BB injectors

[MSlewis]

Anyone have info/exp with the smallest amount of injector pulse width you can get away with. Trying to tune out a very ugly idle fluctuation & I think it's the pulse width going below .5 msecs as I can actually SEE the injector shut down.

[91chevZ71]

How much offset are you running when they shut off? With offset, About the lowest I can go is 1.0, 1.1 msec sync. That's with 675 usec of offset

[Fast305]

Here are a couple of clippings from a 454 SS $85 .bin for a 454 90# injector. Keep in mind the actual biases increase with higher pressure on the injectors.

;----------------------------------------------
; BATTERY VOLTAGE COMP vs ACTUAL BATTERY VDC
;
; Dissassemby of BAMY, LINES = 17
;
; TBL = 1.28 * MULT FACTOR
;----------------------------------------------
ORG $0458 ; MULT FACTOR VDC
;----------------------------------
L8458 FCB 128 ; 100 0.0
L8459 FCB 128 ; 100 1.6
L845A FCB 160 ; 125 3.2
L845B FCB 160 ; 125 4.8
L845C FCB 160 ; 125 6.4
L845D FCB 147 ; 114 8.0
L845E FCB 147 ; 114 9.6
L845F FCB 141 ; 110 11.2
L8460 FCB 131 ; 102 12.8
L8461 FCB 127 ; 99 14.4
L8462 FCB 123 ; 96 16.0
L8463 FCB 119 ; 93 17.6
L8464 FCB 119 ; 93 19.2
L8465 FCB 119 ; 93 20.8
L8466 FCB 119 ; 93 22.4
L8467 FCB 119 ; 93 24.0
L8468 FCB 119 ; 93 25.6
;----------------------------------------------

;---------------------------------------------
; ASYNC/SYNC QUALS, BPW CALIBRATIONS, (BAMW)
;
; CAL = MSEC * 65.536
;---------------------------------------------
L82F3 FDB 0033 ; MIN BPW, (PW LT 504 usec ISSUED W/ASYNC BPW)
L82F5 FDB 0020 ; 305 usec, MIN BPW
;
L82F7 FCB 255 ; 99.6 Kpa ASYNC to SYNC MAP THRESH
L82F8 FCB 255 ; 6375 RPM ASYNC to SYNC RPM THRESH
;
L82F9 FCB 254 ; 99.3 Kpa, SYNC To ASYNC MAP THRESH
L82FA FCB 254 ; 6350 RPM, SYNC To ASYNC RPM THRESH
;---------------------------------------------

L82FB FDB 0018 ; 274 usec, INJ OFFSET BIAS, (ADDED TO BPW)
L82FD FDB 0786 ; 11990 usec, MAX ASYNC BPW
L82FF FDB 0092 ; 1400 usec, MIN ASYNC BPW
; (shorter is saved till later)
;---------------------------------------------

;--------------------------------------------------
; ASYNC MULT vs RPM
;
; THIS MULT IS USED TO CONVERT SMALL PW
; (PW/CYL)TO ASYNC (PW/12.5 Msec) INJ.
; FOR ASYNC INJECTIONS
;
;
; ASYNC IS BOTH INJECTORS, SYMO
; SYNC IS ATRNATING INJECTIONS
;
; FACTOR = (NUM CYLS/2) * (RPM/60) * (0.0125/2)
; .0125 = PULSE PERIOD, (80 Hz)
;
;
; Dissassemby of BAMY, LINES = 9
;
; TBL = 64 * MULT
;--------------------------------------------------
ORG $04D2 ;
L84D2: FCB 8 ; 9 LINE TBL
ORG $04D3 ; MULT RPM
;---------------------------------
L84D3 FCB 0 ; 0.00 0
L84D4 FCB 21 ; 0.33 800
L84D5 FCB 43 ; 0.67 1600
L84D6 FCB 64 ; 1.00 2400
L84D7 FCB 85 ; 1.33 3200
L84D8 FCB 107 ; 1.67 4000
L84D9 FCB 128 ; 2.00 4800
L84DA FCB 149 ; 2.33 5600
L84DB FCB 171 ; 2.67 6400
;--------------------------------------------------


;--------------------------------------------------
; BPW MULT vs BARO
;
; Dissassemby of BAMY, LINES = 4
;
; TBL = 1.28 * MULT
;--------------------------------------------------
ORG $04DC ; %MULT Kpa BARO
;--------------------------------------
L84DC FCB 136 ; 106.3 75.0
L84DD FCB 131 ; 102.3 85.0
L84DE FCB 128 ; 100.0 95.0
L84DF FCB 128 ; 100.0 105.0
;--------------------------------------------------

[MSlewis]

L82FB FDB 0018 ; 274 usec, INJ OFFSET BIAS, (ADDED TO BPW)
L82FD FDB 0786 ; 11990 usec, MAX ASYNC BPW
L82FF FDB 0092 ; 1400 usec, MIN ASYNC BPW
; (shorter is saved till later)

So is the 274 usec(offset) the mechanical pintle lift timing????

L82F3 FDB 0033 ; MIN BPW, (PW LT 504 usec ISSUED W/ASYNC BPW)
L82F5 FDB 0020 ; 305 usec, MIN BPW

Is the 305 usec the true minimum in synch??????

L82F7 FCB 255 ; 99.6 Kpa ASYNC to SYNC MAP THRESH
L82F8 FCB 255 ; 6375 RPM ASYNC to SYNC RPM THRESH
;
L82F9 FCB 254 ; 99.3 Kpa, SYNC To ASYNC MAP THRESH
L82FA FCB 254 ; 6350 RPM, SYNC To ASYNC RPM THRESH
;---------------------------------------------

These appear to be opposite of the setup in my bin.

[oldred95]

I've been known to idle around .4-.6 and it will do it fine until around .5 and any lower it starts to surge a little. The fuel pump doesn't really like being choked down that much though. During DFCO my pulsewidth is at 0 for the longest time depending on what speed I'm coasting down from.

[91chevZ71]

looks like 274 usec is your offset amount, while the 305 usec is the bare minimum for PW


If I leave my offset anywhere near stock, it's AFU.
My 90's are at 15.5 psi and I run 675 usec offset.

[MSlewis]

looks like 274 usec is your offset amount, while the 305 usec is the bare minimum for PW


If I leave my offset anywhere near stock, it's AFU.
My 90's are at 15.5 psi and I run 675 usec offset.
;-------------------------------------------------
; PULSE WIDTHS BDWM, TYPE $0D
; BDWM, L05, MD8, ($0D)
; TBL = msec * 65.536
;-------------------------------------------------
L4963: FDB 0026 ; .397 msec, MIN SYNC BPW
L4965: FDB 0026 ; .397 msec, SYNC BPW IF FINAL BPW LT CAL
L4967: FDB 0026 ; .397 msec, OFFSET BIAS FOR SHORT PW'S
; (See TBL L496F IF L400E b4)


Here's another from the OD hack w/BDWM bin. Appears they are all different depending on injector?

91chevZ71 How much offset are you running when they shut off? With offset, About the lowest I can go is 1.0, 1.1 msec sync. That's with 675 usec of offset

If you are running 675 offset and 1.0 BPW thats .325...you know it just dawned on me why I need to run it or have it switch to asynch below that .397, Too few DRP's in between for alternating batch fire to put out enough fuel to keep idle stable, right?

Thought I saw something in the code about switching back to Asynch if PW calc gets below around 500 msec. Anyone have insight?

[91chevZ71]

Another thing confuses me on this, or maybe I'm just not 100% on it. I compared my stock ARJU to a stock 454 bin (forget the BCC) and the injector offset was the same. 399 usec or normal operating voltages. 61 pph- 399usec 90 pph-399 usec. WTF

[MSlewis]

I think you and I have some of the same issues with fueling.
Maybe the offset is there due to the physical limitations of the injectors themselves. Like I said earlier, and the offset #'s confirm my theory, below 4 msec's I could actually see the injector shut off for a brief period before IAC/RPM logic kicked in and raised PW. Fast presented the idea to run in asynch, and I tend to agree, just don't know the code well enough to do it properly.

I also presented the question over @ TGO as to the time it takes for the solenoid to open the pintle but it was never answered. Guess I'll have to scope it @ 14 volts to get my answer.

[Fast305]

I think you and I have some of the same issues with fueling.
Maybe the offset is there due to the physical limitations of the injectors themselves. Like I said earlier, and the offset #'s confirm my theory, below 4 msec's I could actually see the injector shut off for a brief period before IAC/RPM logic kicked in and raised PW. Fast presented the idea to run in asynch, and I tend to agree, just don't know the code well enough to do it properly.

I also presented the question over @ TGO as to the time it takes for the solenoid to open the pintle but it was never answered. Guess I'll have to scope it @ 14 volts to get my answer.

Its NOT A FIXED TIME, the time changes with the injector size and the pressure it is running at. The TBI pintle is larger than a MPFI injectors pintle and takes increasingly longer to open with higher pressure. This is where the offset table comes in. I usually start with the stock offset for the injector type, if I experience running problems or see the VE table start to look like a U or a bath-tub, I increase the offset.

I have spent the last 2 days sick or I would have already clipped out all the changes that need to be made to go asynch. When I feel like crawling out of bed long enough to go over the changes needed to run asynch, I will.

[MSlewis]

Its NOT A FIXED TIME, the time changes with the injector size and the pressure it is running at. The TBI pintle is larger than a MPFI injectors pintle and takes increasingly longer to open with higher pressure. This is where the offset table comes in. I usually start with the stock offset for the injector type, if I experience running problems or see the VE table start to look like a U or a bath-tub, I increase the offset.


So unless you're running a vacuum adj regulator(wish i had one)the offset should STAY fixed given same injector/same pressure once it is known,with only slight bias difference due to batt volts correct?

Also is the pressure acting against the pintle or the spring, if it's pintle wouldn't you need less bias?

[91chevZ71]

that sounds correct.


I had a rough idle and a somewhat bathtub-shaped VE table with the lower offset, like Fast is talking about.

I've tried async fuel at idle with no success.

I think my 350 is too small for the 90's at idle. Of course, I bet it would work better if I lowered FP and re-tuned, but then I might lose some top end.

[91chevZ71]

Doesn't the pressure act on the diaphragm in the regulator and the pintle?

[MSlewis]

Doesn't the pressure act on the diaphragm in the regulator and the pintle?

In my experience during testing/adjusting with guage the pressure stays pretty much constant once it was set.Although if tested @ KOEO your reading wont be correct due to batt volts being lower. Have to know what it is when running, also the alternator output from mine stayed @ 13.8 +/- .1.

[91chevZ71]

huh? thought we were talking about fuel pressure, not alternator output/batt voltage

[MSlewis]

huh? thought we were talking about fuel pressure, not alternator output/batt voltage

We still are, the pressure rises with output voltage increases due to pump speed.If your alternator is close to taking a crap and can't handle loads well, the pressure will drop as well.

And hey guys, I proffess to know nothing about this tuning stuff, all your input is appreciated.

[MSlewis]

Found this in the hack, applies to the aforementioned voltage point.

;--------------------------------------------------
; INJ OFFSET VS BATTERY VOLTAGE
;
; Dissassemby of BJYA LINES = 17
; 03-08-1994, 10:45:29
;
; TBL = .065536 * usec
;--------------------------------------------------
ORG $4AFB

;--------------------------------------------------
;
; usec VDC
;--------------------------------------------------
L4AFB FCB 26 ; 396.7 0.0
L4AFC FCB 26 ; 396.7 1.6
L4AFD FCB 50 ; 762.9 3.2
L4AFE FCB 50 ; 762.9 4.8
L4AFF FCB 48 ; 732.4 6.4
L4B00 FCB 37 ; 564.6 8.0
L4B01 FCB 31 ; 473.0 9.6
L4B02 FCB 26 ; 396.7 11.2
L4B03 FCB 26 ; 396.7 12.8
L4B04 FCB 26 ; 396.7 14.4
L4B05 FCB 22 ; 335.7 16.0
L4B06 FCB 19 ; 289.9 17.6
L4B07 FCB 19 ; 289.9 19.2
L4B08 FCB 19 ; 289.9 20.8
L4B09 FCB 19 ; 289.9 22.4
L4B0A FCB 19 ; 289.9 24.0
L4B0B FCB 19 ; 289.9 25.6

Wich only created more Questions. Is the higher #'s in the lower voltage ranges a result of pintle reaction time or less pump revolutions? Dont know about the 0-1.6 being the same as 12.8.

[91chevZ71]

We still are, the pressure rises with output voltage increases due to pump speed.If your alternator is close to taking a crap and can't handle loads well, the pressure will drop as well.

And hey guys, I proffess to know nothing about this tuning stuff, all your input is appreciated.

duh. you're right, man. I totally forgot about that...
there are many batt volt comp tables in the tune. good point, man. sorry

[MSlewis]

duh. you're right, man. I totally forgot about that...
there are many batt volt comp tables in the tune. good point, man. sorry

No apology neccessary, and if I get going the wrong way in my thinking someone please slap me back towards the right direction:mushy:

[MSlewis]

OK,after researching various 454 bins I have come to the conclusion that the offset is LOWER using 75# injectors vs 61#. Most of the ones I see are 274 msec vs 397. I also noticed the screw on top of the 75# injectors is out/raised farther than the 61's. It also appears under magnifying glass that the pintle protrusion through the orifice is slightly less.

If the windings are the same, and flow rate is adjusted by pintle protrusion,then that could explain why the bias is less due to the distance traveled being less no?

I was going to do some flow test yesterday when I noticed something about my 75# injectors. As I said before, I can SEE the injector shut off when BASEpulsewidth gets to .4msecs. What I didn't see was the opposite injector to the one I was watching was still spraying just fine. Made me wonder. Swapped sides and it moved with. Tried 3 different 75's with no change. Could it be that this injector, wich is identical in part & build #'s, has the ability to open with same BPW where the other cannot?

[91chevZ71]

so one injector fired at low pw's and the other didn't?
weird

what happened when you dropped offset as opposed to raising it?

[MSlewis]

Sorry for the delay, been sick for going on two weeks. Anyhows just got through lowering the biases and minimum PW's to match the 454 bin's .274 msec's that I've seen. Will be headed to the track this weekend to see what the beast will do, good time to check it on the way down.

[91chevZ71]

how's it idling? how much pw is in at idle? async or sync?

[MSlewis]

Well after 6 hours in line,total track time was about 44 seconds/3 runs. I did not expect it to grab as well as it did, never been to a track before. Had a hard time with launching. The best I could do my first time out was 13.9 @ 96 mph.Fuel is still to fat and timing is suspect as well. My freinds want me to change parts but I KNOW there's another 6-8 tenths in the tune alone, and some takeoff improvements to be had as well.

On subject...I think we are wrong in assuming the higher pressure needs more offset. Most devices using spring pressure use the pressure to close the device, not open it. Raising opposing pressure will only lessen the force needed to overcome the spring. Having said that I'm still on the fence about if this is the case with a TBI injector. What I do know is that when I LOWERED my bias and min PW the shutoff phenomenon I was experiencing all but dissappeared, and idle settled down to a nice 725-750 rpm's. However, when manifold kPa gets to around 20-30 at moderate rpm's, I can feel it shut down and start surging.

[xx_ED_xx]

where at in florida?

[MSlewis]

Located in Jacksonville, north mandarin area.

[xx_ED_xx]

Oh cool i live in jax as well. Work by avenues mall and live by i10 and 295