New Exhaust/Worse Mileage?

[Turbine Doc]

Todd I'm suspicious of blend of fuel used, possibly with higher costs maybe your supplier has shifted to lower BTU/Cetane cheaper for him fuel, coinciding with your pipe install,

We are missing something here that has changed other than the larger ID tube; yours is 1st 6.5 pipe swap I recall seeing mpg drop with bigger dia pipe, tires/tranny same before pipe swap, possibly since spool is faster you don't realize you mite be driving with a heavier foot now ???

 

[Sparky8370]

I'm guessing the heavier foot too. You are not on the highway all the time so, yes your right foot is in the equation. Your probably cranking on it more than you think. I'll put a beer on something too. My bet is that any time you go under a bridge or beside a building that throws a good "echo" back, you give her some just to hear it. I've had mine over a year now and still do it.

 

[toddlnrd]

I will continue to monitor my interstate driving mpg's to see if there is something missing or if it is just me.

Thanks for all the responses.

Todd

 

[JiFaire]

hey Todd.. just curious..

Have you tried driving at different speeds now that you have the big exhaust?

Each vehicle has a happy spot for best mpg, and messing up the airflow equation affects that. BP is a function of volumetric efficiency in a confined space, no? You just changed the size of the space.

 

[Acesneights1]

You should be hand calculating your MPG. You might have your foot in it more to hear the great sounding exhaust. I know my MPG dropped when I strait piped my truck because I could not keep my foot out of it for about 3 weeks.

 

[iamdave0887]

You should be hand calculating your MPG. You might have your foot in it more to hear the great sounding exhaust. I know my MPG dropped when I strait piped my truck because I could not keep my foot out of it for about 3 weeks.

with the 4 inch stack on my truck i can't keep my foot out of it either, nor do i want too. :biggrin5: Video
god i love that sound. my mileage went up as well with the addition of my exhaust. the only thing thats hurt my mileage is the discount fuel stations, dirty fuel filter(goes from 17.5 mpg down to 15 mpg, sometimes less), and my right foot which can really kill MPGs at times. i try to do the speed limit(can't afford a ticket again) and i've found lat week when filling up that it was getting 17.52 mpg and that was with more city than highway driving(but some streets did have highway speeds and not so much stop and go).

 

[Matt Bachand]

I have never heard of a CAT gaining MPG

 

[toddlnrd]

My sweet spot with the old exhaust was about 70 mph. I will have to check and see what the new one might be. Good idea, JiFaire.

 

[JMJNet]

Scangauge is great, but it has to relearn. You have to go several cycle and religiously putting when you fill up and what pct. of original fill up to get to full.

 

[dur0maxx]

Todd, what was the weather like? When I had my old 2000 Z71 i would usually get 13mpg on a road trip. One day the same road trip I got 10mpg because of wind. Just a thought.

 

[hereismylife]

So how are you making out? Update?

How are you making out with the fuel mileage?

 

[VW_Lupo_TD]

With the cruise control on at 70 mph w/stock exhaust, I got approx 20 mpgs.
With the cruise control on at 70 mph w/new exhaust, I am getting approx. 18 mpgs.

Right foot is not in the equation. I am stumped!?

exact same load ??
meaning - road levelness, wind speed & direction, tire pressure, weight in truck ...

exact same engine efficiency ??
air temp, fuel quality, age of oil, ...

i would also use at least 2 tanks to measure mpg.
it gives you an average over your everyday load & driving conditions.
use same gas station and fill it up exactly the same (to click of nozzle) and then average it out ....

2/15/09 201697.7 512.6 fuel ULSV incl add full 31.602 16.22
2/8/09 201185.1 545.3 fuel ULSV incl add full 35.789 15.24
1/31/09 200639.8 544.6 fuel ULSV incl add full 36.059 15.10
1/23/09 200095.2 543.2 fuel ULSV incl add full 35.419 15.34
1/16/09 199552.0 558.0 fuel ULSV incl add full 35.203 15.85
1/7/09 198994.0 535.1 fuel ULSV incl add full 37.121 14.42
1/3/09 198458.9 523.3 fuel ULSV incl add full 30.781 17.00
12/8/08 197935.6 611.8 fuel ULSV incl add full 36.410 16.80
11/27/08 197323.8 537.8 fuel ULSV incl add full 32.044 16.78
11/17/08 196786.0 523.8 fuel ULSV incl add full 31.227 16.77
11/4/08 196262.2 645.3 fuel ULSV incl add 37.022 17.43
10/13/08 195616.9 608.5 fuel B20 incl add full 36.070 16.87
10/5/08 195008.4 539.3 fuel ULSV incl add full 30.268 17.82
10/3/08 194469.1 557.5 fuel B20 incl add full 31.944 17.45
9/24/08 193911.6 624.1 fuel ULSV incl add full 35.967 17.35
9/10/08 193287.5 531.7 fuel B20 no add full 31.755 16.74
9/2/08 192755.8 587.6 fuel B20 no add full 35.267 16.66
8/11/08 192168.2 417.9 fuel B20 incl add full 26.599 15.71

 

[bk95td]

No one has mentioned that by your sig. you still have the stock air filter set-up. The improved flow of the exhaust may be creating a lean condition that would require more throttle[works that way with gassers]. When I put banks exhaust on my 91 6.2 the instructios said to crank the pump up. I didn't do it right away and saw very little improvement in mpg. After I cranked the pump the mpg went up along with the power.
A reprogramed ecm with a higher fuel rate may give you better mpg.

 

[toddlnrd]

Wow! I almost forgot that I posted this.

My first two comparisons were trips from Garner, NC (just outside of Raleigh) to Gatlinburg, TN. First one with the old, stock exhaust and the second with the new warpspeed exhaust.

I calculate my mpg's with the scanguage, not with the "shut the pump off exactly the same way every time" method. I think the scanguage is more accurate. I takes out the idiot factor, me.

I just got back from the same trip 2 weeks ago (We really like Gatlinburg). I averaged 18.3 mpg's for the entire trip. Not too bad with the mixed driving around Gatlinburg/Pigeon Forge.

My air filter is the K&N round type. It was on the truck when I bought it. I would love to get the computer upgraded to the Heath GLE economy program and some new injectors. I have no idea how many miles are on these injectors (230,000 miles on the truck).