Bonneville America Forums Forums Technical Forums General Tech very surprising

I have recently returned from a 5000km ride with my good mate Shawn. Shawn has a 07 softail custom with vance and hines and a dealer re map (or what ever it is that they do for all that money) On our trip my America ( 904, k&n pods, 45 pilots, 150 mains, tbs needles, 3 turns)
consisently returned 240km to reserve (14 litres) or 40mpg, which is fairly respectable considering that I ride up there most of the time. Shawns harley consistently beat me by 2 litres ( half a U.S gallon ) at every fill. I dont know wether it was the six speed box or the EFI. but I found this to be most surprising. Any thoughts?

Post deleted by roadworthy

Thats got nuthin to do wit how much fuel it uses over a certain distance. We were filling at my pace to save on extra stops.

I should imagine it was because the EFI was 'managing' the engine performance via the computer and you were managing yours via the wrist. As a BA owner you must be pretty smart, but you don't get the feedback that the computer does so you can't make the informed decisions as quickly. As well as that, the extra cog on long runs in top gear would give it the extra distance.

So a combination of the two ?

Let me qualify my initial post. Shawn is not all that happy with the sixth gear option sayin that it has no power at all. basically it is just an overdrive. So it really only does come into play on flat highway running. Some of the sections throught the western side of tasmania involved 2hrs of mountain twisties. This is where the Trumpy came into its own. I consistently out braked.and out cornered his softail with him having to get on it hard out of the corners to keep up. In this type of riding he has a much heavier bike, is reduced to a 5 speed box the same as me. Still his fuel consumption was way less than mine???? Is fuel injection so much more efficient at managing an engine than our constant velocity carburettors?

FI is much more efficient, that is why they all change to it eventually.

I think Brummie is right to a point. But don't forget, you are most likely revving a thousand or more RPM's at the same rate of (road)speed as that lower-revving engine is taching on his Harley.

(that's my guess)

I usually cruise between 4500 RPM and 5000 RPM and am getting about 50 mpg. So, I am going to really take a stab and say that the difference between both of your mileage effiencies is a combination of his EFI and the RPMs you were running at.

Soren

It's probably a combination of the EFI managing fuel better and the difference in RPM.

Fuel injection is more efficient, but gearing plays a large part as well. Based on hitting the rev limiter at 72 MPH (116 KPH) on mine in second gear, redline in 6th would be around 160 MPH (257 KPH). That means the engine is barely turning at any reasonable highway speed. They can get away with that because, while that engine is somewhat less than stellar in horsepower and redlines at 5500, it produces huge amounts of torque throughout its operating range.
Years ago, Mobile oil put on an annual fuel economy run inviting major auto makers to show their best. Chrysler always did well because they had found the main factor in fuel saving is to get into top gear as quickly as possible because it boils down to how much fuel goes through the engine per revolution and how many times the engine revolves per mile or KM. So, while everyone else was trying to keep their manifold pressure down to minimize the amount of fuel passing through the engine as they accelerated through the gears, the Chrysler drivers were leaving them in the dust to minimize the time spent in lower gears. When news cameras were present, they even did a bit of wheel spinning and still placed very high in economy.
Anyway, that's what is happening. Even though his engine is about the same size as a type 3 VW, it is geared to turn so slowly that it is actually pumping less air/fuel through than a Triumph twin, or maybe about the same amount but managing the mixture a little better. It may make up the difference if you were to change to an 18 tooth sprocket and resist the temptation to downshift to get the same go power you have now.