The "let's brainstorm how to make a piggyback work" thread

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Originally Posted by Loren

I'm not talking about completely faking the O2 signal and locking it down at a fixed value. It would still respond, it would just be "off" a bit, and the ECU would have no way of knowing that.

A system like the LC-1 is VERY tunable. It works like this:
Say the default narrowband O2 sensor output is .45 - 1.5 volts. (not sure if that's right or not, it's something like that) The center of that range represents exactly 14.7.

The LC-1 has not one, but TWO programmable outputs. You could wire one of them to a gauge that would tell you the ACTUAL AFR. The other one you program as a sort of "hybrid wideband" using the standard narrowband voltage range, but centered on something richer than 14.7.

The ECU sees what it expects to see (even though it's not quite the truth), the signal responds to the ECU's commands, and everybody's happy.

Now that I think about it, some additional circuitry may be required to shift the voltage range, but it should be doable. Probably way easier than hacking the ECU.

Tip: The Miata is a far, far more popular car among racers and tuners, and the factory ECU has never been hacked. The closest anyone has ever come is to overclock it with a faster crystal, which has the effect of raising the rev limit and leaning the mixture. I think asking for or waiting for a hack of the Toyota ECU is unrealistic.

The problem with doing that is that it will probably do nothing, depending on now the open loop fueling works. I assume that the car ignores the narrowband sensor all together in open loop like most new cars do.

The chance of getting a "reflash" type solution is slim. The only hope is that the xd is popular enough to get one, and we could use it as well.

For Subarus and Evos there is open source free software to flash the ECU and make any changes you want. Unfortunately there is not that kind of demand in the Yaris market. Probably a Unichip or other piggy back is the most cost effective solution, with add on fuel and timing controllers coming in 2nd.