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Old 11-01-2008, 04:37 PM   #1
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Default eMission Impossible 2008

So I failed emissions again this year. But this year, I think I may have a plan for fixing it. I'm posting here in case I've missed something, or somebody has other suggestions.

I did some VE analysis prior to going to the test, targeting 14.7. Also, I dropped back timing 6 degrees across the table (MSPNP base map for NA zones). I failed in the 25/25 test as well as the 50/15 test, both failures of high HC and high CO.

Code:
      25/25                50/15
 Reading  Allowed    Reading  Allowed
HC   236  160           224     166
CO   2.7  0.9           1.6    0.93
NOx  862 1179           772    1304
Looking at the numbers, I'm figuring I ran rich, due to the correlation between high in HC as well as CO, rather than one or the other.

Fortunately, I logged the test. Turns out during the 25/25 test, I was running 13.96 AFR at 2167 rpm and 52 kPa. In the 50/15 test, I ran 14.45 at 1850 rpm and 58 kPa. So yes, I was rich. I ran the test through VE analyzer, and it dropped a couple VE points out of the cells surrounding the test conditions. Good.

Next thought: why wasn't the EGO Control bringing me back to stoich? I took a closer look at the AFR target table, and found that my two lowest MAP values were 19 and 50, set to my idle targets. Crap. That's why the EGO correction wasn't helping me. Turns out the log shows very minor corrections. So, I got rid of the top row, where I don't boost to anyway, and added a row at 40 kPa. Then, at 50 kPa, I can set the target to 14.7 unequivocally. No more averaging in any part of my idle cells. Great.

So then, now that I know EGO now WILL help me maintain 14.7, I was thinking. Perhaps I should set the refresh higher? Right now I have controller step size of 1, with authority 10, and ignition events per step of 72. I'm thinking of lowering the ignition events to, say, 30. Fix the AFR sooner, no?

Couple questions:
Anybody know how sensitive HC and CO are to variations in AFR? As in, with my measured AFRs, is it feasible that this was the cause of failure?
What refresh rate for EGO Control are people using?
Any other suggestions for lowering HC and CO at the same time?
Am I dumb for assuming that fixing my AFR will solve this?
Did you actually read this?

Thanks so much guys.
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Old 11-01-2008, 08:43 PM   #2
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You are definitely too rich. I failed at 14:1 last year.

But you also have too much of both unburned and partially burned fuel. When's the last time you looked at the spark plugs? What's their gap? What about the plug wires? What gas? 87 should be a better choice than 93.

Address the above issues if necessary, then lean it up to 15:1, peel back a few degrees more timing, and pass.
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Old 11-01-2008, 08:48 PM   #3
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Thanks for replying.

Looked at the plugs before testing today: looked good, gapped at 0.032. They're only ~400 miles old. One heat range different than stock. Maybe I should throw in some stock gap and heat range plugs for testing. Just picked up some new NGK wires, cause I don't know how old they are. Fresh 93 octane.
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Old 11-01-2008, 08:55 PM   #4
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I'd get some standard heat range 'emissions spark plugs', gap them .045 or so. Would probably close down the gap some after emissions time and run them all winter. I would give you some extra plugs I have in the garage, but at <$2/ea it's not worth the drive.

Lower octane gas will help too.

I've also seen some amazing results from the FLAPS "Lower your NOx" in a can magic potion fuel additive.
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Old 11-01-2008, 11:15 PM   #5
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I've got some stock-spec Bosch Platinums sitting in the trunk. Probably only a thousand miles or so on them...I'll gap 'em, fix the AFR, knock timing back another point and give it a go on Monday.
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Old 11-03-2008, 07:17 PM   #6
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Put in new wires, adjusted the fuel map via VE analyzer, put in stock range and temp plugs, took another point of timing out, and tried again. Fail:

Code:
      25/25                50/15
 Reading  Allowed    Reading  Allowed
HC   184  160           166     166
CO   2.47  0.9           0.58    0.93
NOx  862 1179           772    1304
Squeaked by in the 50/15, but 25/25 was still rich. Right around 14.1 AFR.

Ran the test through VE analyzer and ran the test again. Fail:

Code:
      25/25                50/15
 Reading  Allowed    Reading  Allowed
HC   184  160           164     166
CO   1.70  0.9           0.56    0.93
NOx  862 1179           772    1304
The 25/25 test was still rich, about 14.4. This time, though, VE analyzer tells me to do nothing. As close as it's going to get. Damn.

My EGO correction isn't working though. I figured that with the table close, EGO correction would bring me to stoich. Unfortunately, the logs say it is pegged at 100. Anybody have a guess as to why? I have the step size set to 1, authority 10, with 72 ignition events per step, active above 160 degree coolant and 1500 rpm, with no TPS limitation, using target table "always." Also, the tests MAP and rpm put me in between cells in my AFR target table that all have a stoich target, so no weird averaging here. Anybody see anything wrong with this approach?

The only other thing I'm thinking of doing is rescaling the rpm axis in the VE table to get cells more closely resembling the test situation. Right now I have cells at 1800 rpm and 2300 rpm, with kPa of 35, 55, and 75. The tests run at (25/25) 2100 +/- 50 rpm at 55 +/- 2 kPa and (50/15) 1800 +/- 30 rpm at 59 +/- 2 kPa. Seems that I'm limited in adjustment, as both tests rely on averages between multiple shared cells. I'm thinking of rescaling a table for emissions to have cells at 1800 and 2100 rpm and 55 and 60 kPa. Would take some iterations to narrow in the VE values, but perhaps the only way? Thoughts?

I've been looking at this link that has a section about tuning megasquirt for emissions, and it seems I am on the right track by assuming I'm still rich.

But why, oh why, isn't my EGO correction working?
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Old 11-03-2008, 07:34 PM   #7
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Question: does the EGO correction threshold still 0.1s, even after going to HR? That might explain the lack of correction going on here...

edit: Ok, just found the "Open Loop Mode" options, and saw my Open Loop O2 Correction was set to go open loop at 53 kPa. This solves the lack of EGO correction. Now why the hell aren't those options in the EGO Control box, or the Lambda Sensor Targets box? Geez...

Last edited by Atlanta93LE; 11-03-2008 at 09:38 PM. Reason: found answer
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Old 11-03-2008, 09:21 PM   #8
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I know my posts here have been very SamNavy-esque, but if anybody has any suggestions I'd be greatly appreciative.

edit: especially, now that I found my open loop mistake, should I go retest with that fixed and count on EGO correction to pin down the AFR? Or, rescale the tables to better match test conditions, as I suggested to myself earlier?

btw: I hate this time or year. I could be actually accomplishing things on my car.

Last edited by Atlanta93LE; 11-03-2008 at 09:41 PM.
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Old 11-03-2008, 09:47 PM   #9
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After you pass, please save the map for next year. I'm still amazed at the difference in allowable numbers from 90-93.
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Old 11-03-2008, 09:52 PM   #10
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Definitely will save the map for next year. Unfortunately, I hope to have made some other changes by then
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Old 11-03-2008, 10:34 PM   #11
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50/15 is much harder to pass than 25/25, so you're doing good. You're just too rich still though.

HC is unburned fuel. CO is partially combusted fuel. You can lower HC by reducing fuel in the VE table. If you know what VE table cell you're in, where you were, and where you need to be, you don't need VE analyzer to adjust the table for you. 14.4/15=.96 To go from 14.4 to 15, scale the appropriate cell(s) by a factor of .96.

Your CO is awfully high. Maybe you've got an injector or two that have bad spray patterns or don't shut off? Something maybe to look into later.
You can lower CO by continuing to retard timing. Don't be afraid to pull timing back. I tried to point out that 1 degree isn't really a worthwhile change, pull it back a few degrees. That will give the fuel more time to fully burn. Even if it's burning in the exhaust manifold, it's still burning and will lower CO.

Leaning back and lowering CO is going to raise NOx. So try not to go too much. But luckily lean and retarded will create hot EGT so the cat should hopefully be able to do its job.

Hey what gear are you running it in? You want to run in a lower gear so the engine spins up. It's really hard for the tester to keep the car in range in a lower gear, so they will use a higher gear if you don't say anything. 2nd will work for both tests, but the tester may go to 3rd for the 25 test. I did 2nd for both tests last year and got nearly 0's on all the HC and CO areas. This year they ran in 3rd for the 25 test and the HC and CO figures were higher.

note: if you've got really shitty rings, I guess it could be possible that oil could cause some extra high HC numbers, but I'm really more concerned with how high your CO is. Also, if you have an oiled air filter, take it off for the test. Should help a little.

<edit> to brush upon some of your follow up questions, I can't see any reason to go through the trouble of rescaling the vetable for this as no one else has had to.
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Old 11-03-2008, 10:55 PM   #12
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Thanks. My 50/15 test CO dropped from 1.6 to 0.56 just from getting closer to 14.7 (from ~14.4). That's about the shift I have to go in 25/25 now. I keep reading in emissions diagnostic books that high CO coupled with high HC is a tell-tale sign of being rich. One being high without the other would point to other issues. A rich mixture will cause high CO, no question about it. I'll try a removing a few more degrees of timing, too.

Anyway, it'll have to wait until Wednesday now. Wish me luck.

Quote:
Originally Posted by Ben
HC is unburned fuel. CO is partially combusted fuel. You can lower HC by reducing fuel in the VE table. If you know what VE table cell you're in, where you were, and where you need to be, you don't need VE analyzer to adjust the table for you. 14.4/15=.96 To go from 14.4 to 15, scale the appropriate cell(s) by a factor of .96.

<edit> to brush upon some of your follow up questions, I can't see any reason to go through the trouble of rescaling the vetable for this as no one else has had to.
I wish it were that easy. I tried to explain that it seems to be the cells adjacent to the main cells causing the problem. Also, both test zones use many of the same shared cells. Problem is, I don't know the weights MS is giving to the neighboring cells, so I don't know the effective VE it is using. That's why I considered rescaling the table, so that I had individual cells that more closely resembled the tests. Oh well, we'll see what happens Wednesday, if I can verify that EGO correction is working.

Last edited by Atlanta93LE; 11-04-2008 at 07:10 AM.
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Old 11-03-2008, 11:23 PM   #13
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being from another state and having different testing procedures I'm currious as to what 50/15 and 25/25 is. Is that a speed/time relationship on a dyno?
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Old 11-04-2008, 07:11 AM   #14
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25/25 = 25 pounds of load at 25 MPH and a 50/15 test = 50 pounds of load at 15 MPH
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Old 11-04-2008, 04:27 PM   #15
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just some food for thought. Here in Md. we have a "treadmill" test that is somewhat similar allthough they don't specify load. at least they don't tell you there is a specific load. just speed. any way the point is they will give you an exemption for things like. being to low to to drive over the dyno rollers, or having low profile tires and expensive wheels. one to many lawsuits I guess. you can also get an exemption for spending a certain dollar amount on tune up / emissions related parts.

the only one of my vehicles that has actualy been tested in the last 10 years is my S2000 because that's just an OBD2 plug in test.
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Old 11-04-2008, 05:21 PM   #16
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FWIW, here's my emissions history for my 1.8 T25 turbo.

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Old 11-04-2008, 06:25 PM   #17
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Thanks, that's great info.
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Old 11-05-2008, 01:17 PM   #18
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Finally passed.

Code:
      25/25                50/15
 Reading  Allowed    Reading  Allowed
HC   121  160           142     166
CO   0.66 0.9           0.64   0.93
NOx  148 1179           244    1304
All I did was up the open loop threshold so that EGO correction was active. Targeted 14.7. Oscillated about this for the most part; showed lean more often than rich. Not great numbers, but I'll take them until next year.

Thanks for the suggestions. Emissions 2008 chapter closed. Finally.
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