how to tune your teg with a V-AFC and a volt meter!!!!!!

genesis

tougê hêrmit
Well i have recently added a V-AFC to my mod list and wow is this thing amazing the only problem is i cant start adjusting fuel unless i know the air/fuel ratio. so after thinking long and hard about how to figure out my A/F ratio would be i came up with an idea, why not tap into the primary o2 sensor with a volt meter and then convert the volts to my air fuel ratio. so after looking at ecu pinouts i finally found the wire to tap into(front o2 sensor signal wire). heres how i hooked up my multimeter my red leed to the signal wire from the front o2 and hooked the black to a chassis ground then hooked the battery back up and turned on the car, ingenious *evil laughter* It works!!!!!!!! so now i was interested if anyone else had done this too and i came to find out that there are whole conversion charts to convert volts from the o2 to the air/fuel ratio.
so after doing a couple runs we found my A/F ratio to be extremely rich. I then set my V-AFC ne points down -1 at a time after each run and got down to -5% fuel before i stopped i believe anything lower than -6% would be kind of sketch considering this isnt as acurate as a wideband..... but pretty damn acurate for a narrowband. i have mine set at -5% and am reading 9.2 volts which = a conservative 13.0/1 A/F ratio. this is a great set up my car feelt like i had no one in it when i had my buddy in the car, without him in the car its crazy how much of a difference it made i doesnt bog down any more at 2500 it just go's. why buy a guage when you can do this?:lol:

here are some websites that helped me out
for the conversion table = http://www.zeitronix.com/questions/O2questions.htm
for all hard to find ecu pinouts = http://images.google.com/imgres?imgurl=http://www.alexsracing.com/pictures/pinouts/obd2b_1.jpg&imgrefurl=http://www.alexsracing.com/pinouts.html&usg=__M9dTfNCKwcaky7Tp-0dOBtMwP0U=&h=226&w=640&sz=36&hl=en&start=5&um=1&tbnid=eHGlqo-BZBM3SM:&tbnh=48&tbnw=137&prev=/images?q=obd+II+p+72+B+pinout&um=1&hl=en&client=safari&rls=en&sa=X
 

Aussie

Zoom-Zoom
That's not going to work. A stock oxygen sensor is designed to be used by the ECU to keep the mixture near stoichiometric, which is the optimum air/fuel ratio for the catalytic converter to work. The stock oxygen sensor range is usually only about lambda 0.95 - 1.04, while tuning we usually want a display that will be accurate from lambda 0.75 - 1.10
 

genesis

tougê hêrmit
Aussie said:
That's not going to work. A stock oxygen sensor is designed to be used by the ECU to keep the mixture near stoichiometric, which is the optimum air/fuel ratio for the catalytic converter to work. The stock oxygen sensor range is usually only about lambda 0.95 - 1.04, while tuning we usually want a display that will be accurate from lambda 0.75 - 1.10
Click to expand...
wow thanks for the info!!!! although i was able to to wach the air/fuel ratio lean out while i was doing it on the V-AFC so i dont know?
 


Aussie

Zoom-Zoom
You will get a signal but that doesn't mean it is correct.

Here is an idea of what is going on.



If your voltage is not correct you will also be getting a signal that doesn't exactly represent your correct a/f ratio. For instance on my Hondata I have to offset the voltage a couple of tenths for the signal to be the same as the actual sensor.
 
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