You should run the numbers with your tire size first, see where 8th puts you. 4.10's and 35's [34.6 in my case] works out to high 3.30's range. Pretty close to the 3.21's and 31.5's that were stock on these trucks as far as 1:1 RPM.
7th gear vs 8th gear
First off, trying to take a pic of the tablet with my phone while doing 70 in a crosswind on a two lane farm to market road isn't conducive to award winning photography. Anyway....
I took Bumpy for a 370 mile shakedown with the new 410/8spd combo. In 8th gear with the cruise set on 75 it got 13.5 mpg, the engine turning 2100 rpm. I got on some back roads and set the cruise to 70, fired up the tablet for the Eddy EFI to take a look at things. I noticed something interesting when manually dropping from 8th to 7th.
Look at the numbers for RPM, throttle, vacuum, advance, and injector pulse width. The cruise was set, the only difference is 7th vs 8th gear. Throttle in 8th was averaging closer to 26% rather than the 24 at the moment the pic was taken.
One must also note the short/long term fuel trims and the AFR at the time. In 8th the long term is pulling fuel out but the short term is not despite the 14.4 AFR vs the commanded 14.6. In 7th the AFR is at the commanded setting, but both numbers are positive or adding a bit of fuel to the table. This is a function of the self tune and it is always at work modifying the fuel table to match the desired setting. These numbers are in constant flux so don't read a lot into them at the moment the pics were taken.
So which one would you say will deliver the best fuel economy? The higher RPM 7th gear with more vacuum, more advance, less throttle and a point less pulse width, or will less internal friction in the engine at the lower RPM in 8th gear negate those factors? Before you make comparisons to new vehicles, keep in mind those have dual runner intakes and a host of gadgets to optimize running at low RPM cruise. This 410 has a single plane and a slightly bumpy 110 LSA.
I plan to test this in the near future with an 1100 mile road trip through the East Texas hill country, the self learn will have plenty of time to optimize both gears.
So take your best guess, state why you think it's correct and let's see what happens. Correct answers will get a free trip to Granny Clampett's bottomless bar. Used to be topless, but she ain't as perky as she once was.
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I took Bumpy for a 370 mile shakedown with the new 410/8spd combo. In 8th gear with the cruise set on 75 it got 13.5 mpg, the engine turning 2100 rpm. I got on some back roads and set the cruise to 70, fired up the tablet for the Eddy EFI to take a look at things. I noticed something interesting when manually dropping from 8th to 7th.
Look at the numbers for RPM, throttle, vacuum, advance, and injector pulse width. The cruise was set, the only difference is 7th vs 8th gear. Throttle in 8th was averaging closer to 26% rather than the 24 at the moment the pic was taken.
One must also note the short/long term fuel trims and the AFR at the time. In 8th the long term is pulling fuel out but the short term is not despite the 14.4 AFR vs the commanded 14.6. In 7th the AFR is at the commanded setting, but both numbers are positive or adding a bit of fuel to the table. This is a function of the self tune and it is always at work modifying the fuel table to match the desired setting. These numbers are in constant flux so don't read a lot into them at the moment the pics were taken.
So which one would you say will deliver the best fuel economy? The higher RPM 7th gear with more vacuum, more advance, less throttle and a point less pulse width, or will less internal friction in the engine at the lower RPM in 8th gear negate those factors? Before you make comparisons to new vehicles, keep in mind those have dual runner intakes and a host of gadgets to optimize running at low RPM cruise. This 410 has a single plane and a slightly bumpy 110 LSA.
I plan to test this in the near future with an 1100 mile road trip through the East Texas hill country, the self learn will have plenty of time to optimize both gears.
So take your best guess, state why you think it's correct and let's see what happens. Correct answers will get a free trip to Granny Clampett's bottomless bar. Used to be topless, but she ain't as perky as she once was.
