MS3 Reasonable values in Idle Timing Correction Table?
 

I have a 2000 Miata (AC/PS) with FM no-electronics kit and a new MSPnp Pro. The car is used for casual driving, and for autox and track days.

I'm working on getting the idle tuning done and have not found much info on values for this table. My understanding is that timing will correct swings in rpm faster than the ICV, but that is dependent on stable AFRs to prevent oscillations as the correction deals with movement across fueling cells.

The goal is for my AFRs to be the best that they can be so that the timing corrections needed are minimal. These two are not dependent, but lowest need for timing correction to deal with load changes would indicate the VE table values are not working against me.

What are real world Idle RPM Timing Correction Curve table values that stabilize idle, indicating that my fueling is spot on?

Here is a pic of the table with the values as supplied in my base tune. It seems like a 2 degree reaction to a 400 rpm drop in idle speed is not very much correction, hence my question.

https://cimg8.ibsrv.net/gimg/www.mia...297fcdb768.png

As I've been working on my MS3 setup, I've been doing a ton of searching and reading. I'd done that before the post above as well. In research on AFRs going lean once the engine was really hot,
(most likely due to injectors dead times changing from heat-soak) I found a composite screen shot that included the Idle Timing Correction Curve Table above with the values shown below.
The person that posted that is a well regarded member who often helps out beginners. I'm snipping that and including it below so that others may find it helpful if they need to search the Idle RPM Correction Timing Curve.
Of note is that my values are higher on the add timing side and lower on the subtract timing side. I'm going to retune my Idle VE Table in an attempt to work around my leaning issue and so that I can get my Idle Timing Correction Curve Table values down some.

https://cimg4.ibsrv.net/gimg/www.mia...eb502aea18.png

In my opinion, your timing corrections are still not very aggressive.

1) There is some dependence on what your base timing is. Base + correction gives total for a particular condition.

2) If you are targeting 850, and are sitting at target, by the time you add the 8*, you will be at 450 RPM... very uncomfortable.

I do not remember mine off the top of my head, but my base timing is 10*, and I think I add another 10* by the time I am 100RPM down. I don't use any overspeed correction. However, if I were at a higher base timing at idle, I would.

My result is that I don't drive down to set point quickly, but conversely, I don't go perceptibly down with load added.

Here is mine at present: I am happy with it.

https://cimg2.ibsrv.net/gimg/www.mia...b41226060c.png

Note: This is primarily for electrical loads and Power Steering. Fan and A/C have their own idle-up parameters. I will post them as well:

https://cimg1.ibsrv.net/gimg/www.mia...b679d9fd6d.png


https://cimg6.ibsrv.net/gimg/www.mia...03f8dce3e7.png

I appreciate that. I am already using a couple of the techniques I found that you posted for other facets of my tune (idle VE table tuning). I'm looking forward to seeing what you're doing.

DMak, Can you post your Idle Advance settings? Or, are you not using idle advance? If that is the case, can you post your ignition map for comparison?

Thank you,

DMak, Can you post your Idle Advance Settings? Or, are you not using Idle Advance? If that is the case, can you post your ignition map for comparison?

Thank you,

Chiburbian, Sure.

What I do, is use Idle Advance set fairly low, at 10*. The regular advance table is set more normally, so that as soon as I touch the throttle and go out of CLI, the advance jumps.

So the car is sitting idling at only 10*. Pretty boring... all set at 10*. I suppose I could move it a little with load, but this works pretty well. That gives me lots of room to use a very aggressive correction to limit idle drop when uncompensated loads occur (electrical loads, P/S). The A/C and Fans, as stated above, in post 2.

Here are both my advance tables, as well as the method to engage idle advance:


https://cimg0.ibsrv.net/gimg/www.mia...d74b4425ea.jpg

https://cimg1.ibsrv.net/gimg/www.mia...f1be861ff8.jpg

And in case I have adjusted my correction curve, here is the present one. Yeah, I added some -* to bring idle from the settling point to set point more quickly:

https://cimg3.ibsrv.net/gimg/www.mia...396150f480.jpg

Realistically, at full warm idle, I am at 800RPM, so if it drops by 300, that is 500, and the car would be really struggling. Also, I'm not sure I could get away with this if I had a light flywheel. But I can have my HVAC fan off, be at 800RPM, turn the fan to full, and simultaneously turn on my headlights and I will get a 150 or so RPM drop. It is not pleasant sounding, but not too bad, and that is an extreme test, IMO.