WOT Enrichment

[rjc078]

Hi

I have a problem with a tune i am playing around with. The engine AFR's are perfect at idle and WOT, but when the MAP is less than 100kPa and the engine is above idle the motor is running lean. I have pluged in my simulator and set it up for 2800 rpm, 100kPa, TPS 90% (so i can adjust the MAP) and the Comanded AFR is 9.2 and VE is 86.3% and the BPW is 7.39 msec. If i drop the MAP back to 95kPa, the VE, AFR, RPM, TPS are the same but the BPW drops to 6.96 msec which would cause it to go lean.

Is there a WOT enrichment? I have BLM and Lean Cruse switched off. Any Ideas?

Thanks again for your help

Rob

[Jayme]

as I understand it, thats exactly how its supposed to work. if the VE is set the same for every map, the pulse width still gets bigger as the map gets higher, the fuel is scaled against the MAP pressure and the VE table fine tunes it. thats why the VE map looks fairly level and not a steep slops up towards 100kpa like some aftermaket ecu's.

if you are running it on a real engine and are getting a real lean spot at a certain map and rpm, then the VE needs to go up in that spot.

[rjc078]

Thanks Jayme,

I have gone back to my VE map, changed a RPM point to all the same percentages, pluged in the sim and you are exactly correct! I must admit that I have not paid much attention to the VE maps before. So i guess there must be a constant that goes into the calculation of BPW for MAP?

VL400 gave the following equation;

BPW = BPC*T*A/F*VE*BAT*BLM*DFCO*DE*CLT*LSE*EGR

Where: (everything labeled "term" is from a lookup table)

BPW = Inj pulse width in milliseconds
BPC = KINJFLOW term, Displacement/inj flow rate (Litres/Grams per sec) (0-100% BPW Reduction)
T = Inverse Temp Term (Lookup Based On Charge Temp) (0-100% BPW Reduction)
A/F = Inverse air/fuel ratio term
VE = volumetric efficiency term (0-100% BPW Reduction)
BAT = Battery voltage compensation term (+-50% BPW Correction)
BLM = Block Learn Term (+-50% BPW Correction)
DFCO= Decel Fuel Cutoff Term (0-100% BPW Reduction)
DE = Decel enleanment term (0-100% BPW Reduction)
CLT = Closed loop correction (result of O2 sensor Proportional/integral closed loop)(+-50% BPW Correction)
LSE = Low Speed Enrichment Multiplier term (+-50% BPW Correction)
EGR = EGR Dilution term (0-100% BPW Reduction)

Is it somewhere in there and im just not understanding it correctly?

Thanks again

[VL400]

Its part of the BPC item, along with kinjflow the MAP sensor is also used to create the BPC term. As the MAP is not a configurable item as such its not shown in that equation.

[rjc078]

Everything I understood about the VE table has been blown out of the water now!!! Is there a constant/table that i can change to change the amount the BPW decays with the reduction of MAP or will I just have to change it with the VE or AFR at every MAP/RPM point?

[VL400]

No the MAP component must stay as it is. The 12P guide by holden202 has a heap of good info... https://pcmhacking.net/forums/viewtopi ... =28&t=1089

[rjc078]

OK, so the VE table isn't actualy showing the true VE of the engine, but is just a correction factor for a calculation that the ECU performs.

On another note, after reading holden202's guide, will tunerpro accept accept the data stream from a techedge wb02?

Thanks again

[krusty]

OK, so the VE table isn't actualy showing the true VE of the engine, but is just a correction factor for a calculation that the ECU performs.

On another note, after reading holden202's guide, will tunerpro accept accept the data stream from a techedge wb02?

Thanks again

Yes it will. I use a 2J9 with no issues. Just had to adjust the WB min and max voltage in Scalars/ VE learn parameters/ Wideband 0v AFR and Wideband 5v AFR to range from 10:1 AFR at 0v - 20:1 AFR at 5v

[VL400]

A MAP based delco system is a speed density engine controller, and comes close to obeying the ideal gas law PV = nRT .

The P component is pressure, so in terms of the ECU we have a MAP sensor and VE table and can work out cyl pressure from MAP * VE. Manifold pressure is the MAP sensor value, how efficient the engine is at pumping this pressure and filling the cyl is the VE. So The VE is what you are changing to try and tell the ECU what the actual pressure is that will enter the cyl. The V component is displacement, so the kinjflow value takes care of this (its made up of inj and cyl size). The T component is temp, the inverse temp table which uses charge temp (the air temp that has coolant and manifold temps applied) as its lookup.

[rjc078]

Thanks everyone. I have pulled out the books that I have and have re-read the section on VE and understand it now - but only after reading it 6 times. Thanks for all the very fast replys as well!! Untill next time............