Wideband improvements in mpg?

[i82much]

Saw the "what do you drive to work" thread and noticed there were a few folks with longer commutes that seemed like they didn't use their trucks to commute for fuel economy reasons. Just curious if anybody has installed a wideband and managed to tune their truck to obtain a significant improvement in fuel economy?

[67ChevyRedneck]

A what?!?!?

[truckster]

He's talking about a wideband O2 sensor. It allows you to tune your air/fuel ratio more precisely.

[i82much]

Originally Posted by truckster

He's talking about a wideband O2 sensor. It allows you to tune your air/fuel ratio more precisely.

Exactly! There are some pretty impressive fuel economy gains to be had for some carbureted applications. Your average Holley that runs great at full-throttle is probably pretty rich at cruise, for example. Even a Quadrajet can be miscalibrated, although I guess they are probably less susceptible.

[msgdsrf]

Planning on welding in O2 bungs next week, so I'm going to find out. There's so much room in tuning by To lean if it stumbles, too rich if there's black smoke. I had a Dyno tune performed, but the results were so odd that I have no trust in it.

[burnin oil]

I really did not gain any milage for some reason. Maybe 1 MPG at best and I am still in the single digits. I did get the holley to stop murdering plugs. You could ring them out after a couple of days. My truck has always been backwards. I pulled a race cam out for another cam that was about 15* smaller. Lost 2 miles to the gallon with it. It was a modern grind to boot. I am hoping that OD will help as it takes alot to fuel 400 cubes at 3k+ RPMs.

[burnin oil]

I should also add that the monitor and a vacuum gauge make it easy to really tune the carb in. Especially if you are playing with the bleeds.

[Fatherof3]

I've read lots of good things about using a wideband 02 sensor and gauge to tune with in Hot Rod / Car Craft etc. Lots of good reads online about this.

[i82much]

Originally Posted by burnin oil

I really did not gain any milage for some reason. Maybe 1 MPG at best and I am still in the single digits. I did get the holley to stop murdering plugs. You could ring them out after a couple of days. My truck has always been backwards. I pulled a race cam out for another cam that was about 15* smaller. Lost 2 miles to the gallon with it. It was a modern grind to boot. I am hoping that OD will help as it takes alot to fuel 400 cubes at 3k+ RPMs.

What is your cruise A/F ratio? From what I gather, if you want good full-throttle numbers from a traditional Holley (12.5:1 or so), you will need to enlarge the PVCR's to also get good cruise numbers (15:1 or so).

[72MARIO]

I am planning on installing the auto meter gauge in my 67 this spring when I put the new 355 in it . I need every mpg I can get out of it.

[burnin oil]

Originally Posted by i82much

What is your cruise A/F ratio? From what I gather, if you want good full-throttle numbers from a traditional Holley (12.5:1 or so), you will need to enlarge the PVCR's to also get good cruise numbers (15:1 or so).

I would have to go back and check for the exact number but it is between 14 and 15. My carb is very modified. It started as a 3110-4 4160. Now it has the 4150 conversion with every passage drilled and tapped on the primaries. I can actually get it out to about 17:1 lugging around in 4th gear. Everything is about perfect other than some minor tweaking of the accelerator pump. Tomorrow I plan to switch cams and I can start all over again.

[i82much]

Originally Posted by burnin oil

I would have to go back and check for the exact number but it is between 14 and 15. My carb is very modified. It started as a 3110-4 4160. Now it has the 4150 conversion with every passage drilled and tapped on the primaries. I can actually get it out to about 17:1 lugging around in 4th gear. Everything is about perfect other than some minor tweaking of the accelerator pump. Tomorrow I plan to switch cams and I can start all over again.

Huh. I agree, that seems like bad gas mileage for a pretty good A/F ratio.

I am personally trying to get my 396-powered K10 into daily driver shape. Been doing some research about fuel economy and your post makes me wonder:

(1) Do you do a lot of short trips?
(2) Cold weather?
(3) Do you have a working heat riser valve in your exhaust and is the intake crossover functional?
(4) Do you have a working thermostatic air cleaner with the heat shield on the exhaust manifold?
(5) Do you have a working heavy-duty clutch fan?

My truck lacks all of (3)-(5) and I do short trips in cold weather. I think right now I am getting about 7 mpg, but I've only had the truck a month or so and haven't gotten a wideband in it yet.

[DGulliver]

Well, this is an interesting thread.. Its pretty hard for me to imagine that anyone with MPG worries would even consider driving anything like these old trucks with a V8 in it. After all, you're not going to set any gas miser records, even with fuel injection and an overdrive. There's lots of other vehicles to choose from if fuel mileage is a major concern.

I can understand wanting to have your running gear in proper tune -but beyond that, it doesn't make much sense to me to expect any spectacular fuel mileage from an old hot rod truck.

Of my 7 cars and trucks, only 1 gets over 14 mpg. I just put the gas in and ride and enjoy the V8..

[i82much]

Originally Posted by DGulliver

Well, this is an interesting thread.. Its pretty hard for me to imagine that anyone with MPG worries would even consider driving anything like these old trucks with a V8 in it. After all, you're not going to set any gas miser records, even with fuel injection and an overdrive. There's lots of other vehicles to choose from if fuel mileage is a major concern.

I can understand wanting to have your running gear in proper tune -but beyond that, it doesn't make much sense to me to expect any spectacular fuel mileage from an old hot rod truck.

Of my 7 cars and trucks, only 1 gets over 14 mpg. I just put the gas in and ride and enjoy the V8..

Everyone's situation is a little different. My round-trip commute is 12 miles. I can get away with a vehicle that gets 10 or so mpg. It is a little tougher to stomach getting 7 mpg.

Right now, I have a 2013 Jeep Wrangler Unlimited that gets about 14 in town, my new-to-me 72 K10 396 that seems to get about 7, and my 505 CID 65 GTO that gets about 10 or 11.

If I can get my K10 up to 10 mpg or so with a wideband and some other changes, then I won't feel so bad driving it to work quite a bit. Save some miles on the Jeep, the resale I save on the Jeep might even make up for the fuel $ I spend driving the truck.

I have not considered driving an economy car, but I'd like to be able to say with a straight face that my K10 is as reasonable of a daily driver as my Jeep. I can't say that yet, but I have some ideas.

[burnin oil]

No my truck has none of the things you outlined. 400sb with performer RPM and headers. Only the block and distributer housing is stock. Definatly not a fuel efficient setup but should do better. My blazer in HS got 10-14 with the same drivetrain other than axles with a similiar 400. It had a little less cam and 1/2 point more compression on iron heads.

My normal commute now is around 10 miles each way but not long ago it was around 45 miles a day. Either way lots of traffic and higher speeds. This K20 got 14mpg on the way home but the motor let go not long after that. Getting her back to 10mpg is all I want considering I am pushing over twice the HP of the original 350. 220 miles on a 31 gallon tank gets old. My 5500 diesel 4x4 with 4.44 gears gets 11mpg with over 400hp. The diesel with over 20k lbs in tow gets what my K20 gets every day. It shouldnt be cheaper to drive the mini semi!

Woke up sick this morning so no work. Hoping tomorrow lets me get the cam swapped.

[dznucks]

A wideband can be used for fuel economy improvements, but its easy to go too far and burn up pistons if you dont know what you are doing. its also easy to get mislead by what the wideband is telling you. The wideband sensor is measuring the oxygen (O2) in the exhaust, not the actual air/fuel ratio.

Incomplete combustion due to weak ignition will make the sensor read lean due to more oxygen in the exahust. you will tune the carb accordingly and keep chasing your tail.


I have been running one in my truck for years. i use it primarily carb tuning. When you get each stage (primary, secondary, accel pump, etc) of the carb tuned, overall your efficiency will improve.

[burnin oil]

That is very true. It has been cold around here in the mornings. For the first couple of minutes my AFR reads 15-16 with the choke on. Once it warms up a little and the idle stabilizes it will be in the 10s. All this is just sitting in the drive way. A leak in the exhaust will also show lean. I just went through the dizzy so weak spark is out unless I add a MSD box.

I got the cam swapped out yesterday and drove her gently home. AFR was in the 18s at idle. Only a couple of mile trip so when I got to the driveway she was warm enough to reset the curb idle screws. Idle AFR was 13.4 then. Much better. A quick blast up the road showed lean but safe witn no detonation so I gave her a WOT pass. full throttle was mid 13s so it will need richened up all around but power was definatly up. Pedal to the metal hit fourth gear at 72MPH. The wife thought we were only going 50. That put a smile on my face. Not to shaby for an old K20 with 4.10s. I still need to reset the timing then get some good AFR tuning going.
I think the MPG loss was due to off idle torque. This bigger cam has more pull down low. Funny it takes more to idle and has 5-6" less vacuum. Right off the clutch it surges at a steady throttle. 270/274 duration solid cam installed 1* advanced. I figure this will give the OP something to enjoy.

[i82much]

Originally Posted by burnin oil

That is very true. It has been cold around here in the mornings. For the first couple of minutes my AFR reads 15-16 with the choke on. Once it warms up a little and the idle stabilizes it will be in the 10s. All this is just sitting in the drive way. A leak in the exhaust will also show lean. I just went through the dizzy so weak spark is out unless I add a MSD box.

I got the cam swapped out yesterday and drove her gently home. AFR was in the 18s at idle. Only a couple of mile trip so when I got to the driveway she was warm enough to reset the curb idle screws. Idle AFR was 13.4 then. Much better. A quick blast up the road showed lean but safe witn no detonation so I gave her a WOT pass. full throttle was mid 13s so it will need richened up all around but power was definatly up. Pedal to the metal hit fourth gear at 72MPH. The wife thought we were only going 50. That put a smile on my face. Not to shaby for an old K20 with 4.10s. I still need to reset the timing then get some good AFR tuning going.
I think the MPG loss was due to off idle torque. This bigger cam has more pull down low. Funny it takes more to idle and has 5-6" less vacuum. Right off the clutch it surges at a steady throttle. 270/274 duration solid cam installed 1* advanced. I figure this will give the OP something to enjoy.

Yeah I have a 65 GTO with a 505 CID, solid roller 242/248 @ .050, probably advertised in the 286 range, with a single plane, spacer, Holley 850. It is kind of fussy but it sure gives me a thrill.

The truck is a totally different deal, pretty sure it is a stock 1966 396 out of a Chevelle or something. I want to keep it completely stock, no funny business, dead-on reliable and never any trouble. Honestly, if someone had a fresh 350 and wanted to do the work of swapping them out, I'd let them have the 396 and run a small block. I don't need a ton of power, I just want a reliable daily and to keep some miles off of my Jeep.