David J. Harrington

Hello all. I need to know the diameter of the stock exhaust right before and right after the cat. I believe it is 2.5", but I wanted to double check.

Thanks,
Dave

Renntag

I do believe that you are correct (2 1/2").

Are you modding the Exhaust?

I have access to 3" mandrel bent pipe, and I own a Mig machine. This should make the mod much more affordable.

I will have a big catless exhaust before too long. Havnt decided on a muffler yet though. Any suggestions not too pricey?

David J. Harrington

Renntag951:

You could say I am modding the exhaust. I run chips, lots of fuel, and a gutted cat on my 951. I have it registered out of my county(in a county where smogging is not required). I recently discovered that I had only received a one year registration instead of a two year and that I have been driving illegally for over two months. Well, I would like to register it legally, so I tried to get the emissions down yesterday. I got to within .08% of passing on the high speed CO. Everything else passed. I was pretty impressed with that, but bummed nonetheless. So, to pass, I am just going to cut out my stock cat(cat body) and weld on some flanges. Then weld on a cheap($60) universal cat to go get smogged. Then go home and take the damn thing off. I could probably pass with just running a low octane gas, but I don't want to do that to my baby.

Dave

Rob

Hey Dave,

Why not try the stock chips & a bottle of "guaranteed to pass" if you can find it.

the following came from the turbo and s forum under the subject of
Failed Smog in CA - 952

Then get a bottle of some 'guaranteed to pass' fuel additive, and run through it with a full tank of chevron supreme. Then when you take the test make sure you are using oxygenated gas, it burns cleaner for the sniffers...

he said his 87 passed without a cat. It might be easier than the temp cat.

Later,
Rob

David J. Harrington

Thanks Rob. I am trying to avoid that stuff. It says only to use four times a year, so they make it sound like it has some consequences. I am also thinking of a new ignition coil, but fail to see exactly how that will help CO(read my other post).

Dave

Renntag

Why would you want to use lesser fuel. That shouldnt make a difference with respect to emmisions. Anybody else have thoughts on that?

adie

Flowmaster's are superb boxes to use, check out there site, a coil upgrade will increase the burn of the mixture and therefore produce less waste, if you are that close an MSD might well take you to where you want to be, also check all the breathers as these being partially blocked will hinder emmissions. You mention lots of fuel, I guess you have upgraded the mix for the other mod's. I would go with your idea of putting a cat in on flanges and also make up a straight piece with the same flanges so you can swap at will in minutes.