My New Custom Exhaust SUCKS ...suggestions
 

well I removed the pre cats, went into a Y-pipe into a single mangnaflow hi-flow cat. From there it goes into a new resonator and then just the stock muffler.

Sounds good, nice and quiet BUT at 3.5k and higher there's a tinny resonating sound coming from the Y section! WTF!!!!

Is it too restrictive? Also, it feels like the car has less power now which is NOT good. I think I just wasted money on these new exhaust parts and pipe bends/install.

I just don't get why the noise is coming from the Y section ...the piping is fairly big too. The inlets to the Y are = to stock (I think slightly bigger) and the outlet of the Y is = to the stock piping that goes back to the muffler. Should I ditch the Y pipe and get a 2-inlet, 1 out cat and use that as the Y? I'd just hate to buy another cat only to find out that was a waste too.

What did all you guys do?

Many people have problems with that same buzzing you speak of. I would suggest a 2 into 1 cat in the first place but I am not sure it will solve the issue. If you were gonna modify the exhaust that far why not go with a magnaflow muffler also??

Tom

Sorry it didn't work out. I had a Y into a hi-flow cat to my stebro and it was terrible. I removed the pre-cats and had a huge loss in low end torque and the sound was annoying. I got a used stock set of down pipes with pre cats and it fixed it. I think the SVX likes it's pre-cats to much to let them go without complaining. There are some threads about it and I'm sure someone can explain it a little better as far as reflecting sound waves and low pressures areas goes. Good Luck

Stebro
 

Another vote for Stebro. Pricey and pain to deal with sometimes, but well engineered and in some cases saves money from the trial and error systems installed. :)

Lee

I had the y pipe setup with no cats but recently ditched it for a 2 into 1 cat and it sounds and feels much better now.

The stebro is only a catback.

Yep, there's definitely a "buzz" once you remove the front cats. You might want to consider the "fix" that Mychailo came up with...

http://www.subaru-svx.net/photos/fil...czko/32808.jpg



-Bill

The tinny sound is caused by a constructive resonance the builds between the left and right side cylinder banks. A sonic wave is emitted from a cylinder on one side when an exhaust valve opens. The sound wave travels down to the primary pipe to the y-pipe, reflects at the y-pipe and goes down to the other side of the engine. It hits an exhaust valve and reflects back down the primary pipe just as that exhaust valve opens. This results in a constructive interference. The process then repeats and the sound wave keeps building in intensity. It only happens at a characteristic rpm. The ways to fix it are to add damping (resonators in the primary pipes), stop the reflection from occuring where the primaries join into the single main pipe, or by making the primary pipes different lengths. The 2-into-1 cat does a pretty decent job of stopping the reflection from occuring at the primary-to-main pipe junction. Moving the junction further back lowers the rpm where the resonance occurs. If you are using a 2-into-1 cat, moving it further back will also improve low end torque.

If you feel like dumping more money into your exhaust, switch out that y-pipe for a 2-into-1 Magnaflow cat and put it in the location of the factory resonator. Then put a couple of resonators in the primary pipes before the cat. It will sound sweet and should have better low end torque.

That would be a good solution. :)

I think mbtoloczk has a good solution. This is what I was planning on doing and for the same reason.

Thanks Mr. Wizard, I will put that on my to-do list :D :D :D

Thanks for all the replies.

I guess what I will wind up doing is moving the resonator and cat as close to the muffler as I can and then put two more resonators before the cat in place (one for each bank). Oh and replace the cat with a 2-1 cat

What a pain though.

As a temporary solution maybe I'll put the pre cats back in. I think there was nothing wrong with them - it was the stock 2-1 cat that was leaking and the stock resonator that was buzzing. That's kinda what pisses me off - tried making it better and it didn't work.

Thanks again!!

And aren't resonators restrictive? What would be better - the stock precats or resonators?

By resonator, I just meant a straight through tube muffler with a perforated inner tube like the ones sold by Magnaflow and Vibrant racing. I don't like the louvered style ones that are so popular at Summit Racing.

I called Stebro a few month's back to price out their exhaust,and was told that they also have a 2 into 1 cat that fit's in the stock location that is more free flowing than stock for about $360.00.

Resonator
 

Stebro also has a Euro Resonator that fits in place of the 3d cat if you are not concerned with emissions or a dummy oxygen sensor for an OBDII car (96-97). It would flow more air than their free flow cat.

Lee

I think you 2 are referring to the same piece.