Have a odd IAC logic request

[JeepsAndGuns]

This may seem like a odd question, or request, but theres something I would like for my engine to do. I am not really sure if this is even possiable with the 7427 or not, but I figured I would ask.
This all goes back to my early days when I still had tbi and a 7747. When I would start the engine with the old 7747, the engine would rev up as soon as it fired and then dropped down to idle. I think some call this "flare up" when the engine starts. I actually loved that, as my exhaust sounds good when doing it, it caught peoples attention and helped the engine crank on up. You crank engine, VROOM, then idle.
Ever since I swapped to the 7427, it no longer does this. It just kinda starts, just goes from dead to idle, no vroom or anything. I remember reading that thread on here about the iac logic in the 7747 and it said to reduce the flare up, to lower the iac park position. I searched around on the 7427 and found that and tried to change it, raised it a little, but it made no diffrence, so I set it back. I noticed that when I turned on the key, didnt start the engine, connected tunerpro, it would hold a low number of iac counts. like it ignores the iac park position and sets itself at something diffrent. I found one parameter that was something like "iac added airflow after startup" I have raised this some and it has kinda worked, but its odd, it doesnt do it every time. Most of the time it doesnt do any diffrent, then other random times it will start then the momentairy vroom then idle. I'm just not getting the results I am looking for.
With so many more idle and iac parameters in the 7427, I am wondering if what I am wanting is even possiable. Seems I remember reading the reason the 7747 did it, was the iac parked open, and did not move untill the engine started. So basicly it would hold wide open, engine would start, then the momentairy vromm was simply the ammount of time it took the iac to close.
I am running BMHK, 454, 0E, manual trans bin. I tried (just out of curiosity) a 350, 0D, auto bin (since their are no 350 7427 man trans bins) and startup and idle was pretty much the same (I did find some interesting results with PE, but thats another thread)

So, is there any parameter, or set of parameters I can change to get the result I am looking for?

[EagleMark]

Off topic, but I meant to tell you I looked at all the knock settings in that bin and I don't think knock works? Have you ever got knock?

[1project2many]

That fast idle is often done with spark advance. Start up advance should be high then drop to match what's in the timing table. IAC is usually slower to respond.

[RobertISaar]

i've had IAC settings both cause and fix this, but spark can play a pretty big role as well.

not sure how it would be referenced in $0D though, i'm used to the $A1 nomenclature.

[EagleMark]

I get a kick out of you JeepsandGuns! You get a newer PCM that has this issue worked out and now you want it back... :laugh:

Couple things I would play with are in Scalers under IAC paremeters:
1. IAC Added Air after Startup
2. Decay Period for Initial IAC Flow
3. Time until Initial Idle Speed Decay
4. Initial Idle Speed Decay Period
5.Initial Idle Speed Multiplier if in P/N

[34blazer]

increase the IAC park position counts and decrease the startup IAC decay values?

[JeepsAndGuns]

Mark, number 1 was one of the ones I have changed, with limited results. I may try the decay period. If I understand that right, thats simply the ammount of time for it to stop doing it? Mabey the decay is too short.

Wonder what parameter causes it to not hold the iac at the park position when you turn the key on, wonder if that could be disabled?

[EagleMark]

I may try the decay period. If I understand that right, thats simply the ammount of time for it to stop doing it? Mabey the decay is too short. Yes , and it's very short, like 100msec.

Going the 1project2many route
1. Startup Spark vs. Temperature
2. Startup Spark Decay Rate vs. Temperature
3. Startup Spark Decay Multiplier vs. Temperature

[JeepsAndGuns]

I dont think the startup spark is gonna get me the result I want. Remember this thread? I had a problem with it trying to advance timing while cranking.
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?406-Startup-or-cranking-spark

(http://www.gearhead-efi.com/Fuel-Injection/showthread.php?406-Startup-or-cranking-spark)Gonna try the iac added air flow decay tomorrow and see if anything changes.

[1project2many]

Increase the rpm at which spark advance is applied during cranking. In some cals it's number of ESC counts or maybe number of DRP counts before spark. Also, spark and fuel are often started separately. Increase time before fuel is delivered so IAC and advance are ready to go when fuel hits.

What makes you think IAC is changing when key is applied? Remember to test theory... let IAC have time to park after shutdown then disconnect IAC connector. If you find the rpm isn't where you want maybe problem isn't quite as you think?

I grew up with carbs. A warm engine with a slight amount of fuel in the intake would start with a tap of the key. I like that. The sunbird will start with as little as two revs sometimes when it's hot. And it doesn't flare up because there's no oil pressure to support unnecessary engine rpm. But hey, if you like the Ford route then go with it. ;)

[EagleMark]

What's with Fords trying to rev the piss out of a motor before oil pressure? My moms Ford Focus used to rev so high first thing, I cringed every time it started, but it was correct according to Furd?

People complian about 1227747 as it takes several cranks before it fires up. I like it as I usually see oil pressure gauge move before it fires up.

I've found so many things like what 1project2many describes in $0D I wouldn't know where to start. But then I wouldn't be looking for Furd Flare up of engine before oil flow...

[RobertISaar]

father in law's 03 grand marquis does the same thing.... crank it up when it's anything less than fully warmed and it will idle near 1500 after an initial flare of ~2000 or so.

i like my engines not getting above 1000 or so immediately after cranking. and they're all quite fast at firing during cranking.

[EagleMark]

Now I remember looking into the Furd Flare and it was to build heat for the cat!

I hate cats (cars should have dogs), they are contaminating the world with Platinum, rhodiumm, Cerium, iron, manganese, and nickel. Other then USA Copper is also used, but in UK Nickel is not as it casuses nickel tetracarbonyl pollution. So emmissions fixed a couple things then technoligy found it created differant pollutions?

Also, my theory on global warming as it started same time as cats were introduced...
</rant off>

[RobertISaar]

actually, it's been proven cats contribute to global warming....

it's the tradeoff of air quality is why they're still used.

[JeepsAndGuns]

Fiddled around with the decay some yesterday. Increased it 100 at a time. I am up to 400. It seems to be getting the result I am looking for. However, its not doing it every startup. Crank it up, it does like I want. Then next time I start it, it just kinda stumbles to life, no rev no nothing.
I will look for parameters like you mention, see what I can find. Just to clear something up, I am not wanting a flare up like yall are saying the fords do. I dont want it to rev up super high and hold it there for several seconds. 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?

[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. :laugh:

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... :rolleye:

"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 :laugh:

[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.