Genius or insanity : motorcycle hypermiling

[darkvision]

After participating in the recent Craig Vetter Fuel Economy Challenge in Carmel I have been working on major aerodymamic modifications on my 82 Vision.  I got to meet Craig and other motorcycle hypermiling experts : Alan Smith, Fred Hayes , and Traven Baker and have remained in contact with them as they pursue their various projects to maximize motorcycle fuel efficiency. I started with very simple mods like adding side panels , saddle bags and a Kammback/trunk which I rode with in the Challenge , getting 55 mpg for the ride.  Since then I visited Alan and looked at his Ninja 250 aeromods so that I could make similar ones for my Vision. I made a fully faired front fender, a tall boattail rear section,  rear wheel side covers, a longer taller windscreen.  The bike is somewhat skittish in windy condition as I still using the shark handlebar fairing rather than a frame - mounted fairing but I can definitely feel an improvement in air drag.  My last tankfill was 57 mpg and I'm hoping my next will be over 60 mpg. I'm hoping to stay in the 60 mpg average and possibly break the 70 mpg barrier. 

[QBS]

My goodness, it surely didn't look like that when I saw it in Colorada.  Skinny tires help too.  I think it's great that you are taking the V in a different performance direction.  Cheers to you.

[Extent]

I'd love to see more pictures of that, that thumbnail is pretty hard to make out.  I think you could almost certainly get some better airflow over where the forks meet the fender.  Getting the head frame mounted and wrapped around to meet up with your side covers will help a lot as well.

How much does all that weigh?  Are you doing just straight fiberglass work or are you using like hexcell reinforcements?

[Ron_McCoy]

Too bad theres no easy way to gear the vision higher as that would help too.

[Night Vision]

at first, I thought that this was a poll  :-\  :D

a shower cap and spandex suit might get you a bit more mileage  ;D

[The Prophet of Doom]

Too bad theres no easy way to gear the vision higher as that would help too.

You can gear the vision higher or lower just a matter of swapping the gears under your clutch cover.  Your choices are:

34/72 (2.117:1) Euro/Australasian   
33/73 (2.212:1) USA
31/74 (2.387:1) XZ400

[Kenny]

  N. V.,
       Please put that photo of Rollie Free away?! ;)
                              Ken S.

[darkvision]

Roro,  Thanks for the info,  I wonder if I could order the gears from a Yamaha dealer.  I do plan on going to a slightly taller rear tire after I wear the current 100/18 out.

Extent,  Feel free to send me an email at jagman1346@aol.com and I'll send you some full-sized pix. You are correct about the front end airflow,  I hope to replace the handlebar fairing with a frame-mounted fairing that covers the front wheel, sort of like a dustbin-type fairing.  The mods don't add much weight;  I also removed parts that  I covered over ( seat, tail, old front fender, old windscreen, etc.) so the total weight gain is probably less than 10 lbs.  The front fender is masonite/fiberglass, the sidepanels and tailsection is coroplast sheeting, the framework for the tailsection is wood and sheet metal.

working on the spandex suit, maybe a cape would help.... :D

My last tankfill was 58.3 mpg with lots of short trips so things are looking good. One of the best improvements in fuel economy was cleaning and synching my carbs .
Thanks for the suggestions and support.   Dark V

[Ron_McCoy]

Euro gearing is not that much higher. I have a V with and one without. Looking for gas mileage much higher gearing would be nice.

[supervision]

 Do people wave differently? 

[Brian Moffet]

People do realize that going to a higher gearing may not increase fuel mileage, right?

The amount of horse power it takes for you to do 60 MPH (removing the engine inefficiency part) doesn't change at all no matter what the RPM of the engine.  It's all due to air-resistance, and the friction of the moving parts outside of the engine.

In order to get higher mileage, you need to move the RPMs into the sweet spot for engine efficiency.  The only thing that the gearing will change is where the RPM is for the engine and transmission, which may or may not move the RPM into a more efficient realm.  The amount of power the engine is putting out is dependent on 2 things, RPM and manifold pressure (how much throttle you're giving it). If you drop RPM, you have to increase manifold pressure to get the same power as a general rule.

Brian

[darkvision]

Lowering the rpms benefit fuel efficiency by reducing internal engine friction and reducing pumping losses from using larger throttle openings . The Vision would probably benefit from reduced rpms as it revs relatively high in top gear ( stock US gearing: 5300 rpm@ 60 mph) and has very good lower end torque .  Using the Euro gearing would reduce rpms  to about 4935 rpm at 60 mph ( ~5% difference) .  Using a taller than standard tire would also  reduce rpms.  I'll probably do that first as my rear tire has about another 1k miles on it.   
SV, I get a few waves,  some thumbs up , lots of looks and a lot of questions when I fill up or park.  Yesterday I was riding  and a guy pulled alongside and took a picture.

[Ron_McCoy]

The Vision transmission has a low enough 1st gear that you could raise the overall gearing high enough to use 5th as an overdrive. I live in the mountains and my main commute is on hwy 58, miles at a time on a 7% grade. A vision will pull this at any speed you want in 5th so it makes sense that it would pull higher gearing on the flats and especially downhill. Even if you only used an O.D. downhill, it would improve mileage.

[don_vanecek]

That's for sure, the many, many times I try to shift again after I am already in fifth gear.

At least our US Vision I imagine were geared for the then 55 speed limit, and I could occasionally touch 50 mpg in those days, that doesn't happen at todays higher speeds.

Yup, get that Vision in 5th gear about 35-40 mph and you never have to shift again till the stop sign in the next town!

[Brian Moffet]

Lowering the rpms benefit fuel efficiency by reducing internal engine friction and reducing pumping losses from using larger throttle openings

If you drop RPM, usually you're going to need to have larger a throttle opening to get the same horsepower.  Now dropping the RPM a bit (5%) may help you get into the more efficient range of the engine for a particular speed, say 65 mph, by reducing internal friction.  That's great if true.

However, let's look at an extreme case:  say you could drop your RPM to be 2000 RPM at 65 mph.  You would probably get worse mileage than you would running 65 mph at 5000 RPM.

I would be willing to bet that not many people could actually tell they were getting better mileage by dropping the RPM by 5% and be able to back it up. They might get a much smoother ride, which would be worth it though :-)

Brian

[QBS]

Good low end torque, when connected to high gearing makes it possible to cruise at high speeds with small throttle openings.  The next time one is driving their late model automobile at 65 mph in top gear, take note of the tachometer (if so equipped).  Chances are that it will be indicating somewhere in the 1500 - 2000 rpm range.

[JohnAMcG]

Interesting discussion.  I don't understand how dropping to 2000 rpm vs 5000 at the same speed could possibly lower fuel efficiency, when cruising.  It seems to me to be a function of how much horsepower you need to maintain your speed.  The lowest rpm that delivers that much HP to me would be the most efficient.  Now if you hit an uphill stretch, or need to accelerate, then you need to get in a higher rpm range.  I do this all the time with my little 4 cyl pickup, some hills on the highway it takes more throttle in 5th gear than it does in 4th gear to get up the hill, especially if the bed is full of junk, but always takes less in 5th on flats or downhill. 
    Ill be taking a long drive in a 6 speed vette for my sisters wedding next week.  That thing has HP to spare at any speed in any gear, and it also has an instantaneous MPG reading, digital speedo and tach, so I can get some hard numbers if anyone is interested.  I know they wont really apply to much here, but maybe interesting for the discussion.  When I've driven it in the past, I am always trying to hypermile it, and I get about 28mpg average.  Most of the time doing 60 in 6th gear, the thing is really just idling, and I get the best mileage. 
     As a side note, I visited a friend once in a neighboring state, and it took a full tank of gas to get there (in my pickup), but on the way back I stuck to the tail of an 18 wheeler, like right on his ass.  I do it a lot, and the better truckers know what you are up to, some don't mind, others do.  Well, this one was driving like he wanted me to get the best mpg possible, and I followed him almost the entire way home.  It was crazy how close to where I was going that he was going, and I used about half a tank of gas.  I couldn't believe the difference. 

[Extent]

I think the general rule is the more closed your throttle is the better, but I don't know how much that applies to the metering circuits in a carb.

Check out the first image in this thread
http://www.clubcivic.com/board/showthread.php?t=169226
that's the fuel mapping for a civic, WOT at idle RPM is using more fuel than 1/2 throttle at redline. 

Even if you take a more typical cruising RPM (at least for me) if you figure 21inHG at 4400 RPM (approx 1/4 throttle or so) is using 2.07 fuel, backing off even to the next column of cells the fuel use is lower at every RPM except for absolute peak power (roughly 7500 RPM)

If you could theoretically back this engine off to 1/8 throttle but run it at redline to keep up to the same roadspeed you would save very approximately 20% on your fuel usage.

[Brian Moffet]

Again, you need to have a certain amount of horsepower to go a certain speed to overcome the air resistance, rolling resistance, etc...  So for that chart, you can't back down to another row without changing the horsepower output.  If you were to put a different gearing in, you would need to change the chart.

Here's where I am coming from, in constant speed prop aircraft, you pretty much have control over the RPM and manifold pressure to determine a horsepower output.  In our bikes, it's like having the ability to change the gearing on the fly (or shifting in a much more precise form).  There are combinations that get the best fuel economy, and if you move out of that range for a combined MP and RPM, in either direction, you lose efficiency.

Now aircraft are putting out way more horsepower for a given speed than our bikes are.  But the physics is the same.  It may be more noticeable for an aircraft because your at the top level of power.  All engines have a defined best efficiency RPM range.  (for my airplane, it's around 2500 RPM) If you can move the engine into that area for your cruising speed, you'll do much better.  If you move it out of that area, you'll do worse.  It might only be 1 - 5 % worse, but it will be worse.  (which is why I think people won't really be able to tell without some serious testing equipment that removed the environmental differences)

That's where I am coming from, I don't have a method to reproduce this on a bike, and riding on the road won't do it because the factors depend on temperature, humidity, wind, road conditions, whether Lucky has had a burrito for lunch,....

Brian

[Night Vision]

my brother said he got 58 miles to the gallon on last Sunday's ride  :o

he's not a very agressive rider, but he's not the most aerodynamic pea in the pod either...

so I had to call bs on 58.... that 1/4 gallon or so when you fill these tanks can make a big difference in your mpgs....

he does report getting 50 quite often, and knowing how anal methodical he is about filling to the same level in the tank... I would say he most likely does get 50... somedays... with a tail wind... on the third Sunday of a month...