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Discussion Starter · #1 ·
Has anyone here dropped in the 131 cu in.
I am thinking about getting a 2021 Road Glide and doing the 131.
The stupid question is, how big a hit in fuel range did you take doing it.
I want to take some LONG trips on it and fuel range is a concern.
I want this beast to rip when I twist its tail.

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Discussion Starter · #4 ·
Don't do it. I am on my 3rd 131 motor since May.
That doesn't sound good.
I need a reliable engine.
A buddy has a 117 and that one seems as reliable as a rock.
He has had no problems and it makes lots of torque.
Maybe that's the way to go.

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One thing I have noticed over the years is that it takes more fuel to make more power. Usually. Maybe you could get lucky and get the same, or better fuel economy with that beast of an engine, but somehow I doubt it. Long trips usually means you will be riding in the same rpm range for extended periods. Perhaps you can make a few different fuel maps like one for power and one for economy and just change them out when you need to. If you want to do that though, you can kiss the warranty good-bye unless you use HD's stuff. Maybe Kainam could tell us how he is doing his fuel map(s).
 

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It is very speed dependent. At 65-70 or so I get around 45 mpg. At 80 or so it drops rapidly to 40 mpg or slightly less.

Average so far is ~41 mpg, including breaking in a 114 and 2 131s (first 131 didn't last long enough to count). Coming up on 8000 miles total so far, ~5000 miles on current 131.

This is with the HD download for the stage 4 131. I have purchased the wideband kit, but the MoCo doesn't yet have a basemap for the 2021 bikes. There's been some change to the ECM from 2020 that makes the basemap for those bikes not work on the 2021 bikes.
 

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It is very speed dependent. At 65-70 or so I get around 45 mpg. At 80 or so it drops rapidly to 40 mpg or slightly less.

Average so far is ~41 mpg, including breaking in a 114 and 2 131s (first 131 didn't last long enough to count). Coming up on 8000 miles total so far, ~5000 miles on current 131.

This is with the HD download for the stage 4 131. I have purchased the wideband kit, but the MoCo doesn't yet have a basemap for the 2021 bikes. There's been some change to the ECM from 2020 that makes the basemap for those bikes not work on the 2021 bikes.
Those numbers are very good! Better than my stage one 103". I need to study more and get my fuel map tweaked just right for what I have done to the engine.
 

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Those numbers are very good! Better than my stage one 103". I need to study more and get my fuel map tweaked just right for what I have done to the engine.
I got ~40 mpg highway on my carb'd 103 NightTrain
 

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That's better than I get with a stock 96tc. Most of my riding is city stop and go. My one real trip on the slab I saw mid 40 mpg.
 

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One thing I have noticed over the years is that it takes more fuel to make more power.
I got ~40 mpg highway on my carb'd 103 NightTrain
My Evo went from 62-ish hp and relatively mild stage 2 to 80 hp with the stage 3 and I gained MPGs... from about 38 mpg to 42 (city mpg when I first set it all up, it's gone up to 43 city mpg since the external breather conversion). On the highway, I can get 45-50 mpg on my stage 3 (before I only got 42). Granted, the swings between my city and highway mileage were much higher before and are closer together now, but that's part of how it's tuned and the difference in how it produces power (torque). This is all on 10% ethanol gas... on 91 octane pure gas with my current set up, I have gotten as much as 58 mpg on the highway. And consider this too, when it was a typical stage 2, the afr was about 13:1, which is leaner than my current build that's more like 11.5-1 (average across the entire rpm range of around 1,800 to 5,800, based on dyno pull AFR exhaust sniffer trace in 4th gear pulls... at least I think that's what they do pulls in, 4th gear right?).

Though the cost per mile is different, when it was mild it could run 87 octane, now it has to run a minimum of 91 octane.

Regardless, if you do the upgrades right, that doesn't necessarily mean increased fuel consumption. More power, plus doing it right (which lends to greater efficiency), means you shouldn't lose fuel mileage if you're running normally. Or another way to think of it... two engines going 45 mph, whichever has the more efficient and proper setup will get the best mileage regardless of the overall power; but at the same time, a sufficiently weak enough engine needs a lot more juice to run 45 mph than a much stronger engine (but we're talking like a 40 hp engine vs a 150 hp engine at this point).
 

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