I'm looking at using a straight through muffler like the Borla XR1 with a 60mm inlet/outlet to help with noise reduction on my catless car. Straight through muffler designs tend to keep exhaust flow and velocity optimal, while reducing db. I'd like something that can withstand the heat of the rotary engine's exhaust gasses since it will be closer to the engine.

I'm currently running a dp/cat eliminator, and full stainless catback exhaust system. It is extremely loud to say the least.

Please post your results of using a straight through muffler as a midpipe

any input on any of the following for various straight through mufflers would be great!


Sound dampening (db reduction)
Reducing exhaust resonation (tinniness)
Durability
Flow


I'm also looking at combining it with an EVC (exhaust valve controller) to help, as it's super strict in SoCal for noise output of exhaust systems.

I know I should have gotten a high flow cat if i was worried about sound, but my precats and main cats were clogged and the bonez eliminator was a good inexpensive quality replacement for the three

 

I'm using a bonez racepipe (midpipe with a welded in resonator) and it keeps the sound down pretty well (only one ticket in a year in a state that all aftermarket exhausts are illegal.)

The bonez racepipe uses a louvered core resonator which is somewhat bad for flow, but it's easier and more reliable to do then have a local muffler shop do a hack job on installing a muffler as a resonator/presilencer.

 

right now im already using the bonez resonated midpipe precat/cat eliminator, and it is just too loud on throttle and higher rpms. i plan to hack off the resonator and weld some flanges so the muffler can be bolted on. The bonez resonator simply doesnt reduce db as much as I would like it to

 

What cat-back are you using? An N1 style? That makes a huge difference.

 

I'm using a one-off prototype Tanabe SM Racing catback. Dual muffler, straight through canister, stainless steel design. 70mm to dual 60mm. It is meant for turbo application catback, but the car is currently NA, waiting for transplant next year.

 

for what its worth, that turbo will quiet it down a bunch, maybe just wait for the transplant?

 

I'd like to, but since it will take a bit of time to blow up a low mileage NA, i need to have some streetability I know I can get out of any 'modified' exhaust ticket, but i just dont want to deal with the hassle

 

Get an offset type muffler - this seems to kill a lot of the high frequency resonances.
We use Walker Dynomax UltraFLO, Dynatech, Borla, and Magnaflow mufflers.

We're also experimenting with those perforated cones.
They seem to work, but it's highly dependent on placement.
They work well after the center presilencer muffler and not very well in the tailpipe for some reason.


-Ted

 

what catback?

 

I'm running a CorkSport single. Right now, I'm running the stock manifold -> bonez racepipe -> CS catback.

I was running a pacesetter header (hey, I got it with a new O2 for $40) -> CS midpipe -> CS catback, but that was stupid loud.

For some reason, the stock manifold and Bonez midpipe feels stronger.

 

wow the CS is crazy loud!!

 

Not really, it depends what is before it. If you run a header into it, it will deafen you... if you run a turbo and a resonator into it along with the optional silencer (which always blows out!,) it's quiet.

 

Magnaflows deal well with rotary heat as the mufflers are packed with SS mesh. Run the longest muffler you can fit under the car, and it will do wonders. I had a universal high-flow cat along with dual 3inch magnaflows on a TII. That setup was really loud and droney. I then replaced the cat with one LONG and large-volume Magnaflow muffler, and it got so much quieter, and freeway cruising was so good I could talk on the cell-phone without yelling or saying "what?" every 5 secs.

 

That's how it is on any car.Even running the CS catback and the short resonator of the bonez midpipe, I never really had a problem with that... then again, I never talk on my cell more then 20 sec when in my car. I either tell them to wait or **** off until I'm parked.

 

good good info, thanks guys

I think I may try the magnaflow. SS mesh should hold up very well.

 

Would most resonators last on a rotary. I've only heard (no 1st hand exp) that fiberglass-packed mufflers melt quickly on a rotary.

I was thinking what a glasspacked resonator, teamed with a cheap "N1 style" muffler would do?

 

i still dont understand why it would kill you to just buy a resonator? theyre wayy cheaper than a chromed out magnaflow. same damn thing
straight through mufflers are basically chromed out resonators.

 

Fiberglass anything (i.e. glass packs) will literally last only weeks.

Stick with something that has a warranty.

The Dynomax Walker UltraFLO line of mufflers are limited lifetime guarantee.

The Borla also has like a million mile warranty.


-Ted

 

the car already has a resonator, it isnt enough. Resonators are usually only good for 2-3db of noise reduction.

the construction of resonators and mufflers is much much different.

Magnaflows and Borlas are actually decently constructed mufflers, depending on which model you use...and what you use it for Dont underestimate them just because it is a US made product...that's just being ignorant. Magnaflow and Borla actually have higher manufacturing quality certifications and standards than practically all Japanese aftermarket exhaust companies. (only two Japanese exhaust manufacturers have the same certifications)

 

when i took the resonator out of my honda, it was good for waaay more than 2-3db. a straight thru resonator and straight thru muffler are constructed similarly.
moreover, they work together with eachother to cancel out.. resonation and some noise. a magnaflow straight through with a resonator is still gonna be loud as ****.
youve gotta consider the original muffler setup was a parallel muffler with no presilencer.

 

Who mentioned anything about chromed out?!

http://www.magnaflow.com/02product/universal/oval.htm

5x8" oval is probably as wide as you can fit under the FC if you are going with a full 3inch system.

I believe RETed mentioned this earlier, but a offset/center muffler would do an even better job of cancelling noise without much more of a flow restriction.

 

My setup consists of:

RB 3inch DP
Borla 3inch MP
CS\ebay catback

Before the borla MP, the car was stupid loud; since the installation of the borla asa MP the car is very driveable, the wife doesn't even complain about it! Now sound leves\noise are subjective, what might be loud for somebody, might not be so luod for somebody else; with that said, here is the borla muffler that I sued for the MP:

Part #40944
Diameter 3"
Dimensions 16" x 4 1/2" x 7 7/8"

 

Ted,
Do you have any experience with the Edelbrock RPM muffler? I have one as a muffler on my single exhaust setup with RB midpipe and it is pretty quiet.
http://www.prostreetonline.com/buy/e...ries_mufflers/

 

I used a 2.5" diameter 12" body 17" total length SS Edelbrock muffler for a cat replacement because it was exactly the right length with flanges welded on (17.5"). It made a substantial noise reduction over using a 2" to 21/4" mid pipe. There was also a fair bit of back pressure increase with the muffler. (eg. Boost didn't creep as high or as early) I just finished swapping in a 3" magnaflow cat in place and I think the car is louder than with the muffler, but I can't comment on the performance because I now have a monsterly ported wastegate.

 

Nope, most of the other mufflers are relatively cheaper than the RPM series, but many have commented that the Edelbrock stuff should work pretty effectively in terms of noise suppression also.


-Ted