Perfect tune on E85 shows lean on 93?

[andrewquant]

So my VE is showing 10% less airflow on gas vs E85. I just switched back to 93 after tuning E85 for a while. MAF reading is still completely accurate. Here is the weird thing, its only under 3k RPM where it shows up. Of course I was thinking I should just adjust the Stoich AFR in the right cell, but its perfect for 3K and up so I don't want to skew the fueling as a whole(I don't go MAF only for airflow until 4k btw so its not that). What could possibly cause that? Its perfect on E85. This is a flex fuel car with sensor.

[Ben Charles]

What injectors?

[andrewquant]

Holley 120#

[Ben Charles]

That’s most likely why

[andrewquant]

Its an airflow calc issue, not fueling. My EQ is fine. What table would be referenced to show only the VE airflow calculation different based on the fuel composition %. To be clear, I'm not talking about my EQ reading. I'm talking about my VE airflow.
airflow.jpg

[blindsquirrel]

You're right, it must be something else, and not the famously data-free injectors. That the issue can be caused by the injector data not being correct has to be a complete coincidence.

[hjtrbo]

GMVE = IFR x IPW x AFR_wideband * MAT / MAP
.
GMVE, IFR, MAT and MAP will be the same whether E0 or E85 and AFR_wideband is what it is. GMVE will not modified by ethanol content.

IPW is a function of IFR and GMVE that only leaves IFR or GMVE as the adjustable variables. So one or both of those are wrong in your tune (and / or incorrect fuel pressure reported).

Here is an example from one of my logs that lines up very nicely
GMVE from log = 2575mg*K/MPa
GMVE from tune = 2575.5mg*K/MPa
-------------------------------------------------------
IFR = 14.578g/s
IPW = 13.94ms
AFR_Wideband = 7.5:1
MAT = 31?C = 304.15?K
MAP = 180kPa = 0.18MPa
-------------------------------------------------------
Fuel = 14.578g/s * 0.01394s = 0.20321732g
Air Fuel = 0.20321732g * 7.5 = 1.5241299g
1.5241299 * 304.15 / 0.18 = 2,575mg*K/MPa

[andrewquant]

You're right, it must be something else, and not the famously data-free injectors. That the issue can be caused by the injector data not being correct has to be a complete coincidence.

Totally agree with you. Which is why I built all my own offset data. Holley was useless so I just logged and adjusted all my open loop over a few months until it was perfect.

[andrewquant]

GMVE = IFR x IPW x AFR_wideband * MAT / MAP
.
GMVE, IFR, MAT and MAP will be the same whether E0 or E85 and AFR_wideband is what it is. GMVE will not modified by ethanol content.

IPW is a function of IFR and GMVE that only leaves IFR or GMVE as the adjustable variables. So one or both of those are wrong in your tune (and / or incorrect fuel pressure reported).

Here is an example from one of my logs that lines up very nicely
GMVE from log = 2575mg*K/MPa
GMVE from tune = 2575.5mg*K/MPa
-------------------------------------------------------
IFR = 14.578g/s
IPW = 13.94ms
AFR_Wideband = 7.5:1
MAT = 31?C = 304.15?K
MAP = 180kPa = 0.18MPa
-------------------------------------------------------
Fuel = 14.578g/s * 0.01394s = 0.20321732g
Air Fuel = 0.20321732g * 7.5 = 1.5241299g
1.5241299 * 304.15 / 0.18 = 2,575mg*K/MPa

Thanks for the help with the math. I solved it, posting for anyone else. It was because of open loop gains for intake valve temp. The intake valve temp and injector tip temp is calculated to be colder with E85 than gas. When I stopped to fill up with 93 and drain out my remaining E85, the engine got heat soaked and then reported a much higher value for the intake valve temp and injector tip temp on 93 than previously had been being used under E85 and that put me into a hotter cell for injector offset for tip temp that wasnt able to be tuned while on E85, especially in the cooler weather that is now departing. MAF must not care as much about it. Thanks all.