A/F Ratio Meter via OMR

Hey all,

Ok, have the first Wide Band A/FR mixture meter prototype completed and taking some measurements.... I have some final tweaking to do on it but it's been a pretty interesting research into this oxygen sensor technology...

Here's the first couple paragraphs of the write up followed by some images.... I'll keep you posted as the project progresses, good or bad for that matter...

Due to recent discussions held in the forums regarding my quest in learning the art of carb tuning, jetting and spark plug readings it brought to mind that during a Dyno test, the Air Fuel Ratio (02) measurements are recorded along with Torque and Horse power measurements. With this in mind, my brain started spinning on how cool it would be to have in your tool box an electronic tool that after going through the jetting process you could actually measure the Air/Fuel mixture ratios.

The plan was now in motion, onto the research…. Lol!

Now I could sit here and try to impress you all by technical writing/copy & paste a whole slew of technical BS on sensors I’ve researched into but Blah, plenty of websites where you can research all that yourselves. This is more on how I fabricated my sensor mounting and some basic concepts in the sensor selections and how I measured my Air / Fuel mixtures at idle, cruise and WOT.

I came across something of interest (to me anyways) that a tool for measuring if I was still Rich or Lean was required. In Dyno runs, they use a exhaust tube sensor inserted through the pipe end. Well in my research, I found some interesting article on where this would work no doubt but to what degree of accuracy was the question due to obstructed air flow. Hmmm, I mean this was a ¼” copper tube how much air flow obstruction could that possibly cause? Then there was the need where the tool would have to be used under loaded (ridden) conditions.

Henceforth the only manner for the highest degree of Air Fuel mixture ratio measurements was an Oxygen sensor… Uh-oh…..

I found several A/FR Meters on the web for ~ $250 but as I progressed into my research, the lower priced units use a Narrow band oxygen sensor versus the more expensive models $400+ utilizing a Wide Band sensor that also incorporates a small computer module… Uh-oh….. The narrow band sensor doesn’t provide a full linear voltage measurement, more as an on/off switch at the desired 14.7:1 ratio… Whereas the wide band sensors provide a linear voltage output for more precise and accurate measurements that are used in newer vehicles and motorcycles for controlling the fuel injected systems thus memory mapping!

Holly crapola, now I get it!

Now here’s what caught me off guard, this is a desired mixture for emissions, pollutants and fuel economy and not necessarily for performance builds where you’d prefer to be ~ 12.6:1 for maximum horsepower.

NOTE: @ 12.6:1, I believe this to be accurate for high performance, not necessarily for performance street builds….

With that in mind, 13.5 to 14.2 is the preferred area of operations at cruise and due to my Webcam .365 cam selections, (low to mid performance) that’s @ 4000 to 6000rpm (60-80mph)

Ok, now we we’re getting somewhere…. So in utilizing a Narrow Band sensor, the display (usually LED) would only truly inform you where your measurement was extreme Rich or Lean or in the desired 14.7:1 mixtures for emissions… Anything in between is truly unknown and this is the 02 range we truly want to measure for our performance builds… Translation, Power baby!

Now how the hell do I do that... lol!

I found this chart where 12.6:1 depicted extreme Rich thus carbon build up is most probable. This was a good starting point for discussions with Larry due to concerns of possible head/valve damages and in the regards of air flow into the ported head. After all, didn’t want to ruin the man’s masterpiece he accomplished on my head…. Lol!

Larry provided 13.8:1 A/F mixture is a truly good spot for power and emissions where not throwing a lot of carbon into the head and not running too lean…. When the man speaks, I listen…

Until then....

OMR

Just a couple more....

This sure is improving my fourth grade education. Roy

Your rich my friend! :laugh: :laugh: :laugh:
$$$ and time... :laugh:

For clients tunes' I prefer 13.2@WOT cause those buggers flog it all the time!

Nice setup, now ride it and watch those numbers change

Cheers!

PS. 12:1 is not VERY rich, its only slightly on the rich side. I've known guys who ran bikes in that range for years :huh:



...did you remember to do the cOiL mOd :blink:

:woohoo:

OCD is a treatable disorder.....:woohoo:

:laugh: :laugh: :laugh: :laugh: Tekie... :laugh: :laugh: :laugh:

Based on your voltage chart. I'd say lean the needle out one more clip position. [raise the clip / drop the needle]. If that's too much, find a washer that's half a step and put that under the clip.

Just keep in mind that in your part of the world, the verge of too lean could put significant heat in that motor in summer weather.

keith1 wrote:

OCD is a treatable disorder.....:woohoo:

:laugh: :woohoo: :laugh:

I didn't say it!

HAHAA... no really, OMR just beat me to that setup/post!

I'm in the process of doing the very same.

we all know where this will end up....dave, just get a fuel injection set-up and cut to the chase.....:lol:

"Based on your voltage chart. I'd say lean the needle out one more clip position. [raise the clip / drop the needle]. "

Hey Laryr...
Presently have the YY9 (leaner) needles in clip position number 4... Can drop to clip # 3 no prob.... but first, see answer to your other statement mi amigo for I'm with you there....


"Just keep in mind that in your part of the world, the verge of too lean could put significant heat in that motor in summer weather."


Yupper.... I'm more interested in seeing If I can actually do this with some degree of accuracy before making any carb changes especially on going on the lean side...

I'm fairly confident I'm close and hopefully will be able to get the Dyno test completed.... Then I can compare running readings to some degree anyways....

Should be interesting to see what the results are...

OMR, how many miles have you actually got on her so far?

:huh:

You realize, the carbs are designed to vary the AFR by a very large amount depending on the throttle position, RPM and Load. If you are at low rpm, in gear and crack the throttle wide open, it will probably get into the low 11 or even into the 10's on AFR. If you roll the throttle slowly and accelerate slowly, you will probably be in the upper 12's to 13's. If you hold that throttle position and let the bike get up to speed, you will eventually get up near 14.

If you cruise at part throttle around 55 to 60 mph, you may get up near 15 AFR.

Here's what I've found so far (but am not anywhere done):
kzrider.com/index.php?option=com_kunena&...ew&catid=3&id=307483

Even though the AFR was around 13 when I was holding a steady throttle position, the the AFR drops much lower while cranking the throttle open. (It also goes up real high as you close the throttle while coasting in gear.)