emissions decision- please confirm
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emissions decision- please confirm
Firstly, thanks to all for advice received in prior post.
Recap:
165 ecm L98 MAF with zz4 cam installed since last test
Just as suspected, I failed emissions because my HC ppm was .86 with a limit of .58.
Now, NOx was way down from previous test taken with stock cam at only 37 ppm with an allowed 652 ppm.
CO% allowed was .32 and I registered .19.
Now, I believe I know what to do to get this situation looked after. I'm thinking of raising the timing in the test area (on the rollers, btw) to decrease HC. I know full well that this might adversely affect the other reading but it looks like I have a lot of "wiggle room" in the Nox department. Not that much in CO.
What do we think and most importantly, by how much do I advance to see a difference?. I want to pass on the first retest and prove to the skeptical guy I can save the $125.00 for the emissions failure "analysis" to tell me what parts to throw at it (all new by the way).
Thanks in advance.
Recap:
165 ecm L98 MAF with zz4 cam installed since last test
Just as suspected, I failed emissions because my HC ppm was .86 with a limit of .58.
Now, NOx was way down from previous test taken with stock cam at only 37 ppm with an allowed 652 ppm.
CO% allowed was .32 and I registered .19.
Now, I believe I know what to do to get this situation looked after. I'm thinking of raising the timing in the test area (on the rollers, btw) to decrease HC. I know full well that this might adversely affect the other reading but it looks like I have a lot of "wiggle room" in the Nox department. Not that much in CO.
What do we think and most importantly, by how much do I advance to see a difference?. I want to pass on the first retest and prove to the skeptical guy I can save the $125.00 for the emissions failure "analysis" to tell me what parts to throw at it (all new by the way).
Thanks in advance.
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Take a look at the example on the Megasquirt EFI website. Look under the MS-II tuning page. They showed that decreasing timing helped for
reducing HC.
reducing HC.
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From: In your ear. No, the other one.
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Had the exact same problem last year when I installed the ZZ4 cam (and some aluminum heads, etc) into my L98. Just barely failed HC at idle (passed fine at 2000 RPM). I took some timing out (5 degrees or so) and passed with a comfortable margin.
Just for fun, I replaced my cat and retested again to see if that was involved too. My cat was definitely functionless. The new cat made me pass wtih flying colors. I have a feeling the new cat alone was all I needed, as the ZZ4 is a pretty mild cam.
If you have to retest, pull some timing out at the problem locations (idle and/or @ RPM), and make sure your cat is functioning. If it's not, replace it.
M
Just for fun, I replaced my cat and retested again to see if that was involved too. My cat was definitely functionless. The new cat made me pass wtih flying colors. I have a feeling the new cat alone was all I needed, as the ZZ4 is a pretty mild cam.
If you have to retest, pull some timing out at the problem locations (idle and/or @ RPM), and make sure your cat is functioning. If it's not, replace it.
M
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From: In your ear. No, the other one.
Car: '89 Trans Am WS6
Engine: 350 TPI
Transmission: T5WC
Axle/Gears: 3.08 posi
To be clear, advance the timing timing... I changed the timing from 5.98 to 20 degrees (BTDC) at idle.
Sorry for the confusion.
Sorry for the confusion.
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From: Chasing Electrons
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Originally posted by 2new2funny
That's 2 for pulling timing.
Anyone else?
The cat's a definite necessity. Mine is new. CO% definitely within limits.
That's 2 for pulling timing.
Anyone else?
The cat's a definite necessity. Mine is new. CO% definitely within limits.
RBob.
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Originally posted by Mangus
To be clear, advance the timing timing... I changed the timing from 5.98 to 20 degrees (BTDC) at idle.
Sorry for the confusion.
To be clear, advance the timing timing... I changed the timing from 5.98 to 20 degrees (BTDC) at idle.
Sorry for the confusion.
Thanks for the clarification. Did you use the distributor, or in the chip? I'm inclined to go the chip route.
15 degrees is huge.
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From: Chasing Electrons
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Originally posted by 2new2funny
RBob,
The pamphlet I got after the test says that
lean AFR is a cause of high NOx
RBob,
The pamphlet I got after the test says that
lean AFR is a cause of high NOx
I can state as fact that the Calif calibrations increase the fuel and back off the timing. . .
RBob.
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From: In your ear. No, the other one.
Car: '89 Trans Am WS6
Engine: 350 TPI
Transmission: T5WC
Axle/Gears: 3.08 posi
Cool chart (very useful). Look at a slightly lean (<16) AFR... note increasing NOx. The pamphlet you have likely is referring to this area of the curve, as a typical car is more likely to be slightly lean than VERY lean (which is the portion of the curve that Bob is referring to).
You say you have a new cat, which is good, but how new is it? If it's brand new I can tell you from first hand experience that it takes at least 80 miles to get the cat "burned in". First hand meaning 4 iterations on an analyzer: brand new (0 miles), 40 miles, 80 miles, 120 miles. It was after 80 miles that levels stabilized. (It's nice having friends willing to screw around with expensive equipment).
In any case, richen it up a bit, pull some spark, and re-test. If you fail again, spend the $150 to do "emissions related" work at a licensed shop, then go for the exemption. It's not as difficult as it seems, provided you haven't done any super visible work (i.e. you have all the emissions gear on it at least by appearence).
M
You say you have a new cat, which is good, but how new is it? If it's brand new I can tell you from first hand experience that it takes at least 80 miles to get the cat "burned in". First hand meaning 4 iterations on an analyzer: brand new (0 miles), 40 miles, 80 miles, 120 miles. It was after 80 miles that levels stabilized. (It's nice having friends willing to screw around with expensive equipment).
In any case, richen it up a bit, pull some spark, and re-test. If you fail again, spend the $150 to do "emissions related" work at a licensed shop, then go for the exemption. It's not as difficult as it seems, provided you haven't done any super visible work (i.e. you have all the emissions gear on it at least by appearence).
M
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No mention at all of this chart in the brochure, RBob.
To further complicate matters, the same publication says that high NOx can be caused by excessive spark advance, suggesting, of course, my situation with low NOx means there's not enough advance!
So, in a lean condition, would advancing the timing be a dangrous thing?
Thanks for the chart, RBob.
To further complicate matters, the same publication says that high NOx can be caused by excessive spark advance, suggesting, of course, my situation with low NOx means there's not enough advance!
So, in a lean condition, would advancing the timing be a dangrous thing?
Thanks for the chart, RBob.
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I'm lagging in posting, here!
Yes, I see the slightly lean condition clearly.
Now, by adding fuel, we're talking about identifying the MAF table and adjusting? I thought closed loop directly relied on the O2 sensor.
THe cat has about 1000 miles on it.
Yes, I see the slightly lean condition clearly.
Now, by adding fuel, we're talking about identifying the MAF table and adjusting? I thought closed loop directly relied on the O2 sensor.
THe cat has about 1000 miles on it.
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From: Corona
Car: 92 Form, 91 Z28, 89 GTA, 86 Z28
Engine: BP383 vortech, BP383, 5.7 TPI, LG4
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Allow me to throw in my opinion: You're not lean. You'd notice terrible drivability if you were 20:1. You probably have a misfire on probably 1 cylinder. Possibly induced by too much EGR (and perhaps it's also biased too much to one cylinder), or just some other general malfunction, such as a low flowing injector or vacuum leak, or spark plug problem, or perhaps plug wire arcing.
edit: Yes, reducing timing in that trouble spot can do wonders. Even if NOx is low, less timing can really help cover a misfire. It'll burn better and produce hotter exhaust, which can heat the cat a little more, which can help clean even more.
edit: Yes, reducing timing in that trouble spot can do wonders. Even if NOx is low, less timing can really help cover a misfire. It'll burn better and produce hotter exhaust, which can heat the cat a little more, which can help clean even more.
Last edited by RednGold86Z; Jan 8, 2006 at 02:42 AM.
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RednGold,
Driveability is fine. Again, this test is asm 2525 so the readings were taken at 1300 rpm in drive. The chart does indicate VERY lean. Shouldn't datalogging in this area show problems with the BLMs (or am I too new at this?).
Without the cam, looking at general trends, the NOx was about one third of the limit. This reading showed 10% of the old. Interesting. Does this suggest anything?
I wasn't surprised that HC was high. I was surprised that NOx was very low. Is this a typical result for a bigger cam?
Driveability is fine. Again, this test is asm 2525 so the readings were taken at 1300 rpm in drive. The chart does indicate VERY lean. Shouldn't datalogging in this area show problems with the BLMs (or am I too new at this?).
Without the cam, looking at general trends, the NOx was about one third of the limit. This reading showed 10% of the old. Interesting. Does this suggest anything?
I wasn't surprised that HC was high. I was surprised that NOx was very low. Is this a typical result for a bigger cam?
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Originally posted by 2new2funny
RednGold,
Driveability is fine. Again, this test is asm 2525 so the readings were taken at 1300 rpm in drive. The chart does indicate VERY lean. Shouldn't datalogging in this area show problems with the BLMs (or am I too new at this?).
Without the cam, looking at general trends, the NOx was about one third of the limit. This reading showed 10% of the old. Interesting. Does this suggest anything?
I wasn't surprised that HC was high. I was surprised that NOx was very low. Is this a typical result for a bigger cam?
RednGold,
Driveability is fine. Again, this test is asm 2525 so the readings were taken at 1300 rpm in drive. The chart does indicate VERY lean. Shouldn't datalogging in this area show problems with the BLMs (or am I too new at this?).
Without the cam, looking at general trends, the NOx was about one third of the limit. This reading showed 10% of the old. Interesting. Does this suggest anything?
I wasn't surprised that HC was high. I was surprised that NOx was very low. Is this a typical result for a bigger cam?
RBob.
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I've definitely heard of the self egr-ing and it could be a possibility.
You lost me with the "Try bumping up the O2 rich/lean/mean values for that engine RPM/airflow (however the tables are looked-up)."
What do you mean? Is it a table?
You lost me with the "Try bumping up the O2 rich/lean/mean values for that engine RPM/airflow (however the tables are looked-up)."
What do you mean? Is it a table?
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From: Chasing Electrons
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Originally posted by 2new2funny
I've definitely heard of the self egr-ing and it could be a possibility.
You lost me with the "Try bumping up the O2 rich/lean/mean values for that engine RPM/airflow (however the tables are looked-up)."
What do you mean? Is it a table?
I've definitely heard of the self egr-ing and it could be a possibility.
You lost me with the "Try bumping up the O2 rich/lean/mean values for that engine RPM/airflow (however the tables are looked-up)."
What do you mean? Is it a table?
Code:
;----------------------------------------------
; UPPER ZERO ERROR REF FOR SLOW o2 R/L
; ARAP
;
; 02-20-1997 Dissassemby of ARAP Lines= 9
;
; TBL = .226 * mvdc
;----------------------------------------------
ORG $C459 ; mvdc Air Flow g/sec
;----------------------------------
LC459 FCB 140 ; 619 0
LC45A FCB 148 ; 655 8
LC45B FCB 152 ; 673 16
LC45C FCB 152 ; 673 24
LC45D FCB 148 ; 655 32
LC45E FCB 144 ; 637 40
LC45F FCB 132 ; 584 48
LC460 FCB 128 ; 566 56
LC461 FCB 125 ; 553 64
;----------------------------------------------
;----------------------------------------------
; LOWER ZERO ERROR REF FOR SLOW o2 R/L
;
; 02-20-1997 Dissassemby of ARAP Lines= 9
;
; TBL = .226 * mvdc
;----------------------------------------------
ORG $C462 ; mvdc Air Flow
;----------------------------------
LC462 FCB 120 ; 531 0
LC463 FCB 128 ; 566 8
LC464 FCB 132 ; 584 16
LC465 FCB 132 ; 584 24
LC466 FCB 128 ; 566 32
LC467 FCB 124 ; 549 40
LC468 FCB 112 ; 496 48
LC469 FCB 109 ; 482 56
LC46A FCB 106 ; 469 64
;----------------------------------------------
;----------------------------------------------
; Fast o2 Rich/lean Treshold vs Air Flow
;
; FAST o2 RICH IF LC4AD + LC453
; FAST o2 LEAN IF LC4AD - LC453
;
; (SUB OFF LC454 IF AIR DIVERT)
;
; 02-20-1997 Dissassemby of ARAP Lines= 9
;
; TBL = .226 * mvdc
;----------------------------------------------
ORG $C46B ; mvdc Air Flow g/sec
;----------------------------------
LC46B FCB 130 ; 575 0
LC46C FCB 138 ; 611 8
LC46D FCB 142 ; 628 16
LC46E FCB 142 ; 628 24
LC46F FCB 138 ; 611 32
LC470 FCB 134 ; 593 40
LC471 FCB 122 ; 540 48
LC472 FCB 120 ; 531 56
LC473 FCB 118 ; 522 64
;---------------------------------------------- RBob.
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Originally posted by Z69
Those table should be in your xdf already.
The code snip is to help you see the big pic and maybe convince you to go get a hac and trace those tables through the code to see how they're used.
Those table should be in your xdf already.
The code snip is to help you see the big pic and maybe convince you to go get a hac and trace those tables through the code to see how they're used.
Thanks.
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I might have it! I found a table labelled "closed loop rich/lean threshold vs airflow".
Now, I guess the next step would be to datalog and find the associated airflow at 1300 rpm and make the adjustment.
For the sake of argument, if I find the flow to be at 48 g/s, the O2 threshold at that point is 539.85. "Bumping up", as RBob suggested, would be values higher, correct; say 600?
Now, I guess the next step would be to datalog and find the associated airflow at 1300 rpm and make the adjustment.
For the sake of argument, if I find the flow to be at 48 g/s, the O2 threshold at that point is 539.85. "Bumping up", as RBob suggested, would be values higher, correct; say 600?
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passed:)
Decision (to advance timing) confirmed. I raised the timing in the area of the test to 48 degrees. That alone brought HC emissions down by a third (enough to pass).
Thanks to all for your opinions.
Thanks to all for your opinions.
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That's great news, I'm glad you got it to pass!
At the risk of being accused of hijacking the thread, where would you begin adjust your BIN (or replacing a mechanical part) if the only thing showing high is CO% ? My NOx, HC, etc. were all midrange but the CO is either at or 10-20% over the accepted values?
FYI - my 'Bird has got the A.I.R. system hooked up and operational, but the heads are not drilled for the EGR so that is turned off in the BIN.
Hope someone has some good input on this. I'm "legal" at the moment, but am concerned about why this condition is occurring, and whether it's a symptom of something else that may be (or is) about to rear it's ugly head. I'd much rather be "doing the right thing" and have it completely legal and compliant. That's why I went with the super-expensive SuperRam to begin with <sigh>
At the risk of being accused of hijacking the thread, where would you begin adjust your BIN (or replacing a mechanical part) if the only thing showing high is CO% ? My NOx, HC, etc. were all midrange but the CO is either at or 10-20% over the accepted values?
FYI - my 'Bird has got the A.I.R. system hooked up and operational, but the heads are not drilled for the EGR so that is turned off in the BIN.
Hope someone has some good input on this. I'm "legal" at the moment, but am concerned about why this condition is occurring, and whether it's a symptom of something else that may be (or is) about to rear it's ugly head. I'd much rather be "doing the right thing" and have it completely legal and compliant. That's why I went with the super-expensive SuperRam to begin with <sigh>
Last edited by vernw; Feb 7, 2006 at 02:50 PM.
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Does that 4-gas table assume complete combustion across the entire range of AFR? If so, then you can't rely on its accuracy at extreme ends, or anywhere for that matter. Any misfire in general, as has been suggested, can throw off the results.
I believe a misfire would show high O2 and high HC, which looks like it's a lean AFR problem, but it doesn't mean a lean AFR caused the misfire.
I'm trying to learn from this, as sometimes these things run counter-intuitive.
He advanced timing and that brought down HC by enough to pass. Can we infer that the engine wanted more advanced timing to more completely burn the mixture before the exhaust valve opened? Can we also infer that this fix wouldn't have been as effective if his cat was MORE effective? In other words, late timing works sort of like speed to a healthy cat. But late timing with a marginal cat (let's ignore its new-ness for the moment) does nothing but introduce unburnt mixture into the exhaust, with nothing to finish the job.
I assume NOx went up, but obviously stayed below the max level.
I believe a misfire would show high O2 and high HC, which looks like it's a lean AFR problem, but it doesn't mean a lean AFR caused the misfire.
I'm trying to learn from this, as sometimes these things run counter-intuitive.
He advanced timing and that brought down HC by enough to pass. Can we infer that the engine wanted more advanced timing to more completely burn the mixture before the exhaust valve opened? Can we also infer that this fix wouldn't have been as effective if his cat was MORE effective? In other words, late timing works sort of like speed to a healthy cat. But late timing with a marginal cat (let's ignore its new-ness for the moment) does nothing but introduce unburnt mixture into the exhaust, with nothing to finish the job.
I assume NOx went up, but obviously stayed below the max level.
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Thanks, Vernw.
It's a bit of a relief ( a lot, really), but it does get me to wonder about other things...
The reading was dead-on the limit- next time it might be over, who knows, when it's that close.
I'm not entirely versed in these things (thus the post), but what condition is your cat in? I've heard that's a big factor in CO readings? Mine were very low.
In response to Kev, NOx went up 50%, but in total was still a 10th of the allowable, that's why I permitted myself to use the max advance, as I said initially, I wanted to nail it in one additional try.
The fuel mixture? You're talking above my head. I don't think the cat can be any better, nor do I know to what degree it has an effect on HC. If HC is unburnt fuel, maybe not a lot???
I myself was wondering about the fuel tables.
For next time, clearly, I'm going to have to allow an advance of more than 48 degrees (is that possible, anyone?) or figure out if indeed I'm running a quantity (newbie term, maybe?) of fuel that is entirely too much. Experts, please set me straight here. I'm not talking about AFR. Am I talking pulse width, maybe? or am I talking nonsense?!!
It's a bit of a relief ( a lot, really), but it does get me to wonder about other things...
The reading was dead-on the limit- next time it might be over, who knows, when it's that close.
I'm not entirely versed in these things (thus the post), but what condition is your cat in? I've heard that's a big factor in CO readings? Mine were very low.
In response to Kev, NOx went up 50%, but in total was still a 10th of the allowable, that's why I permitted myself to use the max advance, as I said initially, I wanted to nail it in one additional try.
The fuel mixture? You're talking above my head. I don't think the cat can be any better, nor do I know to what degree it has an effect on HC. If HC is unburnt fuel, maybe not a lot???
I myself was wondering about the fuel tables.
For next time, clearly, I'm going to have to allow an advance of more than 48 degrees (is that possible, anyone?) or figure out if indeed I'm running a quantity (newbie term, maybe?) of fuel that is entirely too much. Experts, please set me straight here. I'm not talking about AFR. Am I talking pulse width, maybe? or am I talking nonsense?!!
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Car: 83 POS monte carlo 2015 chevy P/U
Engine: 92 5.7 tpi 5.3
Transmission: 700r4 6L60E
Axle/Gears: 2.42 too high
vernw, ruling out any bad or weak parts, off hand i can think of 2 ways to lean it out.
1 would be to drop your fuel pressure a pound or 2 & see where the CO is at.
the other way would be to turn the VE down in the lower RPM & high MAP range.
doing either may lower the HC or cause it to go up, & it may also cause the NOx to go up.
2new2funny, a good cat will drop all 3 gases, HC, CO, & NOx by a lot.
the best cats are the factory cats, but they are not cheap, i have seen some reading go up after an aftermarket cat was put on to replace a weak factory cat. most aftermarket cats do fine with CO
& HC, but not so good with NOx. there are some aftermarket cats that do good with NOx but suck with HC or CO.
case in point, where i work at, a few years ago we had a car that failed because of high HC, up around 240~280 PPM, the other gases were well within limits, the cat only had about a 40~50 degree increase in exhaust temps, a good cat will increase post cat temps 100+ degrees.
after the new cat was put on HC was good, in the 30~50 PPM range, but the car now failed because of NOx, the new cat was only able to reduce NOx by 10 PPM at the tail pipe vs before the cat. we tried 2 other brands of cats, but with each one the car still failed either HC or NOx.
it took a $550.00 factory cat to get a pass on all 3 gases. the car passed with flying colors, every gas was very low, HC was down in the 5~10 PPM range, CO was around 0.04~0.08, NOx was around 200~250 PPM.
1 would be to drop your fuel pressure a pound or 2 & see where the CO is at.
the other way would be to turn the VE down in the lower RPM & high MAP range.
doing either may lower the HC or cause it to go up, & it may also cause the NOx to go up.
2new2funny, a good cat will drop all 3 gases, HC, CO, & NOx by a lot.
the best cats are the factory cats, but they are not cheap, i have seen some reading go up after an aftermarket cat was put on to replace a weak factory cat. most aftermarket cats do fine with CO
& HC, but not so good with NOx. there are some aftermarket cats that do good with NOx but suck with HC or CO.
case in point, where i work at, a few years ago we had a car that failed because of high HC, up around 240~280 PPM, the other gases were well within limits, the cat only had about a 40~50 degree increase in exhaust temps, a good cat will increase post cat temps 100+ degrees.
after the new cat was put on HC was good, in the 30~50 PPM range, but the car now failed because of NOx, the new cat was only able to reduce NOx by 10 PPM at the tail pipe vs before the cat. we tried 2 other brands of cats, but with each one the car still failed either HC or NOx.
it took a $550.00 factory cat to get a pass on all 3 gases. the car passed with flying colors, every gas was very low, HC was down in the 5~10 PPM range, CO was around 0.04~0.08, NOx was around 200~250 PPM.
Last edited by DENN_SHAH; Feb 7, 2006 at 10:57 PM.
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Very interesting, info. Thanks!
The dual cats I'm running are Catco (read "cheap") and they're about 2 years old. I suppose they could be the problem. If the cat is supposed to raise the temp 100* F, would using an infra red thermometer on the pipes ahead and behind the cats show that? Or indicate a problem if the temp rise is much less than 100?
The dual cats I'm running are Catco (read "cheap") and they're about 2 years old. I suppose they could be the problem. If the cat is supposed to raise the temp 100* F, would using an infra red thermometer on the pipes ahead and behind the cats show that? Or indicate a problem if the temp rise is much less than 100?
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From: houston
Car: 83 POS monte carlo 2015 chevy P/U
Engine: 92 5.7 tpi 5.3
Transmission: 700r4 6L60E
Axle/Gears: 2.42 too high
thats the main thing i use an infra red thermometer for, although its been a while sense the last time i needed to use one. it just needs to be able to read a high enough temp. the one i use goes up to 1000 degrees.
with good cats the cleaner a motor runs the less the cat will raise the exhaust temps. a very clean motor will do 50 or better, an average motor will do 100+
i have a pair of 4 or 5 year old catcos on my car,. they are the self-cleaning kind,... if you get what i mean
with good cats the cleaner a motor runs the less the cat will raise the exhaust temps. a very clean motor will do 50 or better, an average motor will do 100+
i have a pair of 4 or 5 year old catcos on my car,. they are the self-cleaning kind,... if you get what i mean
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Originally posted by DENN_SHAH
i have a pair of 4 or 5 year old catcos on my car,. they are the self-cleaning kind,... if you get what i mean
i have a pair of 4 or 5 year old catcos on my car,. they are the self-cleaning kind,... if you get what i mean
LOL - yeah, I kow what you mean, considered getting some of those myself
Thanks for the temp info, I'll try to check that out tonight. I've tried using mine to read header temps, but get a lot of variation (+/-100*) between #1 and the #3 and #5 pipes with my SLP Tri-Y headers. Plus with all the A.I.R. cr@p it's almost impossible to read the passenger's side at all. That may turn into self cleaning A.I.R. as well, especially if the Catco cats show up to be that kind....
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89 formula TPI
Tech / General Engine
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Sep 7, 2015 11:06 AM
