Duramax Exhaust on a 6.5

[JetBoater]

Has anyone stuffed a 2002-2004 3.5" Duramax Diesel exhaust into a 92-98 body style style 6.5 ??

I have been pricing out high flow Flow Master systems and mufflers. Exhaust shops must work with silver and gold by the price they charge!

I have a 3" down-pipe, then 3.5" to the stock muffler/tail-pipe currently (2.5"). I was hoping to get a 3.5 to 4" muffler and tailpipe at a reasonable cost... no luck. Local shops are quoting $500-$750 for this.

I am buying a complete Duramax exhaust from 02-04 for $150. Anybody tried this..? If so, what am I in for? Oh.. comments on the muffler are appreciated.

Mike

[More Power]

You can use the tailpipe and possibly another section, but the hangers and some parts of the Duramax factory exhaust system won't fit. With the DM tailpipe, some universal hangers and some straight 3-1/2" pipe, you should be able to make it work. ;)

Jim

[JetBoater]

Jim... I took the whole contraption to Minute Muffler and they turned the rear hangers on either side of the axle 180 degrees and chopped off the hanger in front of the muffler. The hangers fit perfect into the mounts.

They then chopped the exhaust pipe a couple of feet forward of the muffler where it bends.

It fit like it was made for it! Valhalla... a 3.5" Duramax Diesel exhaust on a 6.5!

They added and charged me $98 for a mandrel bent cross-over.... 1.5 hours labor and it was done (it took less than an hour though).

EGT's dropped from from 350° to 250-300° at an idle. I did notice a little power improvement over 2800 rpm. It has a new "throaty" rumble as it powers from there to 3400 rpm. Very nice!

The size of the duramax muffler is HUGE compared to the stock muffler... and way wau bigger than the 4" high flow muff I was going to put in. I was concerned the Dmax Muffler would not be free-flowing enough.

I'm OK with it for now! Thanks!

[DmaxMaverick]

I don't think the Duramax muffler will be a problem on a moderately modified 6.5L. It, as well as the entire system, is oversized for the 6.5L design. They are of similar displacement, but the Duramax can operate north of 20 PSI boost under normal operation, which creates significantly more exhaust volume than a 6.5L at ~10-15 PSI. I know of a couple folks who installed the Duramax exhaust on their 6.5, but straight piped. It's good to know the muffler actually fits, in case someone might use it.

[JetBoater]

I may go back to the shop and have the muffler removed today for $40.

The fellow who did the job says I'll get a little more objectionable noise when I stomp on it, but no difference in sound at low throttle. He advocates a real gain power if I loose the Muffler.

I'll let you know!
Thanks :rolleyes:

[JetBoater]

Duramax exhaust on the K3500 Dually

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/mods008.jpg

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/mods010.jpg

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/mods012.jpg

I'll try to get the muffler removed today and provide some feedback.

[bowtiedude]

Well I know the tail pipe will work thats what is on mine. Can't speak for the muffler it got misplaced.

[JetBoater]

It didn't take much convincing to rip the Dmax exhaust out and do it right... I went back to Minute Muffler and Terry installed a 4 inch from mid truck back. No muffler... all pipe!

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/StraightPipe016.jpg

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/StraightPipe017.jpg

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/StraightPipe024.jpg

http://i97.photobucket.com/albums/l240/jetboater/Trucks/Exhaust/StraightPipe020.jpg

I gained 3 lbs of boost and it comes on without the previous lag... I was amazed.

It does rumble more at idle, especially with part throttle, but it does soften up as the RPMs climb. Oh.. there is slightly more noticeable power throughout the rpm range too! It definately sounds like a Big Power diesel truck.

I'll dyno it after my holidays!

[trbankii]

Just curious, but was this mainly a matter of getting the Duramax system at a good price? Or are there other advantages rather than getting a 6.5 system?

[JetBoater]

trbankii -
I was simply looking for better flowing exhaust, which the stock 6.5 system at 2.5 inches is not.

The dmax exhaust was 3.5 but came with an enormous muffler... the 4" system I had installed removed all concerns of back pressure south of the turbo.

[trbankii]

So you ended up taking out the D-Max system entirely and just using 4" pipe?

[JetBoater]

I am running a 3 inch down-pipe which transitions to 4 inch pipe, to a 4 inch free-flowing muffler, and 4 inch tailpipe.

I had added a 20 inch free-flowing 4" muffler to remove the low harmonic exhaust noise which wasn't very appealing at 5am in my neighborhood.

My dyno numbers were done with the muffler.
;)

[6.5 Detroit Diesel]

What did it dyno at?
As in, what are your power numbers? :)

[JetBoater]

Dyno numbers were 215 HP and 470 lb ft torque at the rear wheels

[6.5 Detroit Diesel]

Sounds good. I was curious as my truck has a tuned IP and the straight 4 inch the whole way back. I know it is high, but max boost has been 22 psi with no issues. I'm trying to guess what the truck is putting out. I am working on setting up a true cold air intake, even though with this weather, I don't think cold air is a problem.