Injector Sizing: REALLY dumb question -Reply

[Tom Sharpe]

10-4 but it all depends upon RPM. Each duration (overlap) value has a
different scavenge RPM and when you are under it (or turbocharged) all kjinds
of unpleasant things happen. I have seen fuel haze "standing" on top of a
carburator from this..  Tom.

Bruce Robertson wrote:

> Just butting in here with my two cents worth...
>
> I thought the whole idea of having the timing overlap was to take
> advantage of the momentum of the exhaust gas passing from the
> combusion chamber into the exhaust port to "scavenge" some intake
> charge. The momentum of the gas is such that once the piston reaches
> TDC it tries to keep going  hence creating a depression if the inlet valve
> were not opening. Because the inlet valve opens the depression is
> satisfied by sucking in some fresh charge. If the overlap was too large,
> and the inlet opened way too soon then I suppose the exhaust gas into
> the inlet would be possible - but doesn't sound too flash to me!
>
> Bruce.