I decided I probably should recalibrate the wideband sensor, since I hadn't done that since I originally installed it back in December. Figured that since I'm trying to finish up the calibration of the VE tables, I should make sure the fueling feedback is accurate. All it takes is pressing the calibrate button on the wideband harness for three seconds to recalibrate the sensor. I never did find a satisfactory answer as to whether the sensor can be recalibrated while still in the exhaust pipe if the car sets for a couple of days, so I pulled it out and let it hang in free air when I did the recalibration. No real big deal, but kind of a pain in the butt just to get to the point where I can press that recalibrate button for three seconds.
So, I took the car out again today (Sunday) to get some more logging done. The rains bypassed us today, so the roads were dry and it didn't look like I would get caught in an unexpected downpour. I needed to get some more cells populated in the boost VE table, so the opportunity presented itself when I "needed" to pass a slow moving truck pulling a trailer. The road was wide open in front of him, so I just let it wind out a bit to get the data I was needing anyway.
So I'm looking over the log display, to see how things look, and the spot where I kicked it into boost is kind of interesting, if I'm interpreting things correctly.
First off, "boost" is the condition whereby pressure detected by the MAP sensor in the intake manifold is greater than ambient barometric (atmospheric) pressure. Barometric pressure at sea level is normally 101.3 kPa, 1013 millibars, 29.913 hg, or 14.692 psi, depending on what sort or yardstick you like to use. I did the screen capture above with the indicator on 103 kPa, which is pretty much the beginning of boost kicking in. I was surprised to see that the engine speed was less than 2600 rpm.
BTW, while I am thinking of it, if you ever have a need to swap out your 1 bar MAP sensor with a 2 bar (or higher) sensor, you need to calibrate your new sensor to ambient barometric pressure. Mine is off slightly, because I didn't know to do that when I swapped out mine. But it's showing 101.0 kPa with the engine off, so I don't think it will make much difference being off such a small amount. EFILive has a MAP sensor scaler table {C6301} that you use to dial in the calibration of the replacement sensor.
Also of note is that the boost seems to peak at 156 kPa (around 8 psi), and then drop very slightly, even though engine speed is increasing. There are 10 lb springs in the wastegates, so perhaps 2 lbs are just being lost because of plumbing overhead. It's hard to tell from that pic, but boost goes from 103 kPa to 156 kPa in just under 3 seconds.
The MAF is indicating constantly increasing airflow (MAFFREQ Hz) even past where the boost plateaus, so this is indicating to me that the engine isn't being starved for air with the turbos just not able to keep up. There was some concern that this might happen with the larger cubed 427. I guess I'm going to have to get one of those GoPro cameras one of these days so I can actually watch the wastegates opening up.
But I'm thinking that I could probably go with stiffer springs in those wastegates to raise that boost level a little bit. Those 10 lb springs do seem to top out pretty darn quickly.
Vehicle speed seems to be keeping a 1:1 ratio compared to engine speed, so I'm taking this as a good sign that the clutch isn't slipping, and the engine is pulling hard up till the moment I take my foot off the gas pedal at 5400 rpm. But I definitely can FEEL where the boost hits that plateau at 8 psi and holds there.
AFR is looking pretty good, and there were no knock retards indicated during the entire run, so the timing is apparently OK.
I figure I don't need very many more runs for data logging before I have the fueling where it needs to be via the two VE tables. Once that is straightened away, I'm going to re-enable the fuel trims and just see whether the car drives better with or without them. There is still some slight surging a low rpms when I take my foot off the gas pedal at slower cruising speeds in higher gears.