ok.. ive been reading these exhaust post for some time now and have a few Q's....
i dont want cats... so if i put a pipe in from the header to the muffler and take out all my cats my 6 ports dont work.... and it will be really loud!? and what do the 6 ports do actually. why does it hurt low end performance with them wired open.. and doesnt the O2 sensor need to connected somewhere?... and how easy is it to wire open the 6 ports.. im not that great a machanic....
ok lets see ya guys awnser those... thanks!

 

Yeah, well series 5 is 89-91 right? i have a new engine, i am not sure the year. i have to go to a mazda dealership and have them look up the serial code. So i can find out what year it is......Pretty sure its not a series 4

 

i removed my cat on my 90 GXL.... well hacksawed it out actually and welded a pipe in its place.
with stock mufflers its not that loud...not noticeably loud anyway.
just recently my friend tells me that my 6 ports arent working for some reason..... on the high end it doesnt pull very hard....... not like it used to.

also what is the small aluminum pipe that runs parrallel to the cat.... i just bent it off with a pair of vice grips.

any way i can get my ports to function properly?

 

bump

 

Hey Dude.
I gutted all my cats cause my 5+6th ports are f-ed up, and it got a little louder not as extreme as some say. I still have the stock cat-back on Lates Matt22

 

Well you can wire them open or you can use a few different methods to have them open up. I suggest you do a search for "5th and 6th ports" Or go to fc3s.org and check out his how-to's.

 

thanks

 

Just replacing the convertors with a straight pipe was good enough for me. To me it was one of the better sounding but still livable setups. I'm going back to that on my street car since ultimate power is not a big concern even though there was an increase when I got rid of my convertors and still had the stock mufflers.

 

where are they located in the engine and how do i go about wireing them open?

 

what's wrong with the presilensor, do you really lose power by having this instead of striaight pipe with a header?
and why does RB now suggest not going with a header but instead the downpipe/presilensor

 

I don't think you lose much at all from the presilencer, if anything prolly not noticeable.

They suggest the "downpipe" with the presilencer for street cars because the header doesn't give "too much" more HP and is a good deal louder. But doesn't every HP count ?

 

arent downpipes only for turbos?

 

Mmm...good question I guess. What do you call the pipe coming from the exhaust manifold on a stock car? I don't know but it is a downpipe of a sort to me. Racing beat calls it a downpipe as well. Everyone think that downpipes are for turbos and headers are for NAs that why the association I think.

Quote from Racingbeat.com:

This Down Pipe* is available for custom applications in a 1986-91 RX-7 non-turbo application. (Shown above with optional presilencer) This 2.5-inch down pipe fits either manual or automatic transmission equipped cars.

This down pipe bolts to the stock exhaust manifold, but the use of our presilencer (or a suitable replacement) is required to connect this assembly to the connecting pipe. Gaskets sold separately.

*Legal in California only for racing vehicles which may never be used upon a highway.

 

Dude. just get a single cat back exhaust system and be legal and not noisey. No cats or gutted cats is childish.

 

Gutted cats is really foolish thinking back. I mean I got extra power, but my 1/4 is the same because the poerband on the gutted cat is choppy

 

I have the exact same, no cat and single side N1 without the silencer in the end of the muffler and it's not to bad at all. Around town is fine. It can get loud when your on the gas hard and revving it up. Sounds really good though and not so loud its irritating.

 

It won't make it any louder to eliminate the cats... it just sounds a little bit differently. You'll like it. Just pull your car up onto the rack at your muffler shop of choice, grab a saw, and tell them all to look the other way (or hit an armadillo *wink *wink and "knock" them off). Both of those methods work well I'm told . But anyway, just have them replace it with a straight pipe. Just make sure that you don't have to do all that emissions junk! Anyway, good luck! God Bless!!
<>< Matt ><>

 

gutted cat....creates some airflow problems. the physics of running through an empty box is still restrictive when compared to a straight pipe.

ok well, my knowledge comes from piston engines so i have some questions for the rx gods in here.

does ripping off the cat have any neg effects on a rotary? i know a piston engine uses the back pressure, and your vavles can wear out sooner with less of it (no valves in rotaries tho...in case you thought i had smoked myself retarded). also will no cats cause you to sacrifice low end torque for high end hp? cuz i want the low end torque...so does that happen with rotaries?

 

also w/ that question: Does replacing the 2 pre-cats on an n/a w/ a straitpipe still create enough backpressure to open 5/6ports?

I think my precats are clogged.
"I smell exhaust."