Fuel Economy

ClassicBronco25 · Nov 15, 2010

I would like to make a bronco a daily driver but the low fuel economy is a let down. I know its not capable of getting anything high but im looking for somewhere in the range of 15 mpg. Any suggestions on how to make a bronco get better mpg?

Looking around the internet i heard some ideas like dropping in a new ford ecoboost and completely changing everything. Im not even sure if that is a viable option.

Bronco_69 · Nov 15, 2010

89-93 mustang efi

or get very good at carb tuning. no lift and small tires help alot.

73azbronco · Nov 15, 2010

small highly inflated tires, take every once of weight out of it, stay below 50mph, keep your foot out of it, coast to every light. You might get to 15mpg.

TN1776 · Nov 15, 2010

Mildly built 302 with EFI and an overdrive tranny, light foot on the throttle, smaller tires, no lift.

This being said, my carb'd 351 with an NP435, 4.11 gears and 37"tires will get 12-13 as-is on the highway.

1970mule · Nov 16, 2010

but you think how much one of those new ecoboost engines cost and how much you spend on gas a year. it will take you 30 years to make up the difference in mpg offset, so like said do a efi mild 302 with od trans. and you should get close to 15 if not better if you drive like granny

DirtDonk · Nov 16, 2010

Years as a daily-driver, 10-11 around town, 14-15.5 on the road at no more than 60 mph. Very consistent.
For a few months, I got 12 and 17.5 respectively, but that was with a super-small venturi 450cfm Holley "Economaster" emissions replacement carb. Only kept it for a short time, because it just didn't have the ooomph when I pushed it. It'd snap your head back from a stop, and got great highway mileage. Loved the throttle response, and for the first time ever I didn't even have to give it gas when I let out the clutch. But I sure did miss the power, so went back to a Carter 500.

Oh, stock height, then 2" lift. 32" tires and 4.11 gears.

Paul

shamu · Nov 16, 2010

I went from 10mpg to 5mpg. I started off with 32x12.50x15 w/3:50 . Now 35x14.5x15 w/4:30 gears. It is a good ride when you can pull a second gear scratch with a c 4 and a detroit.

blubuckaroo · Nov 16, 2010

Set up your gearing and tire size so your motor's maximum torque RPM comes in at your cruising speed. BTW, anything over 60 mph and you won't get the mileage your after so set up for around 60-65.

broncnaz · Nov 16, 2010

15 mpg or even a little more is very doable in a bronco. The engine needs to be tuned correctly no matter what. Jetting timing ect. Next gearing and tire size is also a key factor If your engine is pretty much stock then you need to keep the tire size and gearing close to stock. I'd go no bigger than 33in tires and 3.50 gearing.
If your wanting to tear intot he engine then some mods will help aminly a camshaft picked for the RPM range you will be driving at with your gearing and tire size, next on the list would be a good exhuast system then a 4v carb swap as was said carb size at about 500 cfm is good. Next make sure your iginiton advance curve is optimized all your timing advance should be in by 3000 RPM. All these mods are really needed in conjunction with one another to get the most efficeincy out of your engine.
My 73 with 2.5in lift 33in tires 3.50 gears and a slightly built 302 with a 525 cfm carb pulls 17 mph at 65 mph and 16 at 75 mph as long as I dont have to buck the wind.

Many people will say go EFI but EFI alone doesnt always result in mileage increases unless your engine is way out of tune. With a EFI swap alone I would only expect maybe 1 mpg increase.

70_Steve · Nov 16, 2010

broncnaz said:
Next make sure your iginiton advance curve is optimized all your timing advance should be in by 3000 RPM.

In addition to the mechanical advance curve, make sure you"re running a distributor with vacuum advance, and that it functions properly.

Stoneman · Nov 16, 2010

I have 35" tires, lifted, 351W (carbed) with an AOD and 4.56 gears. I'm getting around 8 mpg....mostly hwy. I was hoping for closer to 13. Would going to 3:50 gears make a big difference in fuel economy?

bmc69 · Nov 16, 2010

Stoneman said:
I have 35" tires, lifted, 351W (carbed) with an AOD and 4.56 gears. I'm getting around 8 mpg....mostly hwy. I was hoping for closer to 13. Would going to 3:50 gears make a big difference in fuel economy?

Could make it worse actually...probably would make it worse. You would be turning the 351 way to slow and far off its design point for max efficiency.

I get an astounding 10 mpg highway with my trail rig..injected 408c/T-18, 4.88 gears and 39.5 radial IROKS...heavy with extra junk too. I say astounding because I never expected much more than 5 or 6..?:?

The best I ever got from either of my daily drivers was 15 (occasionally..13 more reliably) from the 250 6-banger '69 half cab on 35s with 4.10 gears. My other DD..a '68 with 302 and 31's (also with 4.10 gears) got around 12 mpg. Both my DD's had the stock three speed trannies.

Devin · Nov 16, 2010

These threads always make me laugh. Fuel mileage......Early Bronco.....bwahahaahhahaahahahhahaha.

bmc69 · Nov 16, 2010

Devin said:
These threads always make me laugh. Fuel mileage......Early Bronco.....bwahahaahhahaahahahhahaha.

tru dat. It's like the sailboat guys arguing over whose is fastest. Deys all slow..just somes not quite as slow as others.

pcf_mark · Nov 16, 2010

As someone pointed out a properly connected vacuum advance on a properly tuned engine can make a big deal. I put a vac can in a car with stupid large cam/heads/exhaust/gears and went from 8 mpg to 12 mpg!

When you have light load, low throttle you can put in a lot of advance (like 45 degrees!) and burn a very lean mixture to save fuel. You will need to tailor your accel pump to handle this too.

Has anyone tried a lower front air dam? Under the bumper, make it about 6-8" and I get your highway mileage goes up. The Bronco is a brick but if you can keep the air out from under it it will help a lot. Maybe I need to try that next summer on a drive to the beach...

Explorer · Nov 16, 2010

It's comparing apples to oranges, but I'm getting over 18mpg with the engine in sig line. But I feel sure that would lower considerably with straight interstate speeds. She'll cruise 70 easily, but I rarely drive over 55.

jpalmer · Nov 16, 2010

20MPGs on 37"s at 5,000 lbs, but it's not a route for true Ford guys. Not wanting to start a bashing thread, just chiming in to the OPs question.

bmc69 · Nov 16, 2010

Explorer said:
It's comparing apples to oranges, but I'm getting over 18mpg with the engine in sig line. But I feel sure that would lower considerably with straight interstate speeds. She'll cruise 70 easily, but I rarely drive over 55.

An engine that is seriously built and tuned to achieve a volumetric efficiency near 100% and matching that narrow RPM band exactly to desired cruise speed?..yes..I can see that kind of number not pushing my engineer's BS button.

Per my earlier post..I have a beast of an engine in a beast of an EB that gets 10 mpg at 60-65 mph.

Dave · Nov 16, 2010

The transmission is the key! My Bronco getting over 30 MPH with one of these new hybrid transmissions.

[youtube]yjXTOlsE8k0[/youtube]

When my 73 was only a couple years old (14,000 miles 302 / C4) and bone stock except for 31/10.5s, it got in the mid teens as a good average. Generally drove the speed limit and schlepd camping gear and kayaks up and down about every road in the rockies. I remember how horified I was with the milage on my new 83 FSB at 10-12 mpg when I replaced the EB. Mid to high teens is very possible an doable.

About 7 years ago I made some mods to my 83 FSB as I written about before.

http://classicbroncos.com/forums/showpost.php?p=1575305&postcount=1

blubuckaroo · Nov 16, 2010

Devin said:
These threads always make me laugh. Fuel mileage......Early Bronco.....bwahahaahhahaahahahhahaha.

Laugh if you want but it's an important subject. I get a regular 15-16 mpg. If I had to live with 8-10, on a daily driver, like some, I'd have to sell. This thing has to pull its weight. I can't afford it as a toy.

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