Took a run to Pt Reyes in a GT4 re-geared from third gear up with a lightweight flywheel, a GT limited-slip diff, headers, and a tune. First, I want to say kudos to Sharkwerks for developing its future offerings on its own shop cars—rather than customer cars—and for trying stuff out and asking for outside feedback and criticism as it does so...and then saying, "Go ahead, put your thoughts out there, and don't be shy."

What I learned after a couple of hours on good roads: The mods wake the car up nicely, and make the powertrain feel more "GT." The lightweight flywheel might contribute the most significant and immediately obvious shift in personality, with three benefits: a revvier 3.8, subtle GT3 RS gear rattle noises (if you're into that kind of thing, like I am), and a lighter clutch pedal. Alex says Sharkwerks can make the clutch pedal heavier artificially, but one has to ask what the benefit is? The lighter clutch takes a little getting used to for those of us accustomed to GTx cars in this post 997-1 GT3 era, but it's nicer to live with this way—and a heavier clutch pedal doesn't add performance. Also of interest: The auto-blipper in Sport mode still works perfectly, suggesting it can deal with both the lightweight flywheel AND new gear ratios. Hmm. So it seems it may be a bit like PSM, in that it can adapt within a window.

The new third gear is better than the stock ratio for back roads—but a better way forward would be adding a new first and second gear ($,$$$ due to the need for two more new gears and a new mainshaft) or a lower ring and pinion with a taller sixth gear to keep a freeway cog. As is, the new third tops out at 93~ mph, just 9 higher than the stock second. It makes the new third and fourth great for track work, and third better for back roads, but if you shift from second to third at redline, the rpm drop is so small that initial clutch feedback will have you thinking "You missed a shift! Don't let the clutch out all the way!" Effectively, the car has two third gears—and the second third gear would only really make me happy if I was tracking the car a lot, as it is a good gateway to the new fourth and fifth. But the new third gear doesn't make much sense with the stock second gear. The good news is Sharkwerks TRIES stuff, and then keeps fiddling. In this case, it needs to keep fiddling. This feels to me a bit like the 997-1 GT3 RS 3.8 engine that never made it to the sales shelf—no bad thing, because that trial led to the 3.9. Which remains my favorite NA flat six of them all for character.

Back to the GT4: The sport headers with high-flow cats and the stock muffler—the combo Sharkwerks arrived at as its first preference after trying a lot of mufflers—and the retune contribute to 415 hp (claimed). I can't verify that, but the GT4 felt smoother than mine does through the revs on California pump gas, and stronger too. Noises were sublime in either mode, with no drone. There is zero downside to this exhaust other than cost and warranty, as far as I can tell.

That's the quick report from here.

 

Thanks for your thoughts Pete and great work Sharkwerks and GTGears!

 

Probably an obvious question, but are they using their own custom built headers, or using third-party?

 

Thanks for the nice write-up Pete. Your experience would seem to confirm the challenges of re-gearing the car without changing the ring and pinion. Doing one without the other is not ideal.

I'm surprised you weren't more impressed by the power mods. Must be that west coast petrol. Would love to hear your thoughts with a tank of 93 octane in the tank.

 

Thanks for the write up!

 

Eh, the butt dyno is a bit useless for a gain of a few percent, so I'm glad to hear Stout's honesty. That's not to say it's not worth it to do the mods. I like the idea of 415 hp a lot (but will keep mine stock for now), however, I wouldn't expect to experience it by feel. I expect it to shine through during dyno confirmation and also, 30 hp is enough to see an extra 3 mph at the straight at thunderhill which will come out pretty clearly in that data. Of course for something like 450 hp, you'd feel that.

 

Pete, Thanks for your thoughts and time. Good having you on the GT4 forum.

 

good stuff.

 

Those of us who have installed headers and a tune found the improvement in performance to be very noticeable. Not subtle at all. But I suspect most of us are using 93 octane fuel, or higher. It's becoming more evident that octane is a large factor in this engine's ability to produce power. Even Pete noticed it when he put some race gas in his own car.

 

Awesome.

 

Would it be more effective to change the final drive to get 1-2 down and put in longer 3-6 gears instead?

 

Hello Pete,

First off, congrats on the new endeavor. It's all over FB this morning and sounds awesome. Really excited for you and for enthusiast readers.

I want to comment on the gearing. What Sharkwerks has in their car is a motorsports set of ratios. Furthermore, it is the shortest set we've done and was designed to mate best with the 2.05 2nd gear found in some of the other Cayman/Boxster gearboxes. Yes, it is extremely close to 2nd and not what we would recommend/sell to most people.

The more appropriate 3rd for a racer would be our 1.60 gear, which would add another 3-4mph in gear and improve the drop a little bit. If it was a DE car, we wouldn't even go that short and would put in a 1.55 or 1.526 as part of our 3 gear package, which leaves 6th stock. Those 3rd gears top out right around 100mph.

Readers, please don't ask me to go into greater detail here in this thread. Sharkwerks and I are putting together something that should answer all your questions and be included in their build thread. If you have questions for Pete about his impressions, fire away, but I'm not going to flesh out the offerings more here. I just wanted to nip certain questions and concerns in the bud based on what's already been posted.

Regards,

Matt Monson
Guard Transmission LLC

 

Thanks, Matt!

If there's anything I learned in my time with the Sharkwerks car, it's this: This is one street/track Porsche that's really worth playing around with the gearbox on. The new third made the car better on back roads, and fourth actually became useful....

 

Have to keep watching this thread- would be interested in some of these mods on my Spyder at some point...

BTW, congrats Pete- just signed up!

 

Okay Matt. Got it. Looking forward to hearing the rest of the story.