muncie21

iTrader: (14)

Below applies to my 99 SC'ed LS1 C5

On the dyno AFRs only get to 13.8 or so at 3500 RPM in PE mode.
Given that Primary VE, MAF, and PE multiplier contribute towards AFR number, the MAF is disconnected to remove it from the equation.

Now the equation is: Secondary VE and PE multiplier= AFR

AFR goes to 12.01 with MAF disconnected. hmmm looks like we are onto something. Reconnect the MAF- ~13.8. Disconnect again ~12.00. Sooo the Secondary VE table must be richer than the primary right, as that's the only thing that has changed in the equation.....uhh nope. Secondary is actually 8-15% lower than Primary.

How can this be?? What am I missing here?

hondo

iTrader: (2)

plug in MAF...gets leaner...MAF table needs adjustment

bmfcamaro

iTrader: (1)

its the maf table

muncie21

iTrader: (14)

Doa, now why didn't I think of that? Actually, I scaled the MAF using the dynamic airflow calc, but haven't dyno'd it to see if it helps or not. Thanks for the info guys.

jimmyblue

iTrader: (11)

You want to keep the Secondary and Primary in sync. That
eliminates some differences between the tune "modes". An
Excel 'sheet that builds a Secondary from Primary (simply
pulling every other line) is an easy way to go. You don't
need to be doing so much juggling.

I may have missed it, is this a -stock- MAF? As in bone
stock, no file marks, screen in place, that kind of stock?

muncie21

iTrader: (14)

Yup, this is a 'bone stock' no KN filter oil, dirt, fingerprints, filemarks, gunk or otherstuff, GM MAF.

I would of thought that if the MAF was significantly off the PCM would trigger an error for max airflow delta exceeded.

SmokingWS6

iTrader: (1)

Maf is reading very lean, ie: light load. Either do to it being ported, dirty, aftermarketet intake ect. Any of those changes will require the maf to be recalibrated

https://ls1tech.com/forums/pcm-diagnostics-tuning/256989-dialing-maf-tables-anyone.html

SmokingWS6

iTrader: (1)

That answers a few of my questions. Even stock maf's can be off. It might not hurt to try a different maf, I had one slowly crap out on me last year. However I suspect it needs the normal calibration that most gm's do.

muncie21

iTrader: (14)

I've reviewed my MAF #'s with other boosted LS1's and mine seem to be higher than most. Here's the my table starting at 1500:

2.46094 2.85938 3.28906 3.76563 4.66406 5.48438 7.26563 8.31250 11.32031 11.89063 12.38281 13.36719 14.09375 15.42188 16.85156 17.90625 19.27344 20.30469 21.21094 22.96875 24.43750 26.28906 28.54688 30.75000 33.44531 35.97656 38.52344 41.30469 44.28125 47.28125 49.98438 53.46094 57.39063 60.58594 64.54688 67.69531 71.48438 76.54688 79.70313 84.25781 88.50000 93.28125 98.25000 104.00781 109.20313 117.68750 120.42188 126.23438 131.03906 138.53906 149.02344 158.03125 158.79688 164.96094 181.25000 190.67188 191.54688 198.70313 212.18750 215.16406 224.26563 227.14063 234.11719 236.97656 242.75781 255.07813 260.67969 284.89063 296.03125 307.51563 319.36719 331.59375 344.19531 357.19531 370.60156 384.42969 398.67969 413.36719 428.51563 428.51563 428.51563 428.51563 428.51563 428.51563 428.51563

SmokingWS6

iTrader: (1)

Ahh, its a boosted ls1. Nothing about the intake is stock then. That's the main cause of the maf readings. The table seems reasonable to me, low in some cases, but each setup is different.

jimmyblue

iTrader: (11)

Actually that table is very low, not-stock looking, for a '99.
Those used the same "Oreo" MAF as the F-bodies and should
top out right at 511g/sec. But some earlier years did not
properly populate the higher frequency slots (yours flat-
lines). Bad news if you are up onto that part of it, under
boost. Try this Holden MAF table and you may be put right
(or more so):

freq
1500 1625 1750 1875 2000 2125 2250 2375 2500 2625 2750 2875 3000 3125 3250 3375 3500 3625 3750 3875 4000 4125 4250 4375 4500 4625 4750 4875 5000 5125 5250 5375 5500 5625 5750 5875 6000 6125 6250 6375 6500 6625 6750 6875 7000 7125 7250 7375 7500 7625 7750 7875 8000 8125 8250 8375 8500 8625 8750 8875 9000 9125 9250 9375 9500 9625 9750 9875 10000 10125 10250 10375 10500 10625 10750 10875 11000 11125 11250 11375 11500 11625 11750 11875 12000

g/sec
2.14 2.59 3.07 3.59 4.15 4.74 5.4 6.1 6.85 7.67 8.55 9.48 10.5 11.59 12.76 14.02 15.34 16.95 18.66 20.52 22.29 24.16 26.16 28.26 30.48 32.83 35.3 37.91 40.66 43.54 46.57 49.74 53.06 56.55 60.19 63.98 67.95 72.09 76.41 80.91 85.58 90.45 95.5 100.74 106.2 111.84 117.7 123.76 130.04 136.54 143.26 150.2 157.38 164.79 172.44 180.32 188.46 196.84 205.48 214.38 223.53 232.95 242.64 252.6 262.84 273.37 284.17 295.27 306.66 318.34 330.33 342.62 355.21 368.13 381.35 394.9 408.77 422.97 437.5 452.37 467.58 483.13 499.02 511.99 511.99

If you see MAF frequency below 1500Hz ever, you may need to
fill that in with late F-body values and bland it smooth. But with
a S/C I doubt you would have that low of an airflow.

JMBLOWNWS6

iTrader: (17)

Ditch the maf. Run it in SD 2 bar

muncie21

iTrader: (14)

Here's what the Holden looks like compared to mine. Are the differences enough to cause lean issues??