Cooperative Fuel Research (CFR) Engine

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Preliminary Checklist

  1. Check Engine Oil Level
  2. Check Coolant Level
  3. Open Coolant Valve for Pressure Transducer
  4. Input Desired Fuel
  5. Check Compression Ratio
    1. Micrometer Reading
    2. CR=(4.5/(Reading+0.5))+1
  6. Double Check The Head Is Securely Tightened
  7. Check The Valve Clearances
    1. Exhaust: 0.010”
    2. Intake: 0.008”
  8. Set Timing For Current Compression Ratio
    1. Compression Ratio
    2. Spark Advance BTDC
  9. Connect Ignition Wires to 12V Battery
  10. Turn On Circuit Breaker to Engine
  11. Turn On Lab Exhaust Fan

Operational Checklist

  1. Open Exhaust Gate Valve
  2. Engage Starting Motor
  3. Turn On Ignition Switch
  4. Turn Throttle to Wide Open Position
  5. Back Out Fuel Needle Valve, Adjust Until Backfiring Stops
  6. Let Engine Warm Up, Readjust Fuel Needle Valve as Needed

Octane Testing


Engine Speed Constant at 900 rpm
Oil Pressure 25-30 psi
Oil Temperature 120-150°F
Coolant Temperature 209-215°F
Intake Air Humidity 25-50 grains/lb
Mixture Temperature 300°F
Carburetor Venturi 19/32 in.
Lubricating Oil SAE 30

Test Run Preparation

  1. Turn on the main switches, crankcase heater, and coolant heater.
  2. Turn on the circulating cooling water. When coolant temperature approaches 180°F, turn the heater to low.
  3. Fill one of the carburetor bowls with regular gasoline.
  4. Start the electric motor, then turn on the ignition switch.
  5. Turn selector dial to the bowl containing regular gasoline.
  6. After the engine has run for a while, check the manifold temperature. Turn on the heater if it is well below 300°F.
  7. Check the specific humidity while engine is warming up.

Bouncing Pin Adjustment

  1. Check and record barometric pressure.
  2. Adjust the compression ratio of the engine to the corresponding micrometer setting (Manual page 96)
  3. Switch from regular gasoline to a reference fuel with a known octane rating.
  4. Adjust the bouncing pin to read 55+3 on the knockmeter.
  5. Adjust the elevation of the reference fuel bowl until a maximum knock is reached. This varies the AFR.
  6. Now, just read the bouncing pin to the 55+3 reading.

Note: From this point forward, do not touch the bouncing pin

Testing the Unknown Fuel

  1. Drain the reference fuel.
  2. Set up the four bowls in such an order that they can be easily remembered.
  3. Turn selector to the bowl containing the unknown fuel.
  4. Adjust the compression ratio so that the knockmeter reads 55+3.
    1. From this point forward do not change the compression ratio.
  5. Using pipettes and graduates, mix a reference fuel of iso-octane and normal heptane. 200 mL should be enough to run the engine and obtain a good reading.
    1. Use of conversion tables makes it possible to obtain known blends using the reference fuel with either the iso-octane or normal heptane.
  6. Turn the selector to the newly mixed reference fuel blend.
  7. Adjust the bowl containing the newly mixed blend to give maximum knock.
  8. Repeat this procedure until two reference blends not differing more than two octane numbers bracket the fuel.
  9. Interpolate between the two octane numbers to obtain the octane rating of the unknown fuel.

Note: If you want to test more than one unknown fuel, repeat only the 'Testing the Unknown Fuel' section.