<50 mph: 6040 RPM"content-type" content="text/html;charset=ISO-8859-1"> Freedom Machine - Fuel Economy -Chap 34
The Search for Fuel Economy

Pages from a Designers' Notebook

Freedom Machine
The goal: 100 mpg at 70 mph, into a 30 mph headwind, with four bags of groceries.
Chap. 34: 80 mph! 84 mpg! April 25, 2010
The formula for living better on less energy

Streamline it, slow the engine down so it produces less power.

The head winds
The results
I knew as soon as I saw 1 1/2 gallons was used to go 133 miles that we were finally getting the results I have been working so hard for. My goal is to get 100 mpg, at 70 mph, into a 30 mph headwind, carry 4 bags of groceries and be the first choice of vehicles in a garage full of great machines.

I call these "Vetter Conditions"

Lets review the history of this venture:
2008: I began with a stock, 17 hp Honda Helix. On a still day, it might get to 72 mph. It generally got 62 mpg. But, not in "Vetter Conditions" because it is not streamlined.
2009: Fully streamlined, it would now easily go 75 mph and get 64 mpg in the "Vetter Conditions" above. I love the storage capacity. But sidewinds moved it more than I wanted.
2010: The inflatable tail has been replaced with a plastic tail. The sides are open to let sidewinds pass thru. The windshield is now attached to the handlebars. Prius car headlights fit the streamline shape better and point in the right direction. Gears from Jan Vos of Belgium slow the engine down by 20%.
The engine has not been modified. All changes are due to streamlining and gearing. I notice that it is a little slower off the line... for the first 10 feet or so. The slow acceleration is especially noticeable if I am starting up hill. We have a steep hill on Highway 1. Previously, if I accelerated onto its on-ramp, I could get to 65 mph by a certain overpass. It still does it with the new gears.

It used to climb 12% Laureles Grade, at 50 mph. Now it does it at 45 mph. Fortunately, most cars cannot go any faster.

At the end of the day, the geared-up, streamlined Helix gave me 84 mpg!

Remember, this is my first time out with the new gearing... my first and only run. The machine is rough and unfinished. But I am very encouraged.

I am now riding normal, errand-running. We will see what happens in "Stop and Go" riding. I'd bet mileage is better than before. We will know soon. The machine feels so much better with the engine running slower.

Mileage posted June 8, 2010:

May 6, 2010 Quail Gathering road ride: 142 miles, 1/2 in mountains @50 mph, 1/2 into a 30 mph headwind @70 mph, 3 fast laps around Laguna Seca: 90.9 mpg

May 25, 2010 Running errands around town. Lotsa stop & go: 64.8 mpg

May 29, 2010: Running errands, a little more high speed: 69.9 mpg

I do not drive to save gas. I accelerate fast. I go the speed limit or a few mph faster, figuring my speedo lies. Only streamlining and the resulting engine gearing has changed.

The faster I go with the fewer stops, the better the mileage

I love headwinds. I simply do not feel them!

Basic Helix Review:

17.33 horsepower @ 7500 rpm or  12.92 kilowatts

At the 2010 Iron Butt Convention, I met a man who said his Helix on a dynomometer put out 13 1/2 hp at the rear wheel. This helps.

15.16 foot lbs torque @ 5,000 rpm or 20.56 Newton Meters

Below are the readings from my digital tach:

Stock Gearing:

50 mph: 6040 RPM

55 mph: 6640 RPM

60 mph: 7200 RPM

65 mph: 7800 RPM

70 mph: 8400 RPM

75 mph: 9200 RPM

New Jan Vos Gearing:

50 mph: 5200 RPM

55 mph: RPM

60 mph: 5800 RPM

65 mph: 6060 RPM

70 mph: 6640 RPM

75 mph: RPM

80 mph: 8000 RPM

It won't go faster than 81 mph. This is probably because max horsepower is at 7,500 rpm. It has less horsepower at 8,000 rpm... not enough to push it into a 30 mph headwind past 81 mph.

Master Index to the Last Vetter Fairing Story

Page posted April 25, 2010

Updated Aug 17, 2010