Have a odd IAC logic request

[EagleMark]

I want a free rev to mabey 1500rpm or less, and only do it for like .5-1 second. Just like you blip the throttle. Make sense?

Yup! You need to search for the 16197427 to 1227747 conversion! But it cranks more before the start.

I actually saw a paremeter I think would work for a little longer crank time which might be good considering what your doing. Few more cranks to get some oil moving is always a good thing for the engine, especially with a higher rev at startup. I know what your trying to do and understand. Just seems GM built that out... may also be in a coolant factor. With summer temps my Suburban is not revving as high, never really noticed in 12 years until this thread.

[JeepsAndGuns]

What parameter would that be?
Also, you talking about my thread on swapping 7747-7427? or another? What would I be looking for in that thread?

I am off the 4th, so I might get to fiddle around with it some that afternoon. I plan on swapping in a new steering column that morning. Gonna have tilt and headlight dimmer/wiper controlls on the stick. Gonna be sweet. Not sure how long it will take to swap it.

[EagleMark]

I was joking you need to go back to old 7747 ECM...

"Number of Counts for Run Flag"
or
"Number of DRP for Crank to Run"

[JeepsAndGuns]

I saw a parameter like that, was something like number of drp's for crank to run transition (or something like that) and it was 0. Every bin, 0D or 0E was the same, 0. Thought that was kinda odd. I might up that to something. What do you think, 2,3,5, something else?

Swap back to a 7747? HERESY! I will live with this till the end of time before I swap back to that dino

[EagleMark]

Haven't had much coffee yet but BJYL looks like 6 counts to run and 2 DRP crank to run. Now that I think of it I don't think that is going to make it crank a little bit before running... I really don't know why the 7747 does that but I like it and never looked why? Have had people complain because they were used to a carb and it would fire up (and rod knock) on first half turn of starter...

Cold start is probably the most wear an engine gets, this one flaw, or purpose, of cranking a little while could be a reason these old TBI motors last so long. Intresting, always liked it but never thought about it.

[1project2many]

Tried to post some IAC related values to adjust last night but apparently messed that up.

I like carby quick starts but engine has to be right, oil has to be good, etc for no knock.

Several of the 94-95 5.7 tbi truck cals were superceded due to knock on startup. Nothing seriously wrong, but shorter piston skirts allowed more rockin and knockin when cold, aggravated by spark advance. GM's answer was to hide the noise by changing startup advance. Other than noise disappearing, only other noticeable change was dissappearance of what jeepsandguns wants to put back in. No more quick flare then drop.

I'll try to post those values again tonight as well as relevant DRP values. The old Plymouth has taken most of my time lately.

[JeepsAndGuns]

I looked at the bin you mention, BJYL, then looked at mine.
"DRP between crank to run routines" is 3, on my bin its 2
"number of counts for run flag" is 6, on mine its 2

Two other I have noticed and havent figured out, cause it sound just the same as the other parameters:
"number of DRP for crank to run" witch is 2 on both bins
"DRP before crank to run transition" witch is 0 on both bins.

[EagleMark]

Maybe take a look at a $31 bin and see how many? There's a guy who has to crank over 10 times before fires up? May be a mechanical issue too...

[1project2many]

From $0D:

; DRP'S Vs. COOL TEMP
;
; (HOLD OFF CRANKING FUEL FOR N DRP'S)
;
; Dissassemby of BDWM, LINES = 17
;
; TBL = DRP * 1
;----------------------------------------------
ORG $4DC3 ; DRP'S DEG c COOL
;----------------------------------
L4DC3 FCB 0 ; 0 -40
L4DC4 FCB 0 ; 0 -28
L4DC5 FCB 0 ; 0 -16
L4DC6 FCB 0 ; 0 -4
L4DC7 FCB 0 ; 0 8
L4DC8 FCB 0 ; 0 20
L4DC9 FCB 0 ; 0 32
L4DCA FCB 0 ; 0 44
L4DCB FCB 0 ; 0 56
L4DCC FCB 0 ; 0 68
L4DCD FCB 0 ; 0 80
L4DCE FCB 0 ; 0 92
L4DCF FCB 0 ; 0 104
L4DD0 FCB 0 ; 0 116
L4DD1 FCB 0 ; 0 128
L4DD2 FCB 0 ; 0 140
L4DD3 FCB 0 ; 0 152

This will delay fuel during initial crank. Temperature based.

L4EA6 FCB 150 ; 150 Steps park down

Looks like IAC park position. Generally, park position affects how quickly rpm increases as engine begins to fire plus cranking fuel. Increasing park counts can increase startup speed but can also lean out mix if crank fuel isn't correct.

L4EAE FCB 50 ; 19.5% FLOW ADDED AIR AFTER START UP
; (Replaces TPS)

Appears to increase airflow after transition from "start" to "run."

L4EAF FCB 1 ; 100 Msec, DECAY PERIOD
L4EB0 FCB 240 ; 240 Sec's, RUN TIME TO START DECAY OF
;
L4EB1 FCB 3 ; 300 msec, DECAY PERIOD AFTER L4EB0,
; PER 12.5 msecs INT PERIOD

This appears designed to hold rpm high after start (if needed) to help light off cat.

For IAC based flare I'd probably try increasing L4EAE, decreasing L4EB0, and reducing L4EB1. If these values don't affect what you want I can try to spend some time reading code after my kids are asleep and I have all my attention available.

[JeepsAndGuns]

The iac added airflow was the first thing I increased, even before this thread. It helped a little, but not much. I have raised it to 40%. The decay period is what I started raising sunday. Was at 100, I increased 100 at a time and was up to 400. I was slowly getting a little bit of the result I wanted. However, result was completely intermittent. Some cranks it would flare, other cranks it would just do the normal come to life. Just straight from 0 to idle speed. I am using 0E, but I looked at "time for initial idle speed decay" on my bin, witch I have not touched, and its 10 seconds. I didnt get to fiddle with it any today, but I did drive it twice. Both times, and 4 diffrent starts, it didnt flare up one time. So I am at a loss of why sometimes its doing it and sometimes not. So to date, right now the only IAC parameters I have changed have been the "iac added airflow after startup" and "decay period for initial iac flow"

Where is the "initial idle speed" ? I assume its $0E table 4F6C, "added initial idle speed Vs temperature" ? Comments say "at startup" And they are real low, like 50 rpm and less as temp goes up. Wonder if I could take a different approach and try changing that? Mabey start increasing that table, and reduce the "time to initial idle speed decay". Mabey increase the table up a couple hundred rpm, mabey more, and drop the time untill decay down to like 1 second, decay at 500 Ms is probably ok, probably dont want it dropping too fast. This may give me something to try this weekend.

[1project2many]

When does "initial idle speed" occur? If you know that, I can probably direct you to the table you want. Have to think like pcm... when is engine cranking, when is it starting, and when is it idling? All these conditions have different values associated. With older code the park position plus decay period tended to govern startup flare.

Decreasing decay period generally results in faster changes. It's well likely that value you increased isn't used when engine is warm. Change both and decrease wait time at 4EB0. Try to get a handle on when engine is using these tables before increasing park position to prevent hanging high idle.

[RobertISaar]

based on initial idle speed in other masks, i'd say the target idle for the first few seconds of runtime.

is there no cranking added IAC counts table in 0D? that would be the way to do it in A1.

[JeepsAndGuns]

When does "initial idle speed" occur?

I have no clue, all I have to go by is the comment on the table I mentioned (0E table 4F6C), witch states "at startup", and the table is called "added initial idle speed Vs temperature"

Robert, I looked, but didnt see any tables like you mention.