Kinsler_Handbook_#32 December 2017

210 Kinsler Fuel Injection, Inc, 1834 THUNDERBIRD TROY, MICHIGAN 48084 U.S.A. Phone (248) 362-1145 Fax (248) 362-1032 LUCAS FUEL REQUIREMENT CURVE The very best way to determine the proper fuel curve for any engine is to run the engine on a dyno. At each RPM, find the ideal fuel rate to get the best torque. This is called LBT; Least fuel for Best Torque. Plot a curve of the results (see curved line below). Now fit the best straight line curve that the Lucas gives. To run LBT with the Lucas : Hook the fuel cam to a separate dyno “throttle” lever, rather than directly to the arm on the throttle shaft as it normally is. Note where to put the fuel cam lever to have the cam open about like it would be if it were hooked to the throttle shaft. Put about .010” of extra shims in the metering unit, so the unit can be made to go rich. To run the test : Start the engine and take it to a steady RPM at part throttle, with the fuel cam open to a reasonable fuel rate, to warm it up. Go to wide open throttle while moving the fuel cam richer. Move the lever to richen and lean the engine. Record the RPM, torque, and fuel rate where the engine makes the best torque. It doesn’t matter where the fuel cam is indexed... it is just being used to run the LBT test. The RPM increments are usually every 400 RPM, from the lowest to highest RPM that the engine will be run at wide open throttle while racing. For an 8mm 8 cylinder metering unit, divide the fuel rate at 7,000 RPM by 3.5 for the shuttle stroke that is needed in thousandths of an inch. Check the unit with feeler gauges and add or delete shims to get the required shuttle stroke at wide open throttle, see Page #211. Exploded view of Lucas MKII metering unit Increasing the amount of shims under the tower assembly increases the fuel rate at all throttle angles. The origi- nal idle fuel rate may be preserved by lengthening or shortening the hex link to the fuel cam to reindex it. © 2017 Wide Open Throttle Fuel Curves Rotor Sleeve Shuttles Lifter Diaphragm Retainer Shims Fuel Cam Tower