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Today I made another run for max MPG. The variable being tested this time was ignition. I added a 45,000 volt coil (details at end of post), and NGK BPR6EY-11 plugs, gapped to .048 and indexed to face the center of the combustion chamber. The larger gap is allowed because of the greater energy of this coil vs. the stock one. This creates a larger spark of course, giving more efficient burning of the fuel, so you don't have to press the gas pedal down so far.
Atmospheric conditions: clear sky, little to no breeze, temp around 70. Began the test at 6:15 AM.
Car is basically stock except for larger front tires, 155/80x13 on Metro steelies, giving 4.4% overall higher gearing. Rears are 155/80x12, close to stock. Tires inflated to 35 PSI cold. Airbox modded to admit more air at higher RPMs, but this would have no effect at the 2200 RPM (55 MPH) I was cruising at. I did fold in the passenger mirror for better flow, like an L model. No special effort was made to lighten the car; it had a rear seat in it and a full-size 12" spare.
Cruised at 55 MPH on highways surrounding St. Louis, flat to slightly hilly terrain.
I filled up the tank to the very top, drove 85.4 actual miles after correcting the odometer error (1.5% low with these front tires), and filled it again, actually spilling some gas in the effort to make sure it was completely full. It took 1.46 gallons.
Result (drum roll please): 58.49 MPG @ 55+ MPH (it's hard to keep it exactly on 55 all the time). This included a small amount of city driving to and from the gas station, and the small amount of fuel spillage. If I round down to 1.4 gallons to allow for spillage, this comes to exactly 61 MPG.
This reaffirmed to me the value of adding a higher-energy coil and proper use of the plugs. I have done this before with Subarus, getting similar percentage increases in MPG.
Note 1: On my first run at 55 (see my post "MPG run"), I was not as careful filling the tank all the way before the run, so possibly when I filled it the second time to the very brim, it gave a falsely low MPG figure of 51. It may well have been 53 - 54, because even a .1 gallon inaccuracy can affect the MPG this much.
Note 2: When I drove at 45 MPH ("MPG Run, part deux") with the stock coil and Autolite 64 plugs, I got 62.5 MPG, with fuel being carefully added and the same odometer correction. So 10 MPH faster with the electronic mods gave almost the same thing.
Coil info: Got it from Jeg's, 800-345-4545. www.jegs.com Part # 555-40105. It's red, cylindrical and $25. They also have them in chrome (555-40100) and yellow (555-40107). The chrome bracket is 555-40190, $4.
My next runs will be at 60 MPH to be a little more real-world. First with larger, heavier tires (185/60x14 on aluminum wheels); then again with those tires but an ignition timing advance + 93 octane gas.
I'm tempted to make an early-morning Sunday run at 45 MPH, to see if I can break 70 MPG.
Atmospheric conditions: clear sky, little to no breeze, temp around 70. Began the test at 6:15 AM.
Car is basically stock except for larger front tires, 155/80x13 on Metro steelies, giving 4.4% overall higher gearing. Rears are 155/80x12, close to stock. Tires inflated to 35 PSI cold. Airbox modded to admit more air at higher RPMs, but this would have no effect at the 2200 RPM (55 MPH) I was cruising at. I did fold in the passenger mirror for better flow, like an L model. No special effort was made to lighten the car; it had a rear seat in it and a full-size 12" spare.
Cruised at 55 MPH on highways surrounding St. Louis, flat to slightly hilly terrain.
I filled up the tank to the very top, drove 85.4 actual miles after correcting the odometer error (1.5% low with these front tires), and filled it again, actually spilling some gas in the effort to make sure it was completely full. It took 1.46 gallons.
Result (drum roll please): 58.49 MPG @ 55+ MPH (it's hard to keep it exactly on 55 all the time). This included a small amount of city driving to and from the gas station, and the small amount of fuel spillage. If I round down to 1.4 gallons to allow for spillage, this comes to exactly 61 MPG.
This reaffirmed to me the value of adding a higher-energy coil and proper use of the plugs. I have done this before with Subarus, getting similar percentage increases in MPG.
Note 1: On my first run at 55 (see my post "MPG run"), I was not as careful filling the tank all the way before the run, so possibly when I filled it the second time to the very brim, it gave a falsely low MPG figure of 51. It may well have been 53 - 54, because even a .1 gallon inaccuracy can affect the MPG this much.
Note 2: When I drove at 45 MPH ("MPG Run, part deux") with the stock coil and Autolite 64 plugs, I got 62.5 MPG, with fuel being carefully added and the same odometer correction. So 10 MPH faster with the electronic mods gave almost the same thing.
Coil info: Got it from Jeg's, 800-345-4545. www.jegs.com Part # 555-40105. It's red, cylindrical and $25. They also have them in chrome (555-40100) and yellow (555-40107). The chrome bracket is 555-40190, $4.
My next runs will be at 60 MPH to be a little more real-world. First with larger, heavier tires (185/60x14 on aluminum wheels); then again with those tires but an ignition timing advance + 93 octane gas.
I'm tempted to make an early-morning Sunday run at 45 MPH, to see if I can break 70 MPG.
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