I currently have the collected RB system but with the old sckool HKS sport catback Mazdatrix used to sell. From various reading it seems one makes more power with longer primaries merged into a collector and a single muffler vs. true duals( this is with the primary length being tuned on the dyno of course). Due to wanting to keep dual rear mufflers restricting my primary length before the collector and lack of easy access to a dyno for tuning anyway I was thinking of a setup collecting them mid chassis. Just prior to where the stock Y or a catback bolts up. Racing beat descibed this setup in thier old catalog/ tech manual but gave no measure of power vs. short or long primaries, just that it helps with sound. I figured I could cut the collector off my header and either use the RB roadrace pre-silencer or this Magnaflow muffler.
Magnaflow 11378 Magnaflow Performance Satin Stainless Steel Mufflers
Though I'm worried about the Magnaflow surviving. Then once welded up my old header collector would bolt to my catback. Has anyone ran a similar setup. Any idea how this performs vs. the true dual or my current setup. Would it potentially make more power than the true dual or my current setup? A compromise between the two( more than current, but less than the true dual), or a total waste of time? Thanks.

 

Oh, I forgot to mention the engine is a stock port. I'd like to go to a large street port when it's time to rebuild.

 

the magna flow is garbage, will burn out the wool packing and crap, i know from experience. honestly keep the setup you have its only a couple horse power difference, plus its quiet, I'm running racing beat header to silencer, to custom adaptor to the rev2 catback, my motor is extreme so its quiet, than it was when i had a custom system made by defined auto works. if you go single stay at 2 1/2 pipe size, just throw alot of mufflers on it, so its quite.

 

I thought that may be too close to the engine for the Magnaflow not to burn out. I wouldn't even be thinking about changing it if it weren't that save for the header and y-pipe it is getting in rough shape. All the welds on the catback are rusting, leaking, and falling apart so it will be first to be replaced( It's been on the car twelve years and was used when I got it).The y-pipe already rusted and cracked and I replaced it with the one for the dynomax system( just luck it fit right in). Unfortunately in the process the studs broke on the presilencer. Since they are not really studs but bolts welded to a flange I drilled and tapped the bolts themselves and put a couple sizes smaller studs in them. They've held together for the past two years. Presilencer is rusting now too( it's 13 or 14 years old now). Anyway I will eventually have to replace everything behind the header and am just kicking around the above setup.

 

So is it easier to keep stock exhaust manifold on take off all pre cats and big cat go staight pipe into rb cat back then when smog comes around put all the smog back on to stock manifold and youll be good to go this should work right any info would be great
Thanks
Ian

 

I agree ,the magna flow is crap.But on the other hand I have personally used this muffler on one of my rotary motors . The way to make the muffler last is cut the top portion of the muffler in a large square (like half the muffler) ,pull out all the crap packing , buy 1 lb of course stainless steel wool from mcmaster carr web sight , re pack with the ss wool and weld it back together . It will be good for your lifetime .

 

I am resurecting this thread from last year because I am still curious, and also it is no longer a stock port. It now has a streetport using Pineapple Racing's 6-port template for the intake and their EP2 medium streetport for the exhaust on TII rotor housings. I do plan to get a way to tune fuel first but eventually I'd like a different exhaust setup.

 

I currently have the RB Road Race true dual setup and this interests me as well. My plan was to run the true dual until after the presilencer (since I have all these parts already), and then use a 2 to 1 merge collector into a single pipe and possibly hks/apexi/ greddy can. My main reasoning is that I want to help improve low to mid range power as I will be running ITB's that have no provision for the aux port actuators. Basic exhaust tuning would indicate that collecting the exhaust into 1 properly sized pipe should yield in a higher exit velocity.

The question remains: Is it more beneficial to collect after the header or back by the differential?

 

Header. You want the pulses to effect one another. One will cause vacuum pull in the other..

 

Interesting. Alot of the aussie guys collect by the diff.

 

Maybe they're right. My pp setup will not be collected. Still if I was doing a streetport na setup and had to get my powerband finely tuned... I would do it on the dyno. Not speculating the forum. I would try different length header collections and maybe a diff collected one to boot to see whats down under.. Also the intake matters just as much. Do you hsve itbs or just stock manifolds? ( a question to ask yourself) One custom itb setup may want a different collected length than another. That's why its called exhaust tuning.

I would try 16 19 and 26 inch collections as I wrote them down per another builders recomendations


It would be nice if there was... the intake length exhaust length combo info spilled out but as you can see its a lot of effort... try looking at proven examples.

 

Obviously back to back would be the most beneficial. Unfortunately, that idea isn't financially feasible.

It would make sense to collect after the header to ensure that the exhaust is merging at the highest velocity.

My reasoning for collecting at the diff is I could utilize my current road race header and presilencer, minimizing cost.

 

with all N/a stuff.. the last little bit of power is usually the most expensive. you can get 90 percent of your setup with whatever exhaust, but finding the absolute best is going to cost.

 

There are two different setups for collecting them. Short primaries collecting up at the header somewhere or long primaries usually collected as far back as possible. To maximize power on either the collection point needs to be tuned on the dyno as mentioned above. By searching around on here you can find dimensions that would get you close for either one, but that last little bit needs the dyno. RB also as recommendation on their site. You just have dig for them and I've posted a link them on here somewhere. Also it seems most on here that have had a long primary system prefer it over the short. The ITS racers I think all use the long setup. My reason for the mid collected is I didn't want to go single but retain the dual exhaust setup but hoped for some benefit from collecting further back.

 

the long systems, like RB's Street port system, are pretty proven. i did have a car i ran the street port, vs the regular shorty header, and its not 100% apples to apples, as the street port has a bigger pipe after it collects.

the peak power was similar between the two, butt dyno said the short system was actually slightly more. however the midrange was much much better on the long system.

for my P port car, when i build the exhaust someday, i'm going to make it modular, so i can have a 26" header, 50" header, 70" header and 90" header, and we'll see what it wants.

 

I really like long primary exhausts like RB's "streetport" on NA rotaries. They seem to have more power everywhere.

I've built, hmm let me see how many long primaries...

three REPUs
1st gen RX-7
rotary MG Midget

 

You guys almost convince me to go single and collect as close to the rear as I can. I sure do like the look of the duals though. Hence I'm still clinging to this mid-collected idea.

 

An x pipe near the rear subframe should allow for dual mufflers in the back to keep things symmetrical and quieter. I've not read about an x pipe on a rotary, so it's just a thought.

 

I have wondered about using an x-pipe. I was thinking of only keeping them collected a few inches before splitting back apart anyway.

 

I've always been curious about the Defined Autoworks header which is mid-collected but I'm guessing because of the price there are not that many out there. I'd love to see and hear one mated to an RB catback. Without an x-pipe that's probably the best option for keeping the dual exhaust as it appears to collect right before the catback but I don't remember ever reading anything about how an x-pipe affects performance.

 

I'm pretty sure Defined's exhaust headers will not fit a cat back.

 

I'd say there would be some cutting and welding going on, on the cat back. Unless it were to end where the stock cat does. Either way I'd also add a flange on the Defined Autoworks piece.

 

I saw pictures before, I think they were on RCC but I'm not sure. It ended a few inches short of the catback so you'd have to add some piping at the end but it's pretty close. I wouldn't think they just have a bunch laying around like RB so I'm sure they could collect it at the catback.

 

The defined piece looks really nice but too much money for me. I think if I ever do this I will stick with my original plan of cutting up my header to extend the collection point with some sort of pre-silencers thrown in the middle to keep noise down.

 

Here's a link to their four port header with pictures. It looks long to me.

DEFINED AUTOWORKS

http://www.definedautoworks.com/shopcars/DSC01616.jpg


Six port header link.

DEFINED AUTOWORKS


http://www.definedautoworks.com/shopcars/DSC01570.jpg