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Lotus Service Notes Section EMN
Page 25
Distributor
A rotor arm is mounted on a 'D' shaped extension to the rear end of the inlet camshaft, and is retained by
a patchlock screw. Always replace the screw, or retreat with Loctite 242. The rotor arm incorporates a sup-
pressor and has a resistance value of 1.25 kohms. The distributor cap is retained by two screws, and is pro-
tected from oil contamination from camshaft oil seal leakage by a deflector plate.
Note that there is no requirement, or provision made for, positional adjustment of the distributor.
VVC Engines
These engines use a Distributorless Ignition System (DIS) employing a pair of double ended coils mounted
on the RH side of the cylinder block. Each coil supplies two spark plugs simultaneously, one to a cylinder on its
compression stroke, and one on its exhaust stroke, the latter being 'wasted' such that the system is sometimes
described as 'wasted spark'. Coil one supplies spark plugs 1 & 4, and coil two supplies plugs 2 & 3.
Each double ended coil contains a primary winding, connected in series with the supply and the ECM, and
an isolated secondary winding, connected in series with two spark plugs. It is important to note that there is no
connection between the primary and secondary windings. The coils are triggered by the ECM which switches
off the primary voltage and induces a high tension current to produce a spark in the spark plug connected to
each end of the secondary winding. The direction in which the secondary winding is wound determines that
plugs 1 & 2 receive positive sparks, and plugs 3 & 4 negative sparks.
It is important to note that if it is necessary to run or crank an engine with one or more plug leads
disconnected, either the coil low tension must be disconnected, or provision for the spark energy to be dissi-
pated must be made (e.g. fitting a loose, grounded spark plug to the lead); otherwise the electrical stess
produced will cause deterioration of the H.T. coil and/or ECM.
Each coil has a primary winding resistance of 0.71 - 0.81 ohms at 20°C and a secondary winding resist-
ance of approx. 10.5 kilohms.
Note that the coils can tolerate a certain amount of water spray, but contamination with anti-freeze solu-
tion can result in penetration of the insulation, with consequent danger of current leakage and misfire. Any coil
suspected of being contaminated should be renewed.
Inlet camshaft Rotor Distributor
tail arm cap
em207
Oil deflector
plate Rotor arm
fixing screw
Distributor cap
fixing screw