I just bought an 87 RX7 non-turbo and the former owner replaced the exhaust with a straight pipe, no catalytic converters and two $10.00 ebay "mufflers." The noise generates a migraine headache in 4 seconds. I plan to re-install the OEM mufflers, how many of the catalytic converters need to go back on the bring the noise down to a reasonable level?

 

also, your 5th and 6th ports might not be opening...you may want to look into this, if the prob hasnt already been solved (as in wiring the ports open or something to that nature)

there are 2 cats...i dont know about the noise level, as my stock exhaust on a t2 is hollowed, and it is pretty reasonable as for noise. in fact its not noisy at all... im sure if you just reinstall the oems, it will bring down the noise level considerably.. IMO...

 

Just one cat with mufflers should be fine. Ive got a straightpipe going to an RP catback and it sounds like *** not to mention being wayyyyy too loud. The two other converters on the FC are preconverters and as far as I know, dont effect emissions.

 

I run A Bonez SuperFlo High-Flow Catalytic Converter/Presilencer and the stock mufflers (Borla System on its way wee) Its deep as sporty without being anywhere near annoying or harmful

 

And I have one for sale !

 

I have one on mine and is a little bit louder then stock but not by much. Inside the car you cant hear it idle you can only kinda hear it at about 5k+

 

Actually s4's had 3 cats (1 main and 2 pre-cats). If you low noise levels get a something like a borla catback with a magnaflow in place of a muffler, I've heard that sounds quite nice. If you want a cat, go with the previously mentioned bonez high-flow.

 

I can vouch for the bonez system, and i'm quite anxious to hear the results of mating it to this well-built borla system, ill post up pics and a sound clip if i can. Prolly wont be in for like another week and i'll prolly polish the set.

 

you don't need cats.....

 

How many cats would I need to put back on my s4 to build enough back pressure so my 5th and 6th ports open?

 

Racing Beat's system with the inline silencer works great for me.

 

I saw some EASTERN brand Catalytic converters on Ebay--anybody heard anything about these units? Both converters can be bought for about $100.00 which includes shipping. Or is this a case that you got to spend three times as much to get something that works OK?

Eastern Cat. Converter Front Unit

Eastern Cat. Converter Rear Unit

The same company sells a MAGNAFLOW front and rear unit for $93.00. Anybody know anything about these units? Hmmm, becuase this is a "front and rear" unit, does that mean you need two of these or that the one unit does the work of a front and rear unit?

 

it's N/A so there are a total of three cats
two pre and one main cat

also at least with my N/A I'm running the RB header into a straight pipe(not the RB presilencer) with a tube welded in and blown out mufflers in the rear that are just like straight pipes. the 6pi works fine

 

zero?


least mine still open up no problem without a cat. read above pst by me

 

If your 5th/6th arnt opening why dont you just wire them open?

 

Bonez Superflo + Borla is the most beautiful sounding RX-7 exhaust IMHO. You'll like it .