hin532

I installed my headers 2 weeks ago and have gone from 13 to 10mpg. I have Pacesetter LT's with 3" ORY. I dont have any exhaust leaks and did'nt notice any power gain. I contacted Justin to see if it needed a retune and he suggested that the headers could be too big for my truck. I sent him a data log and am waiting for him to get back with me. So is the 3" y too big for my truck or is there some think else going on? The truck is in my sig.

BOSS302

Re-tune, it will make all the difference in the world.

TXSZ66AVLANCHE

iTrader: (7)

Adding performance mods will drop mpg, just part of the game.

BigDaddy0381

iTrader: (7)

now my truck is on 35 inch tires. I swapped to 4.56 gears,HT1 cam, had it tuned and it picked up 2mpg went from 15 to 17. I added SDPS cnc heads 1.8 roller rockers. pacestter LT's and y pipe and it dropped to 14. I thought I was headed the right way for mpg when this adventure started for mpg's.

06Sierra2

my truck gets about the same mpg as it did stock, IF i keep my foot out of it. it mostly has to do with a well combined setup and spot on tune.

1CLNY2K

iTrader: (4)

I am getting about 16.8 MPG with my truck and I have OBX knockoff longtubes. Now mine is a 5 speed manual so I am sure that helps, but I also have 295/70/17's with a 230K mile old 4.8.

AndysC3

iTrader: (14)

My truck got the same MPG before and after my headers. On a mostly stock 5.3 you wont notice much of a gain. Maybe 10-15hp. add a cam, and a better intake manifold like the tbss intake it will be more noticeable.

andrew383

iTrader: (14)

What size did you go with and has it been retuned yet?

Since when? Any mild setup thats not a strip queen will yeild stock or higher mpgs with good tunes,its been shown many times on here..
A stock truck with just headers isnt going to loose mpgs

hin532

They are pacesetter 1 3/4" primaries and 3" y no cats. Engine is an lm7 and is mostly a stock setup besides exhaust and tune. I plan on doing a cam and stall converter by fall I'm just starting to look for parts to slowly peice together everything I need.

I emailed Justin with BlackBear and asked him if I needed a retune for the headers early last week. I also asked him to check out a data log b/c my commanded afr would command odd ratios. He told me the odd commanded afr issue probably needs the cat test disabled. Haven't heated back from him again but I will see.
I drove it to San Antonio today and I picked up some hwy mileage! I went from 18 to almost 19 running @ 80 and 89 octane! My city mileage is at 10.8 from 13 running 93 octane. I will post up my mileage running around in San Antonio and post what Justin has to say when he gets back with me. Thanks

andrew383

iTrader: (14)

Headers need a retune to gain there worth so i dont know why he's leading you to think its something else or something is wrong