MS3X 2000 Miata: RPM jump to 3k with deceleration

[ridethecliche]

First post here thanks for having me.

I'm new to the world of megasquirt but I'm going along and reading as I go. I'm posting here at the recommendation of a user on miataturbo since I'm a bit baffled as to what's going on here.

I'm on a basemap right now which drives pretty well, but there's a weird issue that doesn't seem to make sense to me. If I give the car throttle, it reacts as expected. The second I let off the throttle, the car revs up to 3k rpm no matter what. I could have revved the car to 1k sitting in my driveway idling, and the car will still jump to 3k and then work it's way back down. This happens even in closed loop idle when the car is warmed up and comfortably idling at 850 or so. It also does this while driving, which freaked the heck out of me when I took it out for the first time! There's no resolution on the map for 3k in closed loop idle and I've looked through every menu in idle trying to figure out what's going on.

I'm attaching two logs and my tune. The issue is repeatable. All I have to do is take my foot off the gas.

Details on the car: Naturally aspirated NB1 2k Miata. Only difference is that I have an aftermarket exhaust manifold. AEM X series wideband.

Thanks for any input as to what's going on.

Edit: I've been reading up about engine states etc. Should I try the 1.5 beta update that just came out?

[ridethecliche]

Okay, so I've done a bunch more digging and have a few questions if anyone is able to answer them!

It appears that CL Idle is triggering when i lift off the throttle. I'm guessing that's because of the engine state and because I don't have VSS enabled.
I'm going to mess with this a bit tonight but here's my question:

If I set VSS to a reasonable speed, i.e. say 5 mph. How do I stop the idle from jumping up when it's triggered? I found that my valve settings range from 25-75. At 25, I'm sitting at about 650-680 rpm, which is low for the miata idle, and at 75, I'm sitting at about 3500 rpm which is pretty nuts! If I narrow this range, say to a range of 30-60 for instance, is that the best way to ensure that the rpm won't jump when CL Idle is triggered? My CL Idle target rpm is about 850 when the car is warmed up. I feel like things are defaulting to the idle value obtained by wide open idle valve and then finding their way back down to the CLT based idle settings. Is there any way to have it switch directly to the CLT based table instead of jumping?

Does that make sense?

Is this something that's fixed with the beta firmware? I'm just wondering if I should update it.

[grom_e30]

look at you closed-loop idle initial values table. in the log it takes about 28-30% for your idle speed closed loop kicks in and uses 65 or so from your table hence the rpm rise

[ridethecliche]

look at you closed-loop idle initial values table. in the log it takes about 28-30% for your idle speed closed loop kicks in and uses 65 or so from your table hence the rpm rise

Ah, I see. So on TPS <1 (default setting), it's jumping back to the CL-idle initial values table, where it cross references the table at a given rpm, so when it hits an rpm in the table (i.e. 190 set here) it jumps to the idle valve duty in the table, correct? My default is set in the high 60's which causes the rpm to jump since that's pretty close to my max 75 value which revs at about 3500.

Is that accurate? Looks like I need to play with the CL idle initial values table!

[grom_e30]

Correct

[ridethecliche]

Correct

Got it working last night! Thank you!

What's your take on using VSS for idle? Does it usually cause issues depending on whether or not one is in gear or depending on when one goes into neutral rolling to a stop?

[grom_e30]

i had mine set to use vss for closed loop at about 10mph this was on older firmware before the engine states were introduced. and i couldn't fault it worked fine for me, that way closed loop was kicking in slightly earlier and by the time you had stopped the idle speed was nice and stable. and if you were crawling along in traffic closed loop should be disengaged by the tps being over the min setting.

[ridethecliche]

I tried to switch out of VSS the other day and tune the engine states properly.

Getting the numbers for the states as I've seen described by muaythaiboxr on the development section led to the values that I have in my tune right now. However, I've had incredibly frustrating experiences with tuning idle since the slow acceleration and deceleration thresholds keep getting triggered during idle and the car just oscillates and is unsettled and threatens to stall. Is there anything that jumps out at anyone here? I'm attaching a tune and a log of the idle issues I'm experiencing. The PWM idle duty is also jumping around during this time.

I'm currently running values for slow accel and decel that are 5x what I got via logs just because of how quickly everything gets unsettled. Am I supposed to be using PID to dampen the oscillations here?

I'm thinking of going back to 1.4.1 since that's what most folks are familiar with and have had good luck getting things to work on these cars without issue. Trying to hold off just a little longer but... it'd be nice to have the car running a bit more reasonably.