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Old 03-15-2015, 09:07 PM   #1 (permalink)
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Scooter efficiency and aerodynamics...

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:
================================
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?
================================

So, comments?


Last edited by Cycle; 03-22-2015 at 12:35 PM..
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Old 03-17-2015, 05:39 PM   #2 (permalink)
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calculations

I don't believe that there are any numerical tools which exist which can be exploited for your project.
Thinking out loud:
*I'm not certain that the C.P. would move at all
*You,your riding position, and your riding apparel must be factored into 'equation'
*What you obtain at zero-yaw will not be reflected in crosswind and gust
*The air you 'rob' with the scoop denies kinetic energy to the exterior flow field and could trigger premature separation downstream.
*Outside of aeronautical applications,there's very little data on the success of passive boundary layer control.Typically,useful volumes of air necessary to augment wing performance requires an external power source for either suction or blowing.
*A determination would have to made as whether to provide suction or blowing to achieve the desired effect
*Internal duct wall boundary surface friction will reduce flow to some degree
*The ducting discharge nozzles would have to be modeled and optimized for 'effects'
------------------------------------------------------------------------
It's an interesting proposal and I can see where you're trying to get to.I feel like you'd need to construct maybe a 1/5-scale model and get it into something like Cal Tech's GALCIT wind tunnel and let the grad students tear into the research.
I don't think CFD can do what you need except as a full-scale proposition and Direct Numerical Simulation.Too many researchers have reported on the shortcomings of CFD programs short of DNS.The cost would be enormous also.
And you'd be required to provide the CAD mesh for you and the scooter.
--------------------------------------------------------------------------
A copy of Sighard Hoerner's book,AERODYNAMIC DRAG will have drag tables for any shape you can imagine including the scoops,wings.
Abbott and Von Doenhoff's Theory of Wing Sections will have some segmented wing data.
Hermann Schlicting's book on Boundary Layer Theory will have stuff on blown and suctioned wing sections.
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Old 03-17-2015, 11:05 PM   #3 (permalink)
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I don't like scooters, but I've often thought it would make a fun ecomodding project. It seems like a much less daunting task than doing the equivalent mods on a car, and it's a fair bit cheaper too (try pricing hybrid ceramic bearings for cars!). Potentially the percentage gains are bigger than a car too. Looking forward to this one.
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Old 03-18-2015, 12:19 AM   #4 (permalink)
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Quote:
Originally Posted by aerohead View Post
I don't believe that there are any numerical tools which exist which can be exploited for your project.
Thinking out loud:
*I'm not certain that the C.P. would move at all
It should move rearward and lower, given that we're taking some of the air that would otherwise be acting on the windward side of the bike and transferring it high on the opposite side of the bike.

Quote:
Originally Posted by aerohead View Post
*You,your riding position, and your riding apparel must be factored into 'equation'
I'm going to try to take as much of that out of the equation as possible by having the body faired. I'm thinking along the lines of some material that can bend outward when I put my feet out to balance, but it won't be allowed to bend inward due to air pressure. The rest would be fully faired up to shoulder height.

Quote:
Originally Posted by aerohead View Post
*What you obtain at zero-yaw will not be reflected in crosswind and gust
There should be no net effect on CoP in straight-line riding. But when riding into a side wind, I'm hoping to make it so the effect of that side loading is reduced.

Quote:
Originally Posted by aerohead View Post
*The air you 'rob' with the scoop denies kinetic energy to the exterior flow field and could trigger premature separation downstream.
Hadn't thought of that. Would it be a bad thing to 'rob' air from under the bike? It wouldn't be the totality of the air being pushed under the bike, but enough to lessen the moment of torque that tries to lift the front wheel. The scoop would also prevent that turbulent air being thrown off the front wheel from being sent under the bike, thus keeping what air does flow under there better attached. Wouldn't it?

Quote:
Originally Posted by aerohead View Post
*Outside of aeronautical applications,there's very little data on the success of passive boundary layer control.Typically,useful volumes of air necessary to augment wing performance requires an external power source for either suction or blowing.
*A determination would have to made as whether to provide suction or blowing to achieve the desired effect
The front wheel spinning will tend to act as that 'external power source' to ram air into the scoop, as will the forward motion of the bike. I intend to smoothly reintroduce the redirected air into the airstream higher and more rearward such that it doesn't create turbulence. Not quite sure how, though... do NACA ducts work well in reverse (air flowing out)?

Quote:
Originally Posted by aerohead View Post
*Internal duct wall boundary surface friction will reduce flow to some degree
Yeah, they'll have to be surfaced to prevent laminar flow along the duct walls. Something akin to Power Lynz or similar might do it.

Quote:
Originally Posted by aerohead View Post
*The ducting discharge nozzles would have to be modeled and optimized for 'effects'
Definitely. I have no idea *how* I'll be reintroducing the redirected air smoothly back into the airstream rearward and higher on the bike, but there must be some way of doing it.

Quote:
Originally Posted by aerohead View Post
------------------------------------------------------------------------
It's an interesting proposal and I can see where you're trying to get to.I feel like you'd need to construct maybe a 1/5-scale model and get it into something like Cal Tech's GALCIT wind tunnel and let the grad students tear into the research.
I don't think CFD can do what you need except as a full-scale proposition and Direct Numerical Simulation.Too many researchers have reported on the shortcomings of CFD programs short of DNS.The cost would be enormous also.
And you'd be required to provide the CAD mesh for you and the scooter.
--------------------------------------------------------------------------
A copy of Sighard Hoerner's book,AERODYNAMIC DRAG will have drag tables for any shape you can imagine including the scoops,wings.
Abbott and Von Doenhoff's Theory of Wing Sections will have some segmented wing data.
Hermann Schlicting's book on Boundary Layer Theory will have stuff on blown and suctioned wing sections.
Thanks for the references. I'll check them out.
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Old 03-18-2015, 05:02 AM   #5 (permalink)
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If you haven't seen it there's 15 pages of discussion here:
http://ecomodder.com/forum/showthrea...ers-28298.html

I'm curious about the micro-polishing, and heat barrier and anti-friction coatings. Do you have any previous experience with these?
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Old 03-18-2015, 09:58 AM   #6 (permalink)
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damn! that's alot of work for a scooter! ill be watching this one!
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Old 03-18-2015, 02:24 PM   #7 (permalink)
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Quote:
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damn! that's alot of work for a scooter! ill be watching this one!
Heh, yeah, it's a bit overboard, I'll admit. But I love this bike, it's got plenty of power, it's cheap (the bike only cost $4000 brand new (delivered to my doorstep from the dealer, since I had just had foot surgery and couldn't ride it home at the time), insurance is only $78/year, a fuel-up is around $10), it's a factory-stroked Honda GY6 engine so there are plenty of aftermarket parts for it, I can swap in different cylinders for a larger or smaller bore, it's a simple bike so working on it and fabricating parts for it isn't intimidating, and the thing's never given me any problems. If this bike gets wrecked, I can scavenge parts and drop them onto a similar bike, so the parts and my inventions I'll be using on this bike aren't limited to just this bike and this engine.

With the friction reduction and aerodynamic body, it should make for a quick, fast and economical bike. I see GhostRider on YouTube, with his 500 HP Hayabusa and I think, "Man, who needs that much power unless they've got a deathwish?! That's as much HP as most semi tractors have!" Even stock bikes nowadays are over 200 HP. That's insane. I'll have 1/10th the power (~20 HP), and I'll still hit half the speed they do, which is plenty fast. Even stock, this bike'll do 79 MPH (the speedo on this model has proved to be very accurate against GPS) on a good day with conditions just right, and 75 on any day... so getting it up to 107 MPH with aerodynamic mods shouldn't be too difficult.

I believe the real key to making the bike not only fuel efficient when I want it to be, but fast off the line and with a good top speed when I want, is that toroidal infinitely variable transmission.

But Nuvinci doesn't sell their Delta series IVT to end consumers. I gotta figure out how to get my hands on one.

Anyway, the latest is that the new rear gears that Jan Vos (an ecomodder.com forum member) cut for me are now shipped off to MicroBlue Racing for micro-polishing and tungsten sulfide coating. And the new head is shipped off to Baisley Hi-Performance so they can use it as a template to get the geometry correct for the new roller lifters.

Last edited by Cycle; 03-19-2015 at 12:17 AM..
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Old 03-18-2015, 06:00 PM   #8 (permalink)
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When you look at that other thread, just click Thanks so I will know.
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Old 03-18-2015, 06:20 PM   #9 (permalink)
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scooter aero

Quote:
Originally Posted by Cycle View Post
It should move rearward and lower, given that we're taking some of the air that would otherwise be acting on the windward side of the bike and transferring it high on the opposite side of the bike.
*Only in a wind tunnel can the CP/CG relationship be verified
*As the symmetrical section encounters yaw,the forward stagnation point will also move (affecting your ability to harvest ram air)




I'm going to try to take as much of that out of the equation as possible by having the body faired. I'm thinking along the lines of some material that can bend outward when I put my feet out to balance, but it won't be allowed to bend inward due to air pressure. The rest would be fully faired up to shoulder
height.
*Only a rigid surface can overcome aeroelastic phenomena which occur as the angle of attack varies,and velocities/pressures with it



There should be no net effect on CoP in straight-line riding. But when riding into a side wind, I'm hoping to make it so the effect of that side loading is reduced.
*In crosswind,the windward stagnation point would be a moving target,and the leeward wake also,making it very challenging to vector your air discharge to control your roll moment.



Hadn't thought of that. Would it be a bad thing to 'rob' air from under the bike? It wouldn't be the totality of the air being pushed under the bike, but enough to lessen the moment of torque that tries to lift the front wheel. The scoop would also prevent that turbulent air being thrown off the front wheel from being sent under the bike, thus keeping what air does flow under there better attached. Wouldn't it?
*Any air you rob introduces a transverse contamination to the boundary layer which will affect an otherwise favorable pressure gradient (if you're gonna try a laminar profile).Once you reach the 1st minimum pressure,your at your point of BL transition to TBL and maximum lift
*If you'll spin your front wheel and observe its spin-down time profile,it will suggest it's ability as a prime mover/air handler.I believe that you'll be shocked at its inability to develop any meaningful static pressure.
*The scoop itself may trigger separation itself.
*In a crosswind environment,the leeward side of the front wheel will be in turbulence,offering no useful ram air to the scoop,and affecting the pressure of air entering on the windward side.
*NACA submerged inlets will convert velocity pressure to static pressure if you have an undisturbed pathway leading to the inlet.
*A Baumann scoop (NHRA Pro-Comp hood scoop) can reach outside the boundary layer and harvest the inviscid flow,with very low drag penalty,but needs an unimpeded approach for the air.
*As to the extractors,I recommend you look at Professor Alberto Morelli of Turin,Italy who was instrumental in the high-tech ducting of the 1978 Pininfarina CNR 'banana' car.He got the cooling system air to blend into the outer flow with zero turbulence.
*You will see that a reversed-NACA inlet is NOT ideal as an extractor.



The front wheel spinning will tend to act as that 'external power source' to ram air into the scoop, as will the forward motion of the bike. I intend to smoothly reintroduce the redirected air into the airstream higher and more rearward such that it doesn't create turbulence. Not quite sure how, though... do NACA ducts work well in reverse (air flowing out)?



Yeah, they'll have to be surfaced to prevent laminar flow along the duct walls. Something akin to Power Lynz or similar might do it.
*The walls should be as smooth as possible to delay TBL transition.After that we just pay the man for the surface friction.There's no avoiding it.



Definitely. I have no idea *how* I'll be reintroducing the redirected air smoothly back into the airstream rearward and higher on the bike, but there must be some way of doing it.
*The challenge is WHERE to cite the extractors,since you'll be riding in a fluid battlefield with the goal posts moving all the time.Georgia Tech has been battling this for decades now.
In the future we may have active morphing body capabilities in which active surface sensors talk to the CPU and alter the shape,or porosity to deal with transient pressure domains.



Thanks for the references. I'll check them out.
I think you'll get a lot out of the books.
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Old 03-18-2015, 10:17 PM   #10 (permalink)
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The website MotoIQ.com did some project scooters such as the Honda Ruckus 50cc. Anything you do to with body position to lower shoulder height will reduce frontal area.

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