Control selection

[Jonathan R. Lusky]

Eric Elliott writes:
> 
> Still reading DIY_EFI archives, number of EFI & ignition questions growing,
> required reading list growing fast, need to study more C, not enough hours/day.
> An introduction might be a better way to start, but perhaps my questions will
> adequately describe me. 
 
> How can the C3 TBI ECU do a smooth idle with large roller cam?
> How can the C3 TBI ECU do the increased timing advance needed with Dart
> Sportsman heads?
 
You keep mentioning spark, but don't mention fuel or idle air control...
what are you doing with those?

For spark, you are going to need to completely remap the spark table.
The stock curve is going to be majorly wrong for your cam.  Ignition
advance needs to be a function of Load vs RPM, the table is MAP vs RPM,
and your mods have totally changed the relation between MAP and Load.

> Given these problems:
> 	High MAP due to a cam  of 208/221degrees @0.05" valve lift, 0.474/0.51"
> valve lift.
> 	Less ignition advance due to high MAP.
> 	Idle rough when MAP sensor connected.
> 	Old stock engine & ECU had needed more small throttle ignition advance.

I'm not sure what table the spark runs off when the MAP is disconnected
or what that looks like.  Sounds like your advance is getting slammed
backed when you hook it up.  I'd bump the static timing at the
distributor up 10 degrees and play some more.  

> Am I on the right track? I have the often mentioned soldering iron, a Fluke 97 2
> channel digital storage Oscilloscope, Fluke 87 DMM and a laptop computer. Any
> help will be appreciated, this is my daily driver while working in NY till June.
 
I think your waaaaaay off base, but someone like Dale would have a much
more educated opinion.

> Is an interface and program available to use the ALDL with a laptop PC?
 
Yes, it's called Diacom, put out by Rinda Technologies.  $300 and well
worth it.  Don't have the contact info handy...

> Is a program for analysis and modification of C3 PROM data available for PC?
 
No.

> Does the C3 optimize ignition advance for power/# of fuel or only retard if
> knock is sensed?

My understanding is that when knock passes the threshold level, the ECM slams
the timing way back and slowly creeps it back up.  You don't ever want
to be hitting the knock sensor.

-- 
Jonathan R. Lusky                        lusky at knuth.mtsu.edu
http://www.edge.net/~lusky/                 (615) 726-8700
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68 Camaro Convertible - 350 / TH350  \_/ 80 Toyota Celica - 20R / 5spd