This may be achieved by pre drying means, such as a pump to provide {HEAD ~ a stream} of air after switch off of the engine, {TAIL ~ which air} may be heated by residual heat from the catalyst or engine 
This may be achieved by pre drying means , such as a pump to provide { HEAD ~ a stream } of air after switch off of the engine , { TAIL ~ which air } may be heated by residual heat from the catalyst or engine
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH