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+--- Thread: Oxygen fuel ratio calculations(OFC), fuel density... (/showthread.php?tid=5458)
Oxygen fuel ratio calculations(OFC), fuel density... - kmk - 12-19-2019
Was wondering if anyone can help me with the actual calculations with respect to ofc tables, trying to keep my question as general as possible:D. Thanks.
RE: Oxygen fuel ratio calculations(OFC), fuel density... - Rawze - 12-19-2019
the numbers u see in a calibration for ofc are partial results from a typical fuel-air-mix formula then converted to oxygen fuel control via the lambda. - Essentially most of the math is pre-calculated so that the ecm does not have to do all the math on the fly.
A person needs the correct lambda table for the engine to even start to convert the ofc table back and fourth to fuel-air-mix, so that someone can see what they re doing.
Then, there is also the 'theoretical' model vs real model ... the ecm uses the 'theoretical / stoichiometric' model, bottoming out at roughly ~14.5:1 on the high end, but the real outcome can be as much as over 400:1 depending on conditions, engine modes, torque and power, boost, etc.
some related info / example topic (is for gas engine, but is good document on the subject): https://x-engineer.org/automotive-engineering/internal-combustion-engines/performance/air-fuel-ratio-lambda-engine-performance/
BTW: Those tables are NOT the fuel-air-mix adjustment tables... They are the limiter only, to prevent smoke/soot production during acceleration while the turbo has not yet gotten caught up to the desired pressures. - I.E> raising the numbers a bit allows for a harder acceleration. -- Less fuel limiting during hard acceleration, only while the turbo is lagged, but it also introduces black smoke+soot, the higher it is set. - Poor fuel mileage, more soot in the oil, eventual carbon packing, etc.etc. - and on a stock (non-deleted) engine,.. a LOT more dpf and aftertreatment problems.
-- I can correctly calculate those tables. PM me, give a yell over on my mumble server, or call me (assuming you have my number) some time if you need some specific help figuring something out.