I want to quite my exhaust down consideribly and pass emissions/smog at the same time and I'm looking for new ideas on what parts to use. I currently have a rb road race header to straight pipes to rb muffler, three parts all together.
heres a pic of what I'm working with.
header-straight connection.

picture of the dual straight pipe at the top connecting to muffler.


I will most likely have it custom made since I have never seen any sort of bolt on cat for a rb header,
I would like to hear input on how many cat(s) ? I need to clear smog
Where they need to be positioned to utilize the air pump, or whihc ones can use the stock air pump ?
thanks aaron

 

If you have a visual and tailpipe emission testing then you need to put on the complete stock system.
What type of testing do you have?

 

I'm almost positive that their is no under hood inspection if I pass the first try. Fail the first test and I might need to have an underhood inspection when I pass in the future.

 

In order to pass the tailpipe you will need to install a new catalytic converter, have the air pump hooked up and the ACV installed.
Since you have dual pipes you will need to get a converter that has 2 inlets and I outlet so that you don't have a ton of modifying to do to the system. You also have to take in consideration the distance the cat will be from the header. The further away the harder it is to lite off the cat and the air tube would have to be modified for the extra distance.
I always have kept the stock system around for when emission testing came. That way all I had to do was put all the stock emission stuff back on and get it recertified.

 

Magnaflow makes a good 'hi-flow' cat, I'd give that a try. It'll double as a presilencer.

 

doc I will look into the dual inlet cats, do you know of a rotary proven brand I could research? My only concern is in the first pic my header ends at two different lengths, one tube is 2-3 inches longer/shorter, and the chance of finding a cat that fits that will be hard. I will have a custom made exhaust from the header exit all the way to the muffler inlet created with the positioning of the cat as close to the header exit.

next step is what cat do I go with ?

 

Borla makes a cat system for our cars but it is designed to work with the stock exhaust manifold.

I would recommend going to a exhaust shop where they have catalogs with dimensions of the available cats. You might be able to go online to the various exhaust companies and do the same thing. Remember you have to have one with a provision for the air tube. As far as unequal lenghts on your system it is not a big thing. That can be adjusted on the cat side.

 

Hey,
Thats a nice looking rex...

Just one cat? I though there were three. Perhaps technology has advanced to allow us to only need one.

Btw, any links to good manufacturers?

 

youre fucked. send me your set up and ill send you two stock systems. youll have enough cats to pass any smog test

 

sorry for the ms paint drawing guys.
This is my current idea of what I'm looking to get with my exhaust.


can any one from experience tell me is this setup will 1) pass smog and 2) sound good ?

 

i think itll sound good but you sure as hell wont pass smog.

to pass smog, as the doc stated above, you need a lot more emissions back on the car. youll need the smog pump(working), stock exhaust manifold, cats, and the ACV.

with a header youre **** out of luck. your best bet is to ask around and find someone who might let you slip by or something.

 

anyone know if there is a physical difference between the 81-83 prescilencer and the 84-85 prescilencer if I am already having a custom set up made ?
I can save around $40 new if I buy the 81-83.
thanks

 

I currently have all emissions equipetment still on the enigne, my air pump should still be there (i never removed it) the cat I will be putting on has the inlet for the air pump, I'm not sure about the air control valve but it should still be in working order.
I have been told that it is posible to pass the smog test with a header if all the rest of the set up is working correctly.

 

That is correct. The main thing is to make sure all of the tune-up parts are in excellent condition. The air filter is clean, the oil is not at it's interval change time.

I would recommend when you go in for this that you find a place that will do a pre-test. Meaning they will run it and look at the numbers and tell you if they believe it will pass or not. Some places charge for this others will not. I don't know how your guys are in the part of the Country your in.

As far as the pre-silencers I believe the only difference is the attachment points for the support like at the tranny area. But call Rb or Mazda trix and see what they have to say.

 

Also make sure your air sensors ( I think that's what they're called) that connect to the cat. I just found out today that the reason that my 85 failed was because the connection of these sensors was bad.

 

today I ordered the 2'' bonz blank catayltc converter, it has the tube for the air pump and was reasonably priced and alot of people here have good things to say.
As for the sound I want my car to fly under the radar of the law but still sound a little burly, if I go with a pre silencer/resonator would I be killing the sound ? I haven't heard what a pre silencer sounds like for reference.