Split Air Pipe/Cat... Fun stuff, I promise.
 

Well I decided to start a new thread revolving around this split air business. I have a regular 12A engine with the stock exhaust still on.... barely. It has the 3 cats, and it ends there. I plan on getting the Bonez system very soon, and will finish it off. But before that I need to figure out the deal with this split air pipe.

On my cat, it is welded shut where it is supposed to be and the pipe is totally gone. I have no idea how to go about supplying air to the new cat once I get it without that pipe The service manual is very vague about it in my opinion, it shows it in a couple diagrams and has a brief description on what it does. Reading one of the diagrams I can see a tube coming off of the back of the ACV right to the left of the port air switching valve (looking at the same picture on page 3 of the emissions for the 12A.) I also noted that it looks like the pipe comes down from the side of the first or second cat. Now what I don't know is when air is supposed to come out of that pipe and how I would test it without have to stick my hand there with the car running. Does it send air to the cat while acclerating or decelerating. Could this be why my car chugs a little while staying at a constant speed? Either that or the cat being clogged from not getting air from the pipe? If by some miracle air does pump out of it, would I just have to weld a new pipe in or what?

ditch the air pump, all cats and forget about it. just run a straight exhaust with 2 mufflers, unless you have massive emissions to deal with, then thats a entirely new story...

if your getting a bonez cat, you will need to retain your air pump if you don't want it to burn up FAST.

Like Paradox said, get rid of it. Your not using the air pump/air control valve/split air pipe anyways since it is blocked off on the cat. All your air pump is doing now is robbing your restrictive intake of precious air :) If you ditch these items, you might as well get rid of the rats nest also. Heres a link to the writeup found in the first gen faq section: http://www.ten15.net/Maz.tutorials/

Haha, are you serious? I live in michigan, and I dont think there is emissions tests or whatever anywhere in the state. My stepbrother suggested the same thing, but I'm not too sure about that. Wouldn't it still get too hot?

If you put a muffler or presilencer in place of the cats, you will need to order one specific for the rx7 or one that will withstand HIGH exhaust temps. Don't go with a glass pack because those will burn out very fast also.

So I'd still be spending tons of money.

EDIT: Also, can you do straight pipe off of the stock manifold? Because if I need to buy headers AND a presilencer, that would be super expensive.

go with header and straight pipe to stock muffler. i have the same but a hollowed cat and it is a huge increase in throttle response for me.

or how about a header and a nice single inlet and dual outlet muffler- magnaflow/flowmaster. that might be what i do when i change from stock.

forget the split air pipe, its a decoy. you really want the air pump air to go into the exhaust ports. its a 15minute deal to rig the acv so it does this

http://www.jimrothe.com/mazda/84_tra...raining_4a.pdf

Well I would love to do a lot of the things to the 7, but I am VERY short on cash. I am seeking the cheapest and easiest route, and if it happens to provide a performance increase then its just a bonus. It seems like there is a cat replacement pipe at racingbeat.com

Is there anyone that knows how well this works?

If you have a welder, you could do the same for cheaper. You could even go with a used header if you are still short on cash. Talk to trochoid, he did mine.

Pretty much a straight pipe seems like the easiest way to avoid that stupid split air pipe. I need to think about this. If that air pipe thingy is cut off from where it comes out under the car, should it be welded shut or plugged or something?

I have the same setup, and yes it is a good increase....but not good enough for me :) Im going straight pipe to magnaflow or dynomax soon

forgot to mention that it is going to be loud

Anyone got some used headers laying around then? If not then I will try to run straight pipe off of the manifold. Like I said, I'm not in this for the power, I'm in it so I dont have loud ass right under my seat and so I'm not breathing in all my exhaust.

THanks for that pdf J9FD3S, looks very interesting.

So what exatly do I do with this then J9? Would taking off the catalyst thermo sensor be bad? Where should I have the split air run to instead of the main cat?

take it off, along with the air pump....read the link that I posted

So it wont hurt anything to remove the thermo sensor? Or were you refering to the split air? Because I'm still not exactly sure what the sensor does, but its still down there under my car. I have it zip tied up right now since there is no pipe behind the cat.

Edit: OOOOO. Removing the rats nest involves totally removing the air pump as well? I read that when I first started coming here, and I didnt really understand it well at that point. So removing the air pump doesn't mess up the car at all?

If your car doesn't stink now it sure will once you remove your emissions equipment, BAD. I wish there was some sort of setup to put a cat back under the car without the rats nest etc.

My car doesn't stink...only the exhaust :) The only time I smell it is if Im out of the car...got down near the tailpipe today looking at my fuel tank (rotors spinning at the time) and I thought my eyes were going to dissolve.

If I do decide to go with the bonez system and figure out a way to run the air pipe, then would I still need that thermo sensor? The main reason I was going along with all this straight pipe business is that it will avoid messing with the split air. Right now my goal is to get this car into a dependable daily driver for the summer without spending tons of money. It looks like I can get the bonez cat pretty cheap, and if I can figure out a way to get that air hose back it might be worth it just to avoid my car smelling like ass.

Haha so many decisions to make, how do you guys handle all this stress :P

EDIT: Also, this will probably take someone who actually still has a cat. What controls when air goes through the split air pipe? I would like to test it out tomorrow but I don't know if it will push out air with the choke on or with the car idling. Would I need someone to step on the gas while I feel for air coming out? Also does the thermo sensor have anything to do with the split air pipe sending in air to the cat?

you could go with the bonez race pipe as long as you dont have emissions and it's cheaper
just an idea.

Does the racing pipe bolt directly to the stock manifold?

it looks to me like it does. looks the same as the normal one but with a cat that doesnt have to meet strict emissions. Because of that, the emissions friendly one will be more expensive

Nope. If you want to keep the stock exhaust log, it will need to be custom fabbed. None of RB's systems are emmisions friendly, i.e., not cats.

trochoid, it is the bonez not racing beat. umm here's a link:
http://rx7.com/store/rx7/saexhaust.html

Ah, did not know that was availible. Thanks for pointing that out, junior, lol.

I might be misunderstanding something, but basicly you're strapped for cash, you have no emmisions to meet, and you don't have anyform of exhaust past your cats, which you think are stopped up?

If I'm wrong about missing the stock exhaust past the cats and I'm right about the cats being stopped here is what you do. Take off each cat and run a pipe down in them to knock out all of the catalyst so that they are basicly cat-shaped open pipes. Put your stock exhaust back on.

If you don't have the stock exhaust and you need an exhaust (which i did gather) and your not looking for power then you can knock out the cats and A) Get the stock exhaust from the junkyard or B) go to a muffler shop and buy a MAGNAFLOW (or Dynamax) muffler and have them weld that to your (empty) stock cats.

If you're not strapped for cash and want a new/better exhaust system then buy a header and 2 magnaflows (one will act as a presilencer because having just one is too loud for most) take that to an exhaust shop and have them weld it all together, shouldn't cost but 70 bucks. You'll be out roughly $450 with a pretty great exhaust system.


Oh, and if you don't have anyform of exhaust past your cats like I thought I read, why were you considering buying just a cat and leaving it like it is? And isn't that loud and really gross sounding? If you're really really cheap you can just knock out the cats and put a muffler right on the end of one and do a side exit.

At first I was planning on buying the cat and then bending some pipe and sticking a muffler on. But after talking with my brother, I think we are gonna do straight pipe with two mufflers, or we may do you as you said even. Knock out the cats and put a nice muffler on. Either way, we have decided to not use a cat of any sort and then remove teh rats nest.

yeah, It might sound a little weird with the knocked out cats, but then again it'll sound a little weird with the stock manifold, but I think what you're going with is a good. you might even decide you want an extra little bit of umph and get a header later :)

Haha, I would LOVE to get a header right now.... but I dont see em much cheaper than 220 bucks...... For some that may not be a lot, but it's more than I can afford right now. And actually right now with just the stock cats on it doesn't sound bad but it is pretty loud. Luckily I had some nice speakers, a sub and some tweeters sitting around, only the people not in my car have to deal with it. :)

Were these pace setter headers alright? They arent too expensive on ebay, but I'm normally skeptical aobut ebay stuff.

http://cgi.ebay.com/ebaymotors/PaceS...spagenameZWD1V

yes, they are cheap, but i've heard of them being bad quality and prone to rusting.
this one is cheaper:
http://cgi.ebay.com/ebaymotors/Pace-...QQcmdZViewItem

heres one a racingbeat:
https://www.rx7club.com/showthread.p...ghlight=header

another one:
https://www.rx7club.com/showthread.p...ghlight=header

if you have access to a welder:
https://www.rx7club.com/showthread.php?t=519060

Thanks a lot. I think I might just run straight pipe off of the stock manifold for now, and later on when I have the money buy some headers. I would really like to get the racing beat one since I've heard such great stuff about them and the company in general. Ah, I wish I was rich, then I could sit around and play with my 7 all day...

....does that sound wrong?

yes. but we understand

How come that muffler looks like it has just two tiny holes exiting the exhaust? That's not for real is it?

I think there are some weird foam covers on the chrome tips to protect them during shipping maybe. That's what I assumed at least.

it cant be what it is for real. that would provide zero exhaust flow

But it looks like it could make some fun whistley noises before it exploded.

another one:
https://www.rx7club.com/showthread.p...ghlight=header


hehe i just brought this one 100 shipped deals i tell you:)

probaly wont put it on for a longtime got to many other issues :rlaugh:

looks like part of it tho hmm its a sniper muffler put some ball bearings in there and shoot away

Just a quick question: When I get headers, how hard is it to get to where I have to bolt them on? Would I have to remove the carb? Or can you get to it from under the car at all?

i cant help you on that one. a lift-kinda- was used on mine