injector "start" time
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injector "start" time
I'm interested in how the ECM decides to fire the injectors. Is that something that's done through the ECM code (on eprom), OR is it more of a "hardware/hardwired" thing?
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This is what DFI does....
The factory ecms have to decide when to start to fire the injectors(ASSumingly relative to intake valve closing). Nobody can shed some insight?
This value, displayed in crank angle degrees, specifies the offset point that the Injector Target timing table indexes. This value generally would be the intake valve closing angle, in crank degrees. In order to set this value, obtain the Camshaft Information Card for your engine. As an example, we will use the Accel 74219 camshaft for a small block Chevrolet V8. Locate the angle at 0.050 tappet lift at which the intake valve closes. This is usually read in crank degrees, (ABDC) after bottom dead center. Since the cam card shows the intake valve closing point at 41*ABDC, and we know the crank angle at BDC intake stroke is 540* on a Chevrolet V8, then we can calculate the exact angle in crank degrees at which the intake valve closes. Simply combine these figures, 41* and 540* to net a crank angle intake closing timing of 581* @ 0.050" valve lift. Enter 581 in the table. The ECM will round this value to the nearest factor of 10, so the ECM will display 580.
Range: 0 to 720
Units: crank angle degrees
Resolution: 10
Range: 0 to 720
Units: crank angle degrees
Resolution: 10
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From: Chasing Electrons
Car: check
Engine: check
Transmission: check
In a batch fire system I don't think it is going to matter. Some valves will be open, some closed, some closing, others opening. AFAIK, there isn't a method of changing the injector firing angle in the TPI ECMs. Doesn't mean that their isn't, just that I don't know of how it could be done.
RBob.
RBob.
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From: STL area
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From: RI
Car: 93 Caprice 9C1
Engine: L05
Transmission: 4L60
Axle/Gears: 3.42
Wow that's pretty interesting.
Though one thing confuses me. Is he talking about Accel DFI or a GM ECM?
He also disappointingly failed to mention the results from being able to consistently sync up the injectors to ignition events. Like Rbob said, it probably doesn't matter much.
Though one thing confuses me. Is he talking about Accel DFI or a GM ECM?
He also disappointingly failed to mention the results from being able to consistently sync up the injectors to ignition events. Like Rbob said, it probably doesn't matter much.
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From: Dallas
Originally posted by kevm14
Wow that's pretty interesting.
Though one thing confuses me. Is he talking about Accel DFI or a GM ECM?.....
Wow that's pretty interesting.
Though one thing confuses me. Is he talking about Accel DFI or a GM ECM?.....
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That is a good site. Wonder if it's somebody around here?
.....I understand that injector start time for batch fire is not going to matter much. Still want to figure it out though. Maybe it's not even in the code, something hardware based? Hmmmm...
.....I understand that injector start time for batch fire is not going to matter much. Still want to figure it out though. Maybe it's not even in the code, something hardware based? Hmmmm...
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From: Dallas
Originally posted by 11sORbust
That is a good site. Wonder if it's somebody around here?......
That is a good site. Wonder if it's somebody around here?......
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From: Dallas
Originally posted by 11sORbust
.....I understand that injector start time for batch fire is not going to matter much. Still want to figure it out though. Maybe it's not even in the code, something hardware based? Hmmmm...
.....I understand that injector start time for batch fire is not going to matter much. Still want to figure it out though. Maybe it's not even in the code, something hardware based? Hmmmm...
;---------------------------------------------
; USED IF CPI/PFI MODE
; (TYPE $0D LN2)
;---------------------------------------------
L4969 FCB 94 ; 66 Deg DLY FM DRP TILL INJECTION
; CAL = DEG * (256/180)
;
L496A FCB 80 ; MIN PERIOD IN DBL FIRE
;-------------------------------------------------
Just FYI.
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