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When I was in the market for exhaust I read over 1000 posts on here about the various setups. I went with Kline inconel, but from my research the stock oap do produce drone with an aftermarket muffler. The reason it’s noticeable with an aftermarket muffler is the OAP became a major bottleneck and built up of gasses in the system and that translates to drone when you have a muffler that’s not insanely quiet like the stock muffler when the valves are closed. The stock oaps create turbulence with the exhaust gases.
This, in order to avoid drone with an aftermarket muffler, you have to get RESONATED OAPs. This gives you the best of both worlds - better performance but with no drone. The OAPs in the Kline system are resonated.
resonated OAPs can pair with either the stock muffler or aftermarket and there will be no drone.
non resonated oap with stock muffler will have some drone and with aftermarket muffler it will done.
stock oap with aftermarket muffler will have mild drone.
When I was in the market for exhaust I read over 1000 posts on here about the various setups. I went with Kline inconel, but from my research the stock oap do produce drone with an aftermarket muffler. The reason it’s noticeable with an aftermarket muffler is the OAP became a major bottleneck and built up of gasses in the system and that translates to drone when you have a muffler that’s not insanely quiet like the stock muffler when the valves are closed. The stock oaps create turbulence with the exhaust gases.
This, in order to avoid drone with an aftermarket muffler, you have to get RESONATED OAPs. This gives you the best of both worlds - better performance but with no drone. The OAPs in the Kline system are resonated.
resonated OAPs can pair with either the stock muffler or aftermarket and there will be no drone.
non resonated oap with stock muffler will have some drone and with aftermarket muffler it will done.
stock oap with aftermarket muffler will have mild drone.
Great information. Just to clarify the last part , aftermarket exhaust as long as it's paid with an aftermarket oap's it doesn't matter if it's resonated or not ?
When I was in the market for exhaust I read over 1000 posts on here about the various setups. I went with Kline inconel, but from my research the stock oap do produce drone with an aftermarket muffler. The reason it’s noticeable with an aftermarket muffler is the OAP became a major bottleneck and built up of gasses in the system and that translates to drone when you have a muffler that’s not insanely quiet like the stock muffler when the valves are closed. The stock oaps create turbulence with the exhaust gases.
This, in order to avoid drone with an aftermarket muffler, you have to get RESONATED OAPs. This gives you the best of both worlds - better performance but with no drone. The OAPs in the Kline system are resonated.
resonated OAPs can pair with either the stock muffler or aftermarket and there will be no drone.
non resonated oap with stock muffler will have some drone and with aftermarket muffler it will done.
stock oap with aftermarket muffler will have mild drone.
Thanks for your feedback. So all roads lead to Kline? Hahaha. The main reason I didn't go with Kline was because I perceived the sound (at least in the videos) to be too high-pitched with a metallic ringing tone. It sounded unpleasant to me but now I am told that, that ringing sound is only prevalent at high rpms.
I did hear back from one person who has the BC Fabs rear muffler and their non-silenced OAPs. He reported the same boomy resonance while accelerating in the 2000-3000 rpm range with PSE on. I feel the pressure of that low frequency boomy sound in my eardrums. I also notice that boom even with PSE off because PSE on or off, the valves are closed in that range. I experimented with leaving the PSE switch on/off while accelerating in that rpm range in all the gears. That boom seems unavoidable.
I was also informed that if I installed the resonated OAPs from the same manufacturer, the resonace would be significantly reduced. I am not convinced enough yet to spend another 3.6k only to turn up the volume with no guranteee that the resonance would be diminished to my satisfaction.
Great information. Just to clarify the last part , aftermarket exhaust as long as it's paid with an aftermarket oap's it doesn't matter if it's resonated or not ?
with an aftermarket muffler you need resonated oaps if you want to eliminate / minimize drone (Kline system). If your drone tolerance is moderate or high then you’re fine with non resonated oaps.
if I didn’t go Kline I would first purchase resonated oaps and see if I would be happy with that and the stock muffler. If not then an aftermarket muffler. However, everything I read the Kline system works so well and it’s only sold as a set, the oaps and muffler are designed together, it just made the most sense to go Kline and the price is also “reasonable”.
Thanks for your feedback. So all roads lead to Kline? Hahaha. The main reason I didn't go with Kline was because I perceived the sound (at least in the videos) to be too high-pitched with a metallic ringing tone. It sounded unpleasant to me but now I am told that, that ringing sound is only prevalent at high rpms.
I did hear back from one person who has the BC Fabs rear muffler and their non-silenced OAPs. He reported the same boomy resonance while accelerating in the 2000-3000 rpm range with PSE on. I feel the pressure of that low frequency boomy sound in my eardrums. I also notice that boom even with PSE off because PSE on or off, the valves are closed in that range. I experimented with leaving the PSE switch on/off while accelerating in that rpm range in all the gears. That boom seems unavoidable.
I was also informed that if I installed the resonated OAPs from the same manufacturer, the resonace would be significantly reduced. I am not convinced enough yet to spend another 3.6k only to turn up the volume with no guranteee that the resonance would be diminished to my satisfaction.
Good discussion so thank you.
Anand
in my opinion you should try adding the cheapest resonated OAPs you can get. I don’t see why it needs to be the same manufacturer unless it won’t mount properly. I’m convinced from my research that resonated oaps would greatly improve if not eliminate your drone. In the alternative, sell your exhaust and go Kline. If you PM me your email I can send you some good quality videos of Kline. It is high pitch but not as high as a gt3 and still has some bass tones, but compared to stock it’s a lot higher pitch. The SS would be less high pitch in the higher rpm’s from what I’ve heard.
in my opinion you should try adding the cheapest resonated OAPs you can get. I don’t see why it needs to be the same manufacturer unless it won’t mount properly. I’m convinced from my research that resonated oaps would greatly improve if not eliminate your drone. In the alternative, sell your exhaust and go Kline. If you PM me your email I can send you some good quality videos of Kline. It is high pitch but not as high as a gt3 and still has some bass tones, but compared to stock it’s a lot higher pitch. The SS would be less high pitch in the higher rpm’s from what I’ve heard.
Thank you very much for the videos. I am posting my response here as well for the sake of our public discussion. The Kline sounds very nice and your videos capture the essence of that sound extremely well. And just as I thought, it is a little high-pitched for me especailly at higher rpms but still very nice. Very helpful.
Too high-pitched for me. As is JCR. I won’t be able to take it based on the videos i have seen. I am searching to re-capture the sound of the 981 GTS. Gruff and appropriately loud (for me) with pops and crackles. I think Akrapovic (or resonated OAPs) will do the trick but I am going to give the BC fabs a shot for the next few months before throwing in the towel.
We seek the same. 981 GTS to me is what I am trying to recreate (but with toned down crackle and pop). I have a hunch that headers, resonated OAPs and stock muffler might be the recipe to get the closest, however to my knowledge nobody has reported out on this combination.
We seek the same. 981 GTS to me is what I am trying to recreate (but with toned down crackle and pop). I have a hunch that headers, resonated OAPs and stock muffler might be the recipe to get the closest, however to my knowledge nobody has reported out on this combination.
I am realizing that it is an elusive goal. BC Fabs comes close above 3000 rpms. The sound is quite similar to the 981 and very nice. Below 3000 rpms, it is a subwoofer (hence my new username, hahaha) with the volume turned up especially when the exhaust is warm. I've found that the best way to avoid it is to stay above 3000 rpms and to use a heavy throttle to get past the dreaded boom-boom zone. I went for a 120 mile (all backroads) drive this glorious afternoon in NH and I was fine for the most part and really enjoyed the lovely car. I need to fix the sound. It is not acceptable to me in this lovely car.
I am realizing that it is an elusive goal. BC Fabs comes close above 3000 rpms. The sound is quite similar to the 981 and very nice. Below 3000 rpms, it is a subwoofer (hence my new username, hahaha) with the volume turned up especially when the exhaust is warm. I've found that the best way to avoid it is to stay above 3000 rpms and to use a heavy throttle to get past the dreaded boom-boom zone. I went for a 120 mile (all backroads) drive this glorious afternoon in NH and I was fine for the most part and really enjoyed the lovely car. I need to fix the sound. It is not acceptable to me in this lovely car.
is the drone less noticeable with the top down? There should be some improvement top down vs up?
is the drone less noticeable with the top down? There should be some improvement top down vs up?
I always drive with the top down. My Boxster 25 is basically for entertainment. I don’t use it for anything else. Six months of the year when we are in NH and I've only had the car since last August so about 3 months of driving time so far. I bought it for aimless wandering on backroads.
I always have to shift up even on the highway. For example if I find myself slowing to 60 in sixth on the highway and try to accelerate, a deep boomy sound fills the cabin until I get to 70 and the rpms climb to 3000. Or, I just upshift to fifth to avoid the boom. I doubt resonated OAPs can make a dramatic improvement.
Sorry, I know it stinks when you try to improve things and it has the opposite effect.
No worries. Thanks. You and other folks have been very helpful to me in deciding a course of action. I am waiting to get quote on the Kline to put in an order.
Chasing nostalgia usually doesn't work and I am too old to be wasting an entire season on a sound system that simply doesn't work for me.
A lot of work, but some insulation helps a little. Some form of high quality butyl/aluminum (black) to dampen the resonating metal and a layer of the DEI sound dampening (grey) to take the volume down a notch. Also helps reduce road noise. You don't need to cover the entire area, just part of the floor and some smaller pieces on other panels.
This does not solve the problem in any way, but helps mitigate some of the frequencies, and tones the whole exhaust down by a few db. This helped both the OEM setup on a 4RS which does have a little bit of drone, as well as my current inconel Kline setup. The Kline of course sounds much better, but it feels like that bit of drone is even less than in the OEM exhaust and touch higher in frequency. In an RS you are above 3,000 on the highway anyway so it is not as much of an issue as in a GT4 or Spyder.
Overall, super happy with the Kline exhaust and service from Eric at Supreme. He tries to keep a few things in stock for immediate delivery. Everybody says it is one of the best sounding cars at the track. Still trying to get a good video of it though.
Last edited by lovetoturn; 05-27-2024 at 12:15 PM.
I always drive with the top down. My Boxster 25 is basically for entertainment. I don’t use it for anything else. Six months of the year when we are in NH and I've only had the car since last August so about 3 months of driving time so far. I bought it for aimless wandering on backroads.
I always have to shift up even on the highway. For example if I find myself slowing to 60 in sixth on the highway and try to accelerate, a deep boomy sound fills the cabin until I get to 70 and the rpms climb to 3000. Or, I just upshift to fifth to avoid the boom. I doubt resonated OAPs can make a dramatic improvement.
Top up is very bad resonance.
this was the same issue I had with straight thru OAP and the Akrapovic ... cured by replacing the OAP with CG high flow resonated OAP from @SupremePower
05-25-2024, 10:55 AM
