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So, i been tuning my ride quite a bit after injector replacement this spring. Working on getting my BLMs tightened up towards 128, making good progress. What i have noticed, is a rich condition going down hill, long steep big hill, 60 mph on my way to work. I datalog going to and fro work, no highway mode using TunerproRT. Engine is fully warmed up, when i hit this big downhill. Usually get up to 60, then back off throttle and coast a while till i get down in the valley. Here are a few numbers from my logs:
Narrow band O2 volts 0.866~0.880.
WB showing 12.84~13.59
IBPW is around 1.05mS
Load LV8 is around 32
TPS volts =0.55v (closed throttle)
These values are steady state going down the hill, until i open the throttle. I do not think i am invoking DFCO, as the LV8 isnt quite low enough.
Now, before injector swap, and likely highway mode in, i have seen my WB go waaaay lean, like hitting 20% O2. This is on the display, not a recent datalog. I drive down this hill everyday to work, and obviously up the hill coming home. Any ideas? Injectors are now Bosch III 24lbs. Using $6E tdf, 165 ECM and ARAP based wideband bin heavily modified.....
You're likely at the bpw lower limit. Check the INT. Is it fixed at 128 despite the richness? That is a clue.
Here are some examples of the pw limitation, double-fire, single-fire and dfco events (with 63 lb/hr injectors).
Note: $32B L0033 (MWBG) is not in the standard datastream, so it must be added in order to see the flag. For $6E see L0034 instead.
Here you can see the bpw limitation (flag (0033 MWBG bit 1 1 = FORCE LOW PULSE RESULT OPEN LOOP) and integrator) in effect for a while in double-fire, followed by a dfco event and then a transition back to single-fire mode:
You can see how the pw limitation may cause the mixture to hang rich for some time. It simply can't run leaner (unless the injector is switched off). In a nutshell, this is the problem with injectors that are too big.
In these particular logs I used the stock settings ($32B) and had set single fire mode for testing purposes:
SCALAR: Min Base PW 1.694 msec
SCALAR: Default PW if calculated pw <= Min Base PW 1.694 msec
FLAG: Vats & Tranny Type Flags - Bit 1 - b1 Single fire Set
Good stuff there, t-boy! I think you are on to something for sure. So yes, my INT was locked at 128 during these rich conditions. My injectors maybe slightly bigger than stock, but not that much. Regardless, they must flow better than my stock multecs.
So today's morning datalog into work, got real good data. More about that in a sec, but the pm ride home gave me some data, but the log stopped as i had a com issue. happens with 165 ECM. While i was slowing down, from 60 -49, closed throttle, I hit this rich condition, high O2 volts, rich AFR, and low IBPW. But i was not in DFCO for sure.
Now for the morning ride in, down this long big hill, i hit the rich condition again, with throttle closed. But i also got something else, 5 "lean spikes" during this rich condition. I dug into more, and it was DFCO mode for sure. The IBPW went to 0, rpm dropped a little, AFR pegged lean. These 5 spikes were quite symmetrical and periodic. So, i looked into my DFCO settings, which you know are only scalars, no tables. I have not messed with any of these values, so they should be the same as stock ARAP. It appears that i am set for 1 second in DFCO, and 6 seconds in delay.....pretty much exactly what i recorded. Waay cool!! I like to see things working! So why this logic, only 1 sec in and delay for 6? to protect the engine? I guess sparking and no fuel, should be a brief event? How do you run with it?
There is one setting in there, that I am not so sure about. For %TPS, enable less than 3.1. But for TPS volts, enable less than 0.16, which seems impossible, since at closed throttle, my volts is 0.55. Will never get less than that. So what up with that?
For my default and min IBPW, they are both set to 1.587mS, stock values i think. I been wondering what these values do. If i lowered them, maybe i could avoid this rich condition? Once i get my tune dialed in, i will likely go back to highway mode, which will likely mask or avoid DFCO. I think there is more control in highway mode. Check out my snippet of this down hill datalog.....very similar to what you have seen.
The short duration dfco events are likely due to the load hovering near the enable/disable thresholds. You could increase the hysteresis between them or simply allow dfco to occur at slightly greater load like 50-60 counts in order to stay in dfco longer until the load is increased again naturally via the throttle opening (and increased airflow/rpm).
Reducing both the min pw and default values should allow it to run leaner (assuming the injector still responds to the reduced pw). Highway mode only increases the target AFR, so it won't help with this issue. To run leaner you must reduce the min pw settings, allow easier entry into dfco or run in single-fire mode. Good luck.
Note: I don't like single-fire mode due to the rough transition into double-fire upon PE entry. It may be tolerable with small injectors, but not so much with 63 lb/hr injectors or larger.
;==============================================
; Decl Fuel cut off Tables & Param's
; TYPE $6E MY89 L98 ARAP
;==============================================
LC4EC FCB 48 ; 1200 RPM/25, DECEL FUEL C/O IF RPM GT TRHESH
LC4ED FCB 36 ; 900 RPM/25, REMAIN IN C/O IF RPM GT THRESH;
LC4EE FCB 30 ; 30, ENABLE C/O IF LD VAL LT TRHESH
LC4EF FCB 40 ; 40, STAY IN C/O IF LD VAL LT THRESH
LC4F0 FCB 7 ; 87.5 RPM/12.5, MAX RPM DECEL IN 12.5 MSEC
LC4F1 FCB 80 ; 1 sec's, QUAL TIME FOR DFCO
; cal = Arg * 80,
LC4F2 FCB 8 ; 3%, If TPS LT THRESH, ENAB C/O
; cal = Arg * 2.56
LC4F3 FCB 0 ; -40c COOL, IF COOL TEMP LT THRESH, DISAB C/O
; cal = (Arg + 40) * 256
LC4F4 FCB 15 ; 15 MPH, If Vss <= Disable C/O
LC4F5 FCB 8 ; 3%, C/O Stall Saver TPS Default
; cal = ARG * 2.56
LC4F6 FCB 30 ; 375 msec, C/O Stall Saver T/F TPS Duration
; cal = Arg * 80
LC4F7 FDB 0256 ; 3.906 msec, C/O Stall Saver INJECTION PW
; cal = Arg * 65.536
LC4F9 FCB 1 ; 1, NUM OF C/O STALL SAVER ACEL ENRICH PULSES
LC4FA FDB 0511 ; 6.38 sec's, MIN TIME BETWEEN CONSEC DFCO'S
; cal = Arg * 80
LC4FC FCB 10 ; 3.9%, DFCO T/F TPS Default
; cal = Arg *2.56
Last edited by tequilaboy; Jun 18, 2020 at 02:02 PM.
[QUOTE=tequilaboy;6379859]The short duration dfco events are likely due to the load hovering near the enable/disable thresholds. You could increase the hysteresis between them or simply allow dfco to occur at slightly greater load like 50-60 counts in order to stay in dfco longer until the load is increased again naturally via the throttle opening (and increased airflow/rpm).
Reducing both the min pw and default values should allow it to run leaner (assuming the injector still responds to the reduced pw). Highway mode only increases the target AFR, so it won't help with this issue. To run leaner you must reduce the min pw settings, allow easier entry into dfco or run in single-fire mode. Good luck.
Note: I don't like single-fire mode due to the rough transition into double-fire upon PE entry. It may be tolerable with small injectors, but not so much with 63 lb/hr injectors or larger.
Ya, i can mess with all them parameters for sure, to keep DFCO active longer. Does it hurt the engine to run with 0 PW for a longer time? I dont get the one scalar, for DFCO enable if TPS volts < 0.16. Seems like the voltage would never get that low.
So, i did already make a new bin, lowering the min PW, and a few other small changes. Drove car today, but did not datalog. Going down the big hill to work, i was watching my gauges, and it looks like this change might have helped. But a datalog will tell me for sure. Good stuff!
