Help with rasp (overpipe and catted front pipe)
 

So my car still sounds like a tin can with the following setup below

Auto tranny
Tomei UEL
Motiv overpipe
Berk HFC front pipe
Invidia Q300

EDIT: I need a cat in the front pipe for STX

I have considered the JDL ultra quiet as well as swapping back to the stock overpipe. I also so the Blackheart Hooker has a hemholtz resonator as well but dont think anyone is running it and its cheap to the point im unsure of its quality.

I dont really like the Q300 but its been the best at eliminating rasp so far. I dont mind lound but i want something rumbly not sounding like a Honda.

Does anyone have experiance with multiple brands of catted front pipes and which ones produced less rasp then the others?

It's because it's an automatic...
Jk, my JDL ultra quiet front pipe should be here end of this week, beginning of next. I'll let you know how it works. its does not have 2 cats though, it has 1 cat and a resonator. Not sure if I've seen any one sell a front pipe with 2 cats?

Sorry, didnt mean more then one cat but have people tried more then one brand front pipe with a single cat.

And while you joke the AT part actually does matter since in town my RPMs stay super low. But that has more to due with catback choices then the FP. I think.

Go back to oem muffler, or ceramic coat your exhaust piping.

I have a very similar setup with the stock front pipe and I have zero rasp. Throw the stock front pipe back on and call it a day.

Somehow the oem muffler was worse

Yea the baffling in the OEM muffler is shit. I have the ace header type a 4-2-1 with motiv test pipe and tomei 80r lol
It's loud as fuck and in the car it sounds raspy as hell. But when I had someone else drive it yesterday, it's not all that raspy and made me think if I should have bought the JDL ultra quiet front pipe lol. But on long trips it's too loud so I'm glad I got it. I ordered it on their Labor Day sale and got a really good deal! Jesse hooked it up, with O2 bung and all.

Get one custom made with a better cat. All of these aftermarket front pipes with barely functional high-flow cats will have rasp.

What brand cat would you suggest? The Berk uses a Magnaflow which I thought was pretty good quality

a front pipe with resonator will help you out. my MXP catback has a resonator in the mid pipe which helps out. the front pipe is the only part stock for me and I have no rasp at all.

Well now, finch1750, I have bolded your problem. You have too damn many different brands of parts in your exhaust system.

The exhaust gets all raspy trying to figure out how to move to the rear of the car.

I suggest you put it all back to stock with the exception of the muffler and replace the muffler with this one.

:D


humfrz

Before you go any further, noise suppression and things like rasp are not dictated by whether you have a cat or not. It is dictated by the size/design of the resonator relative to the rest of the exhaust system. A cat is NOT a resonator, especially not any cat that is of the Berk (or similar) HFC varieties.

You have three options:

1) make your own front pipe w/ cat that has a sufficient resonator
2) put on a catted header and run a better front pipe
3) put back to stock front pipe

If you ignore the popping noise (from lack of a cat), you can hear differences:

[ame="https://www.youtube.com/watch?v=iItifvYzrDs"]Blitz Nur-Spec R exhaust w/ Tomei UEL header + Fujitsubo front pipe Scion FRS Subaru BRZ sound clip - YouTube[/ame]



For reference, the Blitz VS/VSR has a similar "rasp" at certain RPMs due to baffle design with straight through everything else. It is similar to OEM muffler.

[ame="https://www.youtube.com/watch?v=sWxvQXjjgaQ"]Blitz Nur-Spec VS/VSR exhaust + Tomei UEL header/overpipe w/ Fujitsubo FP Scion FRS Subaru BRZ - YouTube[/ame]



Or, run the Apex'i header/OP/FP setup and have ZERO rasp of any kind. One cat in front pipe, large resonator, and a quiet exhaust for good performance gains without noise or rasp penalty.

[ame="https://www.youtube.com/watch?v=tVtZcDlphjU"]Blitz Nur-Spec VS/VSR + Apex'i header/overpipe w/ Super Catalyzer front pipe Scion FRS Subaru BRZ - YouTube[/ame]

I probably should have clarified a few more bits. I am building the car to STX so catless headers stay and a HFC front pipe is staying over stock for power. That eliminates the apexi as an option.

You say make my own front pipe with cat and quality resonator, but again isnt the Magnaflow cat in the berk high quality or am I mistaken (Im basing this on itnernet talk so i could be wrong). And if thats true then could i just add a resonator to the berk itself to imrpove on the raspiness?

The Apex'i setup has a catalytic converter in the front pipe, so it's completely STX legal.

The only drawback is the price, as the entire setup is over $2000. Header, overpipe, front pipe.

The problem with your build and the rasp is in the fact that the catalytic converter is doing a poor job at sound suppression, and there's no other functional resonator before the exhaust. As a result, the exhaust is magnifying some harmonic frequency that is causing the annoying noises.

This car ran at Nationals with the aforementioned Apex'i header/OP/FP setup and has one functional cat.

[ame="https://www.youtube.com/watch?v=UcofHkS-qp0"]Blitz Nur-Spec F-Ti + Apex'i header/overpipe w/ Super Catalyzer front pipe Scion FRS Subaru BRZ - YouTube[/ame]


-alex