the problem with that line of thinking is that best performance vs best milage is not a zero sum thing. running open loop so that the mixture can be set at 13 to one to get most power no matter what the fuel quality is will make it run really well. but running in closed loop at the throttle positions and rpm that are "driving the speed limit" and than going to 13 to one when the throttle opens way up or the rpm is really high will yield very good milage and very good acceleration
some would describe that as very good performance - and get good milage while being fast. its very intellectually difficult to tune a open loop bike to work exactly like that, takes a lot of dyno time [by definition a dyno is a closed loop operation] to get it so that at mild throttle at 2100 rpm its running right at 14.6 to 1.
where the issue is is fuel quality - many tuners when working with open loop configurations set the 2100 half throttle position at 13.5 or so in order to be right on when the bike has 20percent alcohol in there. if you set it open loop at 14.6 with gas and then run alcohol fuel you will be way way way too lean for that fuel.
the REASON that hd was forced to mfg engines with closed loop ecm's is that fuel can vary by law and the air fuel mixture needs to stay at a lambada of .98 or so to run right - to make a gas engine run right on a 20percent mixture the gas lambada would need to be .7 something.
whatever used to work - wont work in the future. local use only bikes tuned to gas at a particular gas station brand in a particular area at a particular elevation can be tuned to really scream and get really good milage - drive that same bike from arizona to say iowa, mn, ne, etc - and it will burn up because the ecm has no idea that the gas is at least 10 percent alcohol.
the change from gas that is from a constant source and constant btu to gas that varies from "all gas" to 20 percent alcohol makes the whole idea of running open loop and trying to get good milage just a farce - eventually its not going to work anymore - tuning touring bikes to run open loop is completely silly. they NEED to be closed loop at least from 2000 to 2900 at less than 50percent throttle or they will be gas hogs if they are tuned to run in all 49 lower states.
tuning bar hoppers open loop is just fine -they never stray from a known source of fuel - so there are no real issues. however if the guy with the bar hopper wants to take it somewhere he should ask his tuner to give him a map that will work and be safe where he is going and then change it back when he gets home.
in the 70's I and all the guys i rode with took a carb kit with on trips - when we got to denver we would go a jet small & then switch it back, one guy had a screw in the bottom of the carb and he would just adjust to suit the gas - regular gas, half a turn out, premium gas half a turn in, high in the mountains, half a turn in & so forth. the closed loop system does exactly the same thing - it just does it by reading the exhaust gas.
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Topic: What gas millage are you guy's getting after your builds and tuning??? (Read 2764 times)