Hi All,

New to the S2K world, coming from Vettes and WRX's. I did hours of research on the best dual catback for this car, and I decided on the HKS Hi Power Dual. ("05 AP2 stock cat and header).
I wanted to be careful when it came to drone, and wanted to keep a good quality sound. I was a bit disappointed with the 3K RPM drone, it was much worse than I had anticipated given my research.

I love the VOLUME of the exhaust and the tone is amazing, but the vibration/drone in the 3K RPM range is quite bad. I have read as many forums as I can find on this topic, and wouldn't have posted a new thread if I could find a straight answer for this. Will a HFC help to eliminate some of this drone? I know it may add a bit more volume, but I am really mainly concerned with the brain-rattling drone at that RPM range, especially on decel.
I prefer not to go with a test pipe mainly for the smell. I'd like to stick with a HFC if that will help. It seems like this restriction in the cat is where the issue lies. It completely takes over the sound of the car! Other than that the exhaust is perfect.

I have seen some say yes it totally eliminates it, and some say it made no difference/made it worse. Any help here would be greatly appreciated! I have also heard maybe dynomatting the trunk could help a bit?

Thanks in advance for the help! Stoked to be a part of the S2K community.

 

No, a different cat will not alleviate the drone, nothing will. I ran the HKS for 15 years, loved the sound but hated the drone. I bought a Mugen exhaust to replace it. Much better now.

My doors and trunk are fully dynamat-ed. No difference. I ran my HKS with both stock cat and Berk test pipe, zero change in drone.

 

A HFC or test pipe will absolutely lower drone. I ran an OEM cat, HFC and then a test pipe with my HKS dual and the drone decreased with each step. With a test pipe its basically non-existent.

 

Interesting. I was considering a Berk HFC. The decel has been bothering me less lately, and the cruising drone is basically unnoticeable, but only decel at certain RPM is what bothers me still a bit. In your experience it helped that? I’m also going to be dynomatting my trunk and interior for some general vibration decrease.

 

In my opinion yes, one thing to consider is that I drive my car top down 99% of the time, I very rarely have the top down and I think that does make a difference.

 

You must be deaf. The drone from the HKS in 6th gear at 56-59mph is annoying as hell with a test pipe. Drone on the highway was a constant. No idea if we had the same exhaust or not if you're saying zero drone.

 

Me as well. I really only take it out when I can go top down. I’ve actually thought the drone is less intrusive with the top up anyway. Maybe I will order the HFC and see how that goes! Thanks for your help.

 

That doesn’t bother me so much, I don’t find myself at 55 really. More like 65-70 on the highways near me. If the exhaust note were to get a bit louder that would be fine with me, but that terrible decel resonance is what gets to me!

 

Rural roads around me are 55 so I'd deliberately run at 61-62 to avoid the drone. The drone boom in the 50's is definitely still there top up or down. Highway it's just the constant drone. I truly loved the sound from the HKS but after 15 years I was tired of the droning.

 

Yeah I agree with that. Boom is a good word for it! But like you said, the sound the car makes with that HKS is just incredible. For now it’s definitely worth it for me, especially when VTec clicks over. If it were a daily driver the drone would be too much though. Maybe I’ll try the HFC and see how it changes it for me, since it’s cheap enough!