A Wide Band O₂ Meter...and why!

Well if you want to program your own F.I. system you'll need some way to measure the A/R (Air/Fuel) ratio to know if you are running rich or lean.  After much investigation, I'll present here, the route I took and why.     After much investigation, I figured if I was spending this much to fuel inject my Spitfire I wasn't going to settle for a 'half-assed' meter to gauge it all by. I wanted accuracy. I finally settled on a Wide Band O2 meter. Wide Band?  ok... a bit of explanation.     The simple $25 to $80...  1,2,and 3 wire, heated, and unheated O2 sensors are only accurate near stoic. They operate by simply switching on and off. The resultant duty cycle produces a voltage that varies around 0.5 volts D.C. A little lean, or a little rich, this voltage shifts a little closer to 0.3 or a little closer to 0.8 volts. The meters simply read this voltage and displays it as a linear scale from around 13 to 16 A/R.     A Wide band O2 sensor is much more costly. As an example, just the sensor, a Bosch 5 wire sensor, produced by NTK, sold as a Honda unit retails at around $380. But a little hunting on the internet will net you a good wide band sensor for around $120. The difference here is a wide band sensor will read out a linear scale of 10 to 25 % A/R rather than the narrow 13-17 % of the hi/lo sensor.     Retail, most complete wide band O2 meters start at around $700.00 and can run as high as $2,700.00! Ouch!!  So.... I figured I'd go the D-I-Y route. A quick study, read up on O2 sensors, seems simple enough.... hey... what do you know.... someone's already doing it!  You can check out the D-I-Y-WB Project and the Auzzie Project. (also see the F.I. links page for other projects)      Even with 26+years in the electronics industry, I guess as I've gotten older I've gotten lazy. Or is it simply my schedules? Any way I ended up simply buying the entire Auzzie system pre-built. I bought the meter, the TE5301 display, and the extended length cable. With the Auzzie to U.S. $$ conversion.... an excellent Deal!   Initial testing.... VERY satisfied with it's accuracy and stability. I was able to source the o2 sensor from one of the large parts houses for about $120.

I welded a bung made from a sparkplug anti-fouling adapter, into a short length of exhaust pipe. The O2 sensor is s standard 18 x 1.5mm thread, the same as many spark plugs.     The two 'bolted-on' ears, are captured under a standard radiator hose clamp, wrapped around the outside of the cars exhaust pipe to clamp it in place. just sitting together after initial design All welded together and painted (500° engine paint) You can see just how simple this setup is. The hose clamp around the outside  of the original pipe captures the 'ears' to hold it in place at road speed. Meter at 14.9 sitting on the seat in my '75 Spitfire. On the dash...gas gauge at left (inside steering wheel) at 1/8 tank,  voltmeter just above and outside the steering wheel, showing 13.5 volts    With the long adapter cable, it's quite easy to route the cable up over the trunk, and into the passenger compartment. ....testing results to come.... see the Data logger ************************      Ok...first impressions.....   Well I have tested this unit on my Triumph Spitfire, my daily driver MG BGT, and my MG Midget.  It performs the same on all three vehicles. The display has a tendency to jump around a bit(13 - 19 with an occasional 25), even though the 'average' reading is about right. With a good steady 14.2V supply (engine running), the sensor fully heated (L.E.D. on) the sensor is cooler than it needs to be. The gases back here have cooled dramatically by the time they get to the sensor. So my first test will be to 'up' the sensor current a tiny bit. Otherwise I'll have to add a bung to mount the sensor up near the motor in the exhaust system.

Introduction	First Models		Sensors		Engine Management Basics
Requirements	Sub-systems		Tuning		Sizing Injectors
gas tank mods	Fuel supply system		My first ECU		F.I. Links - Sources
Special Project Wide Band Oxygen Meter					O2/Tach/Vac/Timing Logger
Other peoples Triumph F.I. Installations/Projects
Special Project   Megasquirt - The Quintessential D-I-Y Fuel Injection ECU
Building a Custom GT6 Manifold				Whitey's F.I'ed Spit6 Project
Building an MGB manifold				Experimental twin bodies on a GT6
Building a twin TB MGB manifold				The other half of the story