I was looking through the exhaust components they offer for an S4 n/a Rx7, and I was wondering which would be best. I currently have an Apexi N1 Catback on my FC (Stock ports), and was wondering would the Cat Replacement pipe w/ the Presilencer be better than the Streetable Headers w/ the Presilencer? Which would give me the greatest hp increase?

Also if anyone has sound/video of the set up I want to run that would be helpful. I know it's going to be loud, just hopefully not like this http://www.youtube.com/watch?v=bNXejcb_kp4

 

Cat Replacement Pipe is better for noise, Streetable Headers will eek 1 or 2 more hp, from the butt dyno. It's up to you.

I have a used Cat Replacement Pipe for sale if you want.

 

I have a full s4 na RB true dual in south NJ, PM me.

 

Not looking to by the parts, just trying to get some info. How big would the noice difference be Roen?

 

I will tell you, I went to RB a number of years ago with the intention of buying a header and presilencer, and they talked me out of the header in favor of the simple cat replacement downpipe. I'm not sure you even get the suggested 1-2 more hp based on how that conversation went.

Also, I've driven a S5 NA with a RB header and the noise level is REALLY a lot more than what you'd deal with on w downpipe.

Bottom line, unless you're getting it for a dedicated track car or going to do some serious porting to your engine, get the downpipe rather than the header.

 

It also depends on the ability to tune fuel and timing settings in your car. On stock ECU trim, the difference is pretty much negligible. If you have control of fuel and timing and have a tuner, I would definitely suggest the header.

As for noise, the cat replacement pipe is definitely the quieter of the two.

It's been discussed in some of the NA threads, but the exhaust manifold / NA downpipe combo is pretty much a very short collected header, since it collects right at the end of the manifold. By virtue of the short pipe length before collection, the manifold is tuned to provide it's most efficient power at high rpms. I would imagine that, among other considerations like emissions and margins of safety, the stock ECU fuel and timing settings are set to promote power inline with the exhaust manifold design, near the top of the power curve. Replace the exhaust manifold with a separate header and now you have a longer pipe length collector, which pushes the powerband down. This is good, up to a point, as it gives you more useable power, IF (and this is a big IF) you can change the fuel and timing settings in accordance. Leave the stock ECU fuel and timing maps on with the new header, and you'll have a mismatched tune, which won't really give you much more power.

Personally, I like a civil car as a DD, so I would make sure all my exhaust gaskets are still ok, and use the downpipe / pre-silencer / twin Borla XR-1 mufflers or Racing Beat catback to try and keep the noise level as low as possible for an NA car. The APEX'i N1 Catback will hurt you in terms of noise. I remember my old Trust / GREDDY Power Extreme Mufflers being annoyingly loud, especially cruising at 3000 rpm's, at that was with stock exhaust manifold, pre-cat that was probably gutted, and probably clogged high-flow main cat.

 

Thanks for the info, I'm probably going to go with the cat replacement pipe and pre-silencer. Will this setup pop flames at higher RPMs?

 

Well, you don't have a cat anymore, so you should. I hope it's not your goal for getting the setup!

 

That also means you're running rich as hell.

 

No, jut trying to get the most out of a stock port 13B. That's and added bonus.

 

I had the exact setup in the youtube link. even with the silencer in it was unbearable. the gas mileage was great, but freeway travel would make me sick from the constant droaning. i must admit though that setup was the fastest n/a I've ever drove.

if I were to do it again I would get a used pacesetter header, a custom 3" borla midpipe, and a used RB turbo catback. Then it would be tolerable and cost efficient.

 

If you're trying to get the most out of a stock port 13B, the cat replacement pipe is not the way to do it.

 

Well I meant from the exhaust at least. Not going to do ITBs or antything.

 

I'd understand if you were trying to solve the balance between civility and power, going with the cat replacement pipe. But saying you're trying to make the most power out of the exhaust and going with the cat replacement pipe doesn't really make much sense to me. You may want to revise your goals.

 

Sorry my wording is bad. It's for a DD, that I occasionally take to the track. So I dont mind it being loud. But at the same time I don't want to do anything crazy becuase, it's a DD.