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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Air Fuel Gauge 02 Sensor Lambda Sensor
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<blockquote data-quote="Magnetoman" data-source="post: 108253" data-attributes="member: 2806"><p>Again, Vincent content of this post is tangential. My goal was to see if a 1036 Concentric could be made to work well on a Gold Star without changing the spray tube or drilling the compensating air passage. That is, I wanted to determine if it could be made functional with only the simplest swapping of a few screw-in components in one of these 2-stroke bodies.</p><p></p><p>I made A/F measurements under two sets of conditions, "static" and "transient." I made the former by holding the throttle in a fixed position for ~5 sec. before changing the throttle to a different position. For less than ~1/3 throttle these were made on relatively level ground as well as when going uphill and downhill. Higher throttle settings only were made going uphill to keep the speed within reason given the conditions.</p><p></p><p>"Transient" measurements were made by snapping the throttle open. I use a 1.55 V battery in my throttle position sensor so the first graph shows a 15-sec. section of the data where I was in 2nd gear at ~1/3 throttle (the red curve), then snapped the throttle closed and back open, shifting successively into 3rd and 4th where I finally gave it full throttle. The magenta A/F curve shows brief lean pulses occurred roughly 1/2-sec. after each of these throttle movements, but none are excessive and I felt no hesitation from the engine. In fact, I couldn't be happier with how the engine felt throughout this entire run.</p><p></p><p>As can be seen from the first graph, even in regions where I kept the throttle constant the A/F curves fluctuate by ~+/-0.5 around a mean value. Added to this is the mean value at a given throttle setting at different times during the run (i.e. possibly under different conditions of, say, uphill one time and downhill another) could vary by nearly that much as well.</p><p></p><p>Data from two runs, with nominal '220' and '200' main jets, are plotted on the second graph. Although I watch the bar graph display of A/F ratio as I ride, it takes the better part of 2 hours after each run to find on the stored data the one or two-dozen time intervals worth examination, copy them to Photoshop, format, print, and then mark the AFRs and measure the corresponding relative throttle openings from the 0-1.55V signal from the throttle position sensor. I don't think I could have guessed what this curve would have looked like from just having observed the real-time bar graph display.</p><p></p><p>The first thing to note is changing from a '220' to a '200' should have <em>leaned</em> the previous ~12:3:1 at full throttle to 13.5:1. Instead, the mixture became <em>richer</em> by the equivalent of having changed a 220 to a 225 rather than a 200. I've mentioned several times over the years that I measured a number of '500' Amal main jets on my flow bench and found 25% of them to be as much as 3½ sizes too large or too small. The other 75% weren't perfect, having a spread of almost +/-1 jet size. Anyway, as these two jetting runs show, the '200' in it now is somewhat <em>richer</em> than the '220' that was in the first run. </p><p></p><p>I don't know if the '220' is smaller than its marked size, or the '200' is larger, but they're close enough that it makes sense to plot both sets of data on the same graph. Unfortunately, to measure the relative flow of the two jets would require me to dismantle the carburetor fixture currently on my flow bench, which I'm not inclined to do because I have more measurements I want to make. After plotting all the data I examined the outliers to see if I had made any mistakes, or if I had extracted any of them from graphs where I hadn't allowed the mixture to stabilize for ~4 sec. This eliminated three potential data points, but the three x's between 0.4 and 0.5 are real. </p><p></p><p>The scatter of the data points isn't due to experimental uncertainty in reading the values from the graphs, it is real. The same throttle setting under different conditions (e.g. accelerating on level road vs. climbing a hill) gives somewhat different AFR readings. Also, after the first run the AFR at idle was 12.2, but after the second it was 11.5 even though I hadn't touched the mixture screw in the meantime, and even though the idle "felt" the same. </p><p></p><p>For throttle settings between 0.2 and 0.5 the mixture is slightly leaner than the "optimum" 12-13 for maximum power. Raising the needle another notch isn't an option because that would make it much too rich in that region. However, there are two reasons I don't think this region is an issue. First, the 12-13 "rule" is just a guideline, and only time spent on a dyno would determine if more h.p. could be extracted with slightly different mixtures. Second, most time riding is spent cruising at mid-throttle so having a slightly leaner, but still rich, mixture will save a bit of fuel without costing any actual performance.</p><p></p><p>Trying to find reliable information on the "perfect" air/fuel ratio for gasoline, let alone E10 or E15, quickly takes one down a rabbit hole. If information is correct that 13.5:1 is the ideal ratio for maximum power then the present ~12:1 robs me of ~2% at full throttle. However, if 12.5:1 is the correct ratio, my current jetting essentially robs me of nothing other than the price of having to refuel 4% more frequently if I ride all the time at more than half throttle. On the other hand, if much of my time will be spent between 1/8 and 1/4 throttle the current jetting will provide better economy at the cost of only ~1% of the power in that range. </p><p></p><p>The performance with both the '220' and the '200' main jets felt perfect from idle to full throttle, as well as when snapping the throttle open from various initial positions. So, this work shows it is possible to configure a "2-stroke" Concentric to work well on a 4-stroke machine. Like, say, a Comet[ATTACH=full]27509[/ATTACH][ATTACH=full]27510[/ATTACH]...</p></blockquote><p></p>
[QUOTE="Magnetoman, post: 108253, member: 2806"] Again, Vincent content of this post is tangential. My goal was to see if a 1036 Concentric could be made to work well on a Gold Star without changing the spray tube or drilling the compensating air passage. That is, I wanted to determine if it could be made functional with only the simplest swapping of a few screw-in components in one of these 2-stroke bodies. I made A/F measurements under two sets of conditions, "static" and "transient." I made the former by holding the throttle in a fixed position for ~5 sec. before changing the throttle to a different position. For less than ~1/3 throttle these were made on relatively level ground as well as when going uphill and downhill. Higher throttle settings only were made going uphill to keep the speed within reason given the conditions. "Transient" measurements were made by snapping the throttle open. I use a 1.55 V battery in my throttle position sensor so the first graph shows a 15-sec. section of the data where I was in 2nd gear at ~1/3 throttle (the red curve), then snapped the throttle closed and back open, shifting successively into 3rd and 4th where I finally gave it full throttle. The magenta A/F curve shows brief lean pulses occurred roughly 1/2-sec. after each of these throttle movements, but none are excessive and I felt no hesitation from the engine. In fact, I couldn't be happier with how the engine felt throughout this entire run. As can be seen from the first graph, even in regions where I kept the throttle constant the A/F curves fluctuate by ~+/-0.5 around a mean value. Added to this is the mean value at a given throttle setting at different times during the run (i.e. possibly under different conditions of, say, uphill one time and downhill another) could vary by nearly that much as well. Data from two runs, with nominal '220' and '200' main jets, are plotted on the second graph. Although I watch the bar graph display of A/F ratio as I ride, it takes the better part of 2 hours after each run to find on the stored data the one or two-dozen time intervals worth examination, copy them to Photoshop, format, print, and then mark the AFRs and measure the corresponding relative throttle openings from the 0-1.55V signal from the throttle position sensor. I don't think I could have guessed what this curve would have looked like from just having observed the real-time bar graph display. The first thing to note is changing from a '220' to a '200' should have [i]leaned[/i] the previous ~12:3:1 at full throttle to 13.5:1. Instead, the mixture became [i]richer[/i] by the equivalent of having changed a 220 to a 225 rather than a 200. I've mentioned several times over the years that I measured a number of '500' Amal main jets on my flow bench and found 25% of them to be as much as 3½ sizes too large or too small. The other 75% weren't perfect, having a spread of almost +/-1 jet size. Anyway, as these two jetting runs show, the '200' in it now is somewhat [i]richer[/i] than the '220' that was in the first run. I don't know if the '220' is smaller than its marked size, or the '200' is larger, but they're close enough that it makes sense to plot both sets of data on the same graph. Unfortunately, to measure the relative flow of the two jets would require me to dismantle the carburetor fixture currently on my flow bench, which I'm not inclined to do because I have more measurements I want to make. After plotting all the data I examined the outliers to see if I had made any mistakes, or if I had extracted any of them from graphs where I hadn't allowed the mixture to stabilize for ~4 sec. This eliminated three potential data points, but the three x's between 0.4 and 0.5 are real. The scatter of the data points isn't due to experimental uncertainty in reading the values from the graphs, it is real. The same throttle setting under different conditions (e.g. accelerating on level road vs. climbing a hill) gives somewhat different AFR readings. Also, after the first run the AFR at idle was 12.2, but after the second it was 11.5 even though I hadn't touched the mixture screw in the meantime, and even though the idle "felt" the same. For throttle settings between 0.2 and 0.5 the mixture is slightly leaner than the "optimum" 12-13 for maximum power. Raising the needle another notch isn't an option because that would make it much too rich in that region. However, there are two reasons I don't think this region is an issue. First, the 12-13 "rule" is just a guideline, and only time spent on a dyno would determine if more h.p. could be extracted with slightly different mixtures. Second, most time riding is spent cruising at mid-throttle so having a slightly leaner, but still rich, mixture will save a bit of fuel without costing any actual performance. Trying to find reliable information on the "perfect" air/fuel ratio for gasoline, let alone E10 or E15, quickly takes one down a rabbit hole. If information is correct that 13.5:1 is the ideal ratio for maximum power then the present ~12:1 robs me of ~2% at full throttle. However, if 12.5:1 is the correct ratio, my current jetting essentially robs me of nothing other than the price of having to refuel 4% more frequently if I ride all the time at more than half throttle. On the other hand, if much of my time will be spent between 1/8 and 1/4 throttle the current jetting will provide better economy at the cost of only ~1% of the power in that range. The performance with both the '220' and the '200' main jets felt perfect from idle to full throttle, as well as when snapping the throttle open from various initial positions. So, this work shows it is possible to configure a "2-stroke" Concentric to work well on a 4-stroke machine. Like, say, a Comet[ATTACH type="full"]27509[/ATTACH][ATTACH type="full"]27510[/ATTACH]... [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Air Fuel Gauge 02 Sensor Lambda Sensor
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