• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

New Exhaust/Worse Mileage?

toddlnrd

toddlnrd

My first diesel!
Messages
208
Reaction score
11
Location
Garner, NC
This question was asked over at the other "Place" with no real explanation.

I finally got my 4-inch exhaust installed a few weeks ago. I have been able to take a couple of lengthy trips since then.

Why would my highway/cruise control fuel mileage be down with a more free flowing exhaust? (approx. 1-2 mpg's, measured with my Scanguage)

Todd
 
toddlnrd said:
This question was asked over at the other "Place" with no real explanation.

I finally got my 4-inch exhaust installed a few weeks ago. I have been able to take a couple of lengthy trips since then.

Why would my highway/cruise control fuel mileage be down with a more free flowing exhaust? (approx. 1-2 mpg's, measured with my Scanguage)

Todd
Click to expand...

Strait Piped??? No cat????
 
Sometimes different fuel sources can mean the difference in mileage. I had that happen to me. You shouldn't be getting poorer mileage due to the exhaust change in itself, unless you need to set up you T/M differently or something simple like that. I saw a nominal increase in mileage and power due to quicker turbo spool.
 
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 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!?
 
I get worse MPG using cruise controll.

How many tanks for fuel did thi happen with. I have had bad fuel that I have gotten sh ity fuel miliage with.
 
I will need to do a more controlled test, with the same fueling station on several different runs down the interstate. It would cost nearly $200(maybe I should get a 3rd job) to fill up the tank to check mileage, but I do have a Scanguage that tells me the instantaneous mileage as well as trip mileage. In my opinion the gadget takes out the human error potential in the hand calculation.
 
How can you screw up hand calculations if you went 410 miles and when you filled up you put 20 gallons in your tank all you do is

410 divided by 20 which is 20.5 miles per gallon

It is pretty hard to screw up.
I do not trust the computer sh it for this kind stuff my DIC is way off it says I getting 17MPG when I am getting 23MPG.
 
I totally agree with the 410/20=20.5 calculation method, what I was talking about was the potential error in filling the tank the exact same way for several fills (I really don't want this to turn into a tank filling discussion)
I do trust my little gizmo, because I have tested it on other vehicles.

BTW-what is DIC?
 
In your sig, you´ve got new tires and a tranny rebuild. Any chance they come into play with your before and after #´s?
 
Todd trust me put the cat back on. Hand calc is the best method but the tool you are using has been accurate in the past from my expierence also.
 
Larger system correct? Less BP the Cat will increase your BP slightly and increase milage. On a smaller system you won't notice the cat MIA.
 
More BP = more mpg & put cat back on, Ummm I got to disagree most wholeheartedly,

the whole discourse in the turbo thread using a different turbo, was to drop BP, with TD07 turbo less BP Slim & I both have improved mpg using 4" exhaust and less BP turbo,

The cat on the 6.5 isn't a cat in any sense of the word, they are soot traps, that often plug as exhaust of 6.5 Diesel especially after turbo isn't hot enough to "cook-off" residual fuel and other hydrocarbons, more than one gutted cat has been gutted out of necessity as no light much less exhaust gass pass through it, they get so clogged.
 
Last edited:
I do agree in a sense but Have seen this also work on many occassion.

I'm willing to put a beer on it if you wanna put it on and give it a shot.


Maybe he's just happy with the newfound sound and his right foot has been happier then normal:sifone:
 
Ragin,
That may be your experience and I cannot dispute realworld experience.

But I can tell you that w/ the cruise control set, my right foot does not play a part in the equation.

BTW-I do like the new sound and turbo whistle!!

Todd
 
You must log in or register to reply here.
Back
Top