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Originally posted by digislayer
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Even though the R15 uses an Open Loop FI, it uses an FI system that includes the MAP-Sensor, unlike most other FI systems.
So, it's not as useless an FI system as everyone else is thinking it is.
MAP Sensor:
The MAP sensor can also be used to measure the barometric absolute pressure (BAP sensor) when the engine is not turning, i.e., when the intake manifold is not being evacuated by the engine's pumping action.
When the engine is running, the difference between the BAP and the MAP is the engine's manifold vacuum. As atmospheric pressure decreases with increasing altitude, so must vacuum to maintain the same MAP.
BAP = MAP + Vacuum
(Source: MAP Sensor - Manifold Absolute Pressure)
Once the Intake Air Temperature Barometric Pressure(which can be obtained from MAP as stated above) are determined, the Intake Air Density also can be calculated without the need for an extra Lambda Sensor.
(Source: Fuel Injection)
Alpha-N
There is one other EFI control system that is generally used only in racing called an Alpha-N system. This control system's major inputs are throttle position and rpm. This system was developed because race engines often operate at idle and part-throttle with very little manifold vacuum. This makes using a MAP sensor difficult. This system is less precise than speed density or MAF and is therefore generally only found in racing or on heavily modified street engines with big camshafts. A MAP sensor can still be used with Alpha-N, but it is generally employed as a barometric pressure sensor to detect altitude changes.
(Source: Fuel Injection Basics - Tech Article - Chevy High Performance Magazine)
So, it's not as useless an FI system as everyone else is thinking it is.
MAP Sensor:
The MAP sensor can also be used to measure the barometric absolute pressure (BAP sensor) when the engine is not turning, i.e., when the intake manifold is not being evacuated by the engine's pumping action.
When the engine is running, the difference between the BAP and the MAP is the engine's manifold vacuum. As atmospheric pressure decreases with increasing altitude, so must vacuum to maintain the same MAP.
BAP = MAP + Vacuum
(Source: MAP Sensor - Manifold Absolute Pressure)
Once the Intake Air Temperature Barometric Pressure(which can be obtained from MAP as stated above) are determined, the Intake Air Density also can be calculated without the need for an extra Lambda Sensor.
(Source: Fuel Injection)
Alpha-N
There is one other EFI control system that is generally used only in racing called an Alpha-N system. This control system's major inputs are throttle position and rpm. This system was developed because race engines often operate at idle and part-throttle with very little manifold vacuum. This makes using a MAP sensor difficult. This system is less precise than speed density or MAF and is therefore generally only found in racing or on heavily modified street engines with big camshafts. A MAP sensor can still be used with Alpha-N, but it is generally employed as a barometric pressure sensor to detect altitude changes.
(Source: Fuel Injection Basics - Tech Article - Chevy High Performance Magazine)
that means we can use K'N in R15?
). The R15's FI looks up only the statically stored AF mixture tables, and runs, without any feedback from the exhaust, and without any further real-time tweaking. It cannot deviate from the stock map, or stock AF mixing table in other words. 
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