ox sensor on sequential efi,high overlap cam....

[EFISYSTEMS at aol.com]

In a message dated 11/25/98 5:32:38 AM Pacific Standard Time, JemisonR at tce.com
writes:

<< Subj:	 RE: ox sensor on sequential efi,high overlap cam.... 
 Date:	11/25/98 5:32:38 AM Pacific Standard Time
 From:	JemisonR at tce.com (Jemison Richard)
 Sender:	owner-diy_efi at efi332.eng.ohio-state.edu
 Reply-to:	diy_efi at efi332.eng.ohio-state.edu
 To:	diy_efi at efi332.eng.ohio-state.edu ('diy_efi at efi332.eng.ohio-state.edu')
 
 Wow,  if this isn't an opportunity to make a fool of myself I don't know
 what is.  Overlap is introduced by the cam designer to improve scavenging of
 the cylinder and maximize fresh charge (new fuel / air) into the cylinder.
 To do this, the concept of overlap sacrifices fuel economy and an orderly
 intake/exhaust processing - rather muddling both processes together.  The
 idea works generally in a narrow rpm band (the more scavenging, the narrower
 the band - thought this is also influenced by valve lift and assymetrical
 cam lobes, etc).  BTW, this can be fine tuned with intake and exhaust
 lengths (that's another story).
 
 The point of all this (and I'm very new to efi so take this for whatever you
 feel it's worth); but from a newbie's point of view, O2 sensing specifically
 and air/fuel measurement in general are pretty much worthless in this
 situation just because of the lack of process (intake/exhaust cycle)
 control.  Everything is sort of happening at once, so trying to "tune" the
 mixture based on a test sample of burnt fuel along with some fresh charge
 seems pretty worthless.  This is why those ultra simple constant flow
 injection setups worked so good!  FWIW, carbs also have some problems with
 cam profiles like this.
 
 Actually, might be worth the effort to forget the sequential efi (unless you
 want to impress everyone in the staging area with your flawless idle
 quality) and just batch it (I just found out about this and it has changed
 my whole outlook on efi!).   You have that much cam, you're not idling
 anyway!
 
 rick

 Hi Rick,
       I enjoy discussing camshafts and overlap cyles for a desired
result,,,,,what we have with EFI that carburetion has no concept, is wall
wetting ......with efi we can build a model inside the computers
"brain"(enhanced closed loop) to discover what happens when a camshaft
produces pulses into the intake manifold.....originally it was tried through
the EGR cyle of the computer which in its truest sense is what it really
is...so if you can measure the mass flow of the fuel and the mass flow of the
air, then decifer the waste and know what to do from there with the dynamics
of the entire system you can correct anything.....this is the goal of
ULEV,(Ultra Low Emissions Vehicle) which is supposed to be here in 2004,
ultimate efficiency...which of course equates to ultimate HP with a given
fuel...I guess I may not have answered your querry but the list can expand
from here...............hth's
-Carl Summers