With gas prices on the rise, I am going to be doing an experiment to help improve fuel economy a small amount.
I plan on installing wide band lambda sensors with programmable 0-1 and 0-5 volt outputs in the post O2 (sensors behind catalysts) position and sending the ECU an offset 0-1v narrow band sensor voltage. I am starting with the post O2 sensors vs the front because these sensors have limited authority in terms of how much fuel will be taken out. They are there for catalyst monitor and trimming the closed loop fuel for emissions (I work in emissions..). I may eventually move them to the engine out position for larger gains, but this will provide for a very conservative first step.
The concept of offsetting the sensor voltage is very simple: the sensor will report 13.7:1 AFR when it is actually seeing 14.7:1 stoich, for example. This drives the control system to remove fuel (lean out the mixture), until actual AFR is 15.7:1 and reported from sensor is 14.7:1. These figures are just an example of what I'm doing, I will be making a very conservative first attempt at the sensor calibration!
The plan is to leave the stock sensors in their OE position and keep the heater circuit hooked up to those, to maintain the sensor heater diagnostic in tact. I will feed the signal wire from my wide band sensors to the ECU signal harness side wire. I'll have two gauges that will report the actual
AFR behind the catalysts.
The bosses are going to be installed next week. You can get these programmable wide band sensors now for a couple hundred bucks. I'm using Innovate Motorsports with Bosch sensors. I think they're about $250 each, which is relatively inexpensive for wide band lambda measurement!
I currently average around 13-14 mph with primarily city driving. The wife is the primary driver. Project goal is to bring this up to at least 15 mph.