Just wondering,
I live in ca. and cut the pre cat open cleaned it out and welded it back in place as well as reinstalled the shields. In southern ca. the smog inspections are tight. I would not want to risk getting tagged as "modified".
I guess I could have just swapped it out but it was not real hard to do and it was completely clogged up. I am not running a boost controller and stock twins with a ported engine.

 

My mechanic has done the same . The power was better but the engine bay heat is still traped by the precat . A down pipe is now in place and the gutted pipe is at rest in storage .

 

I am sure there is more heat with the gutted unit but there is far less than with a filled pre cat. The material in the pre cat is real dense and thats what hold in the heat. I will admit it is still more than a down pipe for sure. I really was not sure if my pre cat was restricted, so I cut and pasted it. It looks stock but isn't. Great for smog tests since I need one soon.

 

I know it's been done, but it's a lot of hassle for minor gains, compared to what you can gain with a downpipe. I know from reading this forum there are shops in Cali that will pass you for a price, it seems like you're money and time would be better spent going that route.

Or, if you're up to it, buying a dp, and keeping the pre-cat just for the sniffer test.

 

My mechanic also put the metal covers back on so it looked stock, but the car is so low now they can not tell with the mirror on a stick . Did you see an improvement in power over a good precat ? With a down pipe the hot engine bay heat can go out the openingwhere the precat was .

 

u will pass smog with a dp. none of the coppers ever ticketed me for a dp...they will look for the center cat and that is it.

you can buy my 3inch hks dp if you want. Im going to go with a 3.5 inch.



j

 

He's in CA though, they check the exhaust thoroughly. And a shiny metal pipe attached to the rust colored cat and turbo manifold is a telltale sign. He might as well pull up to the station yelling "HEY THIS IS MODDED!"

 

The risk of being caught in Ca. "missing or modified" is a real bad deal. You may get sent to a referee and the cost of a new one is not included in the overall cost limitations. Worst of all this will turn on up the heat and the techs will look even closer. I had a Ca. smog license until last year when I hurt my back and got out of the business. The engine is new and I am not getting on it as yet so I can't see the difference in power. Honestly with the mods I am going to do I am happy with the power I will have. I wish to keep it together since I do all the work myself and my hands have 2 cuts/burns every 1/2 inch or so. I will say I have never driven a Rx7 until now and it is an amazing car.

 

Well I can tell you, it WILL make a differance gutting it. You got to cut it open though and weld itback together. The insides are made out of metal and you can't break through it like a regular cat.

 

I won't say you would never get caught with a downpipe but there are MANY of us driving in Cali just fine with a downpipe. Many of us pass emissions easily (including the visual). There is nothing on the emissions sheet to indicate the pre-cat. As long as the downpipe you install isn't polished, it will be nearly invisible once you've got a few miles on it.

 

just get a HKS one. they kind of look stock with the hump and the color.

 

I cut the pre cat right at the edge before it begins to get larger in size. It was like trying to break up a shot put from a 2 inch opening. I had to rip and tear the thing until it all was clear. I would like to chuck all this emission stuff but being a tune up and drive- ability tech I just want to stay as clean as I can. The engine does have more power but after I get a smog I will remove all the cats. I'll put a fake one up there. It will look factory but wont be. My engine is ported and I will have to get a cat when it comes time to smog. There no way it will pass with out a fresh cat. After the smog I will store the cat for next time.

 

My fantasy, of course it to have a complete stock engine set up stored just for smog. As soon as I pass, I would go home and swap in a ported single turbo system.

Hell, you could leave the "smogger" on a chromed engine stand in the livingroom and call it art.

Yeah, I know...fantasy.