Xavier8

Had a cheap custom exhaust made for my 12a streetport a few months ago, and it includes 2 Turbo something mufflers that look like big resonators. I looked inside another one that he had and it seems to reduce the noise by completely redirecting the exhaust with a plate positioned just inside the muffler. I do not know what it does after that, but the flow must hit the plate, go around, then travel into the rest of the muffler. I asked for 2 to reduce noise, and it is quiet as long as the secondaries are closed.
So, the question is, the motor just doesn't seem to make the power it should. RB Holley 465, direct fire, big streetport with ported intake, even a very nice stainless steel header made by another company. I am curious as to whether this kind of restriction could make a big difference in power? Thinking of having another custom exhaust made with all racing beat stuff included, like a presilencer and power pulse muffler, but I don't want to spend the bank if it probably won't add much. Post impressions and thoughts. Thanks.

85rotarypower

It is possible that the two mufflers are restricting the exhaust too much. But its hard to say. I don't think the RB exhaust is going to help much either, especially if you use the primaflow muffler they sell. Its most likely just as restrictive as the two you have, but I'm not sure. I don't have any personal experience with racing beat. But there ways sometimes are a little weird.

BTW, what size pipe are you using?

FB II

holy crap man, yes get those mufflers OFF! hahahah, rotaries (let alone PORTED) neeeeed exhaust flow!!!! WOOOOOOOO!!!!!! it will make a huge difference!

85rotarypower

But your going to run into sound level problems if you take them off. If you want it to be quiet, you have to suffer some power loss. But if you don't care about the sound level, take them off and use a magnaflow or something. But be prepared to wear earplugs all the time. Sometimes you just have to deal with lower performance to avoid getting unnessesary noise tickets.

Xavier8

certainly need to keep the sound level down, just hoping that some sort of straight through design would help performance without sacrificing quietness. The current mufflers are far from straight thru.

REVHED

It's a waste of time using anything other than straight through mufflers on a rotary. Especially ported engines as they're more sensitive to backpressure due to increased overlap.

FB II

lol, yea my last post was made in a burst of energy. basically you can get alot better mufflers that will quiet but still give you much needed flow. i have been using magnaflow for abit and with my new turbo setup i am now using the ones listed in my sig. in N/A form with rb streetport header, 2.5" pipe to magnaflows it was awesome sounding. very streetable noise level. gotta have 2 though, run one as a resonator before the axle and one as the end muffler with a tip if you like. you will not be let down! magnaflow ROX!

Xavier8

hmmm, maybe my crap mufflers are robbing me of that extra bit of power. Some say avoid the magnaflow, some say go for it. What model number magnaflow are you using FBII?
So the backpressure will greatly limit power output? The car makes lots of air turbulence sounds at high rpm.

Rotor13B

Are you ******' serious? The RB streetport system was made just for this situation,lol. Where did this misnomer about the primaflow come from anyways?

Rotor13B

Xavier, get the RB setup, you will not be disappointed.

REVHED

I agree that the RB system will perform well while being quiet but the muffler is restrictive compared to other straight through designs.

jimmyjoejoe

the rb's are good and can take the heat, but a straight through will see more than a few extra horsepower. i'm suprised that baffle or whatever in your cheapo turbo mufflers hasn't burnt out yet. rotaries have been known to completely blow out flowmasters that use nothing BUT baffles.

heb09

just leave the headers on it and go for a spin. lol

Tom

Anyone seen a cutaway of the RB muffler? I wonder if there is a baffle plate in there? My hunch would be that it does not..

Anyway- what about a Supertrapp set-up? There was an Rx-3 at Rotorfest that had one. Take the guts out and MAN was that puppy loud!

XLR8

iTrader: (52)

Any straight through with Stainless Steel packing. Apexi universals are very well liked. If your really worried about noise, go with a dynomax. They flow about the best for the noise level.

Good luck

Xavier8

found a local distributor that will sell me 4" round magnaflows for around 30 dollars each for the stainless steel cans. I am going to look at my room again and decide what size to get for the second muffler, but I know I need a 4" round for the first one due to size. I might be able to use a bigger one for the second muffler to keep the sound down. A local muffler shop will also install them for 60 bucks, so I should be able to upgrade to straight throughs for around 150. I am really hoping the straight throughs give me some performance gains over the turbo type. an extra 5-10 hp can make a big difference in a 1700 lb car. I'll keep everyone posted when I get the results.

Xavier8

UPDATE:Finally installed a 4" magnaflow in line with a 5X9" magnaflow muffler to replace the "turbo" mufflers. One word: Awesome!
Car finally likes full throttle better than part throttle, pulls hard to whatever RPM I like, unlike before where the power dropped off at 6700 or so. So much more powerful with usable torque and HP. Did many 100 mph pulls.
Also installed the quick change vaccum secondary kit for the holley and ended up liking the lightest spring. This is two springs lighter than the one that comes in the holley from RB. Car starts pulling hard at 4000 and hits even harder at 5000. Very powerful car now, the kills section will see more of me now. Thanks to everyone.