TLDR:
@thelostartof - I looked at your MS setup & idle log in more detail, and I flat out don't understand how it works.
Long winded version:
I'm not an engine guy and don't have a good feel for fluid dynamics of engine airflow, so this may be confused.
The specs on your V16T cam from the enem web site are:
"Volvo B21/23 V16T: 268/112/12.2/1.5
268/268/110/114/12.2/12.2/1.6/1.2/ 0.40
Sport cam for turbo stage 2/3"
This is 268deg duration (at ??? lift&lash), 110deg intake/114deg exhaust lobe centerlines (in crank deg), and 1.6mm intake/1.2mm exhaust valve openings at TDC. Calculating gives an overlap of 268/2 + 268/2 - 110 - 114 = 44 degrees (crank).
While Wikipedia doesn't have an entry for big ass cams, it does have one for:
https://en.wikipedia.org/wiki/Variable_valve_timing , which I think has similar behaviors. Quoting parts of the wikipedia entry:
With this, I'd expect reduced idle vacuum (aka higher MAP pressure in MegaSquirt) and low MegaSquirt VEs around idle since part of the air/fuel charge has been replaced with inert exhaust gases. For the MegaSquirt VE table, I'd expect much lower than normal VEs on the left, and idle operating at higher than usual MAP values. TLAO's VE table looks nothing like I'd expect (note: IncorporateAFR and MAP_Multiply are both turned on):
View attachment 26637
The idle log is even more confusing to me:
View attachment 26638
This shows idle at ~815rpm at 81kPa MAP, with a ~13.9 AFR and a VE of ~72. From the MS config, it's running huge 1700cc/min injectors, so the 2.465ms PW (with a 1.0ms deadtime) results in the
idle fuel flow of ~37cc/min. <<< This is unbelievable.
I checked my B21FT logs (LH2.4), and another somewhat standard B230FT log (MS2), and found that idle fueling was around
7.5cc/min. I'd expect most any redblock to have pretty similar idle fueling, not the 5x larger fueling. I don't know how an engine would even idle with 5x fueling, so I think I must be missing something basic.
For additional discussion, here's a picture of a traditional vacuum gauge:
View attachment 26639
Can an engine expert explain the "Late Ign Timing" red zone slight loss of vacuum? I'm guessing it's due to late burning of the fuel, resulting in higher residual pressure when the intake valve opens, and higher exhaust-to-intake reversion.
On a related vein, one old school method for adjusting the carburator mixture screws was to use a vacuum gauge and adjust the mixture for highest idle vacuum. How does this work?