CG

One of my friends is trying to convince me to have a local shop build a cat back for the S2K. His idea is to build a lightweight single with a SuperTrapp exiting on the right side. My feeling is that I would stand a good chance of losing power with this setup. I've driven a number of cars with SuperTraps so I know how loud and crappy they sound. Any opinions on the performance aspects of this type of setup?

cdelena

As long as the cat remains as a primary restriction I would guess there are slim gains to be had from changes to the rest of the system.

I have swapped back and forth between the stock system, the HKS, and the Mugen system, with and without a Mugen header, and don't think there is much difference in power. Maybe a little torgue bump on the bottom end but most of the difference is look, sound, and weight.

I have kept the Mugen header and exhaust because I like them but IMO the bang for the buck is not great.

funcar

I have used supertraps before and the results were never good.
If you want a race muffler use Borla's XR-1.
Or just buy a catback system.

The Reverend

Powerhouse Amuse in Japan makes a titanium setup single exhaust system with one resonator and one muffler. Rumor has it that it makes around 11 hp at peak. But it's loud as all hell, very expensive, and I would bet money it kills your low end. I have a 5zigen cat back. There is a flange on it where I can unbolt the last few resonators and mufflers so that I'm just running a straight through with two resonators. When I run it like this, it's very loud, but it makes some good power in the top end. BUT, the low end comes out SO BAD that you can barely keep the car from stalling without launching at 4000 rpms. It probably makes 12-15 hp in the top end, but I must lose half my low end power and a good amount of mid-range. With all the piping and resonators in place, it runs basically like stock. There are lots of places on the 5zigen where the piping gets larger or smaller and even a muffler that sits off to the side with no outlet, so they did all kinds of sh!t to make it perform well throughout the powerboand. As for supertrapps, they kinda suck. Not good flow. They look cool and I suppose it will flow ok with no plates at all on the back (I have a friend that runs two trapps like this on his turbo prelude) but it's very loud.

Besides, as I have had it explained to me, "backpressure" doesn't exactly work the way supertrapp tries to say it does. The idea isn't to provide resistance to the air flow. The idea is to find the proper size exhaust piping for the amount of air exiting the engine in order to maximize exhaust gas velocity. At low rpms, you have not very much exhaust gas coming out, so if you have large diameter piping, the gas will creep through it rather slowly. Use smaller diameter piping and it will spit out with more velocity, like when you make the nozzle at the back of a jet engine smaller. At high rpms, you have more gasses coming out, so the small piping provides too much resistance and you need larger diameter piping to acheive the same effect. I don't know if this all holds true in actuality, but that's the theory behind it as I understand it. And by that reasoning, a supertrapp should be pretty worthless (and from what I've heard, they are, mostly).

[Edited by The Reverend on 02-14-2001 at 01:28 PM]

BB AP1

Hey The Reverend.. where did u purchased your 5Zigen fireball from?? how much for that?? and how does it sound??

CG

Thanks for the replies, they pretty much confirmed what I was thinking.

The Reverend

Mine was the first unit sent to America to test fit on a US spec car. I got it directly through AKT for next to nothing since it was through friends and a test-fit situation. The sound is quiet, kinda raspy and mean, but not loud. My friends say if I blast by them at 8k rpms it sounds kinda like a jet engine and it makes their ears damn near bleed, but under regular driving it's very quiet and even under hard driving you can't hear it much inside the car.

Utah S2K

My friend in Japan says all use the Powerhaouse Muse units and quotes similar gains that you post. I heard a Mugen/Mugen last night. I now know why CD feels the way he feels. It was very good both inside the car and out! Greta engineering.

The Reverend

Well, it does make a 10 or so HP gain, but when they say at "peak" they really mean it. It makes 10 hp for about 200 rpms. Not long enough to actually help your performance any. I'm all for top end power, but when I say top end, I mean about 7000-9000 rpms. not 8800-8850 rpms. Here's the dyno plot from their web site.