Can a homemade exhaust be any good with a cat?
 

I'm heavilly debating whether or not to include a cat in my exhaust. Right now I have a hollowed out one with the factory exhaust, but it smells horrible and all the gaskets are shot so smoke comes out from everywhere on a cold start. It doesn't sound very nice either.

I was thinking about getting an actual system, but there all fairly pricey. Yes I understand you get what you pay for, but if I can get all the fumes and smoke to go out the back of the car, and clean up the emmisions, then why not go cheap? It's free car, so already this is going to cost about 1000 times more than the car does.

Will my plan of a aftermarket header+2.5" high-flow cat+2.5" piping+$50 Craigslist Titanium style Muffler be good enough for daily driving? I'm not looking to pass smog in CA, just not smell that bad when I get where I'm going. I've been searching but I'm not finding alot of info on homemade systems, just complete purchased ones.

This is my daily car with a 12A that will hopefully be getting a Weber 48DCOE to go with that exhaust. (untill I can rebuild a 13b for that special time when the car isn't my daily anymore)

well...chances are i'm going to be the only person to answer your question and not tell you to go search so listen up....you shouldn't have any problems with the 2.5" piping, just make sure you get it done at a decent muffler shop...don't even think about using that cheap flex pipe stuff you can get at the auto parts store...now here's where you gotta make a decision.. cat or no cat...if you don't have to pass emissions (like here in Fl) then skip the cat and get a borla xr-1 and use it as a presilencer...the borla is MUCH cheaper than a replacement cat and will stand up to the heat of a rotary...but if you must get a cat...get a bonz..as far as i know one of the only that'll take the heat....and as for muffler don't bother with any kind of cheapo fart can for 50 bucks...unless you plan on relacing it every couple months....get a magnaflow..sounds killer looks great and lifetime warranty...will take the heat VERY well...so in synopsis good shop, good cat/presilencer, and good maganflow muffler...I'm running the same exact set-up on my 81 12a SP right now whole system set me back 350...installed including muffler and presilencer....hope that helps

the only "advice" i can give is that I am going with .125" thick piping, at 2.5". I got hte .125 from Racingbeat.com, somewhere in their exhaust section. If they make it thick like that, there has to be a reason, yes? :)

no cats!!

i pulled the entire exhaust from my stock 85, bent and welded up some pipe i got at the local parts store and ran straight pipe from the mani back and opted to keep the stock muffler as it was not leaking. i cut the small outlet pipes off the end of the muffler and replaced them with some 2.5" pieces about 4" long the whole thing cost me $30.00 plus some tax and i just used some ole bracket for hangers. also its not very loud at all and sounds super fucking cool. good luck....

oh i didnt use a cat....or presilencer :Kill1:

^^^The only reason your's isn't that loud is because you're using the stock manifold. The stock manifold was definitely designed well when it comes to keeping the noise down. Wouldn't mind hearing a nice sound clip though. My system will be an RB header>straight pipe>RB muffler. No cat or presilencer. The RB muffler is designed very well with noise deadening but keeps a very nice beefy tone. I chose not to run a presilencer to get more noise from the system as opposed to an RB system. I'll try and get sound clips when the system is done

I have just finished up my intake and if it ever stops raining out here in lagarto, ill get you that sound clip. i do have a video of the car smoking tires with a side pipe straight off the mani that just sounds ridiculously (sp?) cool, ive put it on you tube but i dont know how to do the link thing, its titled rx7 smoking tires if anyone wants to check it out. mine is the blue one with the brush behind it that goes through 4 gears..... sweet!!!

http://www.youtube.com/watch?v=VJ7IL-WxlRk

this is the vid of the car a few days after i woke it from a 5 year slumber

GO BABY GO.......ill put the sound pic of the cheapy exhaust tomorrow

Spring for a borla xr-1 trust me it will be the best 120$ you ever spent

Damn, that thing really lit those tires up. Any mods?

im not real sure when i got the car it had been sitting on the side of the road for 5 years, all i did was wake it up. at the time all i had done was strip the whole exhaust off, and replaced it with a side pipe. ill tell you this though my cuz had an 84 that had a holley carb and a 2.5" magnaflow exhaust. it was fast but this thing will smoke it easy if you can keep the tires hooked up. :Kill1: