Ractive header + RB Cat Back: Should I replace the midpipe w/ HiFlo Cat setup?

[Dimitrios]

Ok, so my exhaust setup plans will be primarily composed of:

- Ractive 4-1 Header
- Racing Beat Cat Back.

I have a question for those that replaced their midpipes with anything from MAM or Wagner*

** Edit: I would be looking at a midpipe with a hi-flow cat. Thanks.**

Should I replace the stock midpipe at this point in time? Is the existing cat that restrictive? I'd like to get either Beau's or Andy's midpipe (probably the MAM more than likely), but if it won't make that much of a difference, then should I even worry about opening it up?

I just have a "concern" about going bottlenecking at the end of the collector, running through a smaller diameter tubing and cat (and probably not as smooth of a flow as possible) and then opening back up to the RB Cat Back. Maintaining as similar as possible tubing diameter throughout is important.

 

[tonkabui]

i'll be getting a midpipe fashioned up pretty soon (if $ allows), and i'll let you know if the MAM pipe makes that much of a difference on the dyno (as well as noise levels).

 

[njaremka]

The CorkSport exhaust will bolt up to the header. Then you can run no-cat.

 

[Dimitrios]

The CorkSport exhaust will bolt up to the header. Then you can run no-cat.

Not to be a dick, but how does this answer my question? (poke)

I already have a the RB cat back. My question is pertaining to the midpipe with cat.

 

[Pretzellogic]

Just from an asthetics point of view: anyone know how an RB catback sounds with a header?

 

[njaremka]

Not to be a dick, but how does this answer my question? (poke)

I already have a the RB cat back. My question is pertaining to the midpipe with cat.

Sorry, I read it that you were going to purchase both then work up a mide pipe for connecting.

Talk to your exhaust shop, and get the mid pipe made such that the front pipe (between the header and cat) to be the same diameter as the header outlet, then the rear portion (between the cat and the exhaust) the diameter fo the exhaust inlet. That would seem to me to be the best compromise.

I don't have either, so I cannot comment on the size difference between the two. However, I believe the Ractive header and the RB cat-back are the same diameter. (2.25-inches, right?)

 

[Dimitrios]

/\ I believe they are; I'll check them when I get home.

 

[rktktpaul]

Dimi, I'm not entirely sure, but I believe that an Illinois shop cannot work on a system that has has any of the emissions equipment removed. I believe it has to be like for like, i.e. pre and primary cats. We could always ask Julian Welding.

 

[Dimitrios]

Yeah, I'm going to have the O2 bung welded in (my boss has "connections" - hey, it helps being from the South Side!!). I figured what do they care what I want an extra O2 bung put in? I could want a wideband for all they care. Besides, I'd do it before I start yanking cats and stuff.

 

[viVid]

The RB Catback is 2.375". I'll have my MAM SS Midpipe w/cat tomorrow... let you all know how it goes. So, I'll have the OBX Header, MAM Midpipe and RB Catback... woohoo!

 

[Dimitrios]

viVid, that's basically the setup I'm planning to have (less the OBX header --> Ractive (blah) ).

Keep me posted. BTW, I saw that GB on the MAM midpipes; is Beau still making them (I'll call/email him later).

Thanks,
D

 

[akhilleus]

Shops can work on an exhaust system missing cats, they just can't be the ones to remove the catalytic converter. I would recommend a custom midpipe and hi-flow cat, Random tech, dynomax, etc, to replace the stock one.

 

[scorch70]

Ive got a somewhat similar setup, and I wish I could give you specific hp numbers gain or lost by adding the midpipe, but I cant. My dyno is not working correctly anymore. Anyway, I love my setup, but it is not quiet. Of course, you are going to retain one cat, so that will help some. I never found a good answer about if using a 2.5 inch midpipe with a 2.25 cat-back was a bad thing.

Anyway, good luck.

 

[murda79]

Ok, so my exhaust setup plans will be primarily composed of:

- Ractive 4-1 Header
- Racing Beat Cat Back.

I have a question for those that replaced their midpipes with anything from MAM or Wagner*

** Edit: I would be looking at a midpipe with a hi-flow cat. Thanks.**

Should I replace the stock midpipe at this point in time? Is the existing cat that restrictive? I'd like to get either Beau's or Andy's midpipe (probably the MAM more than likely), but if it won't make that much of a difference, then should I even worry about opening it up?

I just have a "concern" about going bottlenecking at the end of the collector, running through a smaller diameter tubing and cat (and probably not as smooth of a flow as possible) and then opening back up to the RB Cat Back. Maintaining as similar as possible tubing diameter throughout is important.

I'm interested in the results as well, as this is my setup too, OBX & RB cat-back. With this setup there's a really deep humming, if you go under a bridge or something, you'll hear and feel it. It's really quite deep, I wouldn't call it loud as much as i'd call it bassy.

 

[viVid]

Alright, I received my SS midpipe w/ cat yesterday. Everything looked good - it comes with a gasket (for between the midpipe and catback) plus hardware. Unpacking took a little while because the ends of the midpipe were left open (so I had to pick out the compacted shipping peanuts).

After a few confusing moments yesterday, I finally got it installed today. The confusing thing to me was the the only way the midpipe would install is with the cat forward (which brought it very close to the crossmember). After a call to MAM this afternoon, I was assured this was by design (I would have thought the flex joint would have been in the forward position... but hey, what do I know).

Note: For RB Catback owners, you will need to slot the provided gasket a bit for it to fit properly.

Note2: You will almost certainly need to chuck the heatshield under the shifter (that continues to the first bend in the exhaust) or you will almost certainly be guaranteed to have rattling issues. Do yourself a favor and take it off BEFORE you bolt on the midpipe .

Once I got the midpipe in place and loosely bolted, I noticed the cat was sitting on the crossmember (zero clearance). I played with bending the hangers on the midpipe and ended up with about 1/2" of clearance. Don't bend them too far or your exhaust will end up hitting where it goes up and over the axle (see pics below). Once I had the clearance set, I tightened everything up.

Note3: Kartboy hangers are REQUIRED (IMO).

Note4: You will need a 18mm x 1.50 short bolt to plug the extra bung (I didn't pay for the extra bung, but got it anyway - so have one handy just in case). IMO, MAM should have provided this with the hardware - oh well.

Took it for a test dive this evening and didn't have any issues with rattling (although the bend over the axle hits the underbody when starting the car - no biggie). If it is louder than the OEM midpipe, it isn't by much - a little louder at the lower rpms. There was no increase in freeway droning that I could tell. Won't really know if I have gained any HP for a few days or so (via buttdyno).

 

[Captain KRM P5]

Dimitrios, adam (pro5onspeed) has the obx header, catless midpipe and the racing beat exhaust. with the second cat removed he said he felt a noticable "butt dyno" increase. kartboy hangers are required IMO as well. there is a drone with the cat removed but it is a pleasing "my car has balls" tone to it. throttle response is a little better with the cat removed and the gains you feel up top in the rpm range from the header should be a little better.

maybe come up and go for a test drive

 

[Dimitrios]

Ken,

I think I'll take you up on that offer. Keep you posted....

I have a local shop looking to weld a mid-pipe up for me.

 

[Lord_Zath]

Updates vivid? Dimitrios? I'm looking to do something very similar

 

[Dimitrios]

LZ,

I have the header, exhaust, and aformentioned/questioned MAM midpipe (all ceramic coated) collecting proverbial dust. Now that the weather is opened up and I look to be home for more than 36 hours at a time, I can get a'crankin.

D

 

[Lord_Zath]

aah cool well let me know how it goes after you install the parts! I'm sure a bunch of us could help out too if you needed it...