A/F Signal Wire on KA

Post by **ChillyWilly3** » Sun Mar 30, 2003 8:36 am

According to the 96 240SX wiring diagram, the 3-wire front heated O2 sensor has (1) blue, (1) brown and (1) white wire. The blue and the white wire connect back to the ECM. I assumed the signal wire is the blue wire and that the brown and white wires are the heater wires because the rear O2 sensor also has the brown and white wire, but has a black instead of blue for the third wire.

Anyway, after attaching it and running the car for about 4-5 minutes to get the O2 sensor heated up, I noticed the following: starts showing rich (~.95V) then gradually settles around stoich near the lean side (~0.55V) then stays there regardless if I'm at WOT or cruising. Also, when I turn on the accessories such as the wiper, headlights, etc., I see the readings affected (it's showing a drop in voltage).

I thought undet WOT (heavy load) I should see the A/F go rich then settle back to some stoich reading. Also, I thought at cruising speed, I should see the A/F gauge bounce back and forth because the ECM is constanly adjusting. Did I hook the gauge to the wrong wire? do I have a bad ground? do I have a bad O2 sensor (it's relatively new)?

Also, I have a turbo installed on the KA, so I should be shooting for 13.2:1 ratio (~.9V), correct? I heard 12.0:1 ratio from other threads. Hmmm...

Thanks...

Post by **Wolf240SX** » Sun Mar 30, 2003 8:36 am

the white wire should be your signal wire. I know on the s13 that several systems use a white wire for the signal.

Post by **Wolf240SX** » Sun Mar 30, 2003 8:36 am

also take a voltmeter and read each wire with the ignition on. See what wire reads what.

Post by **MikeMurphy** » Sun Mar 30, 2003 8:36 am

Im pretty sure its 12.5:1 but safer at about 13:1 for a forced induction application. Correct me if im wrong

Post by **WDRacing** » Sun Mar 30, 2003 8:36 am

Thats a good Af ratio MM....for power anyway. I always ran in the 12's.

WD

Post by **ChillyWilly3** » Sun Mar 30, 2003 8:36 am

Thanks Wolf! - I'll try and check if the white wire on my S14 is being used as the O2 signal wire like on your S13. I guess it's time to whip out the old multimeter and check it out.

Thanks MM and WD! - I'll try and aim for an A/F ratio between 12.0:1 and 13.0:1.

YouTube · Post by **EZcheese15** » Sun Mar 30, 2003 8:36 am

MikeMurphy wrote:Im pretty sure its 12.5:1 but safer at about 13:1 for a forced induction application. Correct me if im wrong

12.5:1 is optimal for the most power. 14.7:1 is stoich. Less than 12.5:1 is running safe. If you get about about 13:1 then you run the risk of detonating, atleast under WOT.

Post by **Matthew** » Sun Mar 30, 2003 8:36 am

You are not seriously considering tuning your car with a narrow band o2 sensor are you?!?!For reference, 13.2 is very lean for a daily driver, it would be very easy for the slightest change in anything to cause detonation.

YouTube · Post by **EZcheese15** » Sun Mar 30, 2003 8:36 am

Matthew wrote:You are not seriously considering tuning your car with a narrow band o2 sensor are you?!?!For reference, 13.2 is very lean for a daily driver, it would be very easy for the slightest chance in anything to cause detonation.

I agree with Matthew here....hook it up, but then take it to a dyno and get a wide band on it. You can tune better by ear than the OEM narrow band O2. And that's scary.

Post by **SloS13** » Sun Mar 30, 2003 8:36 am

speaking of o2 sensors, has anybody tried one of those home-made deals?

http://www.techedge.com.au/veh...t.htm

my dsm buddy says some of his friends swear by them

YouTube · Post by **EZcheese15** » Sun Mar 30, 2003 8:36 am

j92s wrote:speaking of o2 sensors, has anybody tried one of those home-made deals?

http://www.techedge.com.au/veh...t.htm

my dsm buddy says some of his friends swear by them

I've heard similar things about it. Apparently, that is the way to go. Them aussy guys are crazy, but smart.

Post by **ChillyWilly3** » Sun Mar 30, 2003 8:36 am

Matthew wrote:You are not seriously considering tuning your car with a narrow band o2 sensor are you?!?!For reference, 13.2 is very lean for a daily driver, it would be very easy for the slightest change in anything to cause detonation.

[quote=" EZCheese I agree with Matthew here....hook it up, but then take it to a dyno and get a wide band on it. You can tune better by ear than the OEM narrow band O2. And that's scary. [/quote] Actually I wanted the gauge installed to get an idea of what A/F ratio my car is now running at given the fact that I'm now driving with forced induction. I did consider using it to help with tuning the setup.

I'm still feeling my way through this whole bolt-on turbo setup and any input from fellow 240sx owners is much appreciated. If you guys are speaking from experience and feel that dynoing the car is the best way to go, I'll go with the safer route and do that. Any other good route to take?

Also, I had been using my friends OBDII computer to check on engine stats real-time. I believe it contains O2 sensor readings during open/close loop. Is this a much more accurate and/or helpful tool or is it pretty much the same narrowband data (except it's just coming straight from the ECU)?

Thanks...

YouTube · Post by **EZcheese15** » Sun Mar 30, 2003 8:36 am

ChillyWilly3 wrote:
Also, I had been using my friends OBDII computer to check on engine stats real-time. I believe it contains O2 sensor readings during open/close loop. Is this a much more accurate and/or helpful tool or is it pretty much the same narrowband data (except it's just coming straight from the ECU)?

Thanks...

It's the same narrow band O2 data, just coming from the ECU.

Post by **93semax** » Sun Mar 30, 2003 8:36 am

EZcheese15 wrote:12.5:1 is optimal for the most power. 14.7:1 is stoich. Less than 12.5:1 is running safe. If you get about about 13:1 then you run the risk of detonating, atleast under WOT.

Actually stoich is 14.5, you must be thinking of pressure at sea lvl :icesangel

YouTube · Post by **EZcheese15** » Sun Mar 30, 2003 8:36 am

93semax wrote:Actually stoich is 14.5, you must be thinking of pressure at sea lvl :icesangel

http://www.channel1.com/users/...c.htm

Post by **detforme** » Sun Mar 30, 2003 8:36 am

i have the same problem. the white or brown isnt it. anyone else had this problem?

Post by **ChillyWilly3** » Sun Mar 30, 2003 8:36 am

It's the white wire. Somebody started a thread in Zilvia.net and I responded on how to install an Autometer A/F gauge.

Click on the link below:

http://www.zilvia.net/f/showth...ignal

Hope it helps...

Post by **Projex240** » Sun Mar 30, 2003 8:36 am

I have the exact same reading problems. Also, when it is warmer outside or in the morning, it will read richer. I came to find out that when my heat or Headlights are on, then gauge will lean out more. I hate it, even though i know its not that accurate, I'd just like to have it for added insurance in case of an extremely lean situation...they do work well...juts not as well as wide-bands.Instead of hooking up at the engine bay...would splicing the wire near the ecu be a better way to do it. I have mine spliced at the o2 plug connector, but maybe the ecu will be closer to an accurate reading? Im frustrated with this. My bud's dsm reads perfect all the time. Maybe the grounding points we are using arent as good as they should be?HEEEEELLLLPPP!!!!!!!....tHiS is ReLlY pIsSing Me OfF.......

Post by **tapdeznutz** » Sun Mar 30, 2003 8:36 am

since we are talking about a/f wiring. someone know were or how to hook up a/f gauge (e.i. autometer a/f gauge) to a single wire '93 O2 sensor

Post by **huguetpj** » Sun Mar 30, 2003 8:36 am

Projex240 wrote:I have the exact same reading problems. Also, when it is warmer outside or in the morning, it will read richer. I came to find out that when my heat or Headlights are on, then gauge will lean out more. I hate it, even though i know its not that accurate, I'd just like to have it for added insurance in case of an extremely lean situation...they do work well...juts not as well as wide-bands.Instead of hooking up at the engine bay...would splicing the wire near the ecu be a better way to do it. I have mine spliced at the o2 plug connector, but maybe the ecu will be closer to an accurate reading? Im frustrated with this. My bud's dsm reads perfect all the time. Maybe the grounding points we are using arent as good as they should be?HEEEEELLLLPPP!!!!!!!....tHiS is ReLlY pIsSing Me OfF.......

I could be the grounding points... don't see why connecting near the ECU or near the O2 sensor would make a diff since the wire's resistance is minimal. But it could also be a bad O2 sensor? I didn't know I had a bad sensor until it completely died on me.

Post by **huguetpj** » Sun Mar 30, 2003 8:36 am

tapdeznutz wrote:since we are talking about a/f wiring. someone know were or how to hook up a/f gauge (e.i. autometer a/f gauge) to a single wire '93 O2 sensor

You could connect it to the O2 sensor itself or the ECU. Or connect it to pin19 of the ECU. I don't have time right know to scan the ECU pinout on my FSM. Send me and email and I'll try and do it tomorrow.

Post by **Projex240** » Sun Mar 30, 2003 8:36 am

A bad o2 sensor would account for why it would read lean, but proably would happen all the time, and the voltage output probably wouldnt be affetced by outside currents (i.e.-headlghts, running lights, etc...) Has anyone tried to see if the voltage changes throughout the car when these accessories are used? What about the hyperground systems. Do they help with accessory life? Also, would using a higher output alternator help with these? Im not good at electrical stuff.

A/F Signal Wire on KA

A/F Signal Wire on KA

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