Fuel Mileage

[cudabob496]

Where do you place the sensor? I was driving with my buddy in his '78 Z28 383 stroker. We had a roll on at 50 mph and I smoked him easily. I have to tell you, that felt great!

Summit has kits. Sensor goes on header collector. No need to weld bung, they have strap on bungs now.

[rUNCHARGER]

With the Fitech you can watch your AFR's on the screen and set the target AFR's if you wish.

Sheldon

[john h]

thanks for all the replies.  I did not mean to complain.  I just wanted to see if everything was where it should be and it sounds like it is.  I did about a 300 mile trip right after I posted that and I got around 15.  Same thing, county roads and a little free way where I was doing 65 or so.  I assumed with running 14.4 AFR it was not going to get better that than unless I had some issues with spark, but it runs well so I'll leave well enough alone.  I have considered putting the gear vendors OD unit in but I just don't know if it's worth the money for a car I drive 2500 miles or less a year.

John

[EMCD]

I've thought of the GV unit myself. However, your payback period for the $3k unit verses the 6-8mpg is 2 decades long at 2.5k miles a year.

[rUNCHARGER]

Yup; You can buy a lot of gas with that $$$. It sounds like you have it running right so that's what counts.

Sheldon

[Katfish]

It doesn't make sense financially, but no way I would drive my car 300 miles w/o OD.
Turning 3500-3800 on the hwy just doesn't cut it.

[rUNCHARGER]

I dunno: In the 70's I drove this one to work 100 miles each way a few times. No heater 4.56 gears. We were hardcore back then.

Sheldon

[john h]

Summit has kits. Sensor goes on header collector. No need to weld bung, they have strap on bungs now.

I am using a bung with straps for the O2 sensor.  I was skeptical but it really does seal nicely with no leaks.

John

[74BlueFish]

Just got back from Don Garlits car show.

70 mph 1700 rpm and 17 mph with A/c on.

505 stroker, 3.55 gears and Viper T56 with a .5 overdrive

Put 600 miles on it, even at 80 it was 1900 rpm and 16 mph

[moper]

496", 590hp, runs a Holley 950HP, 727, 2500 stall, 3.23s, in an E body gets 15mpg mixed (mostly highway on that - driving to and from the track.
422" small block, apprx 450hp, runs an 870 Avenger Holley, 727, 2200rpm stall, 3.23s in an E body gets 17.5mpg mixed driving.

I feel you should be at 20, possibly more if you can drive it economically. Check your tire pressures and alignment too. But my impression is your ignition advances are not optimized. I don't know enough about your EFI, but check the total timing at light throttle cruise. Both of those cars I mention run a functional vacuum advance and optimized curves in their distributors. The right amounts of advance are your friend - not a hinderance to performance like many think.

[shadango]

Summit has kits. Sensor goes on header collector. No need to weld bung, they have strap on bungs now.

Where did you see the no-weld bungs? Wonder if they are reliable?

I have thought about adding an AFR meter but shied away due to price and the need to weld.....and there are a TON of different vendors/manufacturers out there....any difference between them?  Is "data logging" worth having?

Also wondering -- is having it on one header collector really accurate since you are only monitoring half the cylinders?

As far as the OP question --- I have consistently gotten 8-10 mpg in my fish around town...maybe 11-12 highway......its a 318 block, Eddie 600 cfm 4bbl, J heads and a big purple cam, 3.55s, 727 with a 2400 stall.....I never thought my mileage was that bad considering my 92 Dakota magnum 318 with an OD tranny and 3.90s and my 03 Durango with OD and 3.90s got about 10 around town too.   My wife could get 12 in the Dakota and Durango.....I have a fat right foot.  LOL  And in the fish I am ALWAYS lead footing it...LOL

Around here we have lots of hills and mountains so that is part of it....

Another thing i wonder is --- is everyone who is posting MPG numbers sure they have accurate odometers/speedos?    Just changing the rear tires up or down a size affects overall speed indicated and of course odometer......

Just sayin.