IAC Closed Loop Question

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ironwill11
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IAC Closed Loop Question

Post by ironwill11 »

Hello,

I am doing a lot of reading on closed loop tuning to prevent my idle from dropping when it goes from Park to Drive.

I am trying to make sure I have my facts straight:

I know the manual talks about entering PID mode on throttle lift which makes sense to me; however, should it be entering PID mode when I shift from Park to Drive? In other words, what makes the idle rpms increase to compensate for the load added at idle from shifting into gear?

Thanks so much for any info.

Will
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

I am really looking for more information on closed loop IAC tuning and how it relates to the idle drop when shifting from park to gear.
muythaibxr
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Re: IAC Closed Loop Question

Post by muythaibxr »

Most likely you will need to get the idle in park really smooth so you can set the P term really high to counteract the rev drop.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

So it should be dropping into closed loop PID control when I put it into gear? I am having trouble getting it to do that. I don't really understand the CL gauge either.

Will
billr
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Re: IAC Closed Loop Question

Post by billr »

I don't think it will "drop into" closed-loop when you put it in gear. It should already be idling in closed-loop, the extra load of putting it in gear just causes the (PID) control loop to change things to compensate.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

Billr,

All the information that I read about tuning to get into PID mode referred to throttle lift. How would I start configuring the ability to get into PID at idle?

Will
billr
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Re: IAC Closed Loop Question

Post by billr »

Post your MSQ, let's see what you have set for idle control now. An MSL showing in/out of gear (at idle) too.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

billr wrote:Post your MSQ, let's see what you have set for idle control now. An MSL showing in/out of gear (at idle) too.

Had some interesting things happen while doing these datalogs.

Here is my MSQ:
2017-02-23_21.52.39_CL_800.msq
The first datalog is from open loop mode where everything is normal. The idle is in the mid 600s (depending on MAP) and drops down into the high 400s when shifting into gear:
2017-02-23_18.43.52_PVD3.msl
Then I did the datalog in closed loop (I left the the target rpm at 800 for now). I shifted from park into gear. Only difference this time is that I saw the CL light coming on at bottom of TS and the CL target gauge was working (didn't do this last time). When I shift into gear it tries to maintain the 800 rpms, but shift out of gear and it jumps up to almost 1700 rpms:
2017-02-23_19.07.00_PvD5.msl

I was curious so I put it back in open loop mode and the rpms were much higher:
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

I was curious to see if I could get back to where I was so I put it back in open loop mode and the rpms were much higher (was not expecting the results of having much higher rpms):
2017-02-23_19.10.25._Open.msl
Any advice would be much appreciated. Kind of addicted to this now.

Will
jamies
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Re: IAC Closed Loop Question

Post by jamies »

are you running air conditioning,
in some installs ive used the a/c idle up (vehicle had NO air cond) to kick up the idle steps when put in gear.

idle timing plays a big part in how much the motor will load down in gear also. the trick is to not over advance and also use adaptive idle timing
SwedCharger-67
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Re: IAC Closed Loop Question

Post by SwedCharger-67 »

Your idle stepper motor seems to react normally after engine start and idling, and when putting into gear. But when you go out of gear back to park your stepper idle valve remains open and does not react to the higher rpms.

I think you have quite a number of settings in your "closed-loop idle settings" menu that you have to go through and modify.
Martin, Sweden
Mopar 512 cui, 8.4 liters, high compression, fuel E85, full sequential control by MS3X, burning rubber just blipping the throttle... :D
turbo conversion
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Re: IAC Closed Loop Question

Post by turbo conversion »

Under Idle Control set Power Between Steps to Always On, I have found this setting works best for most stepper motors.

David

EDIT: also calibrate the TPS, is shows -3.0 through the entire log.
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

jamies wrote:are you running air conditioning,
in some installs ive used the a/c idle up (vehicle had NO air cond) to kick up the idle steps when put in gear.

idle timing plays a big part in how much the motor will load down in gear also. the trick is to not over advance and also use adaptive idle timing
No I do not have air conditioning, and that is a clever idea. I am looking for the adaptive idle timing now. I am not exactly sure how to tune timing. I set the offset and let it do its thing based on the table generator.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

turbo conversion wrote:Under Idle Control set Power Between Steps to Always On, I have found this setting works best for most stepper motors.

David

EDIT: also calibrate the TPS, is shows -3.0 through the entire log.
Changed it to always on. The TPS normally shows in the in the -2.4 range. This was the first time with the -3.0. I will calibrate it again and see how it does.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

turbo conversion wrote:Under Idle Control set Power Between Steps to Always On, I have found this setting works best for most stepper motors.

David

EDIT: also calibrate the TPS, is shows -3.0 through the entire log.

I have re-calibrated the TPS and now it is generally around 0.0 or 0.1%. Also changed the stepper motor to always on. Seems to have the same affect.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

So perhaps I don't understand quite how this works or what has happened. I got the engine running well around 650 rpm in open loop mode. I switched to closed loop and it starts up and warms up nicely to that 650 range, put it into gear and the idle drops to 500. Shut it off and start it back up and it starts in CL mode but the idle is around 850-900 rpm. Put it into gear and it drops to meet the target idle at 675, but idles really rough. The MAP goes from 27 to 40 and the AFR goes really lean. Put it back into park and it goes back up to about 900 but not as rough.

If I change it back to open loop mode it will start up and idle at 900 rpm.

I am not sure what I am getting wrong here.

Should I be trying to re-tune the engine in closed loop mode to a lower RPM when it is started? Or start the tuning process while it is in gear so it is not so rough and lean?

Will
turbo conversion
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Re: IAC Closed Loop Question

Post by turbo conversion »

Post a new data log and msq with your new settings, it just sounds like you still need some tuning.

David
1976 Datsun 280Z L28ET Garrett GT35R T3-T04E stage3 50 trim 63 A/R housing custom grind cam 2000-6000 rpm 440cc injectors intercooled 18 lbs. boost
3" exhaust turbo back LC-1 o2 sensor Hallman manual boost controller EDIS 6 ignition batch fire 60mm throttle body 5 spd T5 borg warner 3.54 lsd
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

turbo conversion wrote:Post a new data log and msq with your new settings, it just sounds like you still need some tuning.

David

Just ran a new datalog off of my current tune:
2017-02-26_17.31.50_CL_Current.msq
Here is the datalog:
2017-02-26_17.21.38_CL.msl
I tried running autotune with it in gear (reverse), which will keep the idle around the target (675) but it is really rough at that MAP. I was trying to adjust the timing to give it a little less but it will not go below 15 degrees.

Will
SwedCharger-67
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Re: IAC Closed Loop Question

Post by SwedCharger-67 »

Assuming you have a GM type stepper motor for the idle valve you don't allow it the full control range. It remains 38 steps open and cannot close.
ironwill11
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Re: IAC Closed Loop Question

Post by ironwill11 »

SwedCharger-67 wrote:Assuming you have a GM type stepper motor for the idle valve you don't allow it the full control range. It remains 38 steps open and cannot close.
I have the GM screw in type stepper motor. However, when I was doing the open loop (warm up) tuning, I found that homing it in the closed direction and having it go down to 17 steps would put me at an idle of 650 (slight variations depending on MAP).

Will
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