alpha-N equations?

[Jemison Richard]

Mike,

Hello.  I'm trying to efi a 4 cyl  inline  4 stroke motorcycle (Yamaha
XS1100) and after talking with some very knowledgeable folks on this and the
EFI332 lists I've settled to this solution myself.  I'm afraid I don't have
any experience with the system yet but intend to implement basically what
you're describing here.  I spoke with Sandy Ganz (CA) and she indicated she
was even working on an efi system that basically emulated the old Hilborn
constant flow injection systems.  Basically, she would just fire the
injectors periodically completely irrespective of crank position!  Although
she didn't say I'm assuming she would monitor rpm and increase flow with
rpm.

She indicated in our conversation (and I've heard this on the lists also)
that the main drawback to the method she's taking is low end / idle quality.

My engine has a 180 degree crank.  Pistons 1 and 4 being a pair and 2 and 3
being a pair.  Each pair is at TDC at the same time but on different strokes
in the cycle.  The ignition system fires the plugs in pairs.  I was looking
to fire the injectors basically the same way and off the same crank pickups.

As for the algorithm, I have thought about this some and I was thinking of a
4 stage system, the stages being:

startup    rpm < 700  TPS = 0
idle	  rpm > 700 for some time period  TPS = 0
normal	  rpm > 1200 and < redline - 2500 rpm  TPS > 0   TPS < max (by some
predetermined amount)
WOT      rpm >= redline - 2500    TPS > predetermined amount above and <=
MAX

Within each "stage" injector pulse width would be based on a 2D table of TPS
versus rpm.  This table would be initially established by experimentation.

I'm thinking of driving this system with a PIC device along with a driver /
drivers to boost the output signal to the level required to fire the
injectors.  At this point here are my variables:

INPUTS:
	rpm 		digital	1
	crank position	digital	2
	TPS		analog	1
	O2		analog	1	(at least for experimental
development of the maps)
	timers		digital	3	(count down timers to time event
durations)
	keypad		digital	3	(1 key for mode (startup, idle,
normal, WOT), 2 keys for increase (+) or decrease (-) )

OUTPUT:
	injector fire signals	digital	2
	
	

These ideas are in their very early stages of development but this is my
thinking at this point.  Let me know what you (or others on the list) think.
That's why I'm here.
> -----Original Message-----
> From:	Mike Morrin [SMTP:mikem at southern.co.nz]
> Sent:	Wednesday, December 02, 1998 7:27 PM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	alpha-N equations?
> 
> Just wondering about alpha-N injection systems (ones that meter fuel just
> from throttle position and RPM, without measuring either MAP or MAF).
> 
> In general, air_volume = f(TPS, RPM).
> 
> Is it necessary to keep a 3D map, or can it be reduced to a 2D lookup and
> a
> calculation to correct for the other parameter?
> 
> I think that the relationship between TPS and air flow is likely to be
> highly non-linear, so the question reduces to whether at a constant
> throttle position, there is an easy relationship between RPM and air
> volume?
> 
> How about if it is assumed that one knows the function VE(RPM) for the
> engine at WOT?
> 
> Just playing with ideas.
> 
> Mike