4" down pipe?
Hotshot
Joined: Dec 2003
Posts: 15,368
Likes: 121
From: Stuttgart, Ar
That was 15 years ago, so no I don't. Lots of things have changed with the 6.0 since then. I beta tested a LOT of parts and a LOT of tunes to help get the 6.0 performance stuff to where it is now. Granny truck is tired (and retired) and all she does is haul grandkids now.
Postmaster
Joined: Sep 2016
Posts: 3,941
Likes: 240
From: Texas
On the down side....
the 4 inch offers no benefit, the 3.5 helps with back pressure on the turbo which is necessary and performs better. Stock is 3 inch with a resonator for my 2003. If you want the 4 inch down to fit, you may have to hammer back the pinch welds on the cab to keep it from rubbing.
the 4 inch offers no benefit, the 3.5 helps with back pressure on the turbo which is necessary and performs better. Stock is 3 inch with a resonator for my 2003. If you want the 4 inch down to fit, you may have to hammer back the pinch welds on the cab to keep it from rubbing.
Fleet Mechanic
Joined: Nov 2012
Posts: 1,347
Likes: 110
From: Lakeland, Fl
What am I missing? How does more back pressure help the turbo?
I run 4" turbo back with no issues, running or fit. No firewall dents but it will hit the frame rail if not positioned right and sound like a bad hub bearing in a turn.
I run 4" turbo back with no issues, running or fit. No firewall dents but it will hit the frame rail if not positioned right and sound like a bad hub bearing in a turn.
Fleet Mechanic
Joined: May 2010
Posts: 1,480
Likes: 161
From: West by God Virginyuh
Super Moderator
Joined: Jul 2004
Posts: 21,113
Likes: 3,939
From: Ohio
Be it only short term, the 4" will offer a lower temp, not much, so you gain lower EGT for a short but turbo lag is the trade off on the lower end over a 3.5 which improves turbo spool up. I and several others, spent time on the DYNO when nothing was really available in the early days, the final decision is what makes you happy. My truck puzzled plenty of people at the time but I have an 03, which in turn seems to be the best year for me. I have probes before and after the turbo to see how it performed, you would be hard pressed to find anyone else who monitors the back side of a turbo.
Super Moderator
Joined: Jul 2004
Posts: 21,113
Likes: 3,939
From: Ohio
Thread Starter
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More Turbo
Joined: Dec 2003
Posts: 571
Likes: 4
From: hondo
Well, I think I got it done. Took a little playing around with it but got lines up with out touching any thing. Will know more tomorrow on my drive to work. Definitely sounds throaty. Thanks for all the help.
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More Turbo
Joined: Dec 2003
Posts: 571
Likes: 4
From: hondo
Well, drove to work this morning 1hr at hwy speeds.
There was no obvious performance gains or loss that I could tell. I really did it to hopefully lower egt.
Im not really happy with it because of the extra noise. Not sure because it's up against the firewall or it's just the way a 4"down pipe sounds. I'll give it a few days and see what happens. I may reinstall the oem down pipe and go 4" from there.
There was no obvious performance gains or loss that I could tell. I really did it to hopefully lower egt.
Im not really happy with it because of the extra noise. Not sure because it's up against the firewall or it's just the way a 4"down pipe sounds. I'll give it a few days and see what happens. I may reinstall the oem down pipe and go 4" from there.
Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
Currently in a similar conundrum myself, after years of driving a 7.3 I'm really enjoying how quiet my 6.0 is and don't want to increase the in-cab noise. Currently my truck has a stock exhaust but looking into options, main duties will be some daily driving and occasional towing of 5-6k. I'm thinking 3.5" down pipe to 4" with some sort of a good quality muffler at this point, anyone with insight that would suggest I'm leaning the wrong way?
Elder User
Joined: Jan 2004
Posts: 900
Likes: 0
From: Arizona
There is no audible sound difference between the 3.5 and 4.0 downtube. If you are hearing any type of additional sound, its probably the installation that is to blame. The slightly larger size is not significant but will help slightly with your EGT. That's really all there is to it.
If your installing a new exhaust system, by all means go with the 4" downpipe.
If your installing a new exhaust system, by all means go with the 4" downpipe.
Thread Starter
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More Turbo
Joined: Dec 2003
Posts: 571
Likes: 4
From: hondo
There is no audible sound difference between the 3.5 and 4.0 downtube. If you are hearing any type of additional sound, its probably the installation that is to blame. The slightly larger size is not significant but will help slightly with your EGT. That's really all there is to it.
If your installing a new exhaust system, by all means go with the 4" downpipe.
If your installing a new exhaust system, by all means go with the 4" downpipe.
Fleet Mechanic
Joined: May 2010
Posts: 1,480
Likes: 161
From: West by God Virginyuh