matt0520

Mine absolutely does, idk if it's the valves being open or the OAPs, but mid throttle has the burbles and the higher the RPM when I shift...the more noises it makes. Some pops have surprised me sometimes, not quiet lol

Westcoast

I would agree that the resonated OAP is in the middle between the open OAP and OEM OAP but...

I would not say that changing the back box will cure drone, some can mitigate it but not cure it! And this is all the more interesting as you are in the EU, I thought your cars were inspected yearly, do you have an exemption for a US model?

Westcoast

I don't agree with this, the cats don't cause drone or boom, they tend to mitigate it, the removal of cats or OEM OAP increases what people call drone and boom.

Xxyion

you'd be surprised. Cats in general reduce the volume but it does so mostly by reducing the db of higher end frequencies. And thats due to the nature of how sound waves work and the material used in the cat. Low sound waves move slowly but can travel a longer distance before dissipating. it's why you always hear the boom first before anything else if you are approaching a concert. Same idea here except now you have all this metal to help resonate. Have you ever noticed in an Eco car when you turn it on you always hear a low rumble? Thats drone, but it's usually so quiet that it doesnt bother people.

In terms of getting the sound you want its about managing where the drone pops up in the freq range. Which is why i suggested the OEM OAP with catless headers. The OEM OAP have the OPF on which are actually more sound restricting than the header cats however having a set of carless headers can essentially produce sound at a different range and it might come out more to your liking.

The reason why removing cats usually causes MORE boom and drone is because people are generally straight piping at that point and it's mostly just volume at that point. But changing the configuration is going to be the key thing here.

Case in point when i had my 2016 BRZ i probably went through 20 different exhaust combinations finding the right tone and clarity. When i ended up with was catless headers, resonated mid pipe, catless front pipe and an axel back with 4" mufflers. Now you'd think that remove all of the cats would have created massive drone and volume, but the resonator changed the tone of the sound coming from the headers, which then opened the tone up for clarity with the front pipe. Then through the 4" mufflers which helped reduce volume but kept the clarity. I had a zero drone system at every RPM that only topped out at about 100db at full throttle. Its all about sound wave manipulation.

BoxKing

OAP's alone could/would fail you at yearly inspection in the EU, so you have a bigger concern on your hands as is, let alone paying to get new pipes/systems.
Removal of the GPF is the issue, which is found within the OAP section.

Westcoast

Hmmm, the speed of sound is constant regardless of frequency... you hear low frequency at greater distances because it does not dissipate as quickly and transfers through a medium more efficiently, you seem to be crossing up a few principles here.

At any rate drone/boom is low frequency and happens in these cars around 1800-2400 RPM, at that RPM the CAT and GPF do a great job of taming it, removing them increases it.

Big Belly 711

Well it's really subjective as others have said, but I DO think there is a slight tone change from stock...it's not as much (obviously) as with a new back box, but it is different to my ears, and slightly louder. Recently had my 3 year service and when the tech started it up, it sounded different than every other vehicle they were working on at the time (likely all stock). I think the R-OAP's open up the sound slightly, just enough. I also have a 2-way cargraphic valve controller installed and usually have valves open. Lastly, drone at lower RPM's is almost non-existent with the R-OAP's to my ear...

Xxyion

yeah sorry i realized i missused some terminology. Dont mean to say that it travels slower because that would defy physics, but more that high frequencies die off faster as opposed to low frequencies. I tend to think of it as slow vs fast but thats just me and i get, thats not really the correct terminology.

subwoofer

I suggest buying the Kline instead of trying a Mickey Mouse fix of what you have.

TRSCobra

All roads lead to Kline...

Cam07

I currently have the Flat 6 OAP’s only. The volume of the exhaust is great, but still dislike the tone of the stock backbox. It sounds like an old pickup truck with a cheap muffler installed at lower rpm’s to me. Past 4k it sounds great, but maybe I’m just picky.

I now have a set of high flow Cargraphic OAP’s & JCR non-silenced valved backbox waiting to be installed. I’m tempted to install the JCR exhaust on the Flat 6 OAP’s, but have heard the drone from that setup may be unbearable. Hopefully this will be the ideal set up for me. I’m curious how muted (or not) the Cargraphic high flow OAP’s will be.

lowbee

I am curious to learn what the filter element in the Cargraphic hi-flow OAP look like when compared to the OEM filter element. It would be great if you can take a picture of that. TIA

Westcoast

I have Akra OAP's (open) ahead of a JCR silenced valved exhaust... my buddy has Akra ahead of non-silenced valved JCR they sound nearly identical with a nod to the latter for sheer volume.

For months I ran the OEM OAP ahead of the JCR, the tonal quality was fantastic, nearly no drone, but the overall volume and characteristic was a little muted for my taste, the Akra opened it up just like I had hoped. But I would be remiss if I didn't mention that the drone definitely increased between 18-2400 RPM.

Looking forward to how the Cargraphic OAP changes the sound, any chance you might try the JCR with the OEM as a base line before installing the CG OAP to test how the volume and drone changes?

Larry Cable

Ive had the Cargraphics high flow resonated OAPs on my Spyder for years now, in combo with the Akrapovic slipon ti main. muffler its a great sound with no negatives

Soulstream

Thanks a bunch! I think I'll end up getting one of the R-OAP options (either Cargraphics or Soul). Until then I'll just enjoy the Flat-6 ones and try to be easy on the throttle in low RPMs