I have a 1993 F250 with 351, 5spd. My truck doesn't require emissions testi g so the guy I got it off reamed out the cat, so insides rattle around and make a lot of noise when down shifting. I was wondering if I can just remove the cat all together when I get new exhaust? Will the computer notice it's missing and try ond compensate? For gas milage and torque should I just stick with 2.25 single muffler and exhaust?
Thanks
mat

 

The computer won't pick up on anything past the o2 sensor.

 

Does your area do visual inspection for emissions tampering?

 

If the cat has been gutted then it should have anything rattling around. I would keep the cat for visual inspection.

I would put a 3 inch single on that 351 or at least 2.5 with a good flowing muffler.

 

If you don't need the cat for any reason i would just remove it , no need to have an expansion chamber in your exhaust a strait pipe will be better.... Lew

 

Sorry, my last post should have read: If the cat is gutted then it should not have anything rattling around inside.

What Lew said is better, but if you have a visual check for inspection like we do in TX then it will fail. Even if you don't have emissions testing you probably have the visual check.

 

I pounded out the inside of my cat last year. Now I just had my truck serviced and the tech said i need to replace the cat becuase it is possible that it will through off the codes. On my ride the o2 is upstream from the cat and the air pump hoses do not even connect to it.

 

That is only possible if your truck is a '96 or newer.

 

Like Conanski said. The 96 year model although it still looks the same is OBDII and has a down stream O2.

 

The o2 sensor on my truck is up stream to the cat, but I don't understand what is the purpose of the sensor in my case, what is its job?

 

I have a 1995 F150 with a 351w auto i removed the whole exhaust from the cat back. I run dual 2 1/2in pipe with dual glass packs. it sounds good and runs great. Have no dumby lights on.

 

It fine tunes the fuel-air mixture so you get better mileage. It has nothing to do with the cat at all.

BTW I have seen talk on other forums of states starting to do visual inspections for smog equipment. It's illegal to remove or even move a cat.

 

What about replacing the exhaust manifolds with headers, have you guys had success removing the egr?

 

On some trucks it is possible to remove the EGR without setting off codes, but if your truck has the DPFE EGR system it is not possible. Besides that the motor will actually get better milage with the EGR functional so it is a good idea to retain it, have a fitting welded on the passenger header or buy smog legal headers with the EGR and O2 fittings already in place.

 

Around here, if the exhaust is loud the State Poopers (Ooops, I meant troopers), have been doing roadside inspections looking for inop or missing cats....They find allot because it is common around here for folks to cut them out and run straight pipes.

They fine the driver and impound the truck.....You know, it doesn't happen much, but it does happen and our local towing companies are making a killing replacing exhaust systems.