a/f gauge install question.
 

quick question, i have an autometer a/f gauge. it has 3 wires, red,blue, and a purple


which wires are which ? i bought the gauge used from someone without instructions...

also, where shold i tap in for these lines ?


Thanks.
Scott

look on autometer's site, they should be able to provide instructions for the gauge.

i've been looking at their website... i can't seem to find anything. just all these links to constructions being made on the site. any help is useful = )

Scott

red power
blue ground
purple singal


http://www.autometer.com/hp/instruct...tions/837j.pdf

Scott for the win ! i love you. ill buy you lap dances at the cottontail ranch in reno when u stop by.

sweet!

http://www.aus-cartalk.com/viewtopic.php?t=21742

have a look at this little write up i did on this topic on another forum. it's a different meter but it is accessing the same wires. i'm not getting my 12v from the wire at the ecu anymore, i'm getting it from the blue wire at the ignition switch. much more current there.
my ecu is in the footwell in front of the passenger seat. i think they might be in a different spot in the american cars but i think the wire colour codes are the same. hope this helps.

very nice link fatty, thanks a bunch. I think i got thw whole thing in now, but im not exactly sure what im suppose to be looking at with the meter.

red = lean = bad
yellow = stoic = good
green = rich = good while under boost right ?

is that a decent assumption for the reading of the gauge ?

also, mine seems to be acting weird....

at idle are there suppose to be readings ?

while crusing, the light goes from red to yellow and back and forth. over and over.

but while im under boost, gauge will go to yellow stay in yellow and edge into the green.

i ran the hot and ground behind the gauge cluster and i ran the reading line through the firewall and sliced it into the o2 sensor wire. (could i be getting interference by splicing the line under the hood )

Scott

it is normal for the meter to swing rapidly between lean and normal or rich when cruising. this is what happens when your ecu is in "closed loop" mode, which is the most fuel efficient for cruising.
this should probably happen at idle as well.
when you take your foot off the gas the injectors stop working until your revs drop back to idle, so as there is no fuel you will get a lean reading.

sounds like your gauge is working fine to me. just watch it for a few days and you'll start to understand what is going on.

if you had a wideband you could read the gauge as the following:

http://www.rev2red.com/images/cars/faq/gauge.jpg

The reason it's hard to tune with the narrowband signal is because you do not get a linear signal output from it:

http://www.rev2red.com/images/cars/faq/voltage.jpg

Your gauge is working how it should be the signal you're giving it. What it's really only going to be helpful with it extreme situations, like WOT you'll know if you're rich or lean, but you won't be able to gauge exactly what the AFR really is.

so where did you tap the signal from? does anyone have pictures?

Even at WOT the gauge may read full rich but a/f may only be 14:1. A wideband is a great investment.

Pretty sure it's pin 2P on the ECU. Don't hold me to it.

Brain, maybe post up that picture you have that explains quite clearly why you need to have a wideband instead of a dummy gauge.

how about facts instead of scare tatics:

http://www.rev2red.com/images/cars/faq/nb02stinks.jpg

The purpose of a A/F gauge is to show your AFRs. We shoot for 11-12.5:1 in boost. A NB will show the same reading for 11-17:1 AFR, what good that does do for you? So the only thing you'll be able to read is if your AFR is below 11:1 or above 17:1.

Voltage outputs on NB are not proportional to the exhaust's o2 content.

NB voltage outputs have no linear relationship between the AFR and the sensor's volt output. Output voltages are approx. 0.5v at 14.7 AFR, and rise quickly to 0.9v as AFR is lowered below stoichiometric. The converse is also true...So the ECU therefore adds fuel till voltage is greater than 0.5v, then kills fuel till voltage is less than 0.5v, and AFR oscillates about stoichiometric...My WB oscillates between 15.2-14.5:1 AFR at idle, your's bounces back and forth and shows you nothing.

red x!

Is it posible to tap a wire of the o2 sensor it's self or does it have to be from the ecu? DO youthink it would be 2p on a 96 as well? Thanks.

yes, you can tap the wire itself.

What of the three wires coming off the o2 sensor would it be? The purple one?

yes as I wrote in post #4

red power
blue ground
purple singal