LUCAS INJECTION

Lucas MK1 and MK2 fuel / petrol injection

 

HOME     HISTORY     TECH     LINKS     REBUILDING     MANUALS     FAQ     PROJECTS    YOUR CAR  
FUEL CAMS
     PLUMBING     PICTURES     STREET     LINKAGE + DRIVES      ENGINES       


NOTES ON INSTALLATION AND CALIBRATION

RACING CARS


PART II.    -  CALIBRATION

(a)             Injection Timing

                  At speeds in excess of half maximum engine speed, the performance
                  of engines developed for racing purposes is not affected markedly by
                  changes in injection timing.

                  It is usual to begin injecting fuel at some portion of the induction
                  stroke when air is moving forward towards the inlet valve.  The
                  beginning of injection is considered to be the point at which the
                  port hole in the rotor just begins to eclipse the hole in the
                  sleeve at the injector outlet to the timing cylinder.  To establish
                  this point, remove the injector outlet connection on the metering
                  distributor.  With all drive backlash taken up, rotate the engine by
                  hand in the direction of rotation until the hole in the rotor is
                  seen to just start to appear.

 

                  This procedure is carried out without any fuel feed to the unit.
                  It may be found necessary to dry out the hole to prevent optical
                  distortion due to fuel remaining in it.

                  Due to the injection delay period, the required beginning of injection
                  may vary between about 60 deg. and 200 deg. B.T.D.C. on the inlet stroke,
                  according to the type of engine.  A recommended starting point for
                  injection timing investigations would be of the order of 100 deg. B.T.D.C.
                  Having determined the optimum timing for maximum power, there will usually
                  be a tolerance of about + or - 20 deg. without significant loss of power.

(b)             Determining Control Characteristics

                  Variation of fuel quantity with throttle opening is achieved by means of
                  a control cam linked to the throttle mechanism and attached to the
                  control stop end of the metering distributor. The cam operates on
                  the adjustable control stop to vary shuttle stroke and hence fuel
                  delivery.  It is therefore necessary to relate the fuel required
                  (i.e. shuttle stroke)  to throttle opening, and to reproduce this
                  relationship by suitably contouring the control cam.

                  The required control characteristic is determined on the engine test
                  bed in the manner described below.

Micrometer Hand Fuel Control

A Micrometer Hand Fuel Control is required. Drawings of this can be made
available upon application to the Lucas P.I. Design Office.

When fitted to the metering unit this device regulates fuel quantities to the
engine by controlling shuttle travel.

( i )             English Measurement

                  The micrometer spindle is machined with a thread pitch of 40 T.P.I.
                  and the control wheel graduated in 25 divisions registering against a
                  fixed datum.  This gives micrometer readings of 0.001 in. for each
                  division on the control wheel.

-3-

Next page
Index