Synch vs Asynch fueling

[jim_in_dorris]

This is a great thread for Sync Async scope patters...

I compared ASDU and ASDZ, there's nothing that would change. It's all EGR, a little spark, some O2 changes, I'm guessing all to tweak a little less emmissions for the communist republic of California.

Hey, they resemble that remark !!!

[POZE]

More patterns. I cannot duplicate the Async pattern. Not sure why. Only thing different is we changed the plugs to cure a misfire. Mark you said you couldn't get Async to work during power braking either ??? Going to try tomorrow on cold engine.

This pattern shows an amp probe on the same injector as voltage. You can clearly see the peak and hold function on the amp pattern. Also notice the voltage spike when the injector opens and closes. The drivers have been known to become weak. They will display irregularities in the hold area of the pattern that create pintle movement and drivability problems.
Red = DRP
Blue = EST
Green = Injector volts
Yellow = Injector amps

[EagleMark]

I can't even get Async to come on when it's supposed to by bin settings to BPW U/sec M/sec even when Injector Duty Cycle is PEGGED at 100%?

AutoProm WB not hooked up here...

[chevmasta]

I was reviewing my last log see attached. Engine Runtime of 358 seconds. I was 100% throttle and the ASYNC Flag showed Yes. The ASYC BPW stayed at 0.00 while I was at WOT.
The ASYNC BPW shows a number virtually all other times than 100% throttle........when the ASYNC Flag isn't "yes". Take a look at the log.

This is a bin that the ASYNC is supposedly turned off.

My "BPW" is about 7.00ms during much of the WOT run in this 7.4l
I also had my "BPC" set to 140..........vs the BANC.bin of 142.

[EagleMark]

That's funny! Your Asnc is set off yet it comes on, my Asnc is set on and it won't come on!

I'll look at your log later and add an Injector Duty Cycle % value. With that and BPW times you should try the stock BPC and calculated BPC to new fuel pressure and see what happens.

FYI the pictures above are a stock engine and stock pressure yest shows 110% duty cycle. All these TBI systems are marginal (short) of fuel to begin with.

Anyone reading this! Every Injector Duty Cycle % value I have found in all ADX files is WRONG! It's only half! $42, $0D etc... 49% = 98%... Static!

[chevmasta]

With that and BPW times you should try the stock BPC and calculated BPC to new fuel pressure and see what happens.

FYI the pictures above are a stock engine and stock pressure yest shows 110% duty cycle. All these TBI systems are marginal (short) of fuel to begin with.

Anyone reading this! Every Injector Duty Cycle % value I have found in all ADX files is WRONG! It's only half! $42, $0D etc... 49% = 98%... Static!

I already tried the calculation with the fuel pressure........we came up with about 120.

I was lean at idle........and lean up top.
150-155BLM values with nothing else touched other than lowering the BPC from 142-120.

[RobertISaar]

the IDC calc being correct depends on if whoever wrote the ADX accounted for the injector firing pattern. my cars are all double-fire MPFI and SFI and their ADXs are setup as such.

[EagleMark]

chevmasta had quoted he found it on FullSizeChevy and I had found it as well, from 2007 IIRC. It was wrong then and it's wrong now for TBI...

[EagleMark]

Back to Async... From what this disassembly says it was never based on time without DRP... the 12.5 is the MAX Async BPW. 80 was divided by firings all based of DRP converted to Duty Cycle.

 ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
; Here to enter asnyc fire, convert sync BPW to async firing time
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;											
L8507	CLRA				;
	CLRB				;Clear out sync BPW
	STD     L3FCE			;TBI injector driver hardware
	JSR     LF08A			;Short delay
;
;-Convert BPW to a duty cycle
;
	LDD     L3FC0			;DRP
	ASLD				;x2 for quad injector firings
	BCC     L8518			;Bra if no overflow
;											
	LDD     #$FFFF			;Clear overflow
;
L8518	XGDX				;Swap result into X    
	LDD     L0271			;Sync BPW
	FDIV				;BPW/DRP x 65536, now %DC 
;
;-%DC x (1/80 firings), or 12.5 msec per asnyc firing

[damanx]

What is Asych and Synch operation?

[EagleMark]

Asynchronous fueling is both injectors firing each DRP (Distributor Reference Pulse)

Synchronous fueling is alternating injector firing each DRP (Distributor Reference Pulse)

http://www.gearhead-efi.com/Fuel-Inj...Asynch-fueling

[damanx]

Ok, that explains why when I was playing with a dso program on my laptop and looking at the injector pulses, they went from alternating to simultaneous, as in this video I made.

Also, is the 1227747 ecm a 2k pulse per mile or 4k? EDIT: looks like 2k per mile.

[gregs78cam]

Asynchronous fueling is both injectors firing each DRP (Distributor Reference Pulse)

Synchronous fueling is alternating injector firing each DRP (Distributor Reference Pulse)

http://www.gearhead-efi.com/Fuel-Inj...Asynch-fueling

I am pretty sure that Asynch Fueling is pulsing the injectors at 80Hz regardless of DRP. That is why you can't have more than 12.5ms injector pulsewidth, because that is 1/80th of 1 second.

[EagleMark]

Yeah, I know, but it still does not make sense... then I found some algorithm that says it uses BPW/DRP to convert to duty cycle before it goes Async. Last post of this thread:
http://www.gearhead-efi.com/Fuel-Inj...-fueling/page6

Sure killed a good thread, no comments so I'm not sure. More I learn about hacks and comments the more I'm sure nothing is guaranteed accurate. Scope patterns in that thread seemed to show Sync to Async firings still at DRP?

One thing I haven't found anyone argue is Async sucks to tune and worse for idle, absolutely horrible on I6 engine conversions I've done...which may prove your right as it's just dumping fuel into intake at timed intervals instead of timed to DRP... but then again it is twice as much fuel I can't tune out? Sync works sweet!

When my kid gets his truck out of the shop I'm going to do Oscilloscope patterns in the Suburban with a Sync and Async bin and prove whatever it is once and for all...

That is why you can't have more than 12.5ms injector pulsewidth, because that is 1/80th of 1 second.

I've thought about that too. But as RPM increase ms time available decreases?

[gregs78cam]

But as RPM increase ms time available decreases?

ONLY if you look at it as being tied to DRP. If for instance you were to enable Asynch at only WOT, then for as long as you are in Asynch mode it will be dumping fuel at 80 pulses per second, and calculating the PW off of that.