kettlekev wrote: ↑Sat Nov 19, 2022 9:35 am
I guess I will need an external BARO sensor as well?
Agreed, the 2nd real-time Baro sensor is optional. I use one whenever I can, as it simply adds to tune stability. One of my personal "rules" is to avoid (as much as possible) anything that makes the ECM work harder to stay on-target, forcing the ECM to make lagging corrections for deviations from tune. The problem with reactive lagging corrections, is that they only work
after the burn, so the run is already incorrect before it tries to fix it. Proactive corrections like Baro work to keep the tune correct, so the deviation from tune is minor and effects are less, while reactive corrections (e.g., WBO2) are hopefully minor. You are herding cats, and Baro helps with that, keeping them mostly in-line instead of chasing them
after they get away.
While the effect is incremental, everything works 'better', from idle or boost control, to AE, timing or detonation control, etc. The less 'edgy' your tune is, or lower requirements for efficiency and performance, the less required or helpful these accuracy enhancers are.
kettlekev wrote: ↑Sat Nov 19, 2022 9:35 amThe boost table controls to a waste gate pressure in Kpa and I assume the BARO sensor is the source for that?
The MAP sensor is the primary boost sensor. While barometric pressure affects it, the system will still target the boost levels set. This means on a high density-altitude day, the turbo/SC will work harder to reach the same boost level. Not relative boost (compared to baro), but actual boost (MAP), e.g., 100kPa ambient will boost 50kPa to 150kPa target. 80kPa ambient will boost 70kPa to 150kPa target. This occurs whether Baro is active or not, but baro can alter fuel and timing if needed to stay on-tune while it is deviating from original tuning conditions.
kettlekev wrote: ↑Sat Nov 19, 2022 9:35 am
The tricky bit is knowing where to start with the boost control map.
The simple mechanical waste gate on the bike slowly opens as pressure builds to a set psi (19-20 psi) where it is fully open. I dont think anyone has tried to 'map' that so that will be a challenge......
Not tricky. Think of it as a target table of where you want boost to go. Any mode will require tuning and tweaking, but starting with simple and moving to PID (if needed) will allow you to refine where the system stabilizes boost pressures on the table. Baseline is the default wastegate set pressure (spring and diaphragm) of your system, and is the lowest available boost. Boost controller opening raises the boost by diverting the pressure used to open the WG, forcing higher boost. Take care to not confuse boost controller open/closed with wastegate open/close.
I may not be reading you right, and boost builds on a closed wastegate, until it reaches close to target boost pressure, and then the WG opens to attempt to hold boost at that set pressure. It is a simple reactive regulator system. The WG should not be 100% open (normally) as that would be at the edge of uncontrolled boost, often seen as "boost creep".
With the default of boost control valve closed, the wastegate will open at its sprung pressure, the lowest boost pressure. With BC diverting the pressure to open it, boost (MAP) may be raised. The more you open the boost valve to divert pressure, the higher your boost rises (for the given conditions). While there are many variables and factors involved, the basic concept is simple—deny the pressure to open the wastegate, and the MAP (boost) will rise.
Of course, I would suggest you work your tune up to this point.
The last thing you would want to do is WOT to "see what it does". You always want to work up to that level, so you have a very good prediction of what it will do and what it will need to be safe. Have fun!