A/F gauge install instructions W/pics

[b4tn]

After a year or so here is my contribution to PT. After doing some searching I couldn’t find anything specific for connecting an A/F gauge to the ECU inside the cabin. The advantage to doing it this way is you don’t have to run any long wires through the firewall down to an 02 sensor. Hopefully I got it right. This was done on a Mazda so the dash piece is probably different but the ECU and wire connections are identical. I prefer a lower profile car so I decided against a gauge pod. The Mazda has a place under the stereo perfect for 2" gauges. I couldn’t find any black plastic locally so frustrated I went to Pep Boys to look for ideas. I ended up buying a truck mud flap (dont laugh). I am glad I didn’t use plastic because the mud flap which is just under a 1/4 inch think is soft enough to bend but hard enough to stay rigid once in place.
here is a pic of the cutting area (my carport)
http://ns1.vs186.server4me.comb4tn/m...ll/cutting.jpg

Some how while trying to fix the links I managed to delete almost the entire post! I have no idea how. But the most important pic is below. if you have any question I will try to answer the best I can.
http://ns1.vs186.server4me.com/b4tn/...all/splice.jpg[/img]

[b4tn]

Well I have to admit I am a bit disapointed :sad: As far as I can tell this thing is worthless, just a cool looking blinky thingy. It seems to be working right though??

Idle: It slowly bounces from one bar lean to full stoich

Acceleration: it bounces back and forth fast from one bar lean to full stoich. If I step on the throttle, not WOT just give it some moderate gas it runs up to one bar rich for a second then back to bouncing between one bar lean and full stoich

WOT: it runs up to 2 bars rich and stays there as long as WOT lasts.

Deceleration: Nothing

So I think It is working? but it just bounces back and forth what good is that? The only usefull info is at WOT which I fugured would be in the stoich area because of my TB and CAI but it wast. I guess I will need someone to show me how to read this thing (skelly )

[skelly]

*ahem* ah yes.. it's working. It'd certainly be useful if you were boosting or running nitrous - something that would have a direct impact on the air/fueling of the engine. As it stand, you can look forward to many years/months of blinking LED's without much to do..

Coincidentally, I JUST this morning re-wired my gauge to the ECu harness rather than running the old line out to the O2 sensor itself. Since I knew of no wiring diagrams online for OBD2 harness, I turned to my trusty Haynes manual for them - boy was that a mistake. Let's just say the manual's wire color coding is flat out WRONG and in no way reflects what is actually on the car: pathetic.

So after splicing into the wrong wire according to the manual, I used a continuity tester to find the line connecting to the desired sensor and spliced accordingly. For reference, I used the front bank sensor (since this is the one I originally ran a wire to being most accessible in front of the engine) and it's wire is GRN w/WHT stripe and is on the center of the three ECU harness plugs.

Ideally one would splice into the one off the Y-pipe before the cat so as to get a reading from both halves of the engine and this is what I had started out to do with the Haynes manual, but was let down abysmally.

I prefer this approach over running a wire to the engine bay solely because I don't want additional wires in the hot engine bay - it's more controlled in the cabin.

[b4tn]

I knew you would find this post sooner or later I suppose since the ultimate goal is N20 It will be ok. Also I noticed something today. I didn't let the car warm up enough when I originally took it for a drive. The more I watch that gauge the more it makes sense. I am actually running a bit leaner than recommended. Once it is warmed up I barely make it into the rich @ WOT. Just a question. On your setup how many bars into rich do you let it go during WOT. And how many bars rich does it show for normal driving?

[skelly]

Well, as you know I have the adjustable FPR on there which is set for ~45PSI @ WOT.. as such, depending on weather (yes, outside air temp makes a significant difference in the reading), cold air (night time/ cold winter days) fully lights all the rich bars @ WOT. But on a warm-to-hot day WOT only shows 3-4 bars rich. At Idle and lower RPM range it swings out to anywhere from 1-4 bars depending on its mood. :rolleyes: It should be noted also that the lean side of my sweep almost invariably touches the very last lean bar.. it's quite a full sweep, never has stuck to the stoic range. Bear in mind that you may experience different results arising from differences between OBD and OBD2 code..

[Black93GT]

i had mine mounted on the A pillar. I found that i watched the swoosh of the led's more than the road... especially at night. lol obvilusly its not a precision instrument but it gives a good estimate of A/F ratio.

[segmond]

wassup guys, although i don't have an a/f gauge/meter installed yet. i can tell you this. do not connect to ground. connect directly to the negative terminal of your battery, that's right do that and you will notice a much more accurate reading.

[b4tn]

Originally posted by segmond
wassup guys, although i don't have an a/f gauge/meter installed yet. i can tell you this. do not connect to ground. connect directly to the negative terminal of your battery, that's right do that and you will notice a much more accurate reading.

I am not saying you are wrong but that doesnt make sense to me. I would think that running a wire all the way to the battery from the cabin would make for a poorer ground. Although not much current is bieng drawn i think I would rather ground it really good to the frame with as short a wire as possible. ANyone else heard this??

[segmond]

Originally posted by b4tn


I am not saying you are wrong but that doesnt make sense to me. I would think that running a wire all the way to the battery from the cabin would make for a poorer ground. Although not much current is bieng drawn i think I would rather ground it really good to the frame with as short a wire as possible. ANyone else heard this??

you already tried that, and your reading sucks. it doesn't cost you anything but a few minutes to try that. so just try it, then come back and tell us if it got worse or better.

[reddawg]

cigerate lighter

i would think that hooking the wire up to the cigerate lighter would keep the gauge on at all times? unless you hook up a switch inbetween. i have a 93 pgt, and i know that the cigerate lighter is hot at all times, not when the key is in the on position. i don't know if that is the same with the newer probes and mx6's though.

[b4tn]

Well I wired the ground strait to the battery with no change in readings. I dont think the gauge was giving messed up readings, I think i didnt know how to read it.

And yes the MX6 Lighter is switched

[KLZEKID]

Well it looks good. U did a nice clean job of it. I want to make one for my glovebox. Thats exactly what my air/fuel ratio does.

[skelly]

Originally posted by segmond
..do not connect to ground. connect directly to the negative terminal of your battery, that's right do that and you will notice a much more accurate reading.

On what basis? The negative battery terminal is grounded directly to the chassis which is where 90% of everything else is grounded to.

[spada]

b4tn, i see you have a 95, the wiring colors may be a little different from the 93/94 PCM, because the one i tapped into was a blue wire with yellow stripe. This one was the input from the LHO2S. Did you tap into the RHO2S? i forget what color that one is, i'll look it up later maybe and edit this post to help out the 94 guys.

[b4tn]

Originally posted by skelly
Well, as you know I have the adjustable FPR on there which is set for ~45PSI @ WOT..

45 psi??? Isnt that basicly stock? I tried setting mine to 45 @ WOT as soon as I put the vacume hose back on it drops to less than 35. I was messing around today and set it to 45 @ idle. bad idea! I went through a 1/4 tank of gas for roughly 20 miles So I bumped it back down and currently have it set to 39-40 at idle, so far so good. if I am not mistaken I think stock FP at idle is 36 psi.