I am looking at ways to get my EGT down while pulling my toy hauler (right around 10k loaded temp is right around 800-1000F). I am looking at 4in turbo back systems but I have yet to find one that I can bolt the CAT back when I get to smog (was done when I bought it last year, should be good until next year).

Truck is a bone stock 2003 F250 6.0

Would it be possible to just put in a CAT delete and a muffler delete pipe and run the stock 3.5in pipe? If so how much do you think it would drop my temp by? Or should just go a head and go with a full kit?

 

I bought an MBRP cat delete pipe for my X back in '05 and it worked good. Reduced T lag by at least 50%. Then I got a T-back MBRP 4" and used the cat delete on it. When I installed the cat delete pipe In the stock system it went in pretty easy and I put the cat back in one time with no problems.

Ed

 

Browsing MBRP, they do make a kit that retains the CAT. Doesn't say it isn't illegal for CA like the rest so it's probably legal?

MBRP | Products

 

The diesel smog laws here from what I understand says its ok to delete the muffler but not the CAT. Its actually part of the visual inspection. Thats why I need to be able to put it back on before my next smog.
Does anyone know if leaving the stock CAT on a 4in kit like this will drop my EGT down?

 

I just took one to the local smog shop up here in Northern Cal. It had 4" from the turbo back. Cat and Muffler were on it and the smog guy didnt even question it.
It did fail because of the P1000 code. A 10 mile drive and a retest and it passed the 2nd time around. I believe scanning for stored codes started in 2015

 

Just my opinion but going to a 4" and then back to a 3 1/2" and back to a 4" will be of no benefit. The restriction is still there. Try taking a 5/8" water hose, install a short piece of 1/2" hose and then back to a 5/8" hose. You've gained nothing.

 

Understood, but what I was wondering about deleting the CAT and muffler out of the stock system. Would that be as good as doing a 4 in turbo back system w/o the muffler or CAT?

 

Logically this makes sense, but in reality things are not so cut and dry. I have an aftermarket exhaust, with the stock cat, and egts run 100* lower than with the stock setup. With the cat delete pipe on, it made no difference at all.

Its not pretty if you look under my truck, but it works fine. Basically, you have to cut the flange off the cat and install a 4" to 3.5" reducer, and another reducer on the other side of the cat to go back to 4". Also if I'm not mistaken, the part of the pipe on the cat that gets cut off is 3.25"

 

I have a full 4" turbo back straight pipe and pass smog. I take it to an old guy with a plug in the cab smog tester, I think that's all they use anymore right? Anyway, he is old and does his visual inspection with a mirror on a stick and he missed it for the last 2 years.

 

Unfortunately we don't have a lazy blind old guy doing smog cks. around here.

 

If you want the cat removed that bad, why not remove it and drill / knock out the catalyst block? It's a bit of work and kind of a pain, but will look stock after you put it back on and you won't have to store you cat and reinstall it once a year. If you really wanted to, you could remove it, gut the center, find some exhaust pipe with an OD that matches the ID of the cat pipes, and then run a pipe through it and weld it in place. It would probably take an oddball pipe size, but if you have the time and the motivation I'm sure you could find what you need online and order it.

 

Amen to that

 

Just gut the thing. It's not too hard. Temps won't be any different and 800-1000 is pretty damn good already.