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E-85 Conversion

Jr 206 E-85 Conversion

Technical Inspection Line-up

Performance Calculations

Fuel Bottle (PDF)

Sources for  B&S 50032, 2.4 hp engines (PDF)

Engine Order Form 206 (PDF)

Engine Order Form 206 (Word)

Engine Order Form 93000 (PDF)

Engine Order Form 93000 (Word)







Henry Fords first vehicles ran on ethanol. To the average consumer, all energy matters are important issues, but, unfortunately, they have been beyond the control of the average citizen. However the average citizen can do many things to conserve energy, in many different areas. A large part of the energy problem can be attributed to our American fixation with the automobile and it’s huge use of finite petroleum resources. Many countries around the world have millions of vehicle running on alcohol today. The idea of using alcohol for fuel is not new but becoming more attractive to the public as our dependence on gasoline becomes increasingly more expensive. In this paper, I will examine and explain the engine alcohol conversion process.


Not all alcohols are suitable for use in internal combustion engines. Not all can be produced cheaply, and others have too high of a boiling point to be used in an engine. However, there are two alcohols that are greatly suited for use in the engine--METHANOL(CH3OH) and ETHANOL(C2H5OH). Both of these fuels are in common use today. Both fuels are made from sources that are potentially renewable. Methanol is what makes sterno burn in a heater,and is generally mad from wood or coal, and ethanol isfamiliar to anyone ever tasting grain alcohol, and is made from almost any biomass, usually corn.


Alcohol is more corrosive than gasoline.

Alcohol doesn’t vaporize as easily as gasoline, making cold weather starts more difficult.

Alcohol has less heat content, requiring richer mixtures.


Octane Rating=The measurement of the fuels ability to resist pinging, and detonation.

Volatility= The ability of the fuel to vaporize or atomize.

Mixture= The ratio of air to fuel.

Richer Ratio= Higher percentage of fuel to the air.


Current carburetor designs were developed specifically for use with gasoline, the amount of fuel needed to be delivered during alcohol operation is much greater. Carburetor modifications necessary to operate the spark engine on different amounts of alcohol fuel are reasonably easy to make. The two types of carburetors in use on small engines are the fixed jet and the variable jet. Carburetors having a variable jet and needle valve to control the fuel to air ratio/mixture are the best to use when experimenting with different fuels. Needle valves are adjusted when the engine is operating. Fixed jet carburetors need many different jets sizes for the many different changes that take place running on ethanol.


The amount of fuel to be metered through the fuel system is complicated and will be determined by the following factors:

A. The heat value of the fuel

B. The operating economy of the engine

C. The amount of power desired

D. Ambient air temperature and conditions.

E. Engine operating conditions


Alcohol fuels have a lower heat value than gasoline. Gasoline has an approximate value of 125,093

BTU’s / gallon. Ethanol has an approximate value of 76,375 BTU’s / gallon. Considering only the heat value of ethanol, it is obvious that more fuel must be consumed to produce an equivalent power to gasoline.


From the heat values given earlier, one can calculate that since ethanol has approximately 66% of the energy of gasoline the fuel flow through the engine will be close to 1.5 times more than gasoline. Jet sizes need to range from standard to as much as 50% more in size. Because of many other factors such as improved compression and longer burn times the fuel mileage is not reduced by as much as 50%.


Performance will suffer with leaner fuel mixtures. With richer fuel mixtures, however, engine response will be considerably greater than with rich gasoline mixtures. This is due to the much higher latent heat of alcohol, which can produce power increases as much as10% to 15% above gasoline. One has to watch the INDY car races and watch as the drivers richer mixtures for more power and speed, or lean out the mixture to conserve the fuel.


In today’s modern automobiles with engine feedback and computer systems, the incoming air is measured for temperature, pressure and humidity. The fuel is then metered in accordance with preset guidelines for the correct ratios during all speed and power requirements. On small gas engines without computers and feedback systems, we need to calculate and adjust mixtures by changing jetting for all of the conditions mentioned above. In cold weather operations and engine start up, correct mixture ratios will be much richer due to ethanol’s low volatility and high heat absorption abilities in the engine chambers and fuel passageways. Alcohol does not vaporize as easily as gasoline and mixture distribution tends to be less even and with larger particles of fuel in the mixture. Preheating the fuel, such as running the fuel line over the cylinder head, can be of value. Operation in warm weather presents fewer problems.


If the engine is going to be running under steady speeds and loads, then the mixture is going to be easier to set for the correct combustion. When the engine speed is changed and the load requirement changes constantly, then the mixture is much more difficult to adjust and get correct. Remember that the ratio changes as engine RPM increases and load requirements change. With the relatively simple carburetors used on small engines, the mixtures will not be correct most of the time, (such as with a computer feedback fuel injected system). This is the time that most of the experimentation comes into use.

Ignition Modifications.

The power duration and timing of the spark needs to be changed Rich fuel mixtures will absorb more heat energy from the spark without reaching burn temperatures. To complicate matters further, ethanol is not as volatile as gasoline and doesn’t vaporize as easily as gasoline. This results in much larger fuel particle size in the combustion chamber prior to firing, also not leaving many particles between the electrodes during the spark.


The standard spark plug will work, however, increasing or widening the gap, changing the heat range to a hotter running plug, or going to multiple gap plugs will show an increase in performance.


Again the stock coil will work. Replacement coils, (super coils), with more power, (wattage), will increase the spark duration, ensuring that more particles of fuel will be ignited.


For all small engines the time at which the spark fires across the plug electrodes is set by adjusting the dwell, (point gap), and is not easily adjusted to the correct value. Some engines have adjustable timing, but it is set to fire the spark at the same under all conditions. In larger engines that are always changing speed and load, requirements for different spark timing follows a curve. Vacuum and centrifugal advance mechanisms are used to maximize the ignition timing curve. On modern engines electronic ignition eliminated the need for mechanical point and condensers. Most of the ignition system is all contained in the coil assembly, which is then attached to the engine block. To change the timing on these engines, the coil assembly needs to be rotated on the block, or the flywheel containing the magneto magnet must be advanced with offset keys. Either of these processes are difficult to do. Also remember that the timing is fixed to fire at the same time always. To much advance will make for very difficult starting. (Have you ever had the starter rope pulled out of your hand on a backfire because of too much advance and the piston will run backwards down the cylinder?) Maybe someday we will have small computer adjusted variable spark timing.


Most modern automobile engines are advertised as having compression ratios between 8:1 or 9:1. These are about as high as low octane fuels will permit without some detonation. Small gas engines with L Head designs often run much lower ratios such as 6:1 or a little higher. Depending on mixture strength ethanol fuels rate from 90 to 120+ octane, and could stand compression ratios as high as 13: 1 or 14:1. By shaving or milling the cylinder head down several thousandths of an inch, the compression ratio can be raised substantially. The higher the compression ratio is the richer the mixture must be to avoid destructive detonation or knock.


Finally there are really only three changes to make on any internal combustion engine using E-85 for the fuel source. The first of these and perhaps the most important is to change the fuel ratio to run a richer mixture, from around 25% to as much as 50%. I have found that by purchasing 6 new stock jets for the fixed jet carburetor used on the supermileage vehicles, then using a tip cleaner for the Oxy-acetylene torch, We have opened up the orifice to many different sizes. I keep them sorted by using 35mm film containers and then labeling them. Secondly , would be to enhance the spark process. There are many different manufactures for the parts necessary, do some research. Third and finally, we increase the compression ratio by shaving off material from the cylinder head thereby reducing the amount of combustion chamber volume. We had to take and carefully remove material from around the spark plug area because of piston interference. Valve to head clearance should also be checked. For more information on E-85, there are numerous sources on the inter net to check out.

Keith D. Anderson, DTE
This email address is being protected from spambots. You need JavaScript enabled to view it.
Past President MTEEA
Competition Committee -MTEEA Supermileage



E-85 conversions are a great challenge for students. Some times they are too challenging for Teams to want to tackle. This is to offer a baseline set up for the Jr. 206 engine. It takes no modification what so ever to the engine and is a jetting kit that will give you all the power you can handle. It is very easy to swap the jets (takes about 10 min from start to finish). This set up is only one of many ways to run a car on ethanol and is only meant to assist teams that have interest in attempting the class.

Contact Jim at Faster Motors (920) 207-9180  for the E-85 Conversion Jet Kit that runs $39.99

A few helpful notes to assist teams getting started. Keep the stock 4100-rpm ignition box and use the longest slide. Any time we changed either of them the rear bicycle wheel and jackshaft bearings would fail.

Advisors can contact This email address is being protected from spambots. You need JavaScript enabled to view it. at for tips and ways to add some extra challenges for students to have to work through to get the motor dialed in.

Tech Inspection Line-up Revised 4-06-13

STATION 1 - Vehicle Safety

1. New Vehicle Verification: Older models must be able to explain changes from other years.I-B-5

2. Stock Engine is box stock? Muffler, air cleaner, spark plug, etc.. Governor can be removed!I-B-1

3. Fire extinguisher of proper size and type (gauge reads full), and placed in an operational position?II-G

4. Helmet & required eye protection? (Motorcycle type DOT or SNELL certified)II-D

5. Safety flag Mount. The flag will be given at the completion of Inspection.II-O

6. Seat Belts required: Must have a 5 point harness. Quick release.II-N

STATION 2 - Vehicle Structure

7. Welds are sound? (Good quality, penetration!)II

8. Wheels mounted securely?

9. Steering system secured?

10. Exit ability - Can the driver exit the vehicle in less than 15 seconds?

11. Driver visibility? A full 180 degrees, 90 degrees of straight ahead.II-L

12. Mirror check? Both mirrors-engine running, (with vibration=geometric shapes).II-K

13. Idle test? - Can the engine idle without stalling or moving the car?I-G

14. Exterior kill switch clearly marked with 2" square of bright color?II-A

STATION 3 - Vehicle Maneuverability

15. Turning ability- can the vehicle turn in a radius of under 35 feet?I-C

16. Brakes & Stopping - (15 degree Ramp Test) (Driver must maintain driving position –driver must hold the vehicle from moving.

17. Longitudinal stability (15 degree Ramp Test) (Driver must maintain driving position -steering wheel turned lock to lock)?I-D

18. 2-3 Kill switches are 1/2" paddle, toggle type? (Driver’s compartment, pit crew, original on engine). Check both switches engine running- third switch on the engine should be functional Test all 3 switches.)

19. Substantial roll cage encloses driver? ** 2" above helmet of all Drivers. * This is to protects all drivers fromroad contact and from other cars.
l-A-4, II-B

20. Floor and side of drivers compartment totally enclosed & constructed of substantial material? **This is to protect the driver from road contact and from other cars.I-B-3

STATION 4 - Vehicle Components

21. Fire wall seals the engine compartment from driver?ll-H-all

22. Exhaust system correct and properly vented?ll-G-all

23. No fuel or lubrication leaks. All push on fuel fittings are clamped? No more than 24” of clear line.

24. Car equipped to safely support official fuel tank? Check Bottle & Official Filter.

25. Moving power train components guarded from accidental contact?

26. Batteries mounted & strapped safely? (for starters, or for use with optional on-board equipment)

27. Electric start - meets modified restrictions?
l-H-1 all

28. First Aid Kit.II-M



Performance Calculations

Engine to Wheel

WC=wheel circumference (in meters)
RPM=revolutions per minute (engine)

A=large sprocket (rear wheel)
B=Clutch (on engine crankshaft)

*No load speed*

[ RPM/(A/B)] X WC X 0.0375 = speed in mph 

@ 3600 RPM (Max RPM)

100 tooth sprocket-12 tooth clutch -700mm tire

[3600/(100/12)] X2.15 X 0.0375 = Max speed = 34.83 MPH

1000 RPM = 9.67 MPH
2000 RPM = 19.35 MPH
3000 RPM = 29.02 MPH
4000 RPM = 38.702 MPH

Engine to Shaft to wheel

WC=wheel circumference (in meters)
RPM=revolutions per minute (engine)

A=large sprocket (jack shaft)
B=Clutch (on engine crankshaft)
C=Freewheel (Drive Tire)
D=Intermediate sprocket (jack Shaft)
*No load speed*

[ RPM/(A/B)(C\D)] X WC X 0.0375 = speed in mph

@ 3600 RPM (Max RPM)

92 tooth intermediate sprocket-12 tooth Clutch -32 tooth freewheel-24 tooth intermediate sprocket-37 inch Tire

[3600/((92/12)(34/24))] X2.2 X 0.0375 = Max speed = 27.4 MPH

1000 RPM = 7.6 MPH
2000 RPM = 15.2 MPH
3000 RPM = 22.8 MPH
4000 RPM = 30.4 MPH

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