07-05-12, 08:47 PM
The following theory was expounded following the consumption of several pints of real ale (Stella) in my local hostelry. The exup valve causes back pressure at low (sub 5000) rpm engine speeds, this in turn prevents unburnt fuel from exiting the exhaust due to valve overlap. At high rpm there is no time for the incoming mixture to get to the exhaust valve. This is the reason for the exceptionally good fuel consumption of my Gen 1, and a good reason for not removing the exup. Any comments most welcome.