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I got delivery with the valves locked fully open, sounds louder at low rpms but it sounds fake, sinthetic, I hate it from the first mile after delivery.
First I swap the rear muffler for a Soul
valved, so much better sound than stock, but little bit louder than Oem mainly below 5k rpm (always with valves fully open), so I decided to take out the OPFs but wanted an OAP with muffler, so I sold the Soul and bought the Kline, and the torque/power difference only happened when the OAP was deleted. My friend bought my soul rear muffler and added akra oap and same opinion so much alive at low/mid rpms.
Here the guy in question
looks very similar to the Cargrgraphic "high flow" OAP
These are crap to please Greenies and their overly Big government.
I'd get rid of those annoying filters mmediately, and forever enjoy the improved exhaust note!!
You do get a HP/TQ increase with the OAP. The flat 6 OAP comes with a dyno sheet showing the gains. 425 HP peak increase, but in the midrange RPM’s see as much as 20 HP. I can tell you there is a definite feeling of more power in the midrange.
Then there is the sound improvement! This really is a must have modification for the North American GT4 and GTS 4.0 cars. You will love it! I do recommend getting OAP with heat shielding.
My suspicion is that they are purposely handicapping the sound of the cars in markets that don’t need the active filter to avoid angry prospective buyers in markets requiring OPFs who would hear the car the way it was intended to sound and potentially impede purchase intentions. This way everyone has the same underwhelming global sound and everyone suffers equally.
My suspicion is that they are purposely handicapping the sound of the cars in markets that don’t need the active filter to avoid angry prospective buyers in markets requiring OPFs who would hear the car the way it was intended to sound and potentially impede purchase intentions. This way everyone has the same underwhelming global sound and everyone suffers equally.
As someone that autocrosses my car regularly, I replaced my OAPs with Akrapovic OAPs when new. I believed (and frankly still do) that the stock pipes are NOT an emissions item, but SCCA has decided otherwise. Therefore, I had to put my stock pipes back on. While no two courses are the same, my delta to other drivers hasn't seemed to change with putting the stock pipes back on. This leads me to believe that if there is a performance gain, it is very minor, and probably has just as much to do with the 18 lbs saved with the titanium Akra OAPs.
So, for now they sit in my garage, with my whining constantly about not being able to run them. ;-) I LOVE the sound of them, so it sucks not being able to run them.
BTW, I think a couple people mentioned it, but everything I've read says they are inert, and are only in US cars as a noise attenuator to avoid the need to design a different muffler vs ROW for noise regulations.
I totally concur with what Ron says above^. Since I also run with SCCA in autocross events, I have the stock OAPs for SCCA events, swap in my Flat 6 OAPs when I run other club events and enjoy the sound and the possible added power in the mid range rpm. Maybe for me the sound of the aftermarket OAPs is awesome enough to motivate me to drive faster , seems that way.
It's a shame that the GT4 is restricted from aftermarket OAP and rear muffler installs. I'd think that even in Calif it could be argued that it is a legal mod, but unfortunately not within the SCCA interpretation.
It was in the March 19, 2020 Car & Driver issue that included a discussion of the Euro vs. the U.S. versions of the particulate filters on the 4.0 liter N/A cars. "United States models use a straight-through filter design without the expensive, soot-trapping precious-metal coating. This makes them inert and nothing more than sound attenuators. Porsche keeps these on U.S. - bound 718 Spyders and Cayman GT4s so it doesn't have to change the specification of the muffler."
I'm guessing it's economically in mass production to make the same OAPs for each continent, and only coat the Euro units with the special metal. Flow would be the same, thus muffler design would be consistent too.
Not hard to swap the OAPs for me, so I can get the enjoyment of them at least part-time.
I would have liked to see the dyno run without any tuning, but he said he only adjusted the timing a few degrees and nothing else. Being a NA engine, it's not like he's able to turn up turbo boost or other big mods. So nearly 40hp increase is a LOT. Now, why is he showing 407hp at the wheels stock? Is that a European number? Or some other adjustment? Because the engine is supposed to be 414hp at the crank, so I would expect at least a 10% drivetrain loss to the wheels.
Some posts here talk about the matrix being inert. That only means it does not function as an emission device, i.e., it does not trap particulates. Inert is not synonymous with non-obstructive. If the matrix impedes flow, it most likely hinders performance. Common sense and one look at the filters should tell us that that is the case with U.S. matrices.
Some posts here talk about the matrix being inert. That only means it does not function as an emission device, i.e., it does not trap particulates. Inert is not synonymous with non-obstructive. If the matrix impedes flow, it most likely hinders performance. Common sense and one look at the filters should tell us that that is the case with U.S. matrices.
True, which is why the car is louder when they are removed, so at the very least they are serving as mufflers.
Some posts here talk about the matrix being inert. That only means it does not function as an emission device, i.e., it does not trap particulates. Inert is not synonymous with non-obstructive. If the matrix impedes flow, it most likely hinders performance. Common sense and one look at the filters should tell us that that is the case with U.S. matrices.
I would agree if the piping was the same size as the before and after, but the housing is significantly larger, so I’d bet the flow is fairly similar.
04-09-2022, 05:28 PM
, seems that way.
