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Thread: Narrowbands Reading Super Lean at WOT ($EE / LT-1)

  1. #1
    Fuel Injected! spfautsch's Avatar
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    Narrowbands Reading Super Lean at WOT ($EE / LT-1)

    Disclaimer: I have no wideband(s) and don't really intend to make that leap. I have cats that I'd have to remove to make a wideband in my x-pipe meaningful, and I'm not sure I want to spend $300-$400 for a wideband, welding in a bung and cat "delete" tubes just to learn I wasted $300-$400. My tuning methodology has been to tune SD and then MAF with the PE TPS threshold jacked way up. I've been using Steveo's eehack + trimalyzer and targeting 2% rich for everything. As far as I can tell this has worked very well. Read on.

    For more background (see mods in sig) I started out tuning my LT-1 build with the factory multec / rochester injectors. Once I was happy with the overall SD tune, and after striking out with some Cheap Chinese Cr@p eBay injectors, I swapped to some 42lb bosch d3 injectors from FIC. Racetronics 255l/hr fuel pump.

    After a few weeks I come to a nice SD baseline tune that runs very well with the bigger 42lb injectors. All the while I've been noticing this anomaly during WOT (super lean narrowband readings) that I never noticed before swapping from the stock 24lb injectors. I didn't really think much of it at this point because I wasn't "done".

    Skip ahead another month or so and I notice kur4o's post about a pump shot adder for $EE that works as a MAF adder / multiplier. This is the nudge I need to finally switch my MAF back on and get it tuned in (same method mentioned earlier of setting PE TPS threshold really high). 600-700 miles of logging later I'm at a point the MAF tune runs great, and I haven't even bothered to mess with the pump shot tables. Driveability is great everywhere - parking lot manners are as good as could be expected with 50+ degrees of overlap and it will suck you into the seat at will. But still noticing aforementioned anomaly.

    So I've reached a point I don't think there's any progress to be made tuning airflow. While I'm sure I'm asking for a barrage of "you should tune to a wideband" posts, I'm not sure it will help. What I'd like to do from here on is to get my PE AFR targets where I want them - ramping down from 14.0:1 at lower rpms to 12.8:1 at rev limit (6800 rpm) and tune for best performance. I'm relatively confident my SD and MAF curves are within +/- 2% at airflows above 70 gm/s.

    The only concern I have is the anomaly (note O2 voltages in screenshot).

    low-o2-at-wot-edited.png

    log: drivelog-10-20-2.eedata

    I've checked fuel pressure with a mechanical gauge during WOT passes and see no discernible loss. Also, I'm seeing zero PE knock above 2800 rpm. Additionally, the O2 readings don't stick at these low values - 7 frames after the one above when I'm letting off to shift, O2s are reading 901mv (left) and 848mv (right) at commanded 12.3:1. Also, preceding these low readings I see 835mv (left) and 808mv (right) at commanded 13.4:1 immediately after stabbing the throttle.

    My theory here, which I'm hoping to have confirmed or dismissed - is it possible my narrowband O2s are getting fouled with raw fuel causing them to read ridiculously lean here? Normally I would expect to see the O2 voltage floating steadily around 800-900 mv like I used to see with the factory injectors, but these numbers are DFCO low. If there's any possibility I'm actually running this lean I'd like to resolve the problem or at least confirm the cause. But short of connecting a fuel pressure transducer to a spare analog input on the ECM to verify that the fuel pump is keeping up, I'm sort of drawing a blank. Has anyone seen anything like this or have other thoughts / suggestions?
    Last edited by spfautsch; 10-20-2017 at 08:41 PM.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  2. #2
    Fuel Injected! steveo's Avatar
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    My theory here, which I'm hoping to have confirmed or dismissed - is it possible my narrowband O2s are getting fouled with raw fuel causing them to read ridiculously lean here?
    no way

    false lean readings are usually exhaust leaks or misfires (things that pump air that hasn't been involved in combustion into the exhaust)

    a tiny spot of lean right after stabbing the throttle is kind of normal. you're introducing a lot of air really quickly. this is what 'pump shot' like routines are for, since they follow the tps instead of waiting until your more accurate but slower fueling methods catch up. it's also what 'burst knock' is for, since a momentary rush of air like that can cause a knock or two. so a blip of lean o2 readings never concerns me if it recovers quickly

    i'm a bit concerned by that, though, since you're already well over 6000 rpm, you'd figure it would have caught up already. you might want to confirm you aren't getting pressure drop or experiencing some other problem.

    or just add fuel and see if that helps?

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    Fuel Injected! Terminal_Crazy's Avatar
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    I’ve been tuning for ever in SD with a wideband.
    I see lots of very lean data on stabbing the throttle open.
    This seems to skew my data.
    I now only count data that’s hit a ve cell on the previous record which has improved.
    Averaging the data and scaling the result by 0.20 for a 13:1 afr I seem to swing from running at 11.00 which is awesome to 15 which is a bit surgey.
    I’ve also seen the trend with the wideband drop about 1 point afr over about 5 data records.
    My wideband is installed just before the cat so I presume the long pipe\ volume is delaying the reading and accuracy.
    This has driven me nuts, so I feel your pain.
    As an aside I previously used Steveo’s trimalyzer with the narrow bands and got excellent results tuning the ve tables.
    Changing back to the wideband it was all over the place.
    It would average between 9 and 18:1.
    Now it seems to be within 2 points so is improving.

    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  4. #4
    Fuel Injected! spfautsch's Avatar
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    Thanks for the feedback.

    Quote Originally Posted by Terminal_Crazy View Post
    I’ve been tuning for ever in SD with a wideband.
    I see lots of very lean data on stabbing the throttle open.
    This is why I went to MAF after learning how the pump shot works. kur4o did a bit of a write-up on it here.

    After sleeping on it and looking with fresh eyes I discovered something funky with fueling. It's easier to see if you download the eehack log and step through starting at frame 19070. afr number below is commanded, not measured.

    19072 maf : 149.77 afr : 13.5:1 ipw : ~11.4ms
    19073 maf : 153.09 afr : 13.4:1 ipw : ~10.4ms
    19074 maf : 155.26 afr : 13.3:1 ipw : 9.89ms
    19075 maf : 159.31 afr : 13.0:1 ipw : ~9.67ms
    19076 maf : 162.92 afr : 12.7:1 ipw : ~9.5ms
    19077 maf : 170.84 afr : 12.7:1 ipw : 9.21ms
    19078 maf : 173.99 afr : 12.6:1 ipw : ~9.18ms
    19079 maf : 178.66 afr : 12.7:1 ipw : ~9.15ms

    This pattern of rising airflow and falling ipw continues until I shift into 2nd. In 2nd it's a bit different, but I think what I'm seeing is the pump shot decaying to zero? This leads me to think my MAF tuning was skewed way lean at higher flows by the pump shot adder. This never occurred to me because I seemed to recall seeing lean numbers running SD also, but that could have been at tip-in. I guess the pump shot works in closed loop? Hooda thunkit?

    So steveo was right again - she wants more fuel!

    I guess I'll have to see about adding the pump shot params to my xdf and do more logging with it disabled.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  5. #5
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    I have to disappoint you. Pump shot can`t be disabled.
    My theory is that you have really lean condition at high rpm. Maybe you have 15.5-16 AFR. What saves you from engine blow is restrictive intake. Really low spark advance and high gears, low weight. I guess engine power suffers alot too. You get some constant 3-4 degree retard, where it comes from.
    As you can see your AFGS from 5000 to 6600 rpm change only from 190 to 220, which is really low. At 6400 you should see 320-500 AFGS depending on engine power. Either your Maf is shot or there is some tune issue. Try scaling upper maf table by 20% and see what happens.
    It is really important to keep the spread between cells from stock table. So you dont adjust single cell but scale the whole region.
    When you tune MAF with wideband at steady throttle, you will get nasty tip in stumble at low rpm when you nail it. Narrowband tuning with closed loop enabled, masks that condition and considering lower weight is normal that you don`t get that lean. I have monitored wideband at tip in and jumps to 16 afr momentary, When you get around 17 you can feel the stumble and misfire. ARound 15.5-16 is not felt. At 13 AFR, power suffers. I am still trying to find the perfect point where you make max power.

  6. #6
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    I have to disappoint you. Pump shot can`t be disabled.
    What if I zeroed the adder cells from 240a to 2412? That was going to be my angle of attack. Unfortunately I had another project fall into my lap and haven't had time to look into creating definitions for the pump shot data you posted. By the way - awesome work finding that!

    Quote Originally Posted by kur4o View Post
    Either your Maf is shot or there is some tune issue. Try scaling upper maf table by 20% and see what happens.
    It is really important to keep the spread between cells from stock table. So you dont adjust single cell but scale the whole region.
    As I mentioned, I came to a baseline calibration on the MAF without considering the pump shot adder. Since I was tuning with narrowbands at stoich I didn't want to get it out on an interstate and run for long periods above 5000 rpms, so all my higher airflow data was skewed by the pump shot decaying out because it was a lot of accel / decel. I feel more comfortable with the lower airflows because about 85% of my logging data was cruising with fairly tame accelleration.

    I always look at the wireframe / graph for tables like this and hand smooth the cells in raw hex but I didn't pay much attention to the size of the step from cell to cell. I guess I'll have to take a look at that. What I did with this table was arrive a baseline that was about 6.5% below stock calibration at lower throttle openings, but at higher airflows the graph diverged quite a bit lean of the factory cal. I guess that should have been a red flag but I didn't give it enough thought.

    What I've done at this point is restored the upper 60% of the MAF table(s) to stock and then scaled those cells back by 2% and smoothed into the curve from the lower airflows that I'm more confident is less tainted by pump shot. It looks like the weather is going to be bad this week but I'm hoping to get one day of logging so if I can't get time to work on the definition I'll probably log with the tune I'm at today and see if WOT passes settle out to steady numbers in the neighborhood of 900mv. At least that will tell me if I'm on the right track.
    Last edited by spfautsch; 4 Weeks Ago at 04:37 PM.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  7. #7
    Fuel Injected! Terminal_Crazy's Avatar
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    $EE doesn't seem to do anything I expect

    Just spent a couple of hours tracing a run of data with AFR dropping.

    AFR DROP IN A CELL

    Line:20042 rpm=1341.0000 map=31.00000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=18.5000 this_VE_Cell=[4,6]
    Line:20043 rpm=1318.0000 map=32.90000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=15.6700 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2179.14000 counts=183.00000 avg afr=11.90787
    Line:20044 rpm=1329.00000 map=32.50000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=14.9600 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2194.10000 counts=184.00000 avg afr=11.92446
    Line:20045 rpm=1289.00000 map=33.20000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=14.3700 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2208.47000 counts=185.00000 avg afr=11.93768
    Line:20046 rpm=1264.00000 map=33.60000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=14.1300 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2222.60000 counts=186.00000 avg afr=11.94946
    Line:20047 rpm=1253.00000 map=34.70000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=13.7200 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2236.32000 counts=187.00000 avg afr=11.95893
    Line:20048 rpm=1247.00000 map=34.70000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=13.4800 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2249.80000 counts=188.00000 avg afr=11.96702
    Line:20049 rpm=1266.00000 map=33.20000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=13.3700 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2263.17000 counts=189.00000 avg afr=11.97444
    Line:20050 rpm=1251.00000 map=34.00000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=13.3700 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2276.54000 counts=190.00000 avg afr=11.98179
    Line:20051 rpm=1267.00000 map=34.00000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=13.0700 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2289.61000 counts=191.00000 avg afr=11.98749
    Line:20052 rpm=1264.00000 map=34.00000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=12.6600 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2302.27000 counts=192.00000 avg afr=11.99099
    Line:20053 rpm=1284.00000 map=33.60000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=12.3600 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2314.63000 counts=193.00000 avg afr=11.99290
    Line:20054 rpm=1290.00000 map=32.90000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=12.1900 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2326.82000 counts=194.00000 avg afr=11.99392
    Line:20055 rpm=1279.00000 map=32.90000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=12.0700 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2338.89000 counts=195.00000 avg afr=11.99431
    Line:20056 rpm=1273.00000 map=32.50000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=11.9500 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2350.84000 counts=196.00000 avg afr=11.99408
    Line:20057 rpm=1267.00000 map=33.60000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=11.8900 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2362.73000 counts=197.00000 avg afr=11.99355
    Line:20058 rpm=1272.00000 map=33.60000 (1400,35) VE_[ 4][ 6] req_afr=13.0000 wideband=11.9500 this_VE_Cell=[4,6] MATCHES PREVIOUS == total afr=2374.68000 counts=198.00000 avg afr=11.99333

    It was only going back to the previous cell where AFR hits 22.39 that I realised I was on overun.
    The Map should have given it away but it's 00:41 now so i'm going to bed!

    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  8. #8
    Fuel Injected! spfautsch's Avatar
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    I just re-visited this thread and saw a couple details I wanted to address.

    Quote Originally Posted by kur4o View Post
    You get some constant 3-4 degree retard, where it comes from.
    This is burst knock retard that happens at tip-in and decays out (similar to pump shot). I'm not sure it can be tuned out but I wouldn't even have tried until I was sure the WOT fueling was relatively close.

    Quote Originally Posted by kur4o View Post
    It is really important to keep the spread between cells from stock table.
    Would / can you explain better? Knowing how TunerPro works, if it's hyper critical to have the spread between cells consistent then the only way to scale this table correctly would be to shift cells by copying & pasting up / down. Scaling a high precision table like this there are all manner of rounding errors that the conversion formulas exacerbate. This is why I've gotten into the habit of smoothing tables in raw hex.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  9. #9
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    Posting your current bin and the stock bin from your pcm will help clear that knock retard issue. Maybe it is normal for manual cars, but for automatic it is strange.

    You should not zero that values because it is a scale factor or a multiplier and when you multiply by zero you will get zero AFGS as result. So if you want to play with this make it at least $01 value in hex.

    Keeping the spread between cells for ve and maf is really important. Of course there will be some break points where the spread will be increased.
    At ve the calculated VE% is an interpolation from 4 adjacent cells, so you always get some mid point as a result. If the spread is way off very small increase in map or rpm can lead to huge change in calculated VE%. And you start chasing tails to tune it.
    At maf calculations the raw maf frequency is converted to two bytes value. First points to the maf cell number in the tune, second byte is an offset that divides the spread to the next cell by 255 and adds the result to the first cell value. So there is always interpolation between two cells in the tune.
    Since the signal is not linear the curve is very important. You can see it in tunerpro when you open the maf table as a graph.

    For scaling the tables use the multiply function. Maf is 16 bit value so rounding is not an issue. You can multiply a whole region with 1.05 or 0.95 to get 5% increase or decrease of the value.

    Here is the most recent xdf with all the values entered.
    Attached Files Attached Files

  10. #10
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    Posting your current bin and the stock bin from your pcm will help clear that knock retard issue. Maybe it is normal for manual cars, but for automatic it is strange.
    I'll try to post bins later but I haven't changed anything relevant to knock retard but to zero the lower cells and reduce the higher cells of the max retard cruising table at 1233A. This is all my own work applied to the original bin so you could easily compare any factory M6 to a factory A4 bin.

    Quote Originally Posted by kur4o View Post
    You should not zero that values because it is a scale factor or a multiplier and when you multiply by zero you will get zero AFGS as result. So if you want to play with this make it at least $01 value in hex.
    I may try that tonight after I get home. I have to make it 60 miles so I'd rather not get too wild into experimentation until she's parked in my garage. There's nothing fun about having to reflash an older bin on the side of the road. :-)

    Thanks for the .xdf - I'll add it to the collective.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

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    So i took another look at the supposed pump shot adder. After I examined some logs of data, I finally figured out what is does.
    At rapid tps change, the maf readings jumps alot too fast, the pcm use this pump shot as a scale factor to gradually increase or decrease the AFGS.
    For example the AFGS jumps from 20 to 100 g/s at one frame interval. PCM blends the increase to 30, 50, 80, 100 over a period of couple of frames. That way you don`t get erratic jumps in fuel bpw and engine runs smoother and more consistent.

    So this factors how fast the transitions happen. I guess the lower the value the faster the transition. Still it needs to be confirmed.
    It turns out maf reacts faster than the time needed for the air to get to cylinder. That`s why there is no ae build in the code.

  12. #12
    Fuel Injected! spfautsch's Avatar
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    Well I wish I had something intelligent to contribute.

    I just looked at the log from tonight's WOT passes and it's a lot of the same.

    What I can't seem to square up with common sense is the pattern of rising airflow and RPM coupled with falling commanded AFR, but falling IPW. It would stand to reason if the engine is trending towards pumping more air and the PE AFR targets are calling for more fuel to air as RPM increases, IPW should be heading towards "more"?!?

    I'm starting to wonder if my wife has been lacing my whiskey glasses with LSD.
    Last edited by spfautsch; 4 Weeks Ago at 08:45 PM.
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

  13. #13
    Fuel Injected! jthompson122183's Avatar
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    Would adjusting the transient fuel tables help? It's like a "pump shot" also.
    97z28 A4 obd1 swap(16188051)
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    Quote Originally Posted by spfautsch View Post
    What I can't seem to square up with common sense is the pattern of rising airflow and RPM coupled with falling commanded AFR, but falling IPW.
    That can happen because rpm are risng, but the airflow stay almost the same. If the rpm increase with no change in airflow bpw will go lower.
    At 220 AFGS at 6600 rpm, I can estimate the engine is around 200 hp. Which don`t make sense with your build.

    Post the MAF table to see if there is something wrong with it. The way I see it you need 20-30 % more AFGS from 190 AFGS up.
    Shot MAF is also a possibiity.

  15. #15
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    Post the MAF table to see if there is something wrong with it. The way I see it you need 20-30 % more AFGS from 190 AFGS up.
    Shot MAF is also a possibiity.
    This is an aftermarket MAF element, the original delphi / delco is no longer available so calibration is suspect. I'm going to add a bunch to everything above 150afgs and see what happens.

    Current bin should be attached.
    Attached Files Attached Files
    '95 C4 LT-1 ZF-6, Polo Green
    Comp 467 / XFI 280, UltraProMag RRs, LE1 Heads, Lunati 73925 Springs

    Somebody stole the spark plugs out of my other car, yet it still runs???

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