I put a 4" cat back exhaust with a donaldson straight through muff. everything else the same and lost about 2mpg. 20 down to 17.5:( any ideas on what gives.

05lly

emissions issue? your right foot?

Get rid of the cat. oh wait your in the peoples republic of Kalifornia, you might need to check your emissions standards as far a diesels go. Im not sure how much of a positive difference your going to see without cutting the cat out.

Yeah, but should he see a negative difference with a 4" exhaust? This is a surprise to me, too (unless, as nekkidhillbilly suggests, he's now putting his foot into it (I am diesel; hear me ROAR)).

Joseph

ya when i got my exhaust put on my milage dropped also i found out it was due to me wanting to hear the exhaust and turbo whistle:eek:.dam simple things that make me happy:D

Yep,right foot problem

me wanting to hear the exhaust and turbo whistle:eek:.dam simple things that make me happy:D


:funnypost

Ain't that the truth! Me too...

I actually lost exactly 2mpg, after the 4" went on.I noticed it right away.

I'm lucky to get 14.5 mpg :damnit1:

Hmmm, gonna have to suggest right foot as well. With my truck "factory" I got 15 mpg. I found that adding a fuel additive actually raised mileage to 16 mpg. I added a "cat free" exhaust and air intake at the same time that netted about 17 mpg. With my stacked programs added to the mix I average 18-19 mpg all the time...highway...city...whatever...UNLESS I generate big black clouds or cruise over 85-90. ;) Truck sits just over 30k miles right now.

My right foot is the culpurt for my greasel milage being so low.Nobodys fault butmy own.If you want milage ,the d max aint it.Its for towing and such.The city stop and go milage goes way down.I love my D-max no matter what the mpg.Ive excepted the mpg as part of the truck.It does what i want and thats all that matters to me anyhow.I spend $50 a day on fuel 6 days a week.

My right foot is the culpurt for my greasel milage being so low.Nobodys fault butmy own.If you want milage ,the d max aint it.Its for towing and such.The city stop and go milage goes way down.I love my D-max no matter what the mpg.Ive excepted the mpg as part of the truck.It does what i want and thats all that matters to me anyhow.I spend $50 a day on fuel 6 days a week.
:eek::eek::eek:

my milelage got better. 18 to about 22 now. i also lost my kiity and have a tuner. i only get on it sometimes. but when i first cut off my kitty. deffinately right foot problem.

I put a 4" cat back exhaust with a donaldson straight through muff. everything else the same and lost about 2mpg. 20 down to 17.5:( any ideas on what gives.

05lly
killl the cat!!!!

Its OK to take off the cat in Cali they did not start checking SMOG on diesels until model year 2007 and later.

What brand of exhaust?

I put a 4" cat back exhaust with a donaldson straight through muff. everything else the same and lost about 2mpg. 20 down to 17.5:( any ideas on what gives.

05lly


How far north in Northern Cali do you live in? Is it posible that you got the first batch of winter fuel?

the sound is more tempting now

Winter fuel?

I put a 4" cat back exhaust with a donaldson straight through muff. everything else the same and lost about 2mpg. 20 down to 17.5:( any ideas on what gives.

05lly
programer? i stack two.

:eek::eek::eek:
not true. 8000 lbs, 20 plus,500 hp wheels. beat that! with a gasser, forget it.

Its OK to take off the cat in Cali they did not start checking SMOG on diesels until model year 2007 and later.
take it all off.let gm figure it out,

I put a 4" cat back exhaust with a donaldson straight through muff. everything else the same and lost about 2mpg. 20 down to 17.5:( any ideas on what gives.

05lly
go t back, the engine will love it. get a programer too.

a mechanic friend suggested that less back pressure might affect the egr amount. To me seems like timing is slow. Does dropping cat do it or is a 4" pipe necassary too?

My right foot is the culpurt for my greasel milage being so low.Nobodys fault butmy own.If you want milage ,the d max aint it.Its for towing and such.The city stop and go milage goes way down.I love my D-max no matter what the mpg.Ive excepted the mpg as part of the truck.It does what i want and thats all that matters to me anyhow.I spend $50 a day on fuel 6 days a week.
i have b dog stacked with hypertech still get over 20 on hwy. empty. 4 inch, and air.

a mechanic friend suggested that less back pressure might affect the egr amount. To me seems like timing is slow. Does dropping cat do it or is a 4" pipe necassary too?
get rid of egr, and pcv. then it will live

a mechanic friend suggested that less back pressure might affect the egr amount. To me seems like timing is slow. Does dropping cat do it or is a 4" pipe necassary too?
get rid of egr, and pcv. then it will live type in kennedy diesel. he can fix for under 200