MIELAGE.. sucks

[Aloicious]

after the collectors? sure, it depends on where your front O2 sensors are located, in a stock truck they're a little ways past the manifold collectors. and technically an exhaust leak up to a foot or 2 AFTER the O2 sensor can have a little effect on them. so even if you have the sensor mounted before the collector, it could be causing an issue.

 

[Hezsus]

oh ok, i dont have anything that close, my 02s are in the collectors but nothing leaks till like 4' after.. thats where the piping got hairy lol

 

[Aloicious]

ah yeah, I see what you're saying, so that far after the collector shouldn't affect them any noticable amount, but a leak at the heads or at the collector will.

 

[Kamml]

My 97ecsbZ71 350 Vortec, auto 3.73 rear, stock exhaust gets 14 city and 18 highway on 87oct. The first tank of gas after purchase was 12 mpg period, but following air and fuel filter changes, trans and diff fluid changes and getting rid of the 420 CEL code with an exhaust repair the mileage went up to tolerable now. But gas was at $3.33 a gallon tonight so I may have to start driving the Camry more to keep my costs down a little.

 

[Hezsus]

My LTFTs are not too far off, after about 5-10 min of driving bank 4 (theres a bank 4???) is way off, everything else around like -4 but bank 4 would be like -24. after more driving they all seem to even out (diference of no greater than 5 or so)

 

[Aloicious]

-4 is pretty good. I don't know what this bank 4 is. you should have banks 1 & 2 and sensors 1&2 on each bank.

 

[FastOrange]

i get about 8-10MPG. but the carb and big cam dont help anything.

 

[Hezsus]

-4 is pretty good. I don't know what this bank 4 is. you should have banks 1 & 2 and sensors 1&2 on each bank.

hmm, it must just show up diferent, its giving me bank 1-4. mabye 12-13mpg is just all i can get how i'm setup now. i'll go over everything again just ot be safe though.

 

[Klumpper]

You mention your advance at idle is 20-25 degrees. What is your advance when on the highway??

Mine is also the 22-24 range at idle (550rpm in gear) but it only runs 25-26 at speed, which is no where near advanced enough to produce optimal combustion pressures.

I'm getting the same 12-14 no matter how it's driven (save for the twice I broke 14.5). L31/4l80/4wd/4.10 gears/255-85r16 tires. 63 or 93mph cruise, it doesn't care. No cats, but I do believe my muffler to be partially plugged from the cats letting go.

In the upcoming weeks I'll be performing the 411 swap, adding timing, and learning some tricks about it before removing it for a 496. Hopefully I'll figure out where it really likes to run and get back to ya. 90 miles a day eats up fuel in a hurry.

 

[Hezsus]

You mention your advance at idle is 20-25 degrees. What is your advance when on the highway??

Mine is also the 22-24 range at idle (550rpm in gear) but it only runs 25-26 at speed, which is no where near advanced enough to produce optimal combustion pressures.

I'm getting the same 12-14 no matter how it's driven (save for the twice I broke 14.5). L31/4l80/4wd/4.10 gears/255-85r16 tires. 63 or 93mph cruise, it doesn't care. No cats, but I do believe my muffler to be partially plugged from the cats letting go.

In the upcoming weeks I'll be performing the 411 swap, adding timing, and learning some tricks about it before removing it for a 496. Hopefully I'll figure out where it really likes to run and get back to ya. 90 miles a day eats up fuel in a hurry.

My timing does rise on the hwy, probably +30 or better. i'll get some exact numbers for ya when i can. yeah it dosent matter how i drive either, my 12-13 is highway too, it only sees a little bit of town. i noticed while a slow down, throwing it into neutral about doubles the mileage while slowing. a 496 would be sweet, i def wanna see that build. i may have clogged mufflers too.. they're flomasters so they pretty well come clogged lol.