I think my fuel mileage went down when I put the 16 gram Dr. Pulley sliders in. They do act like they're equivalent to a 1 gram lighter roller weight, and they widen the range of the CVT. So the engine spends more time at a higher RPM during lower road speeds. This gives better acceleration, but cuts into fuel mileage a bit. I'm going to fill in the centers of the sliders with epoxy to bump up the weight a bit.
Another factor is that my commute is pretty short, less than 5 miles, so the engine's not fully warmed up for part of my ride. I work night shift, so the bike is started up when it's coldest for both the trip to work, and the trip back home. I plan on buying a 150 F block heater and timer, so the engine has a head start on warming up. That should improve fuel mileage a bit.
And I tend to ride pretty much WOT for part of my commute, and that affects fuel mileage significantly.
And finally, since where I live is almost always cool (50s to 60s), and cool weather is detrimental to fuel mileage, that adds to the effect. I'm thinking of fashioning a couple add-ons...
One would be a warm-air intake heat exchanger that takes its heat from the exhaust pipe... that'd have the effect of warming the incoming air to lean out the air:fuel mixture, and cooling the exhaust (and thereby making it more dense, thus increasing flow capability, reducing exhaust backpressure and helping exhaust scavenging a bit).
The other would be a means of grabbing exhaust heat and dumping it into the coolant during engine warmup to get things up to operating temperature more quickly... I've noticed the exhaust heats up pretty quickly (too hot to touch within 30 seconds or so, even with insulation on the exhaust pipe), but it takes as long as 6 minutes at idle for the coolant to warm up. But I have to figure out how to do it without boiling the coolant, and figure out a way of automatically stopping the heat being dumped into the coolant once the coolant reaches near operating temperature.
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I've got the basic design of the heat scavenger down. It'll be a counter-flow exhaust-heat-to-air-to-water heat exchanger.
The engine will pull air through the unit, so no air pump or anything is needed. It'll be a completely passive unit, no engine power or electricity needed.
It'll provide a quick warmup by dumping exhaust heat into the coolant. When the coolant reaches operating temperature, a bimetallic-actuated flapper valve will open to let in just enough cool outside air to keep the coolant going to the engine at a constant temperature. The advantages of this are that in cold weather, you no longer have to block a section of your radiator with cardboard to maintain temperatures, and on really hot days, the heat scavenger will act as an auxiliary radiator to remove heat from the coolant.
Once the coolant is warmed up, the air moving across the coolant heat exchanger will heat up, providing a warm-air intake for the engine. Since our engines are greatly affected by the temperature of the air they breathe, warmer air means better fuel economy.
A second bimetallic-actuated flapper valve downstream of the coolant heat exchanger will monitor air temperature, and will allow in cool outside air if intake air temp is too high. That flapper valve will also have a manual override in the form of a twist-grip on the left handlebar, so the rider can override warm air intake at any time for maximum power.
I was planning on using Nitinol as the valve actuator, since it can provide gobs of torque and withstand millions of cycles, but its limitations preclude doing so. So it's back to the old tried-and-true bimet spring. One advantage of using bimet is that the temperatures will be able to be adjusted, just as you could adjust the old-style furnace thermostats.
There will be a fuel preheater integral to the unit, using coolant as the means of pre-heating the fuel. This should provide a more complete combustion, since more of the fuel will vaporize, and therefore more will burn in the cylinder.
And there will be an integral water preheater, using coolant to preheat the water to just below its latent heat of vaporization. This is for water injection, for fuel efficiency and lean-burn knock prevention via the octane boost that water gives.
Now that I've got the handheld diagnostic tool for the scooter, I can fiddle with the fuel lambda to lean it out for testing.
I'm planning on buying an intake manifold, modifying it to also hold a water injector and a piezo tweeter, and installing a one-gallon water tank on the right-hand side below the ignition switch. One gallon of water should last for quite a while, around 2 fuel-ups, if my guesstimations are correct.
The piezo tweeter will be run by a simple variable-frequency oscillator, and will help to keep the fuel and water as tiny droplets, instead of letting them coalesce. I'll have to do some research as to what frequency would be best to use, and what power level.
To run the water injector, I'll take the fuel injector PWM signal from the ECU, and create a new PWM signal (via a microcontroller) that is proportional to the fuel injector PWM signal and can be adjusted. Thus, the amount of water injected is always proportional to the amount of fuel injected, and can be adjusted dynamically for testing purposes. The microcontroller will also be able to dynamically alter the fuel injector PWM signal coming from the ECU, for testing purposes.
To inject the water, I don't plan on using a pump, since that would increase the current draw on the already-limited electrical system... I plan on tapping off the exhaust manifold where it connects to the engine and capturing the exhaust stroke blowdown pressure peaks via a check valve, and routing that to the water tank to pressurize it. I'm unsure, however, how much pressure I'll get with this technique. If my guesstimations are correct, it should be on the order of 40 to 50 psi.
Alternatively, I could tap a hole in the head and capture the cylinder pressure peaks via a check valve. That'd give me about 227 psi, though, so that'd be way too much pressure.
I'm sourcing bimetallic springs right now that'll be strong enough to open and close the flapper valves.
I'm also interested in getting a corona discharge ignition system built, but that'll come later.
And thus was born the Kymco Yager 200i GTx (experimental), aka FrankenYager.
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