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Improve Fuel Economy on 360

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FASTNASH View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FASTNASH Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 7:19am
What is your driving habits if it's full thottle and stop. That won't help either? Depending what ever do to engine or fuel delivery? How drive the car has lot ot do with it. Would like to know what is very day car is because what ever person have that car like 4 cyl, that 360 can feel rocket ship that won't help either, Because love feel of that power and dual exhaust could make your gas MPG go down. Had people this year at shows said i don't get any gas MPG. See how leave show field and pull out from ever stop. Then you go that's why they don't any MPG. Fun factor comes in? So cost money like everything else.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gwryder Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 7:36am
Originally posted by bigbad69 bigbad69 wrote:

Originally posted by gwryder gwryder wrote:

Years ago, for a project with one of my electronics classes, I made a poor fuel economy minder. Mine used comparators, a vacuum can to turn on a red, yellow or green LEd depending on the manifold vacuum.

 A simple one can be made with a vacuum can, micro-switch and LED. The idea behind this is to have the LED turn on when the vacuum drops to the level the carb's power enrichment system comes into play (~ 8-10"Hg). I put mine on a 1980 Pontiac Phoenix and it worked really well, but was hard to drive without the LED coming on.
My old 82 Caprice had a simple vacuum gauge as a fuel economy meter - no LED, just an analogue sweep. If I kept the needle at max as much as possible, the vehicle's fuel mileage went up.

I found that out too. Driver technique is the best improvement in fuel economy one can make. Add that to some of the techniques talked about here and fuel mileage has got to increase dramatically. Too bad it's the least amount of fun.

Basically, driving by a vacuum gauge is the same thing. Using a light throttle and drive by highest vacuum, one can achieve respectable mileage. My Silverado with the 5.3 and 6 speed auto averages 18.7 mpg. I drive lite and mostly rural driving, so driving technique and minimum stops makes a big difference.


Edited by gwryder - Nov/25/2012 at 7:38am
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Post Options Post Options   Thanks (2) Thanks(2)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 8:40am
Best way to increase mileage is to cheat when doing the calculation, its what most guys do when the want to brag about how good their tune is.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nda racer Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 9:50am
Originally posted by tsanchez tsanchez wrote:

Best way to increase mileage is to cheat when doing the calculation, its what most guys do when the want to brag about how good their tune is.
 
Yep, everybody gets 20+ mpg till you go cruising with them. Or change your rear gear ratio from 2.87s to 3.54s and not change the speedo gear to match.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smills61074 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 10:22am
I definitely agree with mileage being linked to driver habits.  I have a 1993 Cadillac Deville.  It has a instant MPG gauge as well as total MPG.  It definitely teaches you to have a light foot.  Although it is electronic, I assume the instantaneous works off vacuum.  You can see what happens when you leave a stop sign with your foot down, or ease away from a stop sign with a light foot.  I have filled the fuel tank until I can't put anymore in (full up to the neck).  Then I have driven a tank full and refilled it the same way.  This is how to accurately check your mileage.  Believe it, or not, the gauge on the Cadillac is right on.  The car has 230,000 miles on it.  I just drove 1200 miles to Nashville and back.  I averaged 24.5 miles per gallon overall.  In Nashville, I put a can of Seafoam in the Cadillac and a right hand drive Subaru that we picked up for my wife's mail route.  We had to stop about every 275 miles to fill my wife's Subaru up.  The last tank, I actually used less fuel than the Subaru.  The Subaru got 27.3 mpg and the Cadillac was right at 28.  Each had been filled up to the neck each time.  Not bad for a V8.  Cadillac's are deceiving.  The car has plastic fenders, aluminum heads and only weighs around 3600 lbs.  But a light foot is the trick.  So, driving habits play a big role no matter what you are driving.    
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Charles Smiley Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 11:04am
I always blamed the mileage drop on them sitting in the other seat and adding too much extra weight.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Charles Smiley Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 11:11am
I have a '83 Jeep J10 with a 360/auto and Selectrac. On a few trips from LA to Contra Costa county I nursed the throttle (visualizing a vacuum gage) and I got 17.7 mpg. That was with a load of car parts and a passenger. I kept the rpms at 2500, or below, and that was a little over 55-mph. I consider that a record. Any faster and the mileage would plummet.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gwryder Quote  Post ReplyReply Direct Link To This Post Posted: Nov/25/2012 at 2:11pm
I'm not sure if the cheating comment was directed at me, but below is from my Silverado's display of average fuel mileage and how many gallons the average is calculated over. The last photo is my log book. The first calculation is ~19.7 and the last is ~16.5. The latter is probably due to the weather getting colder up here.
 
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Class Guy Quote  Post ReplyReply Direct Link To This Post Posted: Nov/26/2012 at 8:56am
All kinds of good, basic information in this thread.  Some additional perspectives I would add:
1.  It's not just the amount of initial timing that counts.  The ignition advance curve is also critical.  Total advance, rate of advance and the adding of vacuum are all important.
2.  Such exercises take lots of testing which requires lots of record keeping.  You must have some test procedure that is repeatable.  I once did an exercise with an '85 GMC 3/4T Suburban with a 454 because when I bought it, the best it would do was about 10 mpg empty.  It would suck down to about 5 1/2 mpg pulling a 7500 lb trailer!  Since I was also using it to commute about 80 miles a day to work, it gave me an excellent test environment.  Doing nothing more than carb and distributor tweaks along with disabling two smog pumps (!) and the heat riser, the mileage increased to a best of 14.84 mpg (14.5 avg) and 10.5 pulling the trailer.  It took six months of testing.
3.  The 360 has a poor combustion chamber/piston top design for efficiency.  You will not achieve the same level of performance as some other engine designs.  It would be nice to have a good combustion chamber and a piston top with some quench.
4.  Keep in mind that the suggestion for changing to a 4-bbl will also require changing the manifold.  The 2-bbl manifolds have a smaller port cross section than the 4-bbl, so you willl sacrifice some velocity at low engine speeds with a 4 bbl manifold.  That means that the carb selection is important to provide the best fuel atomization.  I have found that no carb beats a Quadrajet for that level of efficiency.  Putting a Qjet on an AMC has its own challenges (not the least is the ridicule from the Forum), but I would suspect it to yield the best performance.  I would select an Edelbrock Performer as the manifold to start with regardless of carb choice.  It has the best cylinder-to-cylinder distribution of any manifold.  Incidentally, the reason for the factories spending so much effort on optimizing the 4bbl carbs during the 1980s was economic as much as performance.  All the engines had to pass smog requirements and it was much cheaper to concentrate on one venue rather than spend $$ on a 4bbl and 2bbl applications.  We all benefitted, however, with some good designs to work with.
5. Lower engine speeds is a given to increased mileage.  Although it is expensive, a swap to a GM 700R4 is a good choice.  A 200R4 is better because it doesn't require the electronic controls, but not as plentiful.  GM used 2.29 & 2.41 rear gears with .73 & .63 overdrives in the 80s to do 20+ MPG in their barges.
6.  You will not be able to stand back and simply throw parts at the car to achieve what you want.  It will take some education, understanding of mechanics and lots of work.  It is a rewarding and fun exercise though.


Edited by Class Guy - Nov/26/2012 at 8:59am
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