hey guys. i've decided to put a single stack on my 6.5 but im wondering how i can get it to black smoke nice... is it as simple as just straight pipe and cut the cat out or is there more to it? thanks for the input!

Jordan

Black smoke is a no-no in a 6.5. A quick puff on take off is ok, but thats it. Removing the cat might do it for you. These turbos spool up really fast tho so the puff will be small. .

would removing the cat do any damage to the motor?

no not at all it will make it more efficent with less backpressure

No, it will not hurt anything at all, if anything it will help.

When did they start putting Cats on the diesels? My '94 doesn't have one, and I didn't know if it came with one and the previous owner had removed it?

it should have one. does it have the stock downpipe?

If the exhaust was replaced from the turbo back then they cat would more than likely have been eliminated.

The "cats" aren't really cats on our trucks. It's a soot trap. Somewhat like a failed attempt at a DPF. The trap was supposed to collect the soot and then when the EGTs got high enough burn the soot off. I don't think the EGTs got high enough and therefore the traps got plugged after a while. Mine was plugged and rusty as hell when i replaced the remnants of my stock exhaust. The new DPF equipped trucks have a "regen" cycle built into the PCM to really crank up the EGTs to burn off the soot.

would removing the cat do any damage to the motor?

Not at all. It is one of the best things you can do for it! it creates a ton of backpressure, especially if it is clogged. It the first thing i did to my truck. second thing was kissing the muffler good bye.

Actually dave, some of them do have cats. Mine is a cat. It depends on the truck. If the sticker under the hood says "catalyst" then it has a cat, if it says "non-catalyst" it has a soot trap. I think it is just the 1/2 tons, tahoes, and maybe those LD 3/4 tons that have cats.

I'll have to look again, but I'm pretty sure mine comes right off the turbo with a 3" pipe and into the muffler ('bout 10" round and 3' long if I remember right) then out the back with a 4" pipe. Like I said, I got it used, so I'm still trying to figure out what's been modded.

Actually dave, some of them do have cats. Mine is a cat. It depends on the truck. If the sticker under the hood says "catalyst" then it has a cat, if it says "non-catalyst" it has a soot trap. I think it is just the 1/2 tons, tahoes, and maybe those LD 3/4 tons that have cats.

my truck said catalyst on the sticker. before i got rid of the original airbox for the round style filter & box. that one says "catalyst" on it as well however.

*shrugs* maybe they all are cats to a certain degree? lower NOx perhaps? Strange thing is my friends 01 dmax never had one to begin with. I wonder if GM scrapped the idea after seeing them getting plugged up on the 6.5s?

If you have 3" downpipe and 4" from there back you have an aftermarket exhaust. The trucks came with a bent up mess of a down pipe and only about 2 7/8 exhaust. You are better off with what u have. I am replacing mine with a 4" exhaust in a month or 2. Lot better sound too.

I'll have to look again, but I'm pretty sure mine comes right off the turbo with a 3" pipe and into the muffler ('bout 10" round and 3' long if I remember right) then out the back with a 4" pipe. Like I said, I got it used, so I'm still trying to figure out what's been modded.

That muffler sounds like a stock muffler. Guess there are aftermarket ones that could be like that too tho. if its 4" out the back, that for sure isnt stock. And if the downpipe isnt all squished and beaten then it isnt stock either.

my truck said catalyst on the sticker. before i got rid of the original airbox for the round style filter & box. that one says "catalyst" on it as well however.

*shrugs* maybe they all are cats to a certain degree? lower NOx perhaps? Strange thing is my friends 01 dmax never had one to begin with. I wonder if GM scrapped the idea after seeing them getting plugged up on the 6.5s?

My moms 01 DMAX don't have one either. Did all 6.5 have these soot traps or converters cause i dont think mine has nothing but a muffler under there?

They all had something, originally. http://en.wikipedia.org/wiki/Detroit_Diesel_V8_engine#6.5L
This info is a bit off tho, since i have the L65 engine and a converter, but the burbs are weird trucks anyways. Even the 1500 burbs have a 3/4 suspension (other than a 9.5" ring gear and 3.42 ratio) including brakes and 8 lug wheels. But they also have the F engine instead of the S engine that you find in tahoes, 1500 pickups and LD 2500s.

When it stops raining here i am going to go look under my truck and see. Do these soot traps look like a cat converter?

They look the same as far as i know.

Yeah, they look the same on the outside.

And about the smoke... You only really want (at most) is a puff at the first couple seconds when taking off WOT then just a gray haze. Normally these trucks don't smoke at all when stock unless they are under a nice load.

Moved to Fuel System, Air, Exhaust, & Emissions Upgrades...