wideband O2 sensor, spoofing stock o2 signal for leaner burn

[estomax]

Hey Guys,

i tried searching and only found some references from 2011, but on my 'project' car Lexus SC400 with a 1JZ VVTI swap i figured out that the stock O2 sensor costs as much as an aftermarket wideband sensor.

So i got an Innovate LC-2 wideband controller and swapped it in place of my stock o2 sensor. I left the stock o2 sensor hanging nearby since the heater circuit from it will cause the ECU to throw a code otherwise.

Then i cut the wire to the O2 sensor input at the ECU and wired it to the narrowband output on the innovate controller (brown wire).

By default the innovate controller outputs a narrowband signal for 14.08 for rich and 15.01 for lean, which made my car idle and run in closed loop mode right around 14.5-14.7 (stoich).

i then went and adjusted the narrowband signal output from 15 to 16 instead of 14-15, and now my car runs closed loop at 15.5-15.7 or so. I will keep an eye on it but this is about a 5% increase in gas mileage while i mind my foot

That was the DIY portion for anyone who would want to have more control over leaning out their fuel mixture without going with a full aftermarket engine management system.

Now my question is, who else here has done this on a non-lean burn motor and what should i be worried about?

cheers
Marko

[Baltothewolf]

Originally Posted by Old Tele man

Does that engine have a "head temperature" sensor or just block temp? The leaner the A/F runs continuously, the more 'head' temperature becomes a possible problem. Too hot and valves burn.

I don't think under light engine load this would be an issue would it? Like flat ground cruising at 70?

I think what you are doing is a good idea, but I would find a way that anything over like 60% engine load trips it back to normal running settings.

[RustyLugNut]

Originally Posted by Old Tele man

There are TWO ways to build-up "heat", heavy load and long duration...what's your driving scenario?

If you run beyond 18:1 air/fuel ratio, the combustion temperatures drop drastically. So does engine torque output. If you can balance your load with a lean combustion mix, you are good to go.

[mazda6john]

I run a tuning company as a side business and i frequently tune hondas/acuras using hondata and neptune which allows you to do the same thing, but with the factory sensor. I have a close friend getting over 35 mpg on e85 with a 12:1 compression ls-vtec making over 220 whp. Its in a crx.

[estomax]

thanks for the input guys, mazda6john how lean do you run the hondas?

so far i've driven it for a bit and any higher engine loads the ECU switches to open loop which is really rich, so i am not too worried about that end. Just was wondering about any effects of cruising at a lean mixture. The engine has a temp sensor on the head and that feeds the ECU, so if it gets too hot it starts dumping fuel and goes to closed loop also i'm sure.

i'm currently making a digital AFR gauge out of a Arduino and 7 segment LED display that i can tuck somewhere and maybe use the arduino for other things also (currently taking 0-5V wideband controller signal and putting out a 4 character LED string to a TM1637 module). cheap AFR gauge for ~30$! plug and play, no soldering or any shenanigans.

cheers
Marko

edit: just ran a datalog run, everything seems ok, AFR in boost is 11-12 at high boost and 12-13 during transition/few psi, not as pig rich as i thought it would be. Wierdly though, my ecu dumps fuel under vacuum decel (in gear). at idle itll be nice around 15.5-16 and then if i go down a hill in gear it will drop to low 12s.. i really want a standalone now