6.0 Excursion, Largest exhaust and best exhaust - Diesel Forum

**jricherson** · 03-21-2006, 09:29 AM

I have a friend that bought a 2003 Excursion with the 6.0 and wants to put in 4" or 5" exhaust. After talking with some people they state that the 6.0 need the cat, in our state diesels are exempt, but need it for backpressure and the largest he could put in is a 4".

Any ideas on what is the largest or best system and is there a sensor for backpressure that needs the cat in it?
Thanks

Stewey · 03-22-2006, 05:15 PM

There seems to be honest disagreement over how much, if any, backpressure is needed for the 6.0. However, I've yet to see any data that supports higher HP gains by going to a 5" system.

sleepies · 03-22-2006, 10:54 PM

I dont get the backpressure thing. Would be great if someone would dyno before an after and put some data on this discussion.

JohnBoyII · 03-23-2006, 08:35 AM

The back pressure thing is a hold out from the naturally aspirated old school of thought....

TURBO DIESELS DON'T NEED BACK PRESSURE - period.....

Having done this on my 03 Ex I traded in...
a good flow thru muffler in a 3.5" downpipe (4" MAY introduce clearance issues) and 4" rest of the way exhaust with good mandral bends will give you the best bang for the buck...

I tried straight pipe - too loud in the echo chamber the Ex is...
I tried no cat - WAY too much turbo whine for this guy and the neighbors were shooting at me here in Texus [img]/ubbthreads/images/graemlins/smile.gif[/img]

With the stock cat (which has tapered in and outs that can match the 4") it was perfect !
[img]/ubbthreads/images/graemlins/biggrin.gif[/img] [img]/ubbthreads/images/graemlins/smokin.gif[/img]

rwhans007 · 03-28-2006, 10:51 AM

I put in a straight 4". I think you will have problems with the 5" clearing the firewall.

As the previous poster explained, waaay too much whine. I re-inserted the 3" resonator at the end of the exhaust and the whine is bearable.

Ronald

FamilyRide · 03-28-2006, 10:43 PM

Well it's pretty GD interesting. I posted a reply last night which had nothing in it that would warrant getting poofed, in fact, it included the reality that the CAT is part of federal emmisions and is a Federal EPA violation to remove regardless of what any state does with inpections. I also added that with my 4" system 3.5" DP and CAT still in place, I haven't had any problems.

I also brought up the EP sensor and my theory that if there was a backpressure issue with the 6.0, I could see it being because the backpressure being read by the sensor would be different that expected and might cause output to the EGR and VGT that could cause them to not operate as expected.

I guess somewhere in there I did something that got it poofed. I don't think there was anything before it. Maybe it's in another post, maybe I was abducted by aliens, maybe I'm being targeted by the Federal Government and they are out to get me. [img]/ubbthreads/images/graemlins/blush.gif[/img] [img]/ubbthreads/images/graemlins/laugh.gif[/img]