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Megasquirt Problems upgrading to MS2

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Old 06-18-09, 10:06 AM
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Originally Posted by toplessFC3Sman
Looking thru the logs, i've noticed that with the staging occuring at a duty cycle of 80%, that acceleration enrichments near the limit trigger the staging code for a split second, then it turns off, then it triggers again once the duty cycle without enrichments passes the setpoint. I was wondering if it'd be possible to put a time-based hysteresis on the staging too; so that once the secondaries come online, they wouldnt be able to turn off for a user-specified amount of time. This could also have benefits when shifting at full throttle, so they wouldnt be phasing in and out.

That's not a bad idea, but with the other ideas I have to further improve duty-based staging this may not be necessary. (Actually the idea came independently from eage8 and Jerry Hoffmann at DIY autotune, but I modified their ideas to where I think they'll work once I get time to implement them. MS3 sequential fuel code has me busy right now).

for the TPS jitter, you can try setting your TPS lag factor a bit lower. This will hurt response a little, but will help filter the triggering at full throttle. You could also increase the duty hysteresis to where the problem doesn't occur as a solution in the meantime.

Ken

Last edited by muythaibxr; 06-18-09 at 10:13 AM.
Old 06-18-09, 10:47 AM
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The TPS jitter problem seems to be mostly mechanical b/c of the engine vibration, so I'll see if I can find a mechanical way of fixing it (be it a new TPS rigged on the end or something to add a bit of friction to the plunger etc). This only really affects the erraneous accel enleanment problems at high RPM. Also, it seems that this vibration only causes enleanments, not enrichments, which leads to the next question: Does the enleanment also only occur if the TPSdot is less than the negative of the minimum TPSdot?

The hysteresis would solve the enrichment>duty for staging => normal < duty issue though, I'll increase that a bit.
Old 06-18-09, 12:33 PM
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It's based on absolute value. If TPSdot < 0 and |TPSdot| > threshold, go into enleanment.

I'm sure the vibration is causing enrichments too, but probably only on the lowest bin of your accel enrichments, making it a bit more difficult to catch.

Also, make sure your MAPdot threshold is really high, it might be happening due to MAP jitter.

Ken
Old 06-18-09, 01:10 PM
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i've been using 100% TPS-based, but based on the datalog, at high RPMs the map signal is more stable, so i'll try throwing 20-40% map-based enrichments in there.
Old 06-18-09, 04:34 PM
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Even if you're using 100% TPS based, MAPdot-based decel can trigger.

Ken
Old 07-20-09, 10:35 PM
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Car's running great, this one isnt a problem so much as some questions. Anywho, in megalogviewer, what are the Gair and Gammae values? Is there a way I can pull up the MAT based fuel correction? The avg AFR at idle seems to move around a bit even when the engines at the same speed/load with no WUE or anything active and i'm trying to figure out why.

Also, i dont really understand the purpose of running the secondary fuel and ignition loads... what does it help to smooth out or assist with? When should it be used?

The timing err% variable in megalogviewer is what the MS calculates to be the actual difference between desired and actual timing? What can be done to minimize this? Im usually seeing +/- 4* of error, with spikes to +/- 12.7. I have the 1st derivative prediction on.

Also, is there a way of keeping EGO correction from engaging when starting the car (espec when warm, so CLT etc corrections wont work) to give the WBO2 sensor time to warm up and start outputting a real value instead of 8 AFR? I still have a little tuning of the PID parameters, but this was the biggest annoyance that i ran into with it.
Old 08-27-09, 08:14 AM
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I've been noticing a random miss at idle. Its not a recent thing, its actually been happening for the whole time i've owned the car, both on the stock ECU and the MS, so I never really thought it was a problem until I heard someone else's 2nd gen that was completely smooth at idle. When it happens, RPM's drop slightly and trigger a tiny bit of oscillation with the CL idle. I only notice it at idle, which is usually between 12:1 - 13:1 AFR depending on WUE, MAT corrections etc. Timing is at 10*BTDC (was at 15* with no noticable difference), and a max dwell of 3 ms. Has done this on brand new plugs and wires, as well as older ones. I'm going to increase the dwell to 3.5 as soon as I replace the turbo (blew it up with a combo of increased boost and launch control), and see if that helps, but does anyone have any other suggestions?
Old 08-27-09, 09:32 AM
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Why are you running such high timing?

I run my timing between -5 and 0 at idle and idle at about 12.5:1, and that gives a VERY smooth idle.

I have tuned every rx7 I've megasquirted that way, and they all act the same.

When I run the table-commanded timing of 10-12 degrees, mine misfires on idle too. Stock unless there's a problem, it should drop down to -5 at idle.

I use the idle advance feature to drop down to -5 on my car when it drops down to idle speed.

Ken
Old 08-27-09, 09:52 AM
  #84  
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Sorry to butt in, but would AC ripple (and voltage spikes) from a bad alternator cause my table corruption in MS2? I had posted in here last year about it when I was trying to run MS2. The spikes were bad (megalog viewer showed as low as 6V up to 19V+ randomly.) The problem was recently fixed and this just came to mind.
Old 08-27-09, 10:36 AM
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Yeah, that could have caused issues with any version of MS.

Ken
Old 08-27-09, 11:53 PM
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I was running it that high because when I was originally tuning it about 2 years ago with MS2, for a given fuel flow rate and idle valve setting, 10-15* gave the highest, strongest sounding idle. -5 had been a bit weak, and tended to cause the idle to get unsteady with changes in load. I'll see if it still does that once I get the new turbo on.
Old 08-28-09, 10:25 AM
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-5 will feel a bit weaker, but it doesn't misfire and usually ends up giving a nice smooth idle... I've found that -3 to 0 work fine if used with closed loop idle speed control for catching sudden loads... I have mine set up with idle advance so that higher loads advance the timing a bit to help closed-loop idle speed control with sudden load increases/decreases... I don't get stalls when that is active, even when I just sit in one spot and turn the wheels (puts a pretty large load on the engine).

Ken
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