Effects Of A Lightweight Flywheel

Hi I found this interesting link about LWF. In this article 3 kg saving in flywheel mass was equivalent to removing 100kg of chassis mass in first gear. http://www.pumaracing.co.uk/FLYWHEEL.htm Can a member with applied mathematics knowledge use the formula in the above article to work out the chassis mass saving if a standard steel flywheel weighs 12 kg and a LWF aluminum weighs 7kg? Then calculate the new 0-100km/h with the "lower" chassis mass, and then the horsepower to accelerate the a standard weight Cayman to the new 0-100km/h. The difference here in hp will be the effect of a LWF. Cheers Herm

Herman, I'm no mathematician, but I believe to achieve the computational accuracy you may be looking for, one needs to know something about the distribution of weight across the flywheel. If you search on "moment of inertia" you'll find a lot of information mostly by bicycle nuts striving to shave that last gram of weight off, preferably, the very outer rim of their $2,000+ bike racing wheels. For a more practical, emperical view/result PM me & I can send you a copy of some 6 before vs. after dyno pulls, done IIRC in 2nd, 3rd and 4th gears in an Rx8 showing the horsepower gains achieved at the wheels from knocking something like approximately 8 gross pounds off the cars flywheel. The gains are slightly more pronounced in the lower gears where the effect in magnified by the rate of engine spool up.

..not a scientist - but did put a light weight alluminum flywheel in a car once and the main difference in feeling is quick revs - less braking aid in downshifts (but also didn't upset the car nearly as much as the sotck steel unit) and most importantly (for some) there was a noticable loss of torque down low... ...some HP gain but up high... ...you will want to keep the revs up more - the power band rises and down low you get more of that "lugging" feel off the line especially...not that great for the street but fun for the track! Z

Some of you may recall that the Carrera GT has no flywheel. Instead, its drive shaft is engineered to have enough torsional flex to take the place of a flywheel. The Cayman has a related setup. It does have a flywheel, but it's "dual mass", which means there are two constituent flywheels coupled with springs. The resulting torsional flex allows use of a lighter flywheel assembly, without letting excessive torsional vibration reach the downstream drive train (with its vulnerable gears). Putting an aftermarket conventional flywheel in (even a non-"lightweight" one) will be grounds for refusing warranty service on the gearbox and diff, at a minimum. It's probably not worth playing with (except for serious race apps -- don't race it if you can't afford to torch it...), and I for one won't be. The "dual mass" idea is pretty cool. Excerpt from an article from European Car on flywheels :

Hi I have an aluminum LWF in my 3.8s Cayman . The new 997 GT3 RS also have a single mass LWF. If this was causing transmission and diff failures Porsche would not have fitted then on the new GT3 RS. This flywheels is a bit noisy at idle and between 2500 and 3000 rpm in the high gears. The noise sounds exactly like the 997 GT3 RS. With the free-sound package the engine revs and sound like a GT3 . If you are using your Cayman only for commuting don't fit a LWF as the two above posts are spot on. For me hearing and feeling the effect on a Cayman is awesome. If you drive a Cayman with LWF you will want to do this mod immediately. Except for the 3.8 engine the best modification so far. Cheers Herman

Herman, Where did you get your LWF for the Cayman ? -Andrew

If you run the engine at a steady rpm there would be no change of HP. You would only see a effect in acceleration. If you change the weight of the flywheel the car will accelerate quicker but you will loose everyday provability. You can do the math and find out a number yes but I would not trust that to give you the true effect. You would also need to know wear the mass is that you are removing as more mass on the outer edges would make more of a difference. I have just seen in a magazine where someone is making a flywheel where the starter gear is able to just turn the flywheel in the starting direction then it disengages itself from the flywheel so there is no loose in turning it.

Hi Andrew Got it from Randy Aase at Aasco Performance in LA during my last visit to him. My LWF is an absolute work of art. Randy and his brother runs a team of 5 GT3 Cup cars, do engine development work and make flywheels. According to him his LWF feels feel like the car has 50 hp extra during acceleration. I would not know how my car would feel with a standard FW as the LWF was installed during the 3.8s engine swap. My car is significantly faster than a 997s during acceleration. (6th gear 40km/h-140km/h, 997s-24.5sec, 3.8s Cayman – 20.3sec) A LWF does not add any power or reduce the torque; it only makes the engine revs up faster during acceleration. I have now driven 1000 miles and do not experience any drivability problems as expressed in the previous treads. I don’t think one can generalize that LWF are only for racing. If you have a LWF that is light it will not work for road use. Sachs makes a spring clutch plate that also reduces the noise and drivability problems. Cheers Herman

how much is LWF?? and where do i order one ? how hard is that to install?

Lwf A lightweight flywheel accomplishes two things. Makes the car rev faster (not as much inertia in spinning the flywheel) thus changes the amount of gas (or time holding the throttle down) when you double clutch for down shifting. I have it on my G/P Spitfire and it took me a while to get used to it because I'd raced with the iron one for several years. Does it make the car faster? Probably not much since you still have to accelerate the mass of the car. But it might make your lap times faster since you can down shift faster, etc. Again not by much but every little bit helps on the track. Down side, it makes it easier to stall the car when starting (not as much inertia to keep the engine reving when you let the clutch out too fast or don't provide enough throttle). Again not an issue on the track but might be for the street. When you get into the dual-mass flywheel, that's a different animal. Primarily used as I understand it to lessen the amount of gear noise and vibration transferred.

does this flwheel work for tips?

No. I don't believe tips have flywheels that can be put on a diet. As mentioned above, the LWFW does nothing to increase actual engine horsepower, it simply removes extra weight in a rotating part (and a very rapidly rotating part at that) the engine (& for that matter the transmission) would otherwise have to accelerate/decelerate, making that power more directly available at the wheels. While and engine dyno would show no increase in power "at the crank" adding a LWFW will show up as "added" horsepower on a chassis dyno "at the wheels." LWFW are most effective / noticeable in high rpm (i.e. wide power/rpm band) engine applications and, generally speaking more apparent in the lower vs. higher gears

Hi Aasco charge $829 for the LWF. Read the article by Puma Racing, the link is in the first post of this tread. In short this LWF will give the effect of removing 150kg from a Cayman in first gear because of the lower moment of inertia of a LWF. I have done the calculations for a Cayman . Gear..... Mass Kg 1..... -150 2..... -55 3..... -31 4..... -22 5..... -17 6..... -14 The power needed per gear to overcome the inertia of a standard FW compare to a LWF in a Cayman 3.8s with 355hp at the crank. Gear..... HP 1..... 38.3 2..... 12.9 3..... 7.6 4..... 5.3 5..... 4.3 6..... 3.3 With the figures calculated now it looks that we will only gain performance in first and second gear (0-120km/h). Cheers Herman

Herman, I am in the process of doing a LWFW and are curious about the "Sachs spring and clutch plate" you refer to. Can you please give me the part numbers? Thanks!

Okay so I purchased a full AASCO LFW & SACHS clutch kit directly from ASSCO Motorsports. The car is going into Porsche tomorrow morning for new front and rear main seals plus a few other things. They're willing to install this full kit for me. 106412-11-pkg- porsche - boxster - cayman -flywheel- sachs -clutch-kit However I am now having second thoughts about the lightweight flywheel. I want the faster revs in the 2005 Boxster S which seems to have a granny gear for first. What's concerning me is the vibrations and possible engine damage. Has anybody been running a lightweight flywheel on a Boxster 3.2 for many miles. Is this something that I should worry about?

I had a LWF installed on 06 CS when I changed to 3.8 x51 engine. Deman Motorsports did it but I don't know who's stuff it was. It does rev and accelerate faster but wouldn't increase your HP. It only gets you to the higher rev band faster. I wasn't crazy about the clutch engagement. I found it was grabby and harder to start from a stop; much touchier.