I have been looking to modify my exhaust system. From what I hear, to do a cat back is almost usless, and my truck does not have the horsepower to warrant an aftermarket down pipe, so I have been thinking about doing a downpipe back exhaust. However, I live in a county where we have our emissions tested ever two years. Usually they just plug into the OBDII. I am assuming that without my cat I will fail that test. What can I do?
Exhaust
- Thread starter workin' diesel
- Start date
If the only plug into obd2 and dont do any checks on ur exhaust. I (if i was in ur situation) would take the cat out and hollow it out and put it back in. That way if they ever do look under the truck it will be there...just with none of the crap inside of it. :thumb: But hope u dont get anyone who knows about our trucks, cause when u cut the cat off of our trucks the smell is totally diff...it smells more like a diesel with the kitty gone.
Almost as cheap to just get a complete turboback system with no muffler and no cat; pm ripmf666.
In CT, they plug into OBD2 and measure the "opacity" of the exhaust coming out. The standard is 20%; the highest I've ever tested with no cat no muffler and a 60hp tune was like ~4% IIRC. In CT they don't test for NOX or anything, not sure what they're looking for out there.
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MBRP S6004PLM 4" Straight Pipe Exhaust for 01-09 GM 6.6L Duramax - No Muffler
265.00 shipped edit sorry should be 280.00 shipped
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You will fail the visual inspection if you remove the cat i believe. Find an empty cat, high flo, etc. Weld in place of the stock cat. You definitely want to get rid of it though. EGT's drop significantly from that, not so much removing the muffler. You can stay with stock size tubing as well if you want.
I'll have to get under my truck one of these days and do a little brainstorming. Last time I went inthey did not look under the truck, but I am sure they are upping the inspection regulations, I suppose I will have to figure something out. Another question: will not having a funtioning cat show when they read the computer?
false. a down pipe will lower EGTs and give you a little better spool up of the turbo. Comparing it to HP that you are currently making is irrelavent.
Ive never heard of that happening nor do i find it true. how can someone fail your truck based on smell when you pass all other tests?
Workin' Diesel. Is your truck a federal emissioned truck or cali emissioned? (the door sticker will tell you) Federal emissioned truck dont have cats or EGRs form factory, mine is this way.
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According to my build sheet I have Federal Emissons. I just haven't gotten under it to take a good look at it. I could always add the down pipe later, couldn't I? Also, the current Flowmaster muffler give alot of cab noise at moderate speeds. Once I am crusing at 60+ MPH, it goes away. Do the staraight throught muffler or astraight pipe cut down on that?
I'm staight piped I don't noticed any extra noice but it's a diesel it is loud. Flowmaster is made to sound the was they sound for years think it just sounds better on a gasser.