NVRANUF

I just did the light weight flywheel, clutch and RS pulley install..... and so far it's a great addition to the GT3!!

On the track I feel a definite "new to me" engine vibration with full throttle beginning at ~7900 RPM through to the shift point. It seems more pronounced on uphill portions of the track where the car is pulling hard through the gears. I also have the WEVO mounts, but they've been in for some time (3 DE's and 2 track days) and I've not felt this previous to the LWFW

Is this normal?

Car is functioning normal in all other aspects, and the "instant" RPM from the LWFW is really a sweet bonus on the track.

Thanks

Carrera GT

I've owned four and driven many others. I've not noticed anything less than perfect balance approaching the red-line. The semi-solid WEVO mounts are great. They will communicate more engine noise and vibration to the driver, but, in experience, that's at low rpm only.

It sounds like something to check out. Drive another car with the same lightweight flywheel setup if possible. Certainly take it back to the installer for a quick check before further experimentation with this engine. You can eyeball the pulley and belt for alignment issues (wear on the belt or any mess around or underneath the pulley.) I'd want to confirm that it's at 7900 rpm in more than one gear and with a foot trailing the brakes to take the rotors and most of the drivetrain out of the NVH equation. But do this kind of thing after a tech inspects the engine and trans to be sure you're not going to bring on further trouble.

NVRANUF

Thanks for your reply, it's in each gear as the RPM runs through 79-8400.... at least 1, 2, and 3 and it's maybe more of a buzz sensation that a vibration... but I asked a passenger at one point, and they noticed it as well.

997gt3north

You may have a particularly sensitive set of senses and notice what others do not

From my own memory, pre install / post install, this is not something I have ever noticed

Also, from 7900 to 8500 usually there is other stuff to concentrate on so 'maybe' I'm missing it

It does not sound correct to me

Give Alex at Sharkwerks a call - he will have more experience than most in this manner - and may have a few client cars in the shop that he can test

911SLOW

Always start checking with what you did last. So with the engine off the mounts check that it is tight down well when back on.
I cant say I noticed it with LWFW and 993 rs mounts on the 996 gt3 and didnt notice it on 997 gt3 with LWFW without pulley and with oem mounts.
Is the vibration felt in the gearshift more or generally its a seat feeling?
Maybe you can pin point it better like that.
Also I agrre with 997north sometimes after a mod you start to watch things more and might worry for nothing.
But have it checked before doing more red line pulls.
Good luck.

John

NVRANUF

Thanks guys, an email was already in to Alex.

I just called my dealer and ran it by my "trusted" mechanic who says it's normal. The original dual disc fly has 15deg of deflection which soaks up this engine vibration.

Perhaps "vibration" isn't the right word here....

MM3.9GT3

You need a second opinion. I picked up my 2007 GT3 from RAC Performance on Monday. It now has the Manthey 3.9 engine, a stronger clutch, and a Cup Flywheel. All the chatter is at idle, and up to about 3500 rpm. After that, everything is very smooth.

rsman

Not normal imo. Had LWFW installed in my GT3 and no such issues. That combined with the Guards GT2 LSD were without question the single best mods to the car and combined with the Tarritt toe links ,proper alignment and corner balance turned a great car into a sensational car.

jenk12m

Yea you should only feel a rattle of any sort at idle due to the LWFW

jason952

serious vectors in play at that RPM, I would want to know the cause prior to a problem arising.

DHI

slightly off topic...
Despite the vibration that is being deliberated here, would you recommend a LWFW for a largely street driven 6GT3?

MM3.9GT3

Not in your case. The benefits outweigh the drawbacks on the track, but on a street car, it is reversed.

Nugget

Agreed. For street use there's no reason to go for a LWFW.

sharkster

Aye the more I think about it maybe you got a flywheel that's out of balance (not very likely with factory parts but...). The transmission "sizzle" noise as it's called is when one lugs the car in the lower rpms and too high a gear. I've heard of a few guys that had certain panels (my a-pillar as an example) that over time develops a nasty "buzz" in higher rpms but that's not really coming from the trans or anything like that. I'd hate to say it but they might want to go back... open things up... balance the flywheel and try again? Hopefully all the flywheel bolts are in there too and tight? I know of Caymans that came from the factory with flywheel bolts that were loose (dual mass as well) that did obviously make noise

NVRANUF

Thanks all for you insights and opinions!

I have a DE in 4 days so I'll see how it performs. Could just be my imagination, but at least my dealer knows and has given a green light.... plus it's under warranty!