarate from point A to point B in less time than with a stock flywheel, after losing grip, it will also allow the tires to spin up to a given RPM more quickly than with a stock flywheel.

And as you said, it just requires better driver control.

 

Anything you change on a car is going to require the driver to adjust. Tires, wheel widths, alignment, power mods, etc...

It's unrealistic to apply the same driving techique to any change to the car and expect it to react the same. However, the flywheel directly causing the car to be 'harder to get back under control' is still absurd.

 

Yep. I wish I could think of a harsher word than "absurd" right now

It also decelerates faster which is why even if we played along your example is backwards.

Using your example you "have your foot in it a little too much in a corner and break the tires loose". This means too much power to the drive wheels caused them to break loose. In order to recover we need to decrease power to the drive wheels. A lighter flywheel is going to allow the engine speed to slow more quickly when the driver lifts slightly to recover the car, so controllability would actually increase over a heavier flywheel.

Since the lighter flywheel allows the engine more throttle response it will allow the engine to react more quicky to the driver's throttle inputs. If the throttle inputs are goofy or wrong it doesn't matter what flywheel is on the engine.

 

I meant 'con' up above.

For the performance-minded FD owner (unless it's a dedicated drag car) there is no good reason *not* to run a lightened flywheel .

 

so is it true that guys are freeing up around 25rwhp in 1st gear and subsequentially less hp in the higher gears with a lighter flywheel?

 

keith is sending me a 13lb'er so when i get it on i'll give a fresh perspective compared to these dinosaurs on here

 

It's not really less in the higher gears. You have the same total power, it just allows you to get to the top a little quicker. However, if you are drag racing, it hurts you getting the car out of a dig since you don't have the enertia of the heavier flywheels (which is what you want to get the car going from a stand-still).

 

I disagree.

It only decelerates faster *after* you have reacted, which requires faster reaction times from the driver.

Throttle modulation will be more difficult with a lighter flywheel. There are pros and cons, you just have to decide which is more important to you as a driver.

Here's a fairly good explanation of pros and cons of lighter flywheels.

It is for motorcycles, but most of the reasoning still applies.

http://www.ducati.net/faq.cfm?id=44

 

Well, cars don't drive themselves these days.

I think everyone would agree with me when I say that since the engine can more easily follow the commands from the accelerator that the engine is easier to modulate.

 

i have just installed a JUN 10lb flywheel and a centerforce clutch setup this weekend....ontop of another S5 tranny.....that said i need to rev to about 3k to get lunched without jerkyness its AMAZINGLY fast....sadly i have a boost leak and need a new lower intake mani....ILL MAKE A VID about drivablity post it up once i chance the manifold!

 

does it affect engine idle?

 

A little. No biggie. I had trouble starting the car from a stop smoothly with mine. Then 15 minutes later I had adapted and it was no longer an issue.

 

are there any pros or cons with regards to having the OEM flywheel lightened?

I guess it depends on what clutch you are using. OEM or aftermarket.

 

Less centrifigul mass means a slight loss in torque at certain rpm. Its not nearly as major as the amount of rev and hp that are freed. Its a great mod. I wouldnt recomend lightening a factory flywheel thought. Its dangerous. The best manufactures of flywheels will use chromoly steel for them. By best i mean Toda, Jun etc. Actual time attack companies. Not Fidanza or act ect. With high horse power you run the risk of the friction of an agressive clutch disk causing detonation of the flywheel after prolonged exposure. Just becaureful with the mods you choose for your car and do lots of research. You own an expensive powerful car. Dont go cheap!!!

 

Flywheels being lighter wont reduce torque output of the motor at all.

It does reduce inertia so when you start off you need to compensate with more throttle.... but it doesnt make the engine 'less torquey', just not launch as well.

 

You sound like you need to read what the effects of lightening the flywheel do to the car, you are actually reducing the rotational mass, theis means the engine "spools up" quicker and subsequently loses revs quicker when you lift off. There is no horsepower gain just responsiveness to the throttle and quicker rev building due to the weight loss.

Pros are, faster spooling, more responsive to throttle pedal commands, easier to do a fast launch by holding RPM and releasing clutch (hillclimbs etc)

Cons are, harder to launch on street until you get used to the difference (about 3 launches) engine loses revs very quickly when you lift (this takes about the same time to get used to) Absolutely no ability to tow (LOLOLOL

Steve

 

just put in an excedy 12lb flywheel (weighed it-more like 10.5) with a street/strip clutch. it is everything that i thought it would be. no noticeable difference in launch rpms. but the car is definetly alive past 3k. i think throttle response is better, and i think there is a small difference in the sound of the car. oh, and it doesn't idle differently maybe a lighter flywheel would but not mine.

 

An update to this thread.

The car now has a 12 lb Racing Beat flywheel in it.

No drivability issues from the flywheel at all.

Thanks for all the input.

 

that's nice to hear. i've used their 17-pound units and i'm getting one of those 12-pound aluminum units for my next engine buildup. i didn't expect any issues since i used a 10-pound JUN flywheel in my MR2T, but it's still good news to me.