Idle steps issue evo

[sbn1979]

i may be missing something here but as an example if im targeting 50 steps to make 950 rpm and i turn it up to 150 steps to make 2000 rpm, why when reducing it back to 950 i have to target 100 steps? and if i continue to repeat the process i soon find myself at 600 steps, min max clamp at 0 - 700

[sbn1979]

or that every time i cycle the ignition i have to adjust the steps like 10-15 steps to bring idle back to target even after waiting the 3 seconds for the start up table to switch off?

 

[Adamw]

It sounds like you are missing some of the basic fundamentals on how a stepper motor works so I will give a quick explanation.  

Firstly you must realise there is no position feedback to the ECU from a idle stepper, the only way the ECU can have any idea where the stepper motor is, is by keeping a tally of how many "steps" it has sent it forward and back since it done the last "home reset" (usually after power off).  

So If you tell it to move 600 steps, but the valve actually hits the mechanical stop or bottoms out after 100 steps - there is no way for the ECU to know this - it  just keeps sending the 500 steps and assumes the motor is moving.  Once you have done this the actual valve position no longer matches where the ECU believes it to be, so next time you go back in the other direction you will get completely different numbers for the same position.

So this is your main problem - For the Evo stepper motors I think the maximum step count they can mechanically move is about 140 - so you never want to command more than this.  Your max clamp should be set around here or less.

 

Secondly, you have got your logic back to front judging by this statement: "if im targeting 50 steps to make 950 rpm and i turn it up to 150 steps to make 2000 rpm".  The actual step number is "steps from fully open", so you should have a smaller number to raise RPM, and a larger number to reduce RPM.  If yours doesnt work this way then you may have the reverse/normal direction setting wrong.

 

18 hours ago, sbn1979 said:

or that every time i cycle the ignition i have to adjust the steps like 10-15 steps to bring idle back to target even after waiting the 3 seconds for the start up table to switch off?

After you turn off the ignition the ECU does a stepper reset (winds it fully open, and zeros the step count, then moves back into position ready for the next start up), so you need to give it a little time to do this after you turn the ignition off - before you turn it on again.  Say 5 seconds or so should do.  

I also suggest you update to the lastest firmware as there was a bug that affected stepper reset under some conditions a little while back.

[sbn1979]

Thank you for teaching me the fundamentals in how a stepper motor works though in this instance all it needed was a firmware upgrade......

[longan]

Hi Adamw,

Logged into the PCLINK software to look at the sample maps. I notice a few things:

 

Why in the sample maps in for the evo 8 and evo 9, the stepper is set to 150 when you said it 140? Should I change it to 140?

Also why is the evo 9 sample maps idle base position is the opposite way to the evo 8 maps? Which is correct way?

9 - goes from 55-100

8 - goes from 90 to 42.5

 

From the guide it states:

The value in the table is the percentage of how open the ISC actuator is from 0% to 100%. When using an E-Throttle you would normally only use a very small portion of this range as it represents the full throttle plate movement range.

 

I read this as 0 percent is not open. So it close. 100 percent is fully open. So allowing maximum air. 

[Adamw]

I assume you are talking about a G4X?  This thread was about G4+ that uses "Steps from fully open" in the base position table.  So the complete opposite of G4X which your quote seems to come from.  

In G4X it uses 0-100% spanned over the max step value range (so 0 should be fully closed and 100 is fully open), the base pos table should have larger numbers at cooler temps.  The Evo 9 map is wrong, it has probably been incorrectly translated from a G4+ map.

I have never tested a Evo 7 stepper even though I own one, but I have a step value of 150 set in mine and have never had any drama with idle. 

 

[longan]

Hi Adamw,

Yes I have a G4X. I will look for G4X based threads from now on. One more question

So to set the initial BISS (base idle speed screw), on a different thread, i believe the procedure was to set to close which was 500 for G4+. Therefore the G4X, it will be set to zero. Is this correct?

 

 

[Adamw]

Yeah that would work.  Make sure you do a power cycle after adjusting that as forcing the valve to its mechanical stops it may lose position so a power cycle will reset it.  Also make sure the keep alive time in the ECU hold power menu has something like 5 seconds in there, I see some of our base maps have this set to 0.

  

[longan]

Hi Adamw,

Yes I can see it set as zero. So i will change that.

Regarding closed loop mode, does it use both the offset table and idle up? or just the idle up. 

 

 

[Adamw]

Actually I just learnt that in G4X the keep alive time can be zero and the ecu will still wait until the reset is done before shutting down so it seems this is no longer important.  

In CL you have both a position offset and an idle up value.  The offset is needed so you arent just relying on the closed loop to notice the change in target and then waiting for it "catch up" and move the valve to achieve the target RPM.   This is often refered to as "feed forward" - you are kind of telling the valve where it will likely need to be, the closed loop will still act on it but it should be somewhere close to the correct position already.  

 

[Vaughan]

And only use the idle up if you want to actively target a different engine speed when that thing is active, if you want the same idle speed then idle up would be 0 and offset would be set to approximately the correct value to correct for the change in load on the engine.

[longan]

Got it. Thanks Adam and Vaughan. Really appreciate the fast response.

[Grant Baker]

The number of steps is wrong (or was) in the G4X base map...

[Boosted4g63]

On 7/17/2021 at 9:37 AM, Grant Baker said:

The number of steps is wrong (or was) in the G4X base im sorry to bring this from the dead, but Im having idle problems as well and to my knowledge when you turn of the car the iac is supposed to open so when you start the car it start faster and as the temp goes up the iac starts to closing and it should be around 40 on idle. If Im wrong please correct me, Im using g4+evo 8 plug in on a 2g dsm and Im use to to see those numbers on ecmlink or evoscan and for some reason on this ecu the numbers start the other way around from -22 degrees at 20 steps and 198-212 degrees at 120 steps which is the opposite of the other ecmlink or even the stock evo 8 ecu using evoscan. Sorry for this long story but something tells me I might be doing something wrong here. 

[Adamw]

The base position table in the G4+ is "steps from fully open" so smaller values means more air.  You should have smaller values at the colder end of your base position table.  

At power off the the idle valve will do a reset, then park at "home" (50 steps from fully open) so the ECU knows where it is at next power up. 

At power up the idle valve will then move to "base position - start up step" while honoring the min and max clamps.  

 

 

[Boosted4g63]

3 hours ago, Adamw said:

The base position table in the G4+ is "steps from fully open" so smaller values means more air.  You should have smaller values at the colder end of your base position table.  

At power off the the idle valve will do a reset, then park at "home" (50 steps from fully open) so the ECU knows where it is at next power up. 

At power up the idle valve will then move to "base position - start up step" while honoring the min and max clamps.  

 

 

Yes I just find out right now, 140 steps are fully close means no air is going thru the iac so 40-50 steps at the start is almost full open so more air is going thru the iac. Now I can see that my problem is tune related.