PLANT PROTECTION

iTrader: (6)

I was just wondering how to remove the start up 'rev.' Is it something to do with "Idle RPM Start Up Position" in winbin? It is labled in 'steps' though so I don't know what to change. On my Olds 307 it starts and instantly goes to the idle speed set for that coolant temp and thats what im looking for. Thanks

mystikkal_69

iTrader: (2)

i too would like to know how to atleast reduce that "rev up" on startup. it's annoying as hell. when i start it up, it goes up to 1500 sometimes near 2000 . can anyone chime in and help us out? thanks.

RBob

iTrader: (1)

See if there is an IAC position vs coolant table or something of that nature. Typically the IAC position is set at key on or key off, then is moved once the engine is running. May also look for an IAC Park position.

If the park position is high then the engine RPM will flare upon startup. At lot of times it is a compromise between cold start and hot start.

On the '747 the IAC position is always the same at crank and will cause a startup flare.

RBob.

PLANT PROTECTION

iTrader: (6)

Do any of these look like they may do it?
-Idle RPM Start Up Position
-Idle Speed Start-up Delay
-IAC Target Speed Deadband For Park/Neutral
-Warm IAC Park Steps vs. Coolant
These are the only ones that I see that may change it. Your are also saying that there may be no way to change it also?

mystikkal_69

iTrader: (2)

i am using the 6E code. i am also using winbin. i have one option that relates with IAC/Idle issues. i don't have the other one's plant is talking about.


-Warm IAC Park (Steps) vs Coolant

what should i do to the values? reduce them right?

thanks again

RBob

iTrader: (1)

-replying to both-

This one looks like a good start:

-Warm IAC Park Steps vs. Coolant

I am not that familiar with the 6E code so I can't just say "change this." Steps are a position, the smaller the number to less air bypasses the throttle blades. Try removing some steps and see what happens.

As far as not being able to change it, on the '747 no, you can not. Park is park whether hot or cold. On a warm start it can be a quick/sharp flare dependent upon the kickdown delay.

RBob.

MikeT 88IROC350

IAC control is a very complicated system. I have been conversing with TC quite a bit lately about these new parameters. TunerCat has added several new constants in the $6E and $32B tdf files. You just have to ask them for the updates. The TC tables and constants are quite similar to those you mention in Winbin.

So here goes what I have learned. With engine cold and off, the ECM sets the IAC position to the "IAC startup park position". This is part of the "reset" mode that they talk about in the shop manuals. This is usually somewhere in middle of the the full range of motion of the motor. Mine is at 144 steps.

Next you crank the engine, then when the ECM "declares running", it goes to the "Warm IAC park steps Vs Coolant" table.

Then there is the "IAC startup delay time". This could be anything from 400msec to 1000msec. My stock setting was 1000msec, ARAP was 400, so I went with 500msec.

Next the ECM goes into "open loop idle control", which adjusts the IAC position 1 step at a time, using the "desired idle speed rpm Vs coolant" table.

Then (maybe) if engine warms up enough and all the conditions are met, ECM goes into full closed loop idle control. It will still use that desired idle speed table for closed loop.

IMPORTANT FACT: open/closed loop idle control IS NOT the same as open/closed loop fuel control. It took me a while to grasp this, but that is what TC told me.

The deadband error values are the max idle errors that can occur before a correction can be made to the IAC position. You may be able to lower these some, but NOT to 0 and be carefull.

I think the idle flare up upon engine start is a GM design. Sure it is annoying, and I have improved upon this with my ride. The warm IAC park steps table is a good place to start. I am using the ARAP values for that table.

You just have to play with all the paramters, they all work togother, and must be balanced out for smooth IAC control. Take good notes of the stock GM values, then go from there.

HTH

anesthes

iTrader: (12)

I like to bring stuff back from the dead.


Let's look at this statement and see if I understand what he said.

It is the MAX idle error before a correction? What does this mean? Is this the threshold - for example, once the idle is >< xxxx it will 'correct' it?

I don't see why someone would want to lower them if that were the case. In fact, I'd think you would want to increase the value say to 100. A 100RPM, especially if you had a larger cam.

Can someone elaborate?

-- Joe

RednGold86Z

iTrader: (1)

The max idle error data will create a deadband, like you're describing. When saying not to put it to 0, he meant that if you do, it will never stabilize and will always keep moving the IAC. If you want more precise RPM control, you could reduce them, if you had an engine + IAC combination that could respond with very small RPM changes for 1 or 2 steps, but it's usually not worth it or not a stable condition (with these old tech engines).

Yeah if your engine's most smooth state is a bit lumpy, you probably should widen the deadband a bit and slow down the reaction speed, otherwise it can force the rpm oscillation (due to the engine speed changes lag the IAC position changes), rather than damp them.
Spark stabilizer is what should be used when inside the deadband to calm the system oscillations, and to achieve the last bit of RPM control for idle.