GT4 - Unlocking the Power Potential!
02-16-2016, 08:54 PM
#301
Rennlist Member
it's pretty obvious the biggest restriction from the factory isn't the headers, or exhaust....it's the throttle body.
If I was to do ANYTHING, it would first be the IPD 82mm plenum and matching 991 throttle body. There is a big reason why it exists, and Porsche uses it.
We already know the exhaust isn't very restrictive, it's already pretty loud. Headers have "GT" less restrictive cats, not regular model versions. The stock airbox should provide more than enough flow for the larger throttle body.
Assuming this fits without issue, this will be your best bang for buck mod, that won't require any additional software, and shouldn't throw a CEL. More importantly, it should help "wake up" the car below 5500 and everywhere for that matter, IMO
IPD 82mm Competition Plenum & 82mm 3.8L 991 Throttle Body
http://ipdplenums.com/products/plenu...-dfi-carrera-s
If I was to do ANYTHING, it would first be the IPD 82mm plenum and matching 991 throttle body. There is a big reason why it exists, and Porsche uses it.
We already know the exhaust isn't very restrictive, it's already pretty loud. Headers have "GT" less restrictive cats, not regular model versions. The stock airbox should provide more than enough flow for the larger throttle body.
Assuming this fits without issue, this will be your best bang for buck mod, that won't require any additional software, and shouldn't throw a CEL. More importantly, it should help "wake up" the car below 5500 and everywhere for that matter, IMO
IPD 82mm Competition Plenum & 82mm 3.8L 991 Throttle Body
http://ipdplenums.com/products/plenu...-dfi-carrera-s
02-16-2016, 09:25 PM
#302
Rennlist Member
I think you need to re-think your modifications plan.......the headers on the GT4 have the same cats all other 981 have, so not sure where you get the info on a less restrictive exhaust system. I do have to agree the PSE exhaust system is pretty good from the factory but headers (even with Cats) will provide a boost in torque and HP specially in the mid rpm range. They are essential and the first building block for any build. IMO are the 1st mod anyone should do and the only one that will not throw a CEL if equip with cats.
The TB and Plenum are on the other side of the engine equation and should complement pretty well any exhaust upgrade, but.....you will get CEL problems so a new ECU or a COBB is mandatory for this mod. We still haven't seen a lot of testing data on this mod so a lot of people are waiting to see the final results of bolting this mod on top of the others. Headers and exhaust on the other hand have a bit more info on the forums with solid results.
The TB and Plenum are on the other side of the engine equation and should complement pretty well any exhaust upgrade, but.....you will get CEL problems so a new ECU or a COBB is mandatory for this mod. We still haven't seen a lot of testing data on this mod so a lot of people are waiting to see the final results of bolting this mod on top of the others. Headers and exhaust on the other hand have a bit more info on the forums with solid results.
The stock gt4 exhaust is already free flowing with flaps open. It's less restrictive than all other 981 even if the cats are identical. Therefore it's already best positioned to benefit from the larger TB/plenum.
this was baked into the cake from the factory.
http://ipdplenums.com/products/plenu...-s-gts-gt4-dfi
Also, I have not seen anywhere where a tune must be used for only an Upgrade to 82mm throttle bodies on the DFI engines. Sure if you remove cats, and/or add hi flow exhaust I can see it , but not with just plenum/throttle body.
Last edited by Mvez; 02-16-2016 at 09:41 PM.
02-16-2016, 09:38 PM
#303
Drifting
I'm inclined to agree with MVEZ. I also recall reading somewhere that the Larger TB and plenum did not throw any CEL's.
02-16-2016, 09:58 PM
#304
Rennlist Member
Even if it does require a tune, if you are looking for power, not just cool sound, this is still going to be the most important part of the equation, for gaining power.
02-16-2016, 10:03 PM
#305
I'm not saying the TB and Plenum are no-good...just saying that IMO going for the headers first followed by the TB plenum is probably a better choice.
The exhaust system in the 981 is also a choking point for the 3.8 engine, which was designed for having a direct and short exhaust route. On the 981 you have a longer path with more curves. So by going to the better-flowing cats and better design in terms on tube length and flow you gain back what was lost on this area. When you see a factory header and an aftermarket one like the one from Cargraphics you will immediately see the improvements, just by looking at it.
Please do a search and read posts by BGB on the TB and CELs....this would be facts from someone with ample experience on these engines.
The exhaust system in the 981 is also a choking point for the 3.8 engine, which was designed for having a direct and short exhaust route. On the 981 you have a longer path with more curves. So by going to the better-flowing cats and better design in terms on tube length and flow you gain back what was lost on this area. When you see a factory header and an aftermarket one like the one from Cargraphics you will immediately see the improvements, just by looking at it.
Please do a search and read posts by BGB on the TB and CELs....this would be facts from someone with ample experience on these engines.
02-16-2016, 10:47 PM
#307
Rennlist Member
I've already seen and read posts from BGB where a "throttle body adaptation" procedure can be done by dealer or Indy with dura metric which to avoid CEL and allow adaptation, and that it does it by itself as well.
I'm sure Jon can clear the air.
I'm sure Jon can clear the air.
02-16-2016, 11:23 PM
#308
Rennlist Member
Isn't the throttle body adaptation to calibrate drive by wire? While ECU/DME's have a pretty broad range of mixture adaptation, I think throwing that much additional air will be a challenge for it to compensate. Time will tell.
02-17-2016, 12:17 AM
#309
Why not just do header, TB, IPD Plenum together? And get it tuned in one go? 
02-17-2016, 05:44 AM
#310
GT4 - Unlocking the Power Potential!
If funds are no problem that's the way to go....but you do need to be aware that beyond headers and exhaust you could be messing with your warranty. A good relation with your dealer goes a long way in flexibility with mods.....
02-17-2016, 05:56 AM
#311
Race Director
^I agree above. The first Mod will be Long tube headers and cats. This is certainly necessary because the stock headers and cats are choking the GT4. Plus- you need the midrange bump to even out the dip around 3500 rpm that is being seen with the stock. I am still waiting for more info on a sport exhaust. The current exhaust on the GT4 is pretty darn competent so waiting for more data and so far drone has been a big issue with some of these after market exhausts
02-17-2016, 07:48 AM
#312
" because the stock headers and cats are choking the GT4"
no they are not, fitting a manifold will net you 5bhp lol
the standard 74MM throttle body is choking the GT4.
no they are not, fitting a manifold will net you 5bhp lol
the standard 74MM throttle body is choking the GT4.
02-17-2016, 08:27 AM
#313
My old 2006 Cayman S had that until I flipped it out for a much bigger one.
So does the GT4 have the same throttle opening software restriction like in the 981 Cayman S? Mind you 74mm is going to do a bit of that anyway...
02-17-2016, 08:28 AM
#314
Rennlist Member
but in the middle rpm range you get around 13 cv and 2 kgm.... i can assure you that you can feel the gains....
once my warranty will be expired i'll add plenum, throttle body and a tune....
once my warranty will be expired i'll add plenum, throttle body and a tune....
02-17-2016, 08:35 AM
#315
He forgot that little detail......the gains in the mid range are real and worth the trouble.