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Old 09-13-2012, 07:21 AM   #9 (permalink)
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Originally Posted by serialk11r View Post
Cable're going to be stuck in lean burn the whole time? Or do you plan to have a lean burn off switch? Acceleration with very lean mixtures will be less efficient.

I feel like the best way to do this would be a wideband O2 sensor and standalone, that way you won't need to remember to manually put it on the original tune to make sure the fuel trims stay accurately calibrated. Along with a button for map switching of course, since your power will be quite limited. Lambda at full throttle is usually 0.9 (typically lower though, to protect catalysts and stuff), so if you're going to run lean your lambda should probably be no less than 1.3ish to reduce exhaust temperatures.
The leanburn idle feature will need to have a manual on/off of some type in order for the fuel cut to work. The reason for leanburn at idle and 1st is for city driving at low speeds or briefly stopped. To accelerate most efficiently to 40-50 mph I don't use leanburn anyway and is easily overridden by depressing the throttle more.

The lambda at full load with this stock ecu/engine is 1.0 up to 2700 rpm then it goes rich to .85 lambda. Only rare WOT occasions does rpm exceed this. Leanburn is 1.55 on a stock VX, that's probably about where it needs to be.

Tuning this type of engine with a standalone system will require a minimum of 3 fuel maps and preferably two different closed loop lambda target values aside from having an egr valve to control. I wouldn't say this is insurmountable, but certainly a load of work if there is even a system out there capable of doing this - if so, I'm unaware of it.
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