rotarenvy

just thought I'd share my impressions about a light-weight flywheel that I just got installed.

I got an exedy flywheel and new std clutch (plate and disc) not long after getting the car but only fitted them today due to warranty concerns. overall with fitting I payed around $1000. about half the cost was the clutch, bearings, seals, bolts etc. turned out I'm extra gentle on my clutch :D and the old one looks like new so I'll sell it shortly to recoup some money. if you didn't need the clutch you would save $400 or so.

honestly I can barely notice the difference. it drives like std apart from the clutch take-up point being closer to the floor. the engagement point is getting better and seems to be returning to normal. I guess it's just wearing in. all the negative points about lightened flywheels seem wrong. it's not hard to drive round a parking lot and has no trouble up hills. on the contrary, I have found starts easier and the car no longer bogs down as much when I take off from lights. yes it does rev faster but not so fast that the difference is night and day.

was it worth it? after all the hype I honestly thought the difference would be greater. I doubt I'd do this again unless I really needed to change the clutch since it was worn out or I needed a stronger one for a turbo. I was heading down the road to more modifications and this high-lighted again how wonderful the car is to start with.

takahashi

Did you weigh the Exedy flywheel?

rotarenvy

I'm sure I would have years ago but I can't recall what it was. the one I'm using is the same as the FEED one and they quote 5.3kg.

timbo

As I think I may have posted before, I have always wondered about the effect of a lightened flywheel on the Renesis (or any rotary, for that matter) because, as I understand it, a lightened flywheel will increase the ability of the engine to spin up to its powerband, but reduces the torque effect of the heavier flywheel. Which is sort of opposite to the characteristics of the rotary engine (already fast-spinning, but low torque -- which is only achieved at relatively high rpm). Discuss:

takahashi

This will put you out of misery

http://www.europeancarweb.com/projec...utch_flywheel/

High revving happy. Torque will increase as rev picks up. It will be a light to light racer nightmare!

rotarenvy

but this is exactly the oposite of what I got. it is easier for me to take off from the lights.

I tend to release the clutch too early and the motor normaly struggles. now I'm still releasing the clutch early but it dosn't struggle to build revs.

the motor can't loose torque can it? you only loose inertia from the reduced mass.
in my circumstance I wasn't using inertia to get the car moving, I was using the torque. since I now have less mass in the drive train, I'm effectively using more torque to get the entire car moving and it doesn't struggle to reach higher rpm. just my guess.

ca18detsilvia

i installed a pettit racing 8.4lb flywheel and uh.....its not nearly as friendly as stock. your flywheel weighs 5.3kg which is around 11.6lbs. on a slight incline i have to concentrate not to stall or slip the clutch but its not too bad. about 2 weeks ago i drove a stock RX8 and wow the clutch and flywheel made a big difference, i installed a competition clutch and it feels way different than stock. i found that it does rev alot quicker and revs drop off fast......i was very happy with it but its sometimes frustrating in traffic and stoplights on a hill

rotarenvy

maybe the extra ~4lb difference would be night and day.

DrewMan

i just got the act racing clutch with the prolite flywheel and counterwight.

will post a review once its in the 8!

rotarenvy

cool.

what made you go with a racing clutch?

DrewMan

The price! it was cheap at the time of purchase so i thought why not? its not like its out of necessity or anything hahahahaha

DrewMan

$120 for act heavy duty pressure plate, clutch disc, bearings etc and all the bits and bobs

prolite flywheel + counterweight was about $550 shipped to aus

DrewMan

gotta love eBay!

EZZY

how many plates? is it a heavy duty clutch or brass button clutch?

DrewMan

heavy duty single plate

any more than one and it would lose the stock feeling

timbo

Hmmm...even a fairly minor effect on a reciprocating 6 as in the M3. Mind you, they point out it's not all that light given the M3 in question has FI.

My overall reaction: given it's a FI M3, why bother at all WOFTAM!

takahashi

For my application Timbo. A lighten flywheel will always free up the requirements wasted to turn a heavy fly. When the car is running at high speed, the less energy require to pick up is better.

For street applications, it may or may not be necessary noticeable. I remember Stu's 8 when having a very light Promaz fly. I would feel the freeness on the top range, but the punch in the freeway in 4th and 5th gear in low rev is not as strong as mine (which was stock).

My superlight clutch/fly is here for me to collect! Wicked.

timbo

It would be good if someone planning this mod takes the trouble to post the same before and after data as in the BMW M3 link you posted. The evidence there is not at all convincing, but then as the writer noted, the change in weight was not all that great

rotarenvy

I agree. there is only so much weight you can remove. if you do just the flywheel then the weight removed is small compared to the overall mass of the flywheel/clutch.

if you go to a lightweight clutch with a smaller diameter (guru racing rx-7 flywheel and clutch) then there will be a much bigger overall weight reduction.

I doubt a lighter aluminium flywheel would be much better than a heavier steel one. reduced mass further away from the centre is the goal and the aluminium ones still need a steel ring gear bolted to them and a steel friction surface bolted to them. most of the additional mass saved is in the centre of the flywheel.

rexi888

Rotaryenvy, no wonder you dont feel much of a difference in performance. Your flywheel is too heavy. 12lbs for just the flywheel and then 2.5 lbs for the counerweight =14.5 lbs. The stock flywheel weight is 16.8 lbs. In my opinion , unfortunately , it has been a waste of money in this instance.
As I have previously said, in order to get significant performance increase you have to go for a superlight flywheel such as my 8lb fidanza flywheel.Then you would have to to be brain dead to not notice a significant improvement in acceleration especially in the top end. Mine absolutely screams to redline.

Regards
Rexi Lightweight poverty pack rx8
Fidanza 8lb flywheel
Agency power crank pulley
Mazdaspeed suspension
Metalcat high flow cat

Rexi

rotarenvy

well there is a difference about as much as a 10kw exhaust IMO.
I'd love to compaire the inertia difference between a steel and a lighter aluminium flywheel. after all the heaviest parts of the clutch assemably is the the pressure plates and they have to be steel and at the same radius. you also have the counterweight as well you realise

auzoom

yes thats exactly the point of a flywheel change. To move inertia to the centre. The stock flywheel has a LOT of its weight on the outter edge of the flywheel. Makes for a comfortable drive on the street but once you are moving it has a negative effect, more effort is spent spinning it.

There is a thread here somewhere on this site that gives an example of a broom. Take a broom with say a head weight of 3kg. hold it in both hands and spin around. Now take that weight and move it from the end of the broom to the middle. Its a LOT easier to both start and keep spinning.

Cheers

Andrew

Revolver

Interesting.

I looked into this a while ago and decided it's only worth it for track use, so didn't go ahead with it.

DrewMan

My flywheel finally came in the mail!

mind you its still got the wrapping on it so i will round down.

XACT Prolite flywheel - 4.5 kg


XACT Counterweight - 1.5 kg

(tilt your head to the right 90 degrees)

icyur2

I recently installed the MazdaSpeed flywheel and LOVE it!! I'm in the processing of "breaking it in," but once that is done, am going to enjoy the easy revs that this lighter flywheel produces for me. Could of went with a lighter one, but don't want to go to the extreme of losing the drivability when in the city..Acceleration is quicker in my opinion, and when I need to shift and rev to match, is VERY easy to do since it doesn't take as much energy to do so when the weight is in the center vs. outer edge...