What exactly is the "downpipe"? Is that the pipe that connects to the turbo and runs down to a flange just a little upstream of the cat?

Yes, it is.


It is a good idea to do your exhaust as a first mod. The downpipe is the start. You will gain the most by removing or gutting the cat and loosing the muffler as well.

Already "mufflerless" and "catless". One hunk of straight 3" replaced them both. Now I got a bead on a downpipe someone wants to get rid of. So I'm gonna help him out and buy it from him.


Aren't I a nice guy?


Is there any hope of getting the bolts on that flange loose? Maybe if i douse them with diesel fuel several times during the week before I try and install the new down pipe? I'll probably have to break out the old fire wrench, depending on how close to other stuff it is.


Any installation tips, or is it pretty straight forward?


Thanks!Edited by: w_huisman

Yeah, you may have to use what I like to call the Blue Wrench http://dieselplace.com/forum/smileys/smiley1.gif


Offhand, do ALL year 6.5's have CATS?


Good luck, this is my next move!

No not all have cats mostly LD 1/2T and 3/4T trucks fort most part HD rated trucks as catless & no EGR.


You may have to buy or fab a downpipe, only "found" ones probably scrapped stock ones.





IIRC QM said Summit had a fair price on a new one

Summit PN FLO-17220... $104.39 + $8.95S&H = $113.34.


I think the price has gone up. Probably cuz steel prices are thru the roof.

My HD 2500 had a Cat. before I removed it

My 95 c2500 suburban has a Cat, I think, there's another component in the exhaust system before the muffler, but it's smaller that cats I'm used to seeing, but I don't have an EGR. Is this typical of this year?Edited by: veggiesuburban

It's a soot trap and pre 94 doesn't have them.

It's a soot trap and pre 94 doesn't have them.





Thats correct.


Didn't some of the 99/2000 also not have cats?


My 97 K3500 has one.


CareyEdited by: Carey Weber

I read that on GM's 6.5 tech page for the hummer but CR's '00 had a trap.

94's in Canada do not have a Cat. we got an extra year of grace.

Quantam came over and installed the downpipe and 3" straight pipe all the way back. Here is the result after 1500 mile tour in OK and LA.


20.3 mpg the best ive ever had was 16.6


Lower water temp


very noticeable increase in power


It's not much louder and you can hear the turbo sing :)


Thanks Again Quantam


Justin

When we pulled Justin's soot trap out and held it up to the sunlight it didn't hardly pass daylight. Simplifing the exhaust reduces the pressure from the turbo back. after that, it can sing, whistle and roar like it should.

Yup, mine had a soot trap, could still see good daylight through it too.