RP Supercat Question
 

As some of you know, I recently purchased and installed an RP SuperCat to go with my GReddy SP2 exhaust. My initial impression was that I liked the sound very much, but now it's gotten louder (which I don't mind) and very buzzy and raspy depending on throttle positon. It seems to be the worst at WOT in 1st through 3rd gears. It pretty much sounds like shit and I'm honestly considering removal of the midpipe because of this sound.

Someone suggested checking it for leaks, which I haven't had a chance to do yet, but I'm wondering if that would cause the sound. Is this just something I'm going to have to live with or is there something that will get rid of the annoying noises.

If it's something that's just going to be like that, I'm probably going to be taking it off, because I can't deal with this every single day.

I'm also going to have Meineke weld a hanger on this weekend, so is there anything I should have them check?

Also, FWIW, this noise is definitely related to the midpipe, because the exhaust never once made any sound like that.

isn't buzzy and raspy how it should sound like? Not sure if this would help, but a resonator can help tone it down a little, not sure if it includes on already.

The Greddy must be a different critter than my Racing Beat catback - sorry to hear it's too loud. There really is nothing to check excpet for leaks or loose hangers. If you pull it, I'm sure someone will buy it.

Well that's what I'm trying to find out. If you've ever hear a severly riced out Civic that sounded like it had a can of angry bees in the muffler then you'll know the sound that I'm talking about.

Its horrendous, but not constant, which leads me to think that there is perhaps something wrong? I'm by NO means an expert on this but I do know that if it's supposed to sound like this, then it is coming off. $400 for something that gives slightly noticeable gains but makes my car sound like crap isn't really justifiable. If the car were fast and sounded like this I wouldn't care but it's not :(.

I could get a resonator but then I'm either hacking my GReddy, or hacking the new mid-pipe. I'd rather not hack the GReddy and I'll sell the midpipe for a loss before I hack it up with a resonator.

Perhaps someone with some experience with exhaust systems, or even with the same or similar setups could comment on this?

It's not too loud, it's a buzzing when I get on the throttle that I can't stand. As far as volume/sound at redline it sounds nice (loud but nice) it's the hideous buzzing sound I get when I'm driving through town that I get if I downshift and accelerate.

Somebody else mentioned this same complaint with a different aftermarket exhaust... I recommended adding a resonator and he said it worked perfectly to eliminate the pissed off hornets in a coffee can sound. I also have an SP2, and I've been on the fence about getting the RP Supercat... I love the sound now, as there is nothing raspy or 'ricey' about it. I would hate to sacrifice that for a few HP with the SuperCat.

I figured I would at least wait until RP revised the design and started shipping them with the hanger though... light weight or not, I can't imagine that wouldn't be banging around when tossing the car around an autocross track or a windy back country road.

Oh it does bang around, I'm going to be going after work to have Meineke take a look at it and to see if they can possibly do anything as far as a resonator goes as well as look into a resonator.

Did it sound like that on there website? From what I seen they had the same combo. Maybe the noise to tone down after a bit. Or maybe you can put some noise absorbing material in you trunk to tone down the cabin noise.

I'm not sure, I'll have to check the sound clip again when I get home. Sound deadening won't help because I hear the buzzing when the windows are down, I can barely hear it with them up.

Good point- I didn't hear anything like that on their clips. I was thinking about those who had a hanger welded on... any chance that deadens some of the vibrations by sending them into a rubber donut, reducing the buzziness? There's a lot to NVH research that I haven't done, but seems like that might play a factor...

That would be awesome if a hanger fixes the problem because Meineke said it would cost about $15-$20 for a basic weld when I called them. I suppose I can have them listen to it also to see if they may have an idea.

i have a good feeling u might have an exhaust leak somewhere from the rp. so check it out.

That's kinda what I'm leaning towards, but I don't have a good place at my house to check it.

Any updates to this? I am going to be installing this same combo in about a week or two from now. I would love to know if there are any problems so I don't run into them.

I suspect a small leak

I suspect a small leak as well.

I dropped off my car at Meineke at lunch time today to have them put a hanger on. I also let them know that I thought I had a leak and asked them to check it out. I'll post updates when I get home with it. I'm hoping it will all be good. *crosses fingers*

hope it all works out for you...probable nothign to worry about. :D

too bad you couldn't ask them to taek pics when they add the hanger..

i think either one of the gaskets is bad...or wasnt' tightened with enough torque to seal it completly.

To answer the original question.

Any small leak can sound like shit. It is amazing that with amount of air flow an exhaust has how any stupid pin hole can be so audible.

I have the SP supercat with stock exhaust and it sounded worse before I had the hanger rod welded on. (The RP might be 11lbs lighter than the 22 lb stock mid-pipe, but that hanger should still be there)

Make sure you aren't having clearance issues (I doubt this is your problem. If the exhaust hits your crossbraces, you will know it.)

The welding on my Supercat looked pretty good. There was one spot where weld didn't look perfect, but there wasn't any leak. I also took good care to tighten every bolt with the appropriate torque, etc.

-Mr. Wigggles

Well the thing doesn't seem to rattle any more and the leak is gone. The buzzing is gone from what I can tell so I'm happy now :)

My whole exhaust has mellowed out considerbly. But the other day I was up at Snoquamie Pass and went through a tunnel - decided to get a little crazy, and I think everyone around me jumped out of their seats! It was all allot of fun, but in a tunnel this car is awesome sounding... :D

what does the butt dyno say about this mod? any diff. ?

According to RP and Nemesis8, the pipe + a cat-back system, was dyno'd to gain around 8-9HP.

Well according to the butt dyno.....not much difference.

It does seem a little peppier, but certainly not a big difference. The biggest difference I noticed is in high rpms, it seems to like being there even more now.

It may also have something to do with me resetting my ecu after putting it on and then going out and really pushing the car. That was a particularly bad tank for the gas mileage, I think I BARELY got 14 mpg and half of that was highway.:o

I suspect you'll find a resonator is the solution. I had the "bee problem" after installing the high flow cat with my Hymee. I was about to take it off until GR8
suggested the resonator option. A 3" x 12" will fit nicely, with minimal flow reduction (3% +/- ) and you'll dig the way it silences the bees but maintains the growl. :cool: