H*LP needed understanding fuel\ignition curve dynamics

[Todd Knighton]

Jim,
	In response to your torque vs. fuel question, yes I hope when 
you bump up the torque, that the fuel also jumps up.  When the engine 
is properly mapped out, the fuel curve at full throttle (at a given 
boost or normally aspirated) should match the volumetric efficiency 
curve almost to a tee.  The horsepower end of it is accounted for in the 
rpm part of the equation, so if you have the same injector pulse at 2000 
rpms and 4000 rpms you're producing double the horsepower at 4000 vs 
2000 rpm's and also using twice the fuel because you should be injecting 
every rpm or at least every other rpm.  But regardless, the time of 
injection should stay relative to the rpm's.   
	If you multiplied out the fuel duration times the tpm's to get a 
specific quantity used per unit time, and plotted it, that plot would 
look just like your power curve (less friction and some small efficiency 
factors).
	Make sure the unit is decreasing the air fuel ratio according to 
boost as well.  Light cruise should be about stoichiometric (14.7/1), 
100kpa or 0 boost should be about 10% rich (13.3/1), and around a bar of 
boost you should be getting to the real low 12's, unless you want to 
burn up a few set of pistons.
	As far as spark goes, it varies with rpm and torque.  At low rpm 
you don't need as much advance due to the time it takes to burn the 
mixture.  At higher rpm the time is about the same to ignite the 
mixture, but the motor is spinning faster, so you must ignite it a bit 
earlier.  At any given rpm, you can almost map advance to the load, at 
light load you can use a lot of advance, where at heavy load you must 
decrease the advance.  How much depends on your combustion chamber 
design, compression ratio as well as fuel.  Try this.

Boost:	250kpa	15deg		18deg		17deg		19deg


	100kpa	18deg		30deg		28deg		32deg


	000kpa	10deg		40deg		45deg		50deg
		1000		3000		5000		7000
				RPM

	Outside of missing about 132 points, this is a close semblance 
to what I run on my Twin-Turbo 911.  Bear in mind that V.E. affects the 
amount of ignition timing as well, as shown by the dip at 5000 rpm's at 
n.a. and high boost.  The only reason that 1000 rpm and high vacuum is 
low is for driveability, idle, and starting conditions.

Hope this helps.

Todd Knighton
Protomotive Engineering
Jim Pearl wrote:
> 
> I've got some tough (IMO) questions!
> 
> Recently I've gotten the new version of DFI's software and it generates fuel curves for you based upon max HP, torque, and the RPMs 
where they occur.
> 
> What I'd like to better understand is how torque and fuel relate along with ignition. I've noticed that when I input a greater torque figure 
that the "hump" in
> 
> Should max fuel occur at max torque? What about ignition? should max spark occur at light cruise? Peak torque? Currently my spark curve is a 
mess with spark pe
> 
> I know this really isn't enough data for specific tips but what I really want to understand better is when I should max spark and fuel. I 
may be able to get ho
> 
> Last but not least (sigh) anyone know which pin on the EEC-IV harness is for the driver's side O2 signal? I currently can't run closed loop as 
my signal is rea