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

[Jemison Richard]

Carl,

Very interesting stuff.  Actually I was answering someone elses question
regarding efi and wild camshafts.  It's been a while but I think they were
trying to understand the dynamics of idle with these camshafts.   I'd love
to know more about the ULVE though.  To be honest, this is the first I'd
heard of it by an actual name.  But I can't imagine a ULEV on a small block
Chevy motor with a 300+ degree cam with less than 100 degrees lobe centers!
Even the best algorithm and efi setup in the world wouldn't work correctly
if the headers and intake runner lengths, dias, etc weren't right - and even
then it would only be right at a small rpm range. 

My quess (and it's only a guess) is that the world will never see wild
cammed emissions vehicles, ha!  Now a turbocharged SBC which typically uses
wider lobe centers and a lot less duration - hmmmmmm.  I've waited almost 30
years to see fi come into its own!  Seems to me efi and turbocharging are a
match made in heaven!

Rick

> -----Original Message-----
> From:	EFISYSTEMS at aol.com [SMTP:EFISYSTEMS at aol.com]
> Sent:	Tuesday, December 01, 1998 3:35 AM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	Re: ox sensor on sequential efi,high overlap cam....
> 
> 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