John@Fabspeed

Our development GT4 has already been returned to its owner, so we can't get that video until another GT4 comes in to the shop for that configuration. If anyone is interested in having some products installed here at our facility, we'd be happy to produce the videos!

The Sport Headers weigh 6lbs less than the stock headers. They weigh a bit more than the Race Headers because they include HJS catalytic converters.

We'd like to see this dyno as well. You can see that the gains from the exhaust are in addition to the gains from the headers. In our experience, the gains from most products are similar - give or take a few points - when installed with OEM or aftermarket products. That's not to say that they would be exactly the same, but we're confident that the over-sized 2.5" inlet pipes that we use on the Valvetronic Exhaust and the free flow design when the valves are open would allow for substantial gains, even when paired with the factory headers.

Not at this time. We only had the opportunity to test this system on our development vehicle with our Sport and Race Headers.

As mentioned previously, we intentionally did not bring the car to redline during our dyno testing out of respect to the owner's wishes. As you can see, the power begins to dip after around 6200 RPM, thus removing any reason to continue winding out the car. Peak horsepower and torque have already been achieved by that point, so there's no need to put unnecessary wear on the engine and drivetrain.

The posted dyno tests were performed with the factory ECU settings. We are a COBB-certified ProTuner, however, and we'll be exploring the additional power gains possible using the AccessPort as soon as we get another GT4. We're optimistic that we'll be able to break the 400whp barrier with a COBB tune on top of our exhaust hardware. If anyone is interested in having us develop the tune on their car, we'd be able to offer a significant discount on the final tuning maps. Please PM me for details if you're interested.

IrishAndy

Not to say it's not a great product (the curve looks very appealing - not just a peaky tune), but I'm pretty sure the gains offered by the Cobb tune wouldn't be quite as much if they had to back it up with a 4 year power train warranty. Unfortunately OEMs have to strike a balance with all sorts of things.

ExMB

How does this answer confirm the 17 whp and ~30 ft/lbs gains claim made previously when using words like similar and substantial. I think the only way to settle this is with a dyno.

Petevb

You don't know what the parts will do above 6900?

Two issues with this. First, you're likely aware that area under the horsepower curve is the critical variable. Other dynos suggest the GT4 should be shifted at between ~7600 and 7800 depending on gear for maximum performance.

Second, multiple other dynos also suggest there is a second horsepower peak at ~7200 rpm, and in fact this is normally higher than the lower rpm peak you're showing. This gives a normal GT4 a relatively wide powerband at the peak with good area under the curve compared to the rather steep decline in power you're representing here:



If that second peak doesn't exist with your system it would be a serious negative to performance. Thus there is a reason to wind the car out, and I'll again suggest it's of critical importance to show what the car does where it would be expected to make peak power.

CarAholic

So is the entire exhaust 2.5" or does it neck down?

GrantG

And Porsche themselves claim the HP peak is 7,400 rpm...

John@Fabspeed

I sat down with our tuner yesterday and had a lengthy discussion to get to the bottom of all of this, as I know many of you are wondering about the cutoff point on the posted dyno charts.

It turns out that a component of our DynoJet was giving a truncated reading to the software which was cutting off the RPM-based data. The car was, in fact, run all the way to the peak power level just shy of redline. The software - unbeknownst to us - was just spitting out a graph based on what the hardware was telling it. The run data itself is all valid and completely accurate; we are simply missing some of the top end data when the graph is set to display in RPM.

I had our tuner re-export graphs based on the wheel speed in MPH rather than on the the faulty RPM data and you can clearly see the secondary power hump that you are all looking for. The data was there the whole time, it just wasn't being associated with and RPPM, and thus wasn't showing up on the RPM-based graphs. We are already in contact with the manufacturer of the dyno and are working to upgrade the faulty component that led to this confusion.

What's important to take away from these graphs is that it is now clear that the modifications (both headers alone and headers with exhaust) make great power gains all the way through the entire rev band! There is no drop-off at peak RPM as some of you were wondering.





We appreciate you all taking enough interest to bring this to light for us. We do our very best to work with our friends here in the community and to present the best possible information for you. We thank you for your patience as we got this all worked out!

Full exhaust is 2.5".

steve0827

I hate to be THAT guy, but I'd love to see the car re-dyno'd after you get that software issue with the dyno resolved.

Petevb

Thank you. Sorry to be a hard a** on your thread, but I feel it's important to keep the quality information on this forum high, and I think this helped.

CAlexio

very cool that you were able to present that to us. looking forward to what your hardware + cobb accessport combo achieves foryou. looks like a very consistent very noticeable, and therefore relevant upgrade... seat of the pants and great sound. oh, and looks beautiful as well.

nice job.. now just waiting for the car.

bhgt2

My fabspeed exhaust and cobb should arrive in the next few days

s2ktaxi

what is now surprising is that the stock power curve reflects that of the Spyder rather than a GT4. The Spyder's peak power is the first hump whereas the GT4's peak power is supposed to be the 2nd hump. I wonder what causes the 2nd hump to not be higher as it should be.

bhgt2

Thanks to John @ Fabspeed, I received my exhaust today and I must say, it is a good looking piece of kit! Can't wait to get it on

John@Fabspeed

It was great working with you! I look forward to hearing and seeing the results once you have it installed. Once you get some miles on the setup with the Cobb Accessport be sure to send me the datalog and we will whip you up a custom file

Yargk

Thanks Pete, agreed.