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hexdmy

additional calibration tables/logic for idle control

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After tuning a few Link G4/Vipecs , I am thinking that although the idle control is ok, it could use some additional control logic and flexibility. I would suggest based on my experience various other systems, with the first four being the most important :

3d look-up target idle speed,  ect (or charge temp) vs. engine run time or revolutions (add axis to existing 2d table)

3d look-up Idle valve position, ect (or charge temp) vs engine run time or revolutions (add axis to existing 2d table)

3d lookup throttle vs rpm idle valve offset table with variable decay (new table)

3d lookup fuel adder, idle valve position vs tps (new table)

3d tables for closed loop proportional gain ect vs idle target error, one for negative, one for positive (add axis to existing 2d table)

2d rolling speed -> target idle speed adder (new table)

2d TPS -> target idle speed adder (new table)

2d target idle speed adder -> idle valve position adder (new table)

Thank you.

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Just bringing this topic back up, looking back at my laundry list, I know it was quite a bit of things to add. If I had to prioritize two items, they would be the 3d look-up target idle speed, and a 3d (or 2d) lookup throttle vs rpm idle offset with decay and threshold settings, basically some sort of throttle based idle offset, with adjustable decay to both smooth the transition from idle to off idle in situations where the idle spark is considerably lower than MBT, and to slow the return to idle. Certainly this is not necessary on a lot of engines, but I tend to deal with engines that have very lazy idle characteristics (big cam, big intake plenum), and this would help make idle -> off idle -> idle transitions a lot more civilized. 

Finally, as a possible way to make more room for what I'm asking for, could there be an option for a PID loop for idle spark control instead of the 3d look-up table that is available now ?

 

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Hi,

There are some small changes to idle control coming in our next PCLink and firmware release. Here is the text from the release notes:

The number of idle up steps (or percent duty cycle) used when ISC goes into hold mode is now adjustable.  This is effectively ISC "Dash pot" adjustment.  Previously was fixed to 2% for solenoid ISC and 10 steps for stepper ISC.

The items you requested are still on our request list.

Scott.

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Have now updated a vehicle with 5.5.3.2804, this is a nice feature to have, although having the "fixed" target idle speed is still a handicap. Can't wait to see the update that has some of the other changes to idle control added. 

Also noticed that even if I zero the idle up steps, when you go into off idle mode there is a offset to base idle position, so this new constant is in addition to the existing off idle adder ?

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Hi ,

I've just been testing this out with an ISC solenoid configuration. During my testing with the base-table set to 0.0 and (all other adders except hold step set to zero) when I exceeded the RPM Lockout the solenoid DC changed from 0.0 to 5.0. I had my Hold Step set to 5.0, so the only offset being applied is that of the Hold Step.

If something different happens for you would you mind posting your basemap and a PC log of it happening? I'll then look into what is going on. If you prefer you can email it to us on tech(at)linkecu.com

Scott

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First of all, thank you for adding some of this logic to the latest firmware v5.5.6 . I have not been able to try it out yet, but I do have a question. Is there a decay to the 3d target idle offset, or does target idle follow the table. In other words, if I'm looking to add a target idle dashpot function, and left the Y axis as engine run time, but changed the X axis from driven speed to throttle angle, is there a delay or a way to delay the return to zero from the offset added from this table. If not, I think I can accomplish what I'm looking to do, by setting the X axis to a timer channel triggered by a virtual aux out. 

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As an update, I've had excellent results using the 3D table option for "Base/Target Table Mode", using the "Idle Target RPM Trim Table" scaling the Y axis with "Engine Running Time" (as it is pre-configured) and scaling the X axis with a timer that I setup to decay over 10 seconds using a "Virtual Aux" that resets when the rpm is less that 2000, and the throttle transitions from open to closed.  This works exceptionally well, and I have been able to eliminate any return to idle speed dips, and start up is much improved. Thank you very much for adding this functionality !

The only thing I could add, is that down the road it would nice to be able offset target idle with vehicle speed, which could be done with a second "Idle Targe RPM Trim Table". 

 

Link G4 idle target RPM trim table.JPG

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Thanks for coming back and posting an update. I'm glad you've managed to get the idle working well and have taken advantage of the changes the engineering team made.

I'll forward your suggestion for a 2nd Idle Target RPM Trim Table' on to the engineers.

Scott.

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