AO

So my supercharged GT needs a new flywheel. When I had it all apart last time and put the Spec 3+ clutch in, I had a shop resurface the flywheel. I gave them the spec sheet on it, and instead of taking the minimum off, they took it down to the minimum spec...

It has worked great for several years, but now it's below spec and has a couple of descent groves in it. Clearly I don't want to put it back in there like that so... I'm in the market for a 60-tooth flywheel.

Here are my obvious choices:

• New one from Porsche. Est. $600 to $700
• Used one Est. $$100 to $300
• 928 Motorsports lightweight flywheel Est. $700

Anyone have experience with Carl's (928 Motorsports)? Anyone have a good used one that can be resurfaced that they'd like to sell cheap? Any other options that maybe I'm not aware of?

Imo000

Doesn't GB sells a carbon carbon clutch?

jcorenman

928 Int'l lists used ones for $300, and it's only 11 months until the next half-off sale!

Mark also lists new ones (928-102-208-03) for $726, PET shows that superseded to 928-102-208-AX (resurfaced) for $469 plus core, $353 if you shop around. It sounds like new ones might be NLA, so talking to Mark or Roger might be a good idea.

Correct, twin-disc carbon-carbon. We have one, as does Rob in his stroker. Works well, short travel but feathers nicely if you hold your lips right.

Madturk

Sorry... Not to hijack but...
Spec 3 clutch, is that same as a gt3 clutch?
Your car is supercharged. I need a new clutch. Thinking about a supercharger sometime in the spring. I'd like something that would hold the extra power that still let's me drive the car smooth. Gt3 clutch was a disaster.
I asked because I'm assuming you will have a new clutch in there as well.

jcorenman

I believe that Andrew has a stage-3 Spec clutch, info here: http://www.specclutch.com/products

There are trade-offs between cost, torque capability, pedal pressure, and smoothness-- sort of a "pick any three" dilemma.

Imo000

How much HP are planning to put down?

Madturk

I'm thinking victors stage 3 sc. Which willl end up close to 500hp. I have a 5 speed from an 87 car. The gt3 clutch was horrid and clunky. I'm pretty sure the stock clutch would drive smooth but won't hold down the power.

mark kibort

you could do a stock twin disc conversion. all you need to do is get the stronger upgraded pressure plate. mine has been great with no signs of any slipping for torque up to 420 at the rear wheels.. dont know how much more you can go, but its a great package and all stock stuff (after modifying the stock pressure plate with a mix of old and new stuff)

dr bob

For increased-horsepower cars, you really should take a hard look at Greg Brown's clutch package. Takes a little getting used to for smooth street launches, but is the king of durability.

AO

Sorry, I had to get through some crazy computational biology issues today at work.

So, thanks for the input. I'm not interested in replacing the clutch. The clutch is fine. It's the flywheels that needs updating. I'll ask Mark and Roger. I was also reminded that Spec makes a FW similar to what Carl is offering (possibly the same?)

The Spec clutch has been great. The car puts down a reliable 500 RWHP. The SPec 3+ is supposedly the streetable version of the clutch, but it's borderline. As Jim mentioned, it's a tradeoff. It takes FOREVER to break-in, but then can be smooth. Part of it is certainly getting used to it. It's not quite an ON/OFF switch, but there isn't a whole lot of range to feather it.

I am a little concerned for a street application of having the lightweight flywheel. Recovery on decel can be an issue with SCed cars. Luckily with the Sharktuner, that can broadly be mitigated by keeping fueling turned on at all RPMs or adjusting the idle speed higher.

I assume my existing flywheel will not work as a core, correct?

Imo000

You want a new flywheel and use the old disk and pressure plate? I would presume the grooves are at the edge where the disk friction material touches the flywheel then?

AO

The clutch PP side is fine - well no major wear. Even the friction looks fine. I noticed a raised ring or groove on the flywheel side - probably from some anomaly in the friction disc. I thought i should have it cleaned up, but it's now out of spec, so I thought getting a replacement FW it the best option.

I may just throw it all back in the way it was and deal with it when it finally goes south.

jcorenman

^^^ This is not a bad plan.

And please, what is "computational biology" ??

AO

Yeah... gonna give that a shot first, I guess. If it all goes to crap, then I'll address it.

I run a software company that makes applications to help researchers sift through the data that come from whole genome sequencing experiments (DNA, RNA, Proteins, etc). There are literally between 50k and 100k data points in each one of these experiments... think of them as variables which can influence each other.

Our algorithms setup huge sets of simultaneous equations with bootstrapping strategies (randomizations) to help identify key biological systems that may be impacted or are prime candidates for therapeutic intervention. Lots of statistics, lots of biology, lots of computer science. I'm the business guy.

Research Use Only... for now. :-)

Imo000

The groove in the disk is in worn with the flywheel therefore, you are better off leaving it as is than try resurfacing it anyways. I would leave it alone until it starts to slip or the flywheel shows signs of warpadge.