Injector Sizing: REALLY dumb question -Reply

[Bruce Plecan]

-----Original Message-----
From: Bruce Robertson <bruce_robertson at MAIL.TAIT.CO.NZ>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Thursday, August 27, 1998 6:54 PM
Subject: Re: Injector Sizing: REALLY dumb question -Reply


>Just butting in here with my two cents worth...
>

We seem to be mixing lots of low speed, and high speed events together.

At low engine speeds there is a pronounced self egr effect.  That is
exhaust entering the intake tract.  The more overlap the worse the idle.

As you begin to get some good VE numbers the tuned lenghts come more into
play, and this self egr disappears.

>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!


Cheers
Bruce
>
>Bruce.
>
>