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Old 12-31-2011, 05:20 PM   #1
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Default AFR and RPMs fluctuate

I'm rebuilding a new to me 1992 Miata after an accident and I am new to tuning.

The AFR ranges from 9 to 21 while idling. When the car is cold, during the first couple minutes of idle the AFR bounces between 12 and 15 about once a second. After it is warm the spikes are much greater, bouncing from 12-18 on average with peaks over 21 occasionally.

My tune and log files are attached.

I also updated my AFR targets today, but that did not seem to help.
Attached Thumbnails
AFR and RPMs fluctuate-afr_targets_2011-12-31_1600.png  
Attached Files
File Type: msq 2011-12-31_15.15.49-afr.msq (36.7 KB, 96 views)
File Type: msl 2011-12-31_15.38.05.msl (553.4 KB, 82 views)
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Old 12-31-2011, 06:24 PM   #2
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Adjusting the targets will do squat unless you setup closed loop to be active in that region and it'd likely make the situation worse..

Can't see your tune as I'm browsing on a tablet, but likely your idle regions are poorly tuned. Make sure the VE table is as flat as possible and rich enough in that area
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Old 01-01-2012, 03:06 PM   #3
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Attached is a copy of my VE table. I do use VE Analyze Live. How would you recommend I change it?
Or is there something else in the tune to look at too?
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AFR and RPMs fluctuate-ve-table-2012-01-01_1404.png  
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Old 01-01-2012, 05:26 PM   #4
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Assuming your req fuel value is correct. Variations in AFR that you are seeing seem a bit extreme.

1) IS your lc1 calibrated and grounded correctly?
2) Do you have the right calibration in tunerstudio for your wideband?

Sounds like your fuel cells are not high enough, but you have enough WUE to not notice it until the car starts warming up. As WUE goes away, you start seeing leaner spikes. Initially you should set all of your VE cells at idle to the same value. Then you can watch gVE iirc in a log to start adjusting around the most stable map point.

Edit: MAke sure your car is completely warmed up, and WUE is 100% when warm
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Old 01-01-2012, 09:33 PM   #5
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I believe the req_fuel of 5.8 is correct. See attachment.

I did an open air reset of the LC-1 a few weeks ago. I just found out that I can connect it to my laptop, but I have not tried that yet. Is that necessary if I did a reset? Can I just assume it will use defaults when it "resets"? What would I need to change?

The project properties are set to use Innovate LC-1 default, 0-5v = 0.5 - 1.5 lambda.

Under EGO control the sensor type is wideband.

Of course there are dozens of other settings that I don't know if they are correct.

Also attached is a screenshot of the datalog.
Purple = RPM
Green = AFR
Blue = MAP

You can see where I revved it a couple times and AFR kinda evened out. Kinda... The actual logs and tune are attached to the first post.
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AFR and RPMs fluctuate-req_fuel_2012-01-01_2015.jpg   AFR and RPMs fluctuate-data_log_2012-01-01_2029.png  
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Old 01-01-2012, 10:52 PM   #6
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Im unfamiliar with the lc1,, but I would run through calibration again since it was reset. Just to eliminate the variable
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Old 01-06-2012, 11:41 PM   #7
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It definitely seems like once the CLT hits 160 and the warm up enrichment stops that that is when the problems begin.

Take a look at the data log screenshot. Nice and smooth until 160.

So I'm going to start looking more at the VE table next.

If I can use VE live analyzer, should I just let it make all the changes? Or do I need to change each box?

Where can I find more DETAILED info on fine tuning the VE table? How about my AFR targets and spark advance table?
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AFR and RPMs fluctuate-clt160_datalog.jpg  
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Old 01-14-2012, 03:16 PM   #8
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I just reset base timing. While adjusting timing with the fixed angle set to 10 the car ran fine. I changed the trigger angle from 65 to 68 to get the timing more accurately set.

As soon as I burned -10 (to use map) for the fixed angle back in the car started running rough again. Change it back to 10 and it idles fine.

Is there something wrong with my spark advance table? And I'm also still not sure about my VE table. Can/should I let VE Analyze Live have full control over it?

Any help would be greatly appreciated.
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Old 01-14-2012, 04:51 PM   #9
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That looks like a lot of noise, enough to trigger enrichments. Do any of the pros second this notion?
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Old 01-14-2012, 04:53 PM   #10
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I'm not one of the pros by any means, but what I see in his logs looks like there is a problem with his grounding or voltage source (Noise). I don't see how it would be physically possible to see 9AFR to 21AFR (And NOT have the engine die at 21AFR!!) at idle otherwise.
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Old 01-17-2012, 12:04 AM   #11
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When you say "grounding problem", are you thinking specifically the o2 sensor, or something else?
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Old 01-17-2012, 12:47 AM   #12
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Quote:
Originally Posted by blaen99 View Post
I'm not one of the pros by any means, but what I see in his logs looks like there is a problem with his grounding or voltage source (Noise). I don't see how it would be physically possible to see 9AFR to 21AFR (And NOT have the engine die at 21AFR!!) at idle otherwise.
Just remember, lean AFR does not necessarily mean lean AFR. It just means oxygen is present. Any kind of misfire, even a rich misfire, can cause this.

OP, bottom line is that your idle area isn't tuned at all. Look at how spark advance bounces. That poor engine is going nuts. Look here for info on tuning MSPNP idle:

https://www.miataturbo.net/megasquirt-18/timing-idle-requesting-some-help-57133/
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Old 01-17-2012, 01:03 AM   #13
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I just looked at your tune. The warm-up table is garbage, enrichments are huge compared to my car with 550s, you have a noise problem...

You can't get going until you address the fuel table. Look at your fuel table in 3d next to mine. Which car do you think drives like ----?


Steps to glory:
  1. Figure out what's wrong with the noise on your log, I don't have the answers for that
  2. Turn off enrichments for now, drive with very slow throttle position changes
  3. Fix that damn fuel table
  4. Tune enrichments
  5. Fix the damn warm-up wizard
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Old 01-17-2012, 02:01 AM   #14
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Uhhh . . . the one on the left?
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Old 01-17-2012, 08:46 AM   #15
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Quote:
Originally Posted by hornetball View Post
Uhhh . . . the one on the left?
Winner!
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Old 01-17-2012, 09:41 AM   #16
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Thanks for the feedback guys! Obviously this is very new to me. I've read the MS manuals and searched around but never found good explanations. Everything seems to be explained in an extremely high overview assuming the reader has been tuning for years. At least that is how it seems to me. With hustler's short guide and hornetball's link things are starting to make sense.

Thanks again and I will update in a few days.
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Old 01-20-2012, 05:21 PM   #17
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Ok. I've made some progress with idle. I used the steps mentioned by hornetball in post #11 on https://www.miataturbo.net/showpost....9&postcount=11 .

It is running pretty smooth at 900 rpm

Attached is my current tune and idle data log. And I uploaded two screencaps of my VE table.

What specific steps should I use for tuning the rest of the VE table? Before I was using the autotune in tunerstudio.
Attached Thumbnails
AFR and RPMs fluctuate-ve-data.jpg   AFR and RPMs fluctuate-ve-graph.png  
Attached Files
File Type: msq CurrentTune.msq (36.7 KB, 71 views)
File Type: msl 2012-01-20_16.01.22.msl (382.6 KB, 156 views)
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Old 01-20-2012, 07:08 PM   #18
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Tunerstudio's autotune works well, but you need to go on long drives and try to get multiple readings on as much of the map as you can. In other words, do some driving at high RPM/low MAP (stretches of 3rd and 4th gear on the highway). Also, do some 5th gear pulls from low RPM to hit the low RPM/high MAP region.

My personal preference is to record data (usually a 40 minute drive -- which happens to be my commute) and use VE Analyze in MegaLog. That way, I can review what the analysis gives me, smooth out rough edges, etc.

Your map is looking a lot smoother. You're on the right track.
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Old 01-20-2012, 07:44 PM   #19
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Thanks. What about the spark table and afr target tables? When should I focus on those and how should the values be determined?
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Old 01-20-2012, 10:40 PM   #20
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There is a stickied thread on spark tables. Check it out. In addition, the MSPNP default spark table is a safe starting point. I drove on it for months. You can use it while you tune fuel and then go to the dyno when you're ready to tune spark.

Spark pretty much has to be tuned on the dyno . . . no effective street tuning shortcuts that I know of. Many people street tune using det cans, and basically advance until they hear detonation and then back off. The problem with this is that MBT ("Maximum Brake Torque") timing may be several degrees prior to reaching det threshold. So, if you street tune to det threshold, not only do you cut the margin of safety for the engine, but you may also be giving up power.

Fuel, OTOH, is best tuned on the street using Phil Tobin's awesome tools. To start, you need to understand the relationship between the AFR target table and the VE table. Your engine basically fuels off the VE table. Under certain circumstances (assuming you have it setup), it will use the AFR target table to trim the fuel (at least to the extent of the Basic Settings==>EGO Control==>Controller Authority that you give it -- I only give my MSPNP 5% authority). When you autotune or use VE Analyze, new VE table values are calculated that should achieve your AFR targets. The ideal VE table achieves your AFR targets without needing to be trimmed at all. A calibrated WBO2 is critical for this.

Nomenclature-wise . . . running from the VE table is called "Open Loop." When there is fuel trimming going on based upon the WBO2 reading, we call it "Closed Loop."

Your AFR target table should be based upon a knowledge of theoretical engine operating conditions and gasoline chemistry. A few relevant AFR's:
1. Stoichiometric is when gasoline and air combust and theoretically produce nothing by water and carbon dioxide byproducts (i.e., no extra oxygen or unburned fuel present and minimum carbon monoxide). This ratio is 14.7:1 (Air:Fuel). NBO2 sensors are designed to switch at this AFR.
2. Maximum torque happens when your mixture burns the most quickly. ~12.5:1 is the target for this.
3. Richening the mixture past 12.5:1 has the effect of slowing combustion. This helps resist detonation.
4. On the lean side, you can go leaner than 14.7:1 and get some economy benefits in parts of the AFR table where it makes sense to do so.
5. In the idle region, going a bit richer than 14.7:1 usually results in best idle quality. You should have seen that during your idle tuning.

So, based upon the above, this is what I'm doing in my AFR table:


Note that I'm running water injection. If you're not, I recommend you richen the boost region by at least half a point (i.e., the 200kPa row would be 11.5:1).
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AFR and RPMs fluctuate-afrtable.jpg  
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