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Originally Posted by Intra
heheh.
Ok Facts.
1. 94 -00 had a change from the Jecs based board which ran a mitsubishi melps 7700 MCU to a denso manufactured board with a Motorola based MCU and now a Hitachi based MCU. There were heaps of logic changes and operational routines which control how the engine reacts to feedback and environmental changes. Not to mention they are all completely different MCU's which need different opcodes to relate back to operands. If we dig even further you'll notice the break down is like this
94 - 96 : Jecs revision with SSM Support
97 - 98 : Changed board revision with SSM Support
99 - 00 : Changed board revision with new connector and obd2 support and SSM support
01 -> current :Changed again , with OBD2 and SSM support and future support to SSMIII
2. "adjusted accordingly" is closed loop, an adjusting of engine conditions based on feedback is what i would classify as closed loop. Open loop is usually based on conditions of throttle or other factors which tell the ecu to then disregard feedback.
3. Emissions didn't seem to be much of a worry early on in the game, Subaru along with other manufacturers are now in a position to keep within emission laws much tighter then before and that can clearly be seen with stock mixtures, more elaborative components such as TGV's to aid atomization on warm up, Air pump in newer models to inject more air to help with burn etc. |
Apologies up front for hijacking the thread, but the humble Unichip was always incorrectly blamed for the OEM
ECU boost spike.
1. Nice start...
2. Further factual data...I am not referring to the entire
ECU process just the Boost. Boost control on pre 01 Imprezas use two main maps. Both are 8x8 in size, but have entirely different functions. Being: "Boost Achieve" and "Duty Cycle Aim". Boost Achieve is two dimensional, and as you know, varied according to both RPM and engine load (some models kept load static).
Duty aim map specifies the "best guess" duty cycles required to deliver the desired boost curve, specified in the Boost Achieve map. This map allows the
ECU to take a
GUESS at the required actuator duty
BEFORE closed loop control homes in on the desired boost. Get your aim map too high, and the boost will overshoot. Get it too low, and spool up will be impaired in lower gears.
Quasi closed loop, virtual open loop until it gets within control parameters, parameters that vary with RPM and load. Yes you are technically correct but given the system does not work its as good as open loop
What happens to boost on a cold night in a pre 01
3. Change is guaranteed! Good discussion.