Shorty header question

[TheKone]

Another question from me. Might as well use the same thread. If I were to run a full length header (race header) and have a cat-back like the magnaflow, how loud would that be? Unbearable for street use and long highway trips?

[TXEP3]

Yes, it's loud. At least my BCRH and S2 exhaust is. Not super overwhelming with the silencer in, but if it's not then it is quite loud indeed.

[TheKone]

Does anyone have any experience with DC products. Ive heard the ceramic stuff rusts really quick. Does anyone use their race header or shorty header? I have found a good deal on DCRH but would like opinions on them.

[Drew1d]

No experience with DC sports but I do have the Comptech shorty header.
The gains would be hard to state. I did my aftermarket cat, and header at the same time. But looking at it, it's very similar to the OEM header. By itself i'm sure it's only a 1-2 hp gain, if any.

SS is lightweight, it resists rust. You could argue that the design on some aftermarket stuff should give gains. If you plan on "hopping up your Honda" I could argue, every little bit helps. Of course, the header isn't the end of the line for the exhaust, since exhaust is created in the engine, and ended out the tailpipe, the header is not even the beginning. But any improvement in the mix can help.

//putting on flame suit
If the engine is an air pump. It works best when air is going smoothly in it and out of it. My gut feeling is that you start at where the air comes in, (an intake) next do the header, than the cat, then the catback. The stock exhaust system is already engineered pretty well. The intake system is not. It's essentially a box, with a snorkel and a filter in the corner that eventually pipes into the throttle body. I would argue a straight pipe with a sock on the end of it would show gains over it. Not just by having a larger chamber before the filter, but having it evenly flow down a pipe. IMO, I don't really see much of a difference between a SRI and CAI. After a certain length of pipe, the flow is even. (But that's a different discussion)

The header takes the exhaust ports and hooks them up to a section of pipe and eventually joins them to a single section of pipe. It's kinda technical, and I couldn't look at one and tell you this over that, but the pulses of exhaust creates pressure, and the bends and lengths of pipe determine the timing of these pulses when two or more pipes are joined together. I believe the reason a race header works better, (aside from the fact it eliminates the cat) is that it can take a longer length of pipes and gives more flexibility when timing these pulses. So my theory, a header by using timing, could be tuned for a certain rpm range. And this is probably more important to realize than just saying it gives x amount of HP.

The cat since it's already a single pipe, only relies on material inside the cat. I bought an aftermarket cat, with metal substrate. (opposed to ceramic?) The cat itself is much smaller than the OEM from Honda. I need my car legal, so I can't run a straight pipe. And as long as your stock one is functioning, I wouldn't replace it.

The catback exhaust is probably the easiest thing to change on the exhaust. There are tons of choices between materials, piping diameter and muffler style. A good flowing/sounding muffler is cool. But the stock is ok for me. (i'd rather be quiet, and it flows ok) After that the midpipe diameter is a way to adjust back pressure and effect what RPM range is improved.

So, aside from an intake, (since it's vacuum) which would improve every RPM range, what RPM range would you improve?
An exhaust that favors higher RPM ranges is going to give you more HP. An exhaust that improves an RPM range you do most of your driving would probably be more fun. So when I chose a header, I went with the Comptech, which advertised more mid-range torque....but I have no way to tell if it does. ;)

//Flame suit off

[TheKone]

Wow thanks drew1d. I get what you are saying. I do have the normal aem sri. I don't see myself getting a cai where I live as I would probably be taking it out every 6 months to clean it. Since I have a cat-back exhaust already that has made all the piping after the car 2.25" all I really have left to improve my air pump is the header. I have recently read that a race header design for whatever reason makes abnormally large power gains for a stock A3. I think one person on here dyno'd a shorty and test pipe combo vs a race header and made almost another 10whp with the race header. So I was starting to lean towards a race header since where I live doesn't have any emission laws. Then I kept reading and was told race headers are unbelievably loud with a high flow cat-back. Not just loud but ridiculously loud. This is my dilemma as I don't care much about the noise but the cops around my city have been on an anti-ricer noise kick for the last year or so. I thought with the shorty and test pipe combo it would be quieter due to the resonator built in to the test pipe and a less aggressive header design. I think I might take my chances with a race header. Apparently DC went from mild steel to a t409 stainless alloy for there ceramic headers in 2009. It's not as good as pure t304 stainless but has 10x the corrosion resistance than the mild steel they were using. I may get some rust but it should stay surface rust due to the chromium content. Keep the opinions coming.