B0200 MAIN VE TABLE question for Joe??

[Gelf VXR]

I am trying to corallate the B0200 MAIN VE Data to logged pids.

B0200 Data: (variable)gramms*Kelvin/kPa

for example if i pick a value of a cell on the VE map = 1.7983 which has been highlighted during play back of a log for which the values of the corresponding pids for that cell when paused read


RPM = 1230
MAP = 54
APCYL = 0.29 (gramms per cylinder)
DYNAIR = 24.57 (gramms per sec)


DYNAIR should equal between: APCYL*4*RPM/60= 23.37 to 24.14 (APCYL is rounded to 2 dp) close enough

How do I arrive at 1.7983 on the VE table?

1.7983*(277(IAT Kelvin))/(54(MAP))= 9.2246

(24.57(DYNAIR))*(54(MAP))/(277((IAT Kelvin)) =4.7898


Whats going on???:help2::help2::help2::help2: Please

[Blacky]

Do you mean table B0101?

g/cyl = VE*MAP/charge temperature
Ve is in g*K/kPa,
MAP is in kPa,
charge temperature is in degrees Kelvin.

Using your figures:

VE map = 1.7983
RPM = 1230
MAP = 54
APCYL = 0.29 (gramms per cylinder)
DYNAIR = 24.57 (gramms per sec)
IAT = 3 degrees C (based on the 277 Kelvin that you showed in your post)

Using the VE*MAP/ChargeTemp you see that:
1.7983*54/277 = 0.350 g/cyl
which is not quite 0.29 g/cyl that you are logging

Note: the charge temp is a value calculated by the PCM and includes engine temp, so I'll work backwards and see what the charge temp would have been to make the figures correct:

charge temp = VE*MAP/(g/cyl)
1.7983*54/0.29
charge temp = 334K = 61C = 143F

Re-doing the calculation using 334K for charge temp:

1.7983*54/334 = 0.29 g/cyl

Note, if you are running with a MAF fitted and working then the g/cyl are calculated from the MAF and may be slightly different form the g/cyl calculated from the VE table. Th ePCM actually computes g/cyl from both the MAF and the VE table and compares them regularly. If they differ significantly then a MAF DTC is reported.

GM.DYNCYLAIR is the grams or air per cyclinder that the PCM calculates from the VE table and should be the value that you use in the above equations.
CALC.CYLAIR is the grams or air per cyclinder that EFILive calculates from the MAF.
Those two values should be *very* close if your MAF is operating correctly and your VE table is accurate.

Regards
Paul

[GMPX]

There is a DMA PID that will let you log the actual calculated VE number if that is what you are after?

Cheers,
Ross

[Gelf VXR]

Do you mean table B0101?

g/cyl = VE*MAP/charge temperature
Ve is in g*K/kPa,
MAP is in kPa,
charge temperature is in degrees Kelvin.

Using your figures:

VE map = 1.7983
RPM = 1230
MAP = 54
APCYL = 0.29 (gramms per cylinder)
DYNAIR = 24.57 (gramms per sec)
IAT = 3 degrees C (based on the 277 Kelvin that you showed in your post)

Using the VE*MAP/ChargeTemp you see that:
1.7983*54/277 = 0.350 g/cyl
which is not quite 0.29 g/cyl that you are logging

Note: the charge temp is a value calculated by the PCM and includes engine temp, so I'll work backwards and see what the charge temp would have been to make the figures correct:

charge temp = VE*MAP/(g/cyl)
1.7983*54/0.29
charge temp = 334K = 61C = 143F

Re-doing the calculation using 334K for charge temp:

1.7983*54/334 = 0.29 g/cyl

Note, if you are running with a MAF fitted and working then the g/cyl are calculated from the MAF and may be slightly different form the g/cyl calculated from the VE table. Th ePCM actually computes g/cyl from both the MAF and the VE table and compares them regularly. If they differ significantly then a MAF DTC is reported.

GM.DYNCYLAIR is the grams or air per cyclinder that the PCM calculates from the VE table and should be the value that you use in the above equations.
CALC.CYLAIR is the grams or air per cyclinder that EFILive calculates from the MAF.
Those two values should be *very* close if your MAF is operating correctly and your VE table is accurate.

Regards
Paul


Excellent response:rockon: thankyou very much:cheers:
I am in SD, and have E40 for which VE table is B0200, GM.DYNAIR_LS2 is the equiverlant of GM.DYNCYLAIR for the E40, formulas work the same :grin: I never thought about the charge blending factor:doh2:

[Gelf VXR]

There is a DMA PID that will let you log the actual calculated VE number if that is what you are after?

Cheers,
Ross


All information gratefully recieved:cheers: Is that an E40 dma pid?

[Gelf VXR]

I am logging pids to determine performance, I'm about to have heads and cam done, I want to be able to compare before and after, Im trying to arrive back at the {B0200} PCM calibration from logged pids as described previously in the thread. I have figured out how to greate the custom calc pids, how ever i am not getting the expected resuts?

24 channel and calc PID's I am logging are, and observed for this example are

GM.APCYL_E40_DMA = 0.49
SAE.MAF = 93.95
GM.DYNAIR_LS2 = 92.83
GM.AFR_B = 14.7:1
GM.TRQTRANS = 329
SAE.ECT = 90
SAE.RPM = 2816
GM.FTC = 11
SAE.SPARKADV = 28
SAE.IAT = 24
SAE.LONGTF1 = -6.2
SAE.LONGFT2 = -3.1
E40.MAP_DMA = 72.1
GM.MAFFREQ2 = 7200
GM.KR = 0
E40.SCALEDCORVE_DMA = 8.210 (gramms*Kelvin/kPa) VE Table Lookup
CALC.BEN1_B = 1.01
CALC.BEN2_B = 0.94
CALC.CYLAIR = 0.5

CALC.VE = 1.32 % ("{SAE.MAF.gps}*{SAE.IAT.C}+273.15)/((364*61.024)*{SAE.RPM}*{E40.MAP_DMA})*212544")

CALC.VE = 38.1 VEpcm ("{SAE.MAF.gps}*({SAE.IAT.C}+273.15)/((364*61.024)*{SAE.RPM}*{E40.MAP_DMA})*6155274.24")
VEpcm is %VE*28.96 (28.96 = molar mass of air)

CALC.VEPCT_V8 = 5.2%. "({E40.SCALEDCORVE_DMA}*231.68)/364"
Calculate VE % by multiplying the VE value by molar mass of air (28.96) and the number of cylinders in the engine, then divide by engine displacement.
V8 is 28.96*8=231.68


At the same time I have

{B0200} GMVE @ MAP 71.3 and RPM 2800 = 2.2242 or traditional VE 90.97%

{B0115} Charge Blend Factor (f) @ 93.8 g/sec = 0.144


None of the above CALC pids come close to VE 2.2242? or 90.97%


I want to find and map the Charge Temp and Charge Temp Blend factor values from logged pids, but I need to know the VE used

charge temp = VE*MAP/(g/cyl)

2.2242*72.1/0.49 = 327K = 54C = 129F

charge temp kelvin = 273.15+IAT+(ECT-IAT*f)

charge temp blend factor (f)= (charge temp-273.15-IAT)/(ECT-IAT)

(327-273.15-24)/(90-24) = 0.45 not 0.144 from {B0115}???

Am i missing something when looking at E40.SCALEDCORVE_DMA = 8.210 (gramms*Kelvin/kPa) VE Table Lookup

Can anyone help me get the formula right for getting back to the PCM GMVE value with Charge TEMP and factor defined?

Thanks in advance

[Blacky]

Not sure if this is the only problem, but the 346*61.024 should be 5.669*61.024 = 346.

The 61.024 multiplier converts from liters to cubic inches.

Regards
Paul

[joecar]

Check that all the units agree across all the factors.

[Gelf VXR]

Not sure if this is the only problem, but the 346*61.024 should be 5.669*61.024 = 346.

The 61.024 multiplier converts from liters to cubic inches.

Regards
Paul

Thanks:cheers:


I replaced 364 with 5.964 which gave these results for

CALC.VE = 80.3 % ("{SAE.MAF.gps}*{SAE.IAT.C}+273.15)/((5.964*61.024)*{SAE.RPM}*{E40.MAP_DMA})*212544")

More realistic, in the ball park for the PCM 90.97% which is high when you take into account the LTFT's and BEN's.

What does the constant 212544 stand for??

CALC.VE = 2325.47 VEpcm ("{SAE.MAF.gps}*({SAE.IAT.C}+273.15)/((5.964*61.024)*{SAE.RPM}*{E40.MAP_DMA})*6155274.2 4" )
VEpcm is %VE*28.96 (28.96 = molar mass of air)

I take it that this is the total molecular mass of air, the range for the PID is 0 to 3000.



That still leaves

CALC.VEPCT_V8 = 318.9%. "({E40.SCALEDCORVE_DMA}*231.68)/5.964"
Calculate VE % by multiplying the VE value by molar mass of air (28.96) and the number of cylinders in the engine, then divide by engine displacement.
V8 is 28.96*8=231.68


I think the issue is still with E40.SCALEDCORVE_DMA?? Should this value be divided by four, the number of inductions per rpm??


CALC.VEPCT_V8 = 79.7%. "(({E40.SCALEDCORVE_DMA}/4)*231.68)/5.964"

E40.SCALEDCORVE_DMA = 8.210 (gramms*Kelvin/kPa) VE Table Lookup

Divided by four = 2.0525


To check this

Charge temp = 273.15+24+(90-24*0.144) =306.654

VE = grams cyl*charge temp/kPa

0.4937*306.654/72.1 = 2.09979

x 4 = 8.399

Perhaps I don't have the precise data that the PCM used or accountd for all the factors for charge temp blend, but these numbers are cose enough to consider that Lookup VE should be divided by four to obtain the PCM VE value?

Would you agree?