Carb tuning with A/F meter

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I don't have access to a dyno but would like to do some carb tuning. To use an A/F meter on an LO206 can the meter be strapped to the existing kart/header or do I need to buy a "test exhaust" and put the sensor in that?

Does my driver need to look at the A/F ratio while driving at different RPM? Is the target ratio for an LO206 14.7:1 or a little lower?
 
In all seriousness, spend your time on driving and chassis set-up. Work on momentum, momentum, and momentum. Nothing to be gained in your endeavors.
 
Yeah. I'm just curious if we have things set up ok - particularly out of corners.
 
Do you have to drill the silencer or the header to install the sensor? How close to the head does the sensor need to go? Saw an earlier post that indicated 12.2-12.5 is a good A/F ratio for this engine.
 
I think there was a thread a couple years ago about mounting an o2 sensor in the pipe, or spare muffler.
a search in the 206 section may find you what you need.
 
Mychron makes a set up that uses a Bosch LSU 4.9 sensor. The sensor would need to be installed in the muffler as it is too big to install in the header. In my opinion due to the exhaust pulses inherent in a single cylinder engine and the short length of the muffler would cause air contamination and lead to inconsistent readings in a moving kart. Performance trends does make a "mini sampler" you could contact them for details but I would doubt they would recommend it for on kart use.
 
All good posts above and probably best to spend most of your time on driving and chassis tuning. But to answer some A/F questions. We ( Baker Racing Engines ) have been studying and using the A/F meter for over 15 years now. The PZ22 type carburetor is a bit tricky to get perfect with the current BS rules. However if you are studying all this on your engine shoot for a Lambda of .80/.82 coming off the corners and up to about 4500 rpm range then start transitioning up to a Lambda of .86/.88 from the 5500 to 6000 rpm range for good top end power.This of course is with standard automotive pump gas, Methanol has different A/F levels.

Lambda = measured A/F ratio divided by 14.70.

Steve
www.Bakerracingengines.com
 
I have one of the Performance Trends remote sensors on my dyno. It works great.
You put a tube in the exhaust (metal brake line) and that goes to the Performance Trends box.
The Box has a small vacuum pump in it that draws exhaust past the heated O2 sensor.
It would be cumbersome to use on a Go Kart and require a 12 volt power source. I would just install the O2 sensor in the muffler. FWIW I have not seen any issues with reversion giving a falsely lean signal.
 
For the LO206 carb all I can set is the idle mix, float level, and clip position. We have the clip 2nd notch from the top as a default blue slide cadet setting. Since we run the float at .900 (bumpy track with hairpins and elevation change) and we are near sea level (600' elevation) I was wondering if going to the middle clip might help things. I guess I could just try this instead of buying a new header and the $400 AIM lambda meter. Do folks run on the middle clip for cadet (blue slide) or is that crazy?
 
All your settings are close to spot on. My additional thought would be to watch the humidity and move the clip up or down with the rise or drop in density. More moister in the air. Usually early morning . The more you can lower the clip on the needle.
 
So we had a good race and set a PR lap time. In the finals though as it was cooling off the engine was idling really high, and during the race with WOT the engine stumbled badly on a straightaway. I don't know the air density at race time but right now per airdensityonline.com it is 98%. Last year (when the engine was set the same and running rich) we were running in hot humid conditions that had an air density of more like 85%. For these kind of swings should we move the clip up (for practice on hot summer days) and also down to P3 (middle) for races at night if the AD is approaching 100%?
 
Normally you would change the jet size the same % that the air density changed. That is providing that mixture was correct to begin with.
That means you need to calculate the area of the various jet openings.
Since it's illegal to change the jets in a 206 you would move the needle clip to try to compensate.
The higher the air density the more fuel it would require, move clip accordingly.
The lower the air density the less fuel it would require, move the clip accordingly.
 
If I plug weather data from the local airport into an online calculator I get a race time AD of 95% when things were observed to be borderline lean. If I put in typical summer practice weather (when things were running rich - black soot all over the exhaust) the AD would typically be more like 86%. Is a swing between these 2 enough to make a change in carb tuning (e.g. move the clip up or down?).
 
I believe that if you get the info from the local airport they are giving you figures that are "corrected to sea level" and not usable. You need to calculate the info using your own measurements at the track. Perhaps some one more knowledgeable can chime in on that.. Additionally don't look at your exhaust pipe, read the spark plug.
 
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