How to build a low cost EFIE
 

I know there is another thread about this same issue, but all the information had been removed by the original poster so since I found it on the internet I thought I'd post a link so anyone who wants to give it a try can benefit. The cost should be under $10.

https://www.youtube.com/watch?v=PEHJ9te7gvk

I thought I'd update this thread. I have made one of the EFIE's, but haven't installed it on the car yet. I'll be using my 505K mile Escort for experimenting!!!! I did put a battery in it and tested to see how much I would be able to adjust the 02 sensor voltage and it gave me 0.0-0.54volts of adjustment so I should be able to lean out the mixture a little bit after doing a little testing to see where the voltage normally runs. I'll just have to be careful and not over do it. I'll start out small and work my way up until it acts like I'm getting in the detonation/danger zone then I'll lower the voltage back down. Looks like it's going to be a while before I get to do the initial testing and installation of the EFIE since we are still getting snow and having lots of weather that's colder than normal for us this time of year.

Don't test it on the 505K mile car! You have to see how long that car will last without any unnatural influences... :D

I second that!

I've got to try it on something and all the other cars are in much better condition with the exception of my wifes '87 Chevy Celebrity and she's against the idea of trying it on her car. I'm not sure, but I suspect if I get it too lean the ECU will kick it into open loop just as it does when the 02 sensor goes bad.

the thing is with a false o2 reading the ECU may never know that it's too lean. I've wanted to mess with this, but i'm putting it off till i have a way of checking exhaust temp.

wouldn't the knock sensor be the safety for that? I would think that the knock sensor would protect the motor and the ecu would richen up the mixture to keep from getting detonation.....I think......maybe

That's exactly the point of doing this mod.

Way to make me sound like a dumbass.

I was replying to this:
"I suspect if I get it too lean the ECU will kick it into open loop just as it does when the 02 sensor goes bad."
I have little faith that this will happen before the point of damage.

The EFIE has been installed now for just over 500 miles. The first fill up after installing looked terrible, (176.2 miles on 5.301 gallons or 33.23 MPG, worst fill up in my gas log) but I think I may have been turning the EFIE on before the car went into closed loop and may have been causing it to stay in open loop. As usual I am still topping the tank off and filling before the tank gets to the half way point. The last fill looked better than it has in months (197.9 miles on 4.908 gallon or 40.32 MPG). This still isn't as good as it was doing prior to changing the timing belt last summer, but it is a great improvement. I never did figure out why the mileage dropped after the timing belt change, but that's a different story. The car seems to be running fine without any signs of detonation and I think I still have a quite a bit of adjusting to do to the EFIE before I get to the maximum I can add, but I'm trying to move slowly so if there's any negative effects I know about what the maximum voltage is I can add to the 02 signal. The last tank was adding 125mA to the signal, when I filled the tank up I increased it to 150mA and according to the fuel gauge looks like the mileage has increase more, but sometimes this fuel gauge acts kind of crazy so who knows. I've been keeping a digital multimeter hooked up to the pre EFIE signal so I can monitor it to make sure the signal isn't running extremely lean for long periods of time, but I've also ordered an a/f gauge to hook up so I can see where it runs.

I'm also planning to put a hydrogen generator on it as soon as I can come up with the materials and time, hoping that even if the hydrogen doesn't help mileage it will allow me to lean it out further.