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Just ordered a set as well...before I take delivery in April.
 
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This time the correction factor (vs. stock car dyno launch) was more severe, 0.96 vs 0.97, so the difference w/ the fabspeed manifolds is bigger uncorrected.
The biggest differences are visible @3600rpm (about +25Nm and +13hp corrected ; +30Nm and +15hp uncorrected) and @5000rpm (about +15Nm and +11hp corrected ; +18Nm and +13hp uncorrected).
That's how the engine should have been from the beginning.

 

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We have also tried a set of BMC drop-in air filters, that showed ZERO gain.

P.S. The fabspeed manifolds showed a loss in power and torque between 1800 and 2800rpm, but in my opinion this is a speed range that doesn't matter at all.
 
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Discussion Starter #26 (Edited)
cox thank you very much for posting up your data! The GT4 is continuing to show it's potential. We recently protuned one in house via the COBB Accessport and hit 390whp. The vehicle tested had our full Race system installed previously. We are quite confident the GT4 is an IPD Plenum/TB upgrade away from hitting 400whp. Have a blast with the new upgrades!:cheers:
 

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The GT4 is continuing to show it's potential. We recently protuned one in house via the COBB Accessport and hit 390whp. The vehicle tested had our full Race system installed previously. We are quite confident the GT4 is an IPD Plenum/TB upgrade away from hitting 400whp.
Using a 15% drivetrain loss, I'm equating your 390whp to around 460 at the crank. What was the original whp of this car, completely stock? If you hit 400whp, with 15% drivetrain loss you're hitting ~470 at the crank.

Let's see... the 991 GT3 is 475, right?
 
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I saw this thread and decided to join. I just had a local car shop install the sport headers, exhaust, air filter and Cobb tuner. I am very pleased with the results and can't wait to take it to the track. I also have the throttle body mod on the way.
 
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Discussion Starter #33
I saw this thread and decided to join. I just had a local car shop install the sport headers, exhaust, air filter and Cobb tuner. I am very pleased with the results and can't wait to take it to the track. I also have the throttle body mod on the way.
Thanks for chiming in! :)
 
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Discussion Starter #35
Will these work on a 981 Spyder?

Is a tune required?

Can I install these myself?

Has anyone tried a gt3 Throttlebody yet?
The GT4 Headers have been confirmed to fit the new Spyder 3.8l :) You can install them yourself, luckily the Boxster/Caymans are relatively "right there" in terms of exhaust design haha. If you are at all not comfortable installing them yourself, we recommend you take them to any shop you have used before to accomplish the install. The 82mm GT3 throttle body has been used on several 981 owners in the community with success as I'm sure you will see. As for the new Spyder in particular I cannot say, although we will have a GT4 in here shortly to document the installation.
 

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The GT4 Headers have been confirmed to fit the new Spyder 3.8l :) You can install them yourself, luckily the Boxster/Caymans are relatively "right there" in terms of exhaust design haha. If you are at all not comfortable installing them yourself, we recommend you take them to any shop you have used before to accomplish the install. The 82mm GT3 throttle body has been used on several 981 owners in the community with success as I'm sure you will see. As for the new Spyder in particular I cannot say, although we will have a GT4 in here shortly to document the installation.
I am sure there won't be anything comfortable about it, but I have the ability.

Thanks for the info....
 
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Discussion Starter #37
I am sure there won't be anything comfortable about it, but I have the ability.

Thanks for the info....
If you have access to a lift it is much easier. If not, get the car up as high as you can on jack stands. Once you remove the rear wheels it is pretty self-explanatory from that point forwards. I might recommend hitting the bolts with some PB Blaster or some other form of penetrant and let it soak for a day, just in case haha.

No problem, and when you are ready to get the ball rolling on a set give me a shout :)
 

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Here's a (thankfully) shorter video with better audio. (I am experimenting with different locations. Using interior at present, will move outside soon, I promise.)

https://www.youtube.com/watch?v=Q9M7Jdb2Gk0
This is just a straight on-ramp acceleration to a very surprising speed...
 

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...There are no secondary cats downstream from the headers on the GT4. In regards to the check engine light I can only say we have put 200+ miles on the vehicle and have had no CEL. Our theory is that Porsche may have desensitized the O2 monitoring system as the GT4s are built with track use in mind....or VW designed the monitoring system ;)
Can you guys please clarify this once more for me? The GT450 package is essentially a straight pipe system with the O2 sensors plugging in at the end of the manifold, and this is no problem for emissions?? Is there confidence that the system will be stable like this (no CEL) for the long term? I'm no expert in emissions or pollution control, but in the old days inspection stations would look to see if your cats were installed and, if not, you failed. Currently in NC, they just plug into the OBD2 port.
Capture-fabspeed.PNG
 
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