Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post

MIMF · 02-24-2012, 01:08 AM

The last several days, there has been some discussions concerning higher fuel prices in this forum and of course, all over the media. For along time, I have been thinking about what an over sized exhaust with low restriction muffler might do to increase fuel mileage and efficiency.

Back in the mid and late '90s, I had a heavy half GMC with the good old 350 in 'er. When the exhaust rotted and needed replaced, I had a 3" diameter exhaust system complete with lower restriction muffler installed that really brought that old 350 alive! I immediately noticed a "throatier" sound that was in no way objectionable in the cab. At least DW never said anything about it but, it was also notice that at lower RPM ranges, she seemed to have a little more torque. There was also, about a 2 mpg gain at highway speeds.

Does anyone have any advise and experience in doing this to their Duramax? I have no interest in chipping or reprogramming because, I do not want to break anything.

Thanks, everyone.

02-24-2012, 01:08 AM	#1
MIMF Montana Master Join Date: Jan 2005 Location: Goshen Posts: 1,058 M.O.C. #2827	Oversized exhaust system The last several days, there has been some discussions concerning higher fuel prices in this forum and of course, all over the media. For along time, I have been thinking about what an over sized exhaust with low restriction muffler might do to increase fuel mileage and efficiency. Back in the mid and late '90s, I had a heavy half GMC with the good old 350 in 'er. When the exhaust rotted and needed replaced, I had a 3" diameter exhaust system complete with lower restriction muffler installed that really brought that old 350 alive! I immediately noticed a "throatier" sound that was in no way objectionable in the cab. At least DW never said anything about it but, it was also notice that at lower RPM ranges, she seemed to have a little more torque. There was also, about a 2 mpg gain at highway speeds. Does anyone have any advise and experience in doing this to their Duramax? I have no interest in chipping or reprogramming because, I do not want to break anything. Thanks, everyone.