0KStuned

I am constantly being asked by people when talking about tuning if they can use their Autometer Air/Fuel gauge, you know, this one:


I have even seen posts in expensive car forums, (where I would hope the owners were aware of the accuracy of the products that they are installing on their cars)about using the Autometer (or similar) gauge to tune for a larger turbo, more boost, or whatever. Unfortunately when using a stock (narrowband) sensor it is impossible.

This gauge has been offered as a "cheaper alternative to a wideband unit." I need to illustrate why this is absolutely untrue! It is irresponsible or ignorant to try to use a gauge that reads from a narrowband sensor for tuning the air/fuel ratio in full throttle, high performance applications. So in an attempt to spread the facts about the necessity of a wideband air/fuel ratio monitor I am going to talk about the limits of the Autometer (and similar) gauges when using your stock (narrowband) O2 sensor.

First of all, your stock O2 sensor outputs 0-1 Volt reference to your ecu. The higher the voltage, the richer the air/fuel ratio. The problem with a narrowband is that it has an "accuracy window," which means it is accurate ONLY from 14.3:1 - 15.3:1!!! (To make this easier to read from here on I will write this as: 14:1-15:1)


14:1-15:1 or right near "STOICH" is where your air/fuel ratio will be in idle, during cruise, and other light throttle conditions... BUT for full throttle situations, in a turbo car, your target air/fuel ratio must be somewhere near 12.0:1, and not much leaner for pump gas. Even in an all motor car, you don't want to see much leaner than 13.5:1 when wide open. Your stock ecu even recognizes the limits of the stock sensor and goes into "open loop" above a certain throttle angle. "Open-loop" means the ecu ignores the O2 sensor because it knows it is incapable of measuring the air/fuel ratio above a certain throttle angle.

Here is an illustration to show the limit of the stock narrowband sensor.


The stock sensor is incapable of measuring richer than 14:1, or leaner than 15:1! Your Autometer gauge would read a full green LED, FULL RICH at any air/fuel ratio richer than 14.3:1!!!! Now how can a gauge with a sensor that can measure air/fuel ratios from 14:1-15:1 be used when you are aiming for 12.0:1? The stock sensor is incapable for high performance tuning!

The stock sensor reads only at Stoichiometric which is chemically, at sea level when a ratio of 14.7 parts of air and 1 part of fuel create a perfect mixture where all of the oxygen and all of the fuel is consumed. But at full throttle we cannot be anywhere near stoich or we would be burning up engines left and right!

The solution:
You don't have to throw away your Autometer (or similar) gauge. PLX Devices has a product to use the Autometer gauge with a wideband sensor. Using any M-series wideband controller (PM me for the best price) and a $35 converter, your Autometer gauge can read air/fuel ratios from 10:1-20:1!!! Problem solved.

Here is an illustration of the output of the PLX wideband sensor:


What it comes down to is that a "wideband" sensor must be used, in conjunction with a controller to measure air/fuel ratio. A good wideband sensor can read from 10:1-20:1, and in my experience a "digit display" is the best where LARGE digits display the air/fuel ratio so you can see it.

When tuning you will most likely be datalogging, and most wideband kits include an output to your laptop or other datalogging device. If you are going to just datalog, and don't need a display, you can save some money and purchase the PLX M-250 which list price is only $299. Compared to two years ago when you either had to pay $700+ for the FJO, or make your own Techedge, it's awesome to be tuning cars right now!

Hope this clears things up, I really hope people can understand now why they can't use their autometer gauge for full throttle conditions!

turbo*s2k

good write up!


Modified by TurboChrgd_Civic at 11:48 AM 9/24/2004

Syner-G-Racing LLC

so...I cant use it with a narrow band o2?

just kidding...I prefer the zeitronix wide band $288.00 shipped
it offers datalogging and additional sensor logging for additional cost obviously.

good write up also. this should get posted in one of those read before searching post.

FOrSfEd

nice write up no doubt

Muckman

iTrader: (2)

I hate the autometer AFR gauge. I dont understand why they dont make the same gauge in a 0-5v version that would work with any wideband. I asked Autometer that and they told me there was no market for that. And I told them their narrowband gauges are useless and only appeal to the ricer crowd. Then there was silence. haha

boostincoupe

**** what you say, my AF gauge looks COOL!

Muckman

iTrader: (2)

lol ricer

boostincoupe

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">lol ricer </TD></TR></TABLE>

racinskittle

Mine for sale BTW


JK NICE WRITEUP!! I got my TE 2.0 on the way

Thanks for contributing

0KStuned

$288 shipped for the Zeitronix? I sell PLX for $285 to Honda-Tech members all day long! Includes narrowband AND wideband output for datalogging. And you can use your existing Autometer display

Syner-G-Racing LLC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hondaddict &raquo;</TD></TR><TR><TD CLASS="quote">$288 shipped for the Zeitronix? I sell PLX for $285 to Honda-Tech members all day long! Includes narrowband AND wideband output for datalogging. And you can use your existing Autometer display </TD></TR></TABLE>

I didnt say yours sucks
I just felt like stating my preference. that sounds like a good deal you offer though, my friend is looking for a wideband setup for his turbo H23...if you offer that $285.00 shipped to hawaii then hell probaly buy one from you...if not then he'll end up with the Zeitronix setup.

Snail EK

093turbo16

iTrader: (2)

Great write-up, if any one is dumb enough to tune with a narrow-band... Ha thats me, no just for regular driving, on boost it is soo rich its pathetic. I can't wait to get a wideband though.

96-EJ6 B18C

Good write-up Reid.

Bump for the WA PLX Distributor!

AzntaggeR

very nice write up.

Hyaboosta

for the best tunning wouldn't the digital numeric display be best rather then just seeing an led display?

MonkeyMagic

anyone know anything on the aem wideband? saw it on jegs.. looks like the ricer a/f guage but with a digital readout in the center.

best thread so far this year

AcuraFreak

We need a Group Buy on a wideband don't we... Nice write up !

0KStuned

Need a groupbuy huh? Can definitely be worked out. I have LOTS of these. Seems most people are interested in M-300. Anyone want WIRELESS datalogging!? Don't turn this into for sale though. I will work on something for the sponsor forums.

Hyaboosta

^^ sounds like a plan. I could use one for my set up

AcuraFreak

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hondaddict &raquo;</TD></TR><TR><TD CLASS="quote">Need a groupbuy huh? Can definitely be worked out. I have LOTS of these. Seems most people are interested in M-300. Anyone want WIRELESS datalogging!? Don't turn this into for sale though. I will work on something for the sponsor forums. </TD></TR></TABLE>

Works for me keep us posted !

turbo*s2k

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hondaddict &raquo;</TD></TR><TR><TD CLASS="quote">Need a groupbuy huh? Can definitely be worked out. I have LOTS of these. Seems most people are interested in M-300. Anyone want WIRELESS datalogging!? Don't turn this into for sale though. I will work on something for the sponsor forums. </TD></TR></TABLE>

let us know when it's posted.

mahalo motorsports

me too pm sent.