Surprised this hasn't been brought up already but something to consider.
MS6 vs Genwon vs Poo all have a different OEM catback set up. Additionally, all the aftermarket kits are not going to be the same nor perform the same.

I would be surprised if there were not at least some gains to be made with a new CBE, even thouhg I have been here for long enought to see the "noise maker" theory thrown out quite a bit.

I just think the magnitude of the gains are not that easy to quantify in general terms. It is going to depend on car (6 vs won vs pu) what other exhaust work is done (cats, etc.), what other mods in general, what tune, etc., etc.

Lol this post has forced me to post a WTB for the midpipe to complete a full turbo back exhaust >)

Random thought:

Wouldn't the gains be more from the fact there is less backpressure which means the turbo will spin a bit faster for an equal amount of WGDC which means more boost...so unless you're maxing out your WGDC, would not increasing WGDC across the board result in similar gains without any hard parts? Long and short, the gains are probably from the byproduct of increased boost and not from the exhaust itself.

Decreasing the back pressure cannot be replaced by just upping the WGDC.

Backpressure also affects your volumetric efficiency...more is less, less is more.

For those who can't afford the catback here's some results from a 3 inch axle back. I posted the link but here's the graph in this thread specifically. FUG your CF 1.01. Again, these were done SAME DAY on the SAME ROAD. Not just the Same road but down to the same point. I mark it by a Sign on the right.

Like the OP I gained 10g/s MAF; IDC went up 5 percent; calculated load went up .9; and 60-80mph went down 2 tenths of a second; And BAT's were 108 for red line and 109 for blue line. So pretty much identical.

http://i.imgur.com/0sBc4wL.jpg

I'm catless with the CNT and my car is not obnoxiously loud. Catback prices are a bit steep, that's why I went with the one I did. $350 shipped and I'm happy with the quality. I'm more upset about my dp/tp fitment. Corksport's tp does not like to fit to my m2. I think it's getting choked off there.

interesting. i just pulled the trigger on the UR CBE myself, so i've made a mental note to do some logs with my stock CBE.

unfortunately even if my results back this up, there will need to be an asterisk. in addition to the CBE, i'm putting on a new intake (CS for Aeros, need that CARB cert). but i can't imagine that would make a huge difference. so i'm curious to see what my gains will be from what will essentially be just a CBE.

like OP, i have a UR testpipe but OEM downpipe. i'm not on E yet (i know, i know), so i'm absolutely below 300 on this Cali 91 piss.

Or you could, you know, just do the catback first and do the intake later since it's by far easier of the two mods.

For science!

i thought about it, but i'm doing it all at once after i smog the car. tight for time. there isn't a big enough difference between the two intakes to really skew it that much, right? neither intake is 3" or bigger.

The big thing will be flashing a new map for the differences in maf calibration...which will skew your results.

I gained right at 20whp going from stock to CNT CBE when at the ~400whp level...


http://i77.photobucket.com/albums/j6...Ebothat69F.jpg


Thread here:

http://www.mazdaspeedforums.org/foru...xhaust-121759/

yeah, that was the other thing. i'll be getting a revised tune. i'll take the logs and post everything either way, still might give some insight for the sub 300whp people.

There are several variables to consider here. If the tune is not changed, a CBE will often result in higher boost so many of these dynos and pulls are not 100% consistent in measuring just the decrease in pumping losses. However the fact that you get a bit more boost is a legitimate gain from an exhaust.

Due to higher pressure differential across the turbo you will need a lot less WGDC for the same boost and it may even creep in the cold especially if catless.

When I went from a catted CPE downpipe and OEM CBE to a full 3" COBB CBE I saw around a 15whp difference around the 370-380whp mark - similar to what @cld12pk2go; saw.

It also looks like the gen1 catback is less restrictive than the gen2. The larger muffler on the gen2 probably plays a role.

So what youre saying is...just go axle back on the pu? :)


Sent while granny shiftin' and not double clutching like I should

I went axle back with no muffler

Visually the gen2 muffler is not nearly as direct flow wise as the gen1 and is the biggest restriction on the catback.

http://i39.tinypic.com/4ih8g5.jpg

http://i527.photobucket.com/albums/c...exhaust002.jpg

Same here.

I don't have logs to back up the before/after though.


Sent from tappin them titties

I listen to 3 people when it comes to mods and tunes. @atvfreek; @ms3blackmica; and @rfinkle2;
If they say its worth it to do it, i do it.

They may be fly by night tuners and builders, take no pride in their work, but shiiiiiiit, they put out some fast ass cars to date.

I hear rfinkle2 just parrots things he hears from his *real* tuner.

This is kind of what I was trying to hint at...that boost may creep up a bit with all other things unchanged other than a CBE and that can be what causes some of the power gains. Thanks Lex.

There is a reason that the boost creeps up. Yes, some gains may be attributable to higher boost levels, but that is exactly what you want. That shows you are increasing the pumping efficiency of the system overall.

I don't see how that is any different than increasing the efficiency of the turbo on the intake side with a less restrictive intake.

If you wanted to make the same power and work the turbo less, so be it, but a CBE is increasing the efficiency of the overall system. That is exactly what the point of any aftermarket part is.

i also saw 12hp 20 tq difference after catback

I haven't had the opportunity for another log to confirm / deny the gains from my OP, and it's slated for a bullet resonator addition tomorrow to hopefully curb the part throttle obnoxiousness. I *really* wish I had gone axleback or cut-out instead, as now I've got to modify the mid-brace due to the minor rattles.

I agree with Lex the OEM muffler is a beast and probably the culprit for impeding exhaust flow more than anything, and it's really the only part you need to streamline. Save the cash and get a quality axle back without the headaches IMO.

For the Pu*

Because Freektune. lol

BNR is updating his FB, you'll be getting plenty of mid-turbo action in short order. Curious though I see you doing engine builds - is that going to become a limited or full time service?

I know if my shit splodes or starts to get a lil tired on the compression some day, I'd prefer to get Freekbuilt to go with my Freektune.

Right now engine builds are kind of a limited/part time service. It's time consuming and a one man show, but I'm doing my best to keep up with the demand on that side of things.

So I wonder if I would see the same gains only doing something like this...

Definitely, imo.. but without a resonator, that shit will be LOUD.

With a muffler delete, you will see some gains. It LOOKS like the muffler is the biggest pressure accumulator in the exhaust system on the PU besides the cats.

Louder isn't always a bad thing lol but there would still be a resonator in the midpipe

You cant go wrong with any fly by night type guys.

Lookit me, built by a fly by night, tuned by fly by night types.


Im fucking fast, and im going to set more records this year. FBN FTMFW!

The main muffler will quiet things down much more than that resonator. Resonators typically reduce noise via sound reflection and mufflers via sound absorbtion with some kind of packing.

Any cat delete and no muffler with the resonator on this car may sound a little SRT-4ish.

Damn right BECAUSE FREEKTUNE!
honestly that was just changing from stock catback to 3inch straight pipe with no touch up tune (ill email you shortly tho)

I think I may try this out and see how it sounds with my catted CPE downpipe I have on

I thought it was weird seeing that the majority of the community excluded cat backs from their mod list on k04 applications. Me included, just went with the flow!

Even in the Honda community most members ran 3in cat backs for K series motors!

I have an appointment with an exhaust shop tomorrow, I am going 3in mandrel bent just havent decided what muffler (if any). I'll report back with my findings.

Let me know how much the shop charges to make the midpipe! ;)

They gave me an estimate over the phone, $380 for 3in mandrel bent cat back 3in flange, magna flow exhaust and 4.5in tips or $240 for straight piping + tips!

Wow, that's cheap as shit.