Lotus TURBO ESPRIT Service Manual page 397

SECTION LD
Page 25
I n addition, the small depression below the airflow sensor causes a lesser purge to
take place through canister port 'C'
.
At
water temperatures above 70° C, with wide throttle openings and high rpm,
when turbo boost pressure i n developed, inlet manifold pressure becomes positive,
and the manifold air r a i l hose is sealed by the one way valve, and A/C idle
up
solenoid (will not open above 1400 rpm). Purging now takes place through
canister port 'C' to the depression (greater now with increased airflow) below
the airflow sensor.
Cra nkcase Breather Va Ive
.
Crankcase fumes are ventilated via the crankcase breather valve into the a i r cleaner
housing. Positive crankcase pressure developed during normal running, i s able to vent
through the one way breather valve into the a i r cleaner housing.
I n order to prevent these fumes, under low airflow engine idle conditions, escaping
through the i n l e t trunking to atmosphere, the valve i s also connected via a smaller bore
hose, to the mild depression below the airflow sensor. This enables crankcase fumes a t
idle to pass directly into the intake tract and supresses opening of the breather valve.