I'm not disagreeing with much of your point. But a RATIO is not pressure or volume. Pressure is not volume. Volume is not pressure.
MAPs frequently make assumptions and can short circuit because they can infer based on a specific engine. This is why ECUs cater to specific engines.
Pressure doesn't care about volume. This is why I keep asking you what you're trying to figure out? I believe you're simply not asking the right question and I can't figure out what you're trying to ask.
Are you asking how to correlate manifold pressure with a given boost?
But a RATIO is not pressure or volume.
The ratio is of pressure, expressed in kpa or psi or bar to atmosphere, only. My question is if there's a theoretical calculation like BMEP, or torque ratio, to compare engine performance, why can't there be a total compression ratio per cylinder? Not of volume, not of density, but the two combined into their related pressure, and measured as a ratio to the static air pressure. Then you could have a way to compare engines, based on their boost pressure and compression ratios.
The ratio is of pressure
No, the ratio is of VOLUME. It knows nothing of pressure. To know the pressure would require knowing the density on the intake side. Which we do not have or know. Likewise, it varies from day to day and location to location. In the normalized turbo example above, that 10lbs at 10K on one day could be 12lbs at 10K on the next day - or 200 miles later.
MAPs use engine displacement and some measure of air flow or density to infer various calculations. This is how and why open loop works. Closed loop is based off of measurement, which in turn still infers based on engine geometry. They also use a fair bit of fudge and assumptions. This is why programmers are able to increase output so much, because they are removing much of the fudges built into the system for universal operating safety (and yes, for EPA qualification too).
This is why, for example, a MAF attempts to measure a weight derived from airflow over time. With a weight you can infer density. The density allows you to do MAP lookups to infer A/F charge. Which you can then correct and infer based on EGT and intake/exhaust pressures and so on. All of which modern ECUs do in one form or fashion. But notice, the open loop is much more conservative because it's based on complete guesses, with correction based on whatever sensors it has available at the time.
based on their boost pressure
This is one of the issues. Boost doesn't care about volume. It says nothing about volume. You would have to infer this based on the total intake plenum and pipes AND cylinder volumes. Remember, boost is boosting the entire intake side and not just the cylinders.
Hopefully you understand where I'm coming from now. There is much more involved and many unknowns and variables which a ratio completely ignores.
Likewise with BMEP and TQ ratios. BMEP has nothing to do with the actual pressure going through the cylinder. It's a way to compare similar engines. Computers prefer to use look up tables than make calculations, if you have a way to make reliable relationships and plot them as a LUT, you can save computational resources. So I'm just thinking of ways I can create LUTs for certain things to speed up some processes.
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