flywheel/horsepower gain

90T5I · Apr 1, 2009

so im changing my clutch cause it took a poop on me and i think my pressure plate is shot beceause im not getting full disengagment. it is still drivable but has a slight creep in gear at a stop and it hard to get into gear from a stop. but anyway im going to a stage 3 clutch and was curious how much of a difference i would get if i went to to lighterweight flywheel im kinda tight on cash so im hoping not to have to replace it if i dont have to. but a resurfaced stock one is gonna be alot cheaper then a new light weight one. i guess what im asking is how big a difference would i feel going lighter? also if i im not grinding gears and not forcing shifts will i cause any dammage to my tranny? if i cant get it into gear from a stop i dont force it i jst turn it off put it in gear then restart it in gear. ghetto i kno :confused:

jeremylee_7 · Apr 2, 2009

Well the first question is what the car is used for, is it drag, road race, or simply street use.
A lightweight flywheel does not add horsepower, but decreases rotating mass on the crank thus allowing faster revs. The flip side to this is that the reduced mass then allows the rpms to drop faster as well. On a drag car this can be help full because after the shift it can put your car at the bottom of your optimal RPM range. For a road race this drop in rpms can actually be more harm then good by the time you are ready to accelerate out of the turn. Also, for a daily driver (or one that will regularly see street traffic), the fidanza flywheel may be a little too light and some people have actually complained about idle issues. I had an ACT chromoly flywheel on my 90 gst and liked it.

Also, if your car is having trouble shifting gears you should make sure the master/slave cylinders are working correctly and that clutch line does not need bleed. While a bad pressure plate or throw out bearing can cause shifting problems, the clutch hydraulic system is the more likely culprit.

Sorry for the novel, hope this information helps.

kottyking · Apr 2, 2009

Like he said, the purpose of being lightened is less rotating mass. If this is your daily, my personal preference would be a resurfaced stock flywheel.

LTUDSM · Apr 2, 2009

jeremylee_7 said:
Well the first question is what the car is used for, is it drag, road race, or simply street use.
A lightweight flywheel does not add horsepower, but decreases rotating mass on the crank thus allowing faster revs. The flip side to this is that the reduced mass then allows the rpms to drop faster as well. On a drag car this can be help full because after the shift it can put your car at the bottom of your optimal RPM range. For a road race this drop in rpms can actually be more harm then good by the time you are ready to accelerate out of the turn. Also, for a daily driver (or one that will regularly see street traffic), the fidanza flywheel may be a little too light and some people have actually complained about idle issues. I had an ACT chromoly flywheel on my 90 gst and liked it.

Also, if your car is having trouble shifting gears you should make sure the master/slave cylinders are working correctly and that clutch line does not need bleed. While a bad pressure plate or throw out bearing can cause shifting problems, the clutch hydraulic system is the more likely culprit.

Sorry for the novel, hope this information helps.

Less rotating mass=More HP
You should read the Forum bro....... Everybody saying,that if you replace stock pullys to the light aluminium ones,you will get some extra HP.The same thing is with the flywheel....

snakeyes711 · Apr 2, 2009

lighter flywheel will only get you faster acceleration.

viperlp01 · Apr 2, 2009

A heavier flywheel makes for a better LAUNCH... You know you love to launch.. Stock flywheel ftw..

FORMONTOYA · Apr 2, 2009

LTUDSM said:
Less rotating mass=More HP
You should read the Forum bro....... Everybody saying,that if you replace stock pullys to the light aluminium ones,you will get some extra HP.The same thing is with the flywheel....

He was correct...

A lighter flywheel does not create HP, it just "frees-up" HP that would otherwise be used to rotate the mass of the engine and can be used further down the line to rotate the tires.

It will allow the engine to rev faster, plus drop off between shifts quicker.

They actually work well on a road course up to a point. I didn't like an 8lb flywheel, but the ACT 12lb is nice...just a little "blip" of the throttle between shifts and the revs will be correct while down-shifting.

I don't drag race so I couldn't comment on that.

Using under-drive pulleys as an example isn't a good argument as they don't really shave off enough weight to really make any difference that you can measure. Maybe on a "butt-dyno", but that's probably because one spent so much money for so little bang.

My opinion...I wouldn't go less than the ACT streetlite for a DD/weekend warrior, but that's just me. You might stall it once or twice, but you'll get used to it real quick.

jeremylee_7 · Apr 2, 2009

My GST had an ACT flywheel and was a daily/weekend warrior. I loved it on mine, gave me quicker revs and worked well with my big16g (rpm wise).

One more option you can do is to get a lightened stock flywheel which is in between the 11-12lb ACT and the 18-19lb stocker.

timsturbotalon · Apr 2, 2009

i have one and love it. rpms do fall fast though. but hey to get something you have to give something

jrohner · Apr 2, 2009

Maybe it would show higher hp if you dynoed in 1st gear, but the engine doesn't rev up fast enough in 3rd for it to make big difference. The engine will rev up considerably faster in neutral and 1st, but I can imagine there being much difference anywhere else. I run an alum flywheel, and I have no complaints. The engine does slow down extremely fast though, making the RPM's go lower than idle for a split second. You will spin quite a bit easier with the light flywheel though.

To the guy that referred to alum pulleys - the so-called hp gain is usually attributed to the accessories running slower, not that the pulleys are lighter.

FORMONTOYA · Apr 2, 2009

jrohner said:
To the guy that referred to alum pulleys - the so-called hp gain is usually attributed to the accessories running slower, not that the pulleys are lighter.

OK, I'll give you that. However, I would still argue that the gains from under-drive pulleys whether from weight savings and/or slower running speeds, there is not enough "bang-for-the-buck" to make the investment worth the cost unless you make money from your car and need every .xxx to win.

Better ways to spend money IMO.

dsm-onster · Apr 2, 2009

If you drag the car or like to drag the car, then a stock FW is better. From my actual experience, even with the heavier xact streetlite flywheel, the revs fall to fast between shifts, causing the syncros to do alot more work. A motor that stays up in rpms between shifts will make up for sh!tty stock dsm syncros. I gained little to no MPH swapping to a lighter FW. I'm interested in going faster not getting every ounce of HP from a 3rd gear pull on a dyno.

If you're into autox rally or other circuit racing, then things may be different.

rts91tsi · Apr 2, 2009

I'm running the ACT Streetlight on my street machine. Faster revs,for sure. Loss of inertia though when going uphill.

toxicity883 · Apr 2, 2009

I always thought a heavier flywheel was ideal in an awd drive car, and that switching to a lighter flywheel slowed the launch because less rotating mass=less rotating inertia=less pull on all 4 wheels

chadnum1 · Apr 2, 2009

Ive always installed a fidanza flywheel with clutch jobs. Its all apart already might as well get it over with LOL

. I like the feel of the fidanza, faster revs great to spool up the turbo

tkelly27 · Apr 2, 2009

What if you are using NLTS? Your RPM will (should

) go to a set RPM, so the rev's dropping off is moot.

Also, the amount of kinetic energy in the flywheel is based on the mass of the flywheel and the rotational speed^2.

Rotational energy - Wikipedia, the free encyclopedia

Assuming you're originally launching from 4k with an 18lb-ft^2 flywheel you would need to launch up near 5k with a 12lb-ft^2 flywheel and 6k with an 8lb-ft^2 flywheel. Because it's exponential, as you get higher up it's not quite as bad, using the same assumption with an 18lb-ft^2 @5k to an 8lb-ft^2 is at 7.5k.

If you have launch control, shouldn't it be easy to bump that up to compensate for it? I could see it getting annoying around town though.

UGOT8UP · Apr 3, 2009

I wish there was a company that made heavy fly wheels, I just installed a XACT flywheel and the only thing I noticed is that it takes more RPMs for a good launch.

SeMi380 · Apr 3, 2009

My flywheel is somewhere between 7-9 pounds and it's kinda hell to drive on the street. Sometimes when I come out of gear the rpms will fall too fast and the car will stall out. I regret not putting in the 12lb one now.

The Chazz · Apr 8, 2009

I have an 11.00lb Exedy chromoly flywheel.

I feel it fits the motor MUCH better considering blipping downshifts is signifcantly easier.

You'll get worse MPG on the highway as well (less inertia).

I think 8.0lbs is way too little for street use IMO.

boostforfun · Apr 8, 2009

I like a stock flywheel for launching. If you are a guy that likes to feel the car and heel-toe shift on the street, you might like the quicker response from a lighter flywheel. All in all, there are much better ways to spend money if you are looking for performance.

Make sure the shop that resurfaces stock grinds it instead of turning it on a lathe. That is the only way to eliminate the hotspots.

birdygoesboom · Apr 8, 2009

I think its all about personal preference. I installed an Exedy Stage 2 Clutch kit With a 8lb Fidanza Flywheel. I love it, I have never had a problem with it, and to the references about stalling the car and possibly bad shifty, it's never happened. My idle is never weird, I shift on time without any huge drop in rpms, and never any drops below my idle (800-900 rpms).

92nolatist · Apr 8, 2009

UGOT8UP said:
I wish there was a company that made heavy fly wheels, I just installed a XACT flywheel and the only thing I noticed is that it takes more RPMs for a good launch.

fidanza billet steel flywheel- same as stock one but with replaceable friction mating surface.
Fidanza Steel Flywheel

The Chazz · Apr 8, 2009

Wow, Billet Steel...looks like a really nice piece.

The Chazz · Apr 8, 2009

birdygoesboom said:
I think its all about personal preference. I installed an Exedy Stage 2 Clutch kit With a 8lb Fidanza Flywheel. I love it, I have never had a problem with it, and to the references about stalling the car and possibly bad shifty, it's never happened. My idle is never weird, I shift on time without any huge drop in rpms, and never any drops below my idle (800-900 rpms).

Yea I agree.....im sure actually driving an 8lb around wouldn't be much different than 11.0lb.

Gotta love the Exedy ceramic though

My1GLaser · Apr 8, 2009

I have an RRE 14lb cut-down stocker. I love it. I really didn't notice much diff b/w the Xact 12 lb FW that I had on my FWD Laser. But I know they are 2 different cars. It sounds like a good compromise to me. I launch at 5-5500 and pull consistent 1.6-1.7 60ft.

Edit: I just checked their website and I don't see it...maybe they don't cut down stock flywheels anymore. :confused:

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flywheel/horsepower gain

90T5I

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LTUDSM

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FORMONTOYA

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FORMONTOYA

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