Occasional high idle

General support questions and announcements for MS3. See also MS3 manuals.

Moderators: jsmcortina, muythaibxr

Post Reply
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Occasional high idle

Post by humjaba »

Hi there. I have not been able to reliably recreate this, but sometimes my car likes to idle high - high enough to bounce off the fuel cut. Usually if I shut off the fuel cut it will lower back down, but for some reason today it decided to hang out at 2500rpm for a couple minutes and then settle down. I have no idea why, but looking at CL idle target RPM I have no idea what it's doing (see attached log). The only time it seems to happen is if I don't give the RPM enough time to settle after starting... It seems to need at least a minute before I take off or the idle speed goes up as described.

Would love if you have any ideas. This is on a 95 Miata, with a 2002 VVT Miata engine. MS3 Basic built by MSLabs running speed density. I've attached my idle settings - Idle VE and Idle Advance are off.

Thanks guys!
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: Occasional high idle

Post by Matt Cramer »

It's not in closed loop at that point. Try less spark advance at that RPM / load.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Re: Occasional high idle

Post by humjaba »

Thanks, I'll give that a try. I've also turned on idle advance - we'll see if that helps at all.

I think I saw that you will be at road Atlanta this Monday with jzilla? This will be the first event I've done since the swap, and this is my first time tuning a car. I'm running the advanced group.
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Re: Occasional high idle

Post by humjaba »

Still happens.. But I'm not sure what's going on. Can you look at that log I posted again and explain what happens at 1743.362s? Closed loop target rpm spikes from 1207 (wrong) to 2444 (very wrong) and then ramps down to 900 (much better), and the rpm and pwm idle duty cycle follow it down after the spike.

What's going on here?
muythaibxr
Site Admin
Posts: 8228
Joined: Thu Oct 14, 2004 12:48 pm

Occasional high idle

Post by muythaibxr »

The target will start wherever the current RPM is and ramp down from there. Most likely you need to use the initial value table to get things close when CL is engaging (MAT based), then adjust the RPMdot and MAP thresholds. The RPMdot one should be set to just higher than actual RPMdot at steady state with RPM just above idle. The MAP threshold should be set to just below the lowest MAP you see on idle.

The initial value table is the single most important part though.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Re: Occasional high idle

Post by humjaba »

Okay thanks I'll give that a shot. I was thinking that might be a good idea, because "use previous" seems terrible if "previous" was wrong. I guess I'll just have to log and see what a good baseline for the initial value table is? My basemap has zeros for that whole thing.
muythaibxr
Site Admin
Posts: 8228
Joined: Thu Oct 14, 2004 12:48 pm

Re: Occasional high idle

Post by muythaibxr »

Yes. Use logs to fill it in. Use IAT for the y axis.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Re: Occasional high idle

Post by humjaba »

Had a great time at road Atlanta yesterday, was nice to meet a couple of the diy guys. I'm bummed I didn't get to run against the mx3 a bit more, it seems like we were pretty close. I ran a 1:52.5 in the last session if Kevin is interested in comparing.

Switching to the table has fixed the high idle and it works great now. It nearly stalls after starting now, though the rpm climbs up to the target after a few seconds. Will work on that next.

Unrelated, but is there a way to log the digital output from my innovate lc2 in tuner studio? I'm trying to find an accurate way to calibrate what my mega squirt sees vs what the lc2 reports.
racingmini_mtl
Super MS/Extra'er
Posts: 9128
Joined: Sun May 02, 2004 6:51 am
Location: Quebec, Canada
Contact:

Re: Occasional high idle

Post by racingmini_mtl »

You can use the digital output directly in the MS3 using the CAN bus and my TinyIOx: http://www.msextra.com/forums/viewtopic ... 67&t=44280. You also then get the same data in TunerStudio.

Jean
jbperf.com Main site . . . . . . . . . . . . . . . . . . . . . . jbperf.com Forum
Image
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Re: Occasional high idle

Post by humjaba »

racingmini_mtl wrote:You can use the digital output directly in the MS3 using the CAN bus and my TinyIOx: http://www.msextra.com/forums/viewtopic ... 67&t=44280. You also then get the same data in TunerStudio.

Jean
I would like for this to be my long term solution. I thought of making something similar using a teensy 3.1 but also using it to control a small screen displaying some data. Do the serial commands come from the ms3 or your firmware? Finally, I have an lc2 - I guess this means I have to buy the serial to stereo adapter from their site?

Also, your site says ordering is disabled - are they available?
racingmini_mtl
Super MS/Extra'er
Posts: 9128
Joined: Sun May 02, 2004 6:51 am
Location: Quebec, Canada
Contact:

Re: Occasional high idle

Post by racingmini_mtl »

Ordering should be back on in a few weeks after I receive a new batch of boards. But if you need one now, PM me as I still have a few in hand. And you would either need to buy the adapter or make one yourself.

The serial connection is handled by my firmware. But it only reads the data from the LC1 or LC2 or MTX-L; it doesn't send any command as those devices continuously broadcast the digital AFR data. My firmware reads the data in the standard format and the default configuration. This data is then sent to the MS3 or MS2 over CAN once you have configured the MS to use the CAN data.

Jean
jbperf.com Main site . . . . . . . . . . . . . . . . . . . . . . jbperf.com Forum
Image
humjaba
Helpful MS/Extra'er
Posts: 35
Joined: Fri Sep 26, 2014 11:17 am

Re: Occasional high idle

Post by humjaba »

Okay.. I might just do that. In the mean time, I think I will try my hand at writing a little utility to log both at the same time and generate some kind of mapping. Would be handy for calibrating beyond just eyeballing it for anyone who doesn't want to cough up the dough for a can adapter.

Edit
Not the first one to think about this. Though maybe ill save myself the headache and just buy your tinyiox... http://www.msextra.com/forums/viewtopic ... 22&t=39696
Post Reply