closed loop idle ineffective/random droops
 

I thought I had my warm idle tuned the other day and set out to tune warmup as it was about 30*F out. Intake temperatures were reading 45* Trying to tune warmup and it is requiring a LOT of enrichment... WTF? It finally warms up and it won't idle. So I go back to tuning my warm idle...

The idle cells in VE table are now 47 where they were ~40 the last time I did this (it was warmer then fwiw). ???

Then I switch over to closed loop to see how that is responding and it's really bad. When there are extra loads (headlights or heater fan - I have no PS or A/C) it is always leaner than what I have tuned the warm idle and there are strange and sudden drops with varying recovery speed depending on load. I've searched and read the manual and posted my log and tune...


What is happening in the log:

I hit the headlights it responds fairly quickly and idle well for a few seconds. Then it will randomly drop ~100 RPMs but respond fairly quickly. It does this twice. Then I turn the headlights off.

Then I turn the headlights and crank the heater fan at the same time and RPM drops wayyy down to about 600 RPM. almost stalls. Responds, but then it does the dropping down to ~800 RPM thing again but responding very very slowly. It does this three times and then I stopped the log.

It sounds like you're landing in cells in the VE table that need retuning. You'll need to adjust the VE to avoid leaning out before you try to tune closed loop settings.

MSPNP1 or 2?

Thanks, I messed with that w/o much success but maybe that was due to my VE table scaling. When I turn those additional loads on the MAP goes up ~33kPa, normal idle is ~27. My VE table has the bottom two points at 19 and 35 kPa.

Think I'm going to change these to 25 and 35 or add the 25 row in between and try re-tuning the warm idle.

Some of the base map idle settings don't make sense to me:

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Sorry, MSPNP1. Been trying to use the idle tuning procedure you posted in that other thread...

Looking at your VE table, you have a big VE discontinuity when you go down to 19kPa. You should consider the 3x3 block from 19 to 35kPa and 800 to 1800RPM your idle area. You want to make sure things are relatively stable (not necessarily all the same value -- but not a 12 to 14 point VE jump either) in that area. BTW, the time that you will get to 19kPa or lower is during closed throttle deceleration from a higher RPM. Looks like you may almost be killing the engine lean there. The closed-loop algorithm won't be able to recover from that.

I've attached my current VE table for reference -- please don't copy the VE values -- just observe how things are "stable" in that lower, left corner:

Your spark table looks OK to me. One of the things people are doing with lower idle advances is using two spark tables to increase idle advance to help handle an AC load. You don't have that issue. In fact, given your loads (alternator only), I'd be tempted to tune warmup-only mode and call it a day. You really don't need closed-loop.

Do make sure your cranking advance is reasonably low to avoid kickback during starting.

Oh sh* I was wrong about my VE table axes... But yeah I hadn't touched 19kPa for idle tuning because I wasn't hitting that part of the table - on the log MAP min is between 26 and 36. Everything I've done for idle tuning so far has been sitting in my driveway.

I would love to use warmup only as it seems simpler but turning the headlights/fan on was dropping the RPMs significantly so I thought I would need closed-loop. Maybe I just need to refine my VE table in the 19-35 region. I will just put in more time tonight and post an update.

Any general thoughts on my AFR targets while we're at it? Only running NA right now...

https://www.miataturbo.net/attachmen...ine=1359737481

Here's a thread for you:

https://www.miataturbo.net/megasquir...-please-63878/

Here is where I ended up. It doesn't really hunt, but it doesn't seem to respond to the initial droop when I turn on the accessories as fast as I would expect it to. I guess it's not really an issue as I doubt I'll see this full-heat + headlights very often if at all.

I played around trying to do warm-up only with the accessories on and I just couldn't accomplish anything. I just couldn't get it to idle at speed - it was bogged down to ~800 RPM.

In the log:
Idle, turn the headlights on + heat on full, it slowly comes up to ~900 (target), throttle blip, settles back to ~900.

mspnp1, sounds normal, itll never react well to load.

Agree. Normal.

Warmup is just a static air opening. The idle speed ends up being whatever it ends up being. But it will be stable (assuming fuel and spark advance are relatively stable).