Exhaust Modifications For Better MPG

[TurboDiverArt]

Hi All,

I don

[MTTwister]

Art - there was a Pay-Back spreadsheet set of formulas given in another thread - the "major" drawback was how much the MPG would increase for the modification - that would be tough to estimate.
Here: http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=008990
- posted by Moondoggie about 1/2 way down.

[DA BIG ONE]

Summit has 3"or 4" FlowMaster Univ. tailpipe systems all mandrel bent real cheap.

You can use your existing exhaust pipe flange (at turbo) by cutting it off then welding it to new down pipe. To make down pipe you will need to weld 2 sections of pipe from kit together.
Next you will need a few sections of straight pipe, a flow through muffler and some hangers if your old ones are shot.
Way in the back you need to fab pipe over rear diff then out to side of truck.

[TurboDiverArt]

Originally posted by MTTwister:
Art - there was a Pay-Back spreadsheet set of formulas given in another thread - the "major" drawback was how much the MPG would increase for the modification - that would be tough to estimate.
Here: http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=008990
- posted by Moondoggie about 1/2 way down. Yes, thanks. I've seen the spreadsheet. The problem is that I don't know how to estimate the mileage benefit for changing the muffler to a straight through or the DP. DP and muffler are only $150 so it's a cheap mod and will probably sound cool. I just don't know if it'll actually buy anything MPG wise.

Anyone out there that replaced the muffler with a straight pipe have any MPG data? Interested if you replaces the CAT at the same time. I picked up 2 mpg by

[TurboDiverArt]

As an FYI. I ordered a straight through 3" muffler from Summit Racing for $25. I'm hoping to put it on in the next couple of weeks. I'll report back when I have some data if it makes any difference. I'm trying to re-gauge my MPG highway just to make sure nothing changes but 16-MPG highway seems to be a constant. After the muffler swap I

[Marty Lau]

Art;
I went with the 3 inch Jardine exhaust set up way back at the early days of the TDP. I left the soot trap and I have straight through 3 inch muffler. I kept track of mpg for about 5,000 miles before and after the swap and I found a 7% increase in MPG. I think the amount of heavy towing makes a difference as the more the DP restriction comes into play with high power situations and the larger the increase in power and MPG's. So I think if you plug in 6-10% in the spread sheet it would be close. At the time I towed about 5,000lbs with little wind resistance.

[damork]

TurboDiverArt,

I've been full circle with the exhaust upgrade option and being I have a Yukon I decided to put a cheap set of pipes on before shucking out the big cash on a Kennedy, Pinnacle or similar system.

I pulled out the converter, bolted a flanged pipe to the converter flange and ran 3.5" to the tail end. Biggest expense was a 3.5" universal tailpipe kit from Flowmaster.

Anyway, I log every drop of fuel that runs through my truck, and have the full complement of gauges. Thermostats are 180's, and the airfilter is a 97+, with some other improvements including DSG gears.

I won't deny there is a small power increase and a bit quicker low end spool up, but overall I didn't see the gains I wanted and went to a stock replacement tailpipe for my rusted out muffler. I didn't gain in economy, exhaust temps at 60-65 dropped maybe 25 degrees F, and the Donaldson muffler I used had more noise than I was willing to live with (nice rumble but it got old quick).

Maybe if I had 18:1 pistons and other performance add-ons and planned to tow it may have been different, but I got far more benefit by installing the DSG gears, the Race chip from BD, and the cooling upgrades. I've hit 21 mpg with my truck the way it is, and 19 is very common. For what it's worth, my brother just bought an '03 F0rd Superduty PS and pulled the cat off it with no change to the MPG.

[TurboDiverArt]

Thanks for the info. My thoughts exactly. My CAT was definitely plugged up after 120K. There were clearly tubes that were clogged. Picked up 2 MPG by "cleaning it". With the muffler I figure it

[moondoggie]

Good Day!

The reason I posted the spreadsheet instructions was so folks could at least make an informed guess. You almost always have to guess what mpg change you might see, but if your guesses are realistic, it can help make decisions about such things easier. ;)

I was REAL glad I did some research B4 I bought my Gear Vendors Aux. OD. The consensus was ~ 2 mpg gain, which is almost exactly what I've seen.

[i]