Hi, all. New poster, although a long-time reader.
Ok, so I'm reworking my scooter, a 2010 Kymco Yager GT 200i (174.5 cc, liquid cooled, fuel injected, single-cylinder, 4-stroke engine) for better fuel efficiency.
My first foray into higher fuel efficiency entails getting the bike itself as efficient as possible. Here's what I've got planned:
1) Higher rear gearing. I was referred to Jan Vos by Craig Vetter. Jan cut new higher gears for me. The old rear gears were 8.408:1, the new rear gears are 7.15:1. I'll be sending the new gears to MicroBlue to get them micropolished and tungsten sulfide coated to reduce friction.
2) For the time being I'll run the OEM CVT and clutch until I can find a toroidal IVT for sale. So I've reworked the clutch a bit to allow a slightly wider gear ratio (by using a Dremel tool to lengthen the cam grooves and flatten the sheaves where they meet, so they can squeeze together more) and installed 1000 RPM springs (which will cause the clutch to start engaging at about 1000 RPM, which will be about 2800 RPM on the engine). The old clutch spring was 1500 RPM, which is 4200 RPM on the engine. I also corrected a manufacturing error that prevented the clutch swing arms from retracting fully, and polished all the pivot points and lightly greased them, but that's just me being anal retentive. Once I find a toroidal IVT, I'll remove the CVT and clutch. The IVT will be controlled via a twist-grip on the left handlebar.
3) I'm having a microcontroller built that'll control two small mag-drive coolant pumps, to replace the OEM coolant pump. It'll have the following features:
a) Control of two pumps and two radiator fans. Two pumps for redundancy and emergency cooling ability. The pumps can go up to 5 amps each, the fans up to 10 amps each. Higher-power MOSFETs can be swapped in if bigger pumps or fans are needed.
b) Lead / Lag pumps. One pump is lead pump, the other lag. If the lead pump fails, the lag pump automatically picks up.
c) Run-time leveling. It keeps track of the run-time of each pump, and switches the lead / lag of the pumps to keep wear rates similar.
d) Quick warm-up mode. It pulses the lead pump at user-configurable on and off periods to get the coolant around the cylinder head warmed up quicker than the overall temperature of the bulk coolant.
e) Throttle-based mode. If the rider just jumps on and rides without warming up properly, as soon as the throttle is cracked, the microcontroller goes from quick warm-up mode to throttle-based mode. Pump speed follows TPS. If the throttle is then closed and coolant temperature hasn't yet reached operating temperature, it goes back into quick warm-up mode. If coolant has reached operating temperature, it goes into ramp mode.
f) Ramp mode. It ramps lead pump speed up and down to maintain coolant temperature within a user-configurable range.
g) Emergency overheat mode. Both pumps come on full speed and both cooling fans come on if the microcontroller senses an overheat. It monitors coolant temperature, head temperature and exhaust temperature. All the temperature setpoints are user-configurable.
h) Run-on mode. When the bike is shut down, the lead pump can run for a user-configurable amount of time to prevent heat soak. This can be turned off if not needed.
i) Dash readout. I opted for a display that you can just glance at to see how the system is operating. I could have gone with a full display of pump speed and coolant temperature, but when you're riding, you don't have a lot of time to look at the controls. So I opted for an LED bar graph readout. If it shows green, your pumps are operating in their normal range. If it shows red, you've got an overheat situation.
j) User interface. All the operating parameters of the microcontroller are user-configurable via plugging it into a computer via USB. Temperatures can be incremented by as little as 1 degree F.
k) Because the engine on this bike is small, the coolant pumps are small. The electrical draw of the pumps and microcontroller will be something on the order of ~22 watts (not including the single cooling fan on this bike, which is already accounted for in the electrical load on the bike). This will replace the OEM pump, which can require up to 1/4 HP at WOT.
4) All the bearings on the bike are going to be replaced by hybrid ceramic bearings, except for the two needle bearings (which don't have a ceramic counterpart). They've been ordered from MicroBlueBearings, and I'm awaiting their delivery.
5) I bought a new piston and cylinder head. I'm going to have new roller lifters fabricated by Baisley HiPerformance, to replace the flat tappet lifters. This will allow a new cam grind with more aggressive lift and close and slightly longer open duration than would be possible with a flat tappet. Baisley will use the new head to ensure they get the geometry on the roller lifters correct. I do note the geometry on the OEM flat tappet lifters isn't ideal... the valve lash adjusters hit the top of the valve stems at an angle.
6) After Baisley HiPerformance is done with the head, I'll ship it and the new piston to SwainTech Coatings for a coat of ceramic heat shield on the piston face, underside of the head, and the exposed parts of the valves.
7) After SwainTech is done, I'll order a new cylinder and Total Seal gapless rings, and ship the piston, cylinder and rings to WPC to get them surfaced for anti-friction.
8) After WPC is done, I'll ship the cylinder to MicroBlue to get the tungsten sulfide coating on top of the WPC anti-friction metal surfacing. This combination should provide superior ring seal with very low friction, as well as hardening the metal surface of the cylinder for better wear characteristics.
9) The new cam that will be ground will have zero valve overlap. Yes, this will hurt traditional cylinder scavenging, except that I'll build a custom expansionary exhaust that will reflect a negative pressure pulse back toward the cylinder just before the exhaust valve closes (at least, at the engine speed associated with highway speeds, 6500 RPM). This will lock that partial vacuum in the cylinder (due to the WPC treatment and gapless rings), allowing the cylinder to get a head-start on pulling air in when the intake valve opens. The cam will have altered valve timing to compensate for the zero overlap.
10) I'm going to replace the OEM generator stator and ground-shunt voltage regulator with a proper alternator and voltage regulator. I'll do this by removing the OEM stator and fabricating a second flywheel with magnets that will sit inside the OEM flywheel in the place where the OEM stator used to sit. It'll be driven via the magnetic interaction between the two flywheels. The second flywheel will be mounted on the shaft of a brushless 20 amp alternator, which will be mounted outside the case where the OEM stator used to sit. The OEM stator pumps out all the current it can for any given engine speed, and the ground-shunt regulator dumps any excess to ground. The new setup should save about 100 watts worth of power.
11) Water injection. Since I'll be experimenting with lean burn, I'll use a second injector to inject water. This will work as internal cooling and will help to quench the high temperatures associated with lean burn, as well as adding to cylinder pressure. Since low HC and CO is inherent in lean burn, but NOx emissions go up when burning lean, the water injection should knock down NOx generation, making for very clean exhaust.
12) I'll be building a custom muffler / exhaust heat recovery system. It will heat the fuel and injection water. The point is to vaporize the fuel as quickly as possible, and to get the water as close to its latent heat of vaporization as possible, so it just has to absorb a little heat in-cylinder before it flashes to steam. That will maximize the amount of water injected that will then absorb heat which will be converted to motive power via steam expansion.
13) A constant-temperature air intake will provide the engine with a more controlled operating environment.
14) A new ECU (MicroSquirt) will allow me to tweak the fuel and water injection maps for lean burn.
15) Corona discharge ignition. Siemens sells a corona discharge unit, but it's too large and power hungry for a scooter, so I've got to have my own built. The trick is to pulse high voltage on and off so quickly that the spark can start the high-voltage corona discharge phase, but the voltage is clamped off before it can enter the high-amperage arc phase. Thus, the cylinder is flooded with free radicals (electrons), and given that combustion is just a free radical cascade, this should ensure reliable lean-burn combustion. A second benefit is that since the spark never enters the high-amperage arc phase, corona discharge uses less current than traditional spark ignition. It just uses the electricity more efficiently.
16) All LED lights. I had to search far and wide for an LED bulb that would work with the OEM headlight reflector. The headlight bulb aims 3 LEDs backward toward a round concave surface to simulate the light coming off an incandescent bulb's filament. The other 3 LEDs aim forward through a focusing lens. The power savings for all the lights is about 60 watts.
17) Sprag clutch and new rims. Since the rear wheel is only 12" and the front 13", solid disc rims won't have much of an effect from side winds. The new solid disc rear rim will house a Stieber ALF2D2 30-500 sprag clutch so I can idle back and coast without engine braking or geartrain drag slowing the bike down.
And finally:
18) After the bike is as efficient as I can get it, I'll work on an aerodynamic body for it. It's already pretty aerodynamic... the little 174.5cc engine can push the bike to 79 MPH (on a good day with conditions just right, usually to 75 MPH) and has reached 75 MPG maximum, but I'm looking for 107 MPH maximum and at least 150 MPG when riding at sane speeds. Part of the redesign will be removing the under-seat helmet box and reconfiguring the bike for a more feet-forward, lower profile while still allowing me to put my feet down at stop lights.
So, after that overly long intro, here's my question:
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Fully faired bikes tend to heel over alarmingly when hit with a cross-wind, and act like a wing when leaning to turn. Especially light bikes like mine. The forces tend to want to make the bike lose traction. Even when riding straight line, the air rushing over the bike tends to want to lift the front of the bike, contributing to instability.
So I got to thinking about it. What if there were an air scoop at the rear of the front tire. It'd open forward and downward in an arc around the back of the front tire and be angled outward at about 15 degrees on each side, such that the forward movement of the bike and the spinning of the wheel forced air into a pair of ducts. Those ducts would cross-over each other, and exit along the side of the bike higher up and toward the rear.
So say we have a side wind at 15 MPH and the bike's moving forward at 75 MPH. This is akin to the wind hitting the bike at a 10 degree angle at 76.5 MPH. A well-faired bike would act like a wing, with the 'lift' of the wing pulling the bike in the same direction as the wind.
But duct inlets and cross-over ducting would force the leading edge (where the air is effectively hitting the bike due to the forward motion of the bike) to channel that air to the opposite side of the bike, thereby 'stalling' the wing.
Because the air is being ducted from forward and low to rearward and high, it increases the leverage of that air exiting on the downwind side of the bike while decreasing the pressure (and thus the leverage) of the air on the upwind side of the bike, thereby moving the effective CoP (Center of Pressure) lower and rearward.
A couple side benefits:
1) As the bike's speed increases, normally the CoP would move forward, contributing to instability, especially if the CoP moves forward of the CoG (Center of Gravity). The ducting works to counteract this effect.
2) The front wheel spinning and the forward motion of the bike acts to ram air into the duct. Thus it removes air from under the bike and lowers the moment of torque trying to lift the front wheel at speed.
Are there any calculations that can be used to determine what size ducts and duct inlets would be needed for highway speeds?
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So, comments?
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