oange ss

iTrader: (50)

what would cause relatively low Dyn Cyl Air on a heads/cam/bolt on car ? stock MAF, long tubes, full exhaust...only seein .73 at WOT in 4th gear....timing is at 26, AFR 12.9...thanx

SSpdDmon

iTrader: (10)

Dirty MAF or uncalibrated MAF would be my first guess.

oange ss

iTrader: (50)

MAF is stock descreened so that sounds right...but I thought Dyn Cyl Air was calculated, not derived form the MAF flow ?

SSpdDmon

iTrader: (10)

Are you using EFI Live or HPT?

oange ss

iTrader: (50)

HPTuner

SSpdDmon

iTrader: (10)

IDK about HPT .pids. You might want to make sure you have the right one selected - especially if you have as many as we do. I know in EFI Live, we have a .pid that's a direct look-up* for cylinder air mass for when we are in MAF mode and a different direct look-up* .pid for when we are in SD. These are the ones to use for spark reference.

There's also the GM.DYNCYLAIR.pid that's considered a 'predicted' air mass value. I don't use that one because I want actuals, not predicted. Then, we have a general, calculated .pid that takes the MAF airflow (in grams/second) and multiplies it by 15/RPM. I don't use that .pid either becuase I'm not sure if the MAF is 100% correct.




*FYI for the EFI Live guys - Direct look-up .pids are distinguished by their Parameter name on the PIDs (F8) tab. They all end in _DMA, which stands for Direct Memory Access. The data from these .pids is pulled directly from the operating RAM as the current conditions the PCM is operating under. Further details about DMA .pids are available in the help file for the scanner (hit F1 and scroll to page -88- of the document).

oange ss

iTrader: (50)

cool, thanx for the info

jimmyblue

iTrader: (11)

I am seeing similarly low CylAir on the H/C/I car I've been working
on. I suspected the MAF, swapped on my saved virgin stocker and
it changed from 0.71 to 0.76, still well short of the 0.80 - 0.84 I
saw on mine (with less mods, but a good commanded=actual tune).
With the low airflow numbers the car apparently was showing lean
on the dyno.

Dynamic Cylinder Air and Dynamic Airflow follow MAF airflow pretty
much, at least up top. It will vary some with elevation (your BARO
vs 105kPa). Me, I'm 4 feet above sea level.

I wonder what the ideal CylAir number is for our displacement and
100kPa ambient. Too lazy to try and calculate it. But that would
be a good sanity check for a 4000RPM WOT number (where the
airflow is not limiting it).

SSpdDmon

iTrader: (10)

I see numbers in the .86~.88 range IIRC on my H/C car. I'm usually floating around 97~98kPa on my MAP at WOT and live ~800ft above sea level.

oange ss

iTrader: (50)

around 900 ft above sea level...MAP around 96, AFR was mid 13's, i added fuel and seems to run better but havent had time to check the affects on Dyn Cyl Air yet...

PACKETFOCUS

iTrader: (2)

So a 85-90 GM.DYNCYLAIR.DMA would be consider good at WOT on a H/C/E car? (98 Ls1 logged with EFILive with grams/cylinder).


Does nitrous have an affect of this calculation?

I just see that my 98 PCM used that PID and RPM to calculate HIGH OCTANE SPARK (B5913)

joecar

Stock runs out at 0.76-0.77 g/cyl.

H/C takes it up from there, typically 0.80-0.90 g/cyl depending on H and C.

My understanding:
GM.DYNCYLAIR [g/cyl] and GM.DYNCYLAIR_DMA [g/cyl] are computed from VE.
GM.CYLAIR_DMA [g/cyl] is computed from MAF.

PACKETFOCUS

iTrader: (2)

Thanks for the clarification Joe! I was just looking over my logs last night and saw that in EFILive the Spark High Octane table had GM.DYNCYLAIR_DMA on the top row and RPM on the vertical side. So I was just trying to figure out what cells I would be using most in the b5913 (high octane spark) table when at WOT and if my head/cam combo was flowing about right.

Seems to be around .91 g/cyl at WOT.

PACKETFOCUS

iTrader: (2)

In theory, shouldn't nitrous increase the GM.DYNCYLAIR_DMA reading since its injecting the n20 @ 1000-1100lbs?

Just curious..

5.7 ute

Only if you are using a VE multiplier like with COS5 or your MAP increases.