Topic: Gas Miser Bike project

[Cowboy]

OK gang, I've been inspired by Craig Vetter's motorcycle fuel efficiency contests, and I want to build a Gas Miser bike designed for regular, practical use. 

(See Vetter's web page to learn about the contests, and how a motorcycle managed to get 470 mpg in (almost) normal traffic conditions.) http://www.craigvetter.com/pages/470MPG/470MPG%20Main.html

I've decided to try my hand at building a gas miser bike. Here are the parameters I've set:

First the target:  I'm shooting for 150+ mpg (US gallons) in everday use, commuting to work, and recreating on the weekend.

1. It must be able to keep up with traffic at secondary road speeds (65 mph, without wrapping up the engine to get there.)

2. I want readily available, off the shelf parts availability for all the mechanical parts of the bike, so there can be no major modifications to the running gear unless the modified part is just as available as the original part it replaces.

3. No two-strokes. (I'm a former air quality enforcement attorney, so I know what comes out of two stroke exhausts. Two stroke engines, of any size, should be banned. For purposes of this project, they are!)

3. I want the fairing to enclose the bike fully enough to make riding in cold weather more comfortable. I suspect that any fairing design that achieves high gas mileage is likely to achieve this goal without much further modification anyway.

4. It must be comfortable to ride long distance. One of the problems Vetter noted in the entries in his contests is that most required a riding position that would be uncomfortable over a long distance.  I'm thinking that I will want a sit-up-and-beg position much like our Honda SOHCs, but perhaps modified a bit, with the seat recessed down into the frame (in order to lower the rider's height, and thereby reduce wind resistance) and with a back rest built into the rear fairing. I'm planning a single-rider bike here, since that is the way most people ride 90% of the time anyway. I'm thinking about something along the lines of Vetter's streamliner bike, but not quite so laid back: http://www.craigvetter.com/pages/470MPG/1981%20Fuel%20Economy.html


So here's a question for the collective brain here at SOHC. I can cover the design elements necessary to meet goals three and four. But what bike should I choose as a base model for the project, to satisfy elements 1 and 2?  According to Vetter, some large displacement bikes in the early competitions achieved very resectible efficiencies, with nothing more than off-the-shelf Vetter fairings and a light touch with the throttle. Most of the entries in the later years were small displacement bikes, from 100 to 250 cc, though they did not uniformly perform better than large displacement bikes.

I'm thinking I should start with a 250cc cruiser style bike, because the low seating position will reduce wind resistance. Cycle World's efficiency feature gave good marks to the Suzuki GZ250, which gets in the range of 75 mpg. I understand that the Honda or Yamaha equivalents get similar mileage.  It gets me a long way toward my goal to start with a bike that already gets me halfway there, before I put any sort of fairing or smaller sprocket on it.

I've also considered various of the Honda CB series twins and singles, just because I like the idea of starting with a familiar bike.

So choose two bikes, and tell me why you choose them. One bike  in current production, and one that can be anything back to around 1970. But most importantly, tell me why you would choose that bikes, and how you would modify them to get better mileage.

I'll be doing testing with the base bike, over 1000 miles or so, to establish baseline performance before I start modifiying the bike. I'll try to do about 25% in town driving during the baseline testing, and 75% highway. Then I'll try to duplicate the same driving conditions and driving style after I modify the bike and install the fairing.

I'm pretty certain that I will actually build this experiment in the next year or so. Anybody want to join me, and modify their bike for fuel efficiency? We can compete on a percentage improvement basis, so that it doesn't matter whether we start with the same bike.

Any takers?

[crazypj]

Get something smaller , around 200cc (CB125 with an XR200 motor?) A Honda S90 will just about do 70mph,110mpg and thats from 1965.
PJ

[TomC]

Get something smaller , around 200cc (CB125 with an XR200 motor?) A Honda S90 will just about do 70mph,110mpg and thats from 1965.
PJ

Hi Crazypj
     As an ex S90 owner, I gave it to a then girl friend, I agree with 110Mpg but 70mph!!!!!
          TomC

[Cowboy]

I already own a 1964 Honda CT200 which is very similar to the s90. (See the red bike in the photo at left.)  I think the engines are basically identical, though I'm not sure of the gearing.  I guess I could make a quick test by switching sprockets on my ct200. It came from the factory with a large sprocket for trail use, ovelaid on a smaller sprocket for road use. I have to chuckle a bit at the thought of going 65 mph on the CT200. I've only ever ridden it with the large sprocket in place, so I think of it as a very slow bike!  I think I would be scared out of my wits going 65 on that tiny thing!

Tell me this, guys, would you recommend riding 70 mph on an s90 for, say, 50 miles at a time? In other words, is it reasonable to drive that fast for extended periods, or is that really a "theoretical" top speed, that will overheat the engine if you go that fast for an extended distance? Also, will you actually get anything like 110 mpg on a steady run at 70 mph, or do you start burning more gas at those high engine speeds?

[masonryman]

I think I would start with a endro type bike, that is if you truely want to ride it like a daily rider, xr400 or xr650r they have tons of torque so you could gear the heck of it.

[Cowboy]

Enduros already have a history in Vetter's contest. The 477 mpg winner was based on a Honda XL125. I wisk I could find information on the mechanical modifications that were done to that bike.

Your suggestion that enduros have lots of torque makes me curious whether Honda used the same engine, but with different gearing in the various street, enduro and motocross models.  Is that the case?

[Pinhead]

Start looking at cylinder head designs. For max efficiency you want an chamber with squish/quench and high compression. Some of the new(er) Honda dirt bikes are running 13.5:1 compression from the factory. Close the squish clearance, "edge" the squish pads and cut "Singh Grooves" into them, run "PowreLynz" into the intake runners, cut "PowreRingz" into the back side of the valves, bump the compression a hair more, and gear it up. With your fairing you should be able to get some really impressive MPG numbers.

If you're willing to experiment, try Omni Valves (www.omnivalves.com) to vastly increase your low-end torque without sacrificing high-end horsepower. This will allow you to low your engine RPM's dramatically.

With those types of fairings, wind resistance will be virtually nil (especially compared to stock). You'll need very little horsepower to cut through the air in a streamlined machine like that. If my CB650 can get 50mpg going 70mph at 5500rpm, just think what it could do with 1/8th the wind resistance and 3000rpm. That's with no engine mods. If you could find a bike with a 6-speed, the sixth gear being a LOT higher than 5th you wouldn't be sacrificing acceleration, either.

www.mpgresearch.com
www.somender-singh.com
www.fueleconomytips.com

[yesplease]

I'd go with a 400-650CC Honda outfitted with TB's/SAFI (MS&S or whatnot) so you could selectively deactivate two cylinders. Honda has a prototype system that completely closes the cylinders for a 30% gain in efficiency, so since you can only cut fuel to two cylinders, you may only see 20%. This would allow you to accelerate briskly up to your target speed, then cut two cylinders to cut pumping losses in half. As usual, synthetic lubes are always good. 10% may not seem like a lot on a truck that gets 15mpg, but if you're already getting 150mpg, that'll bump you up to 165. Hard compound tires with low rolling resistance as well as slight overinflation will help, as will a lean mixture. Now, the thing is, I wouldn't lean it out in the city because NOx spikes would contribute to smog too much imo, but if you're on the open road, I suspect it wouldn't do very much. After all, the EPA let OTR rigs get away with relatively high NOx emissions levels, probably because they spend most of the time on the open road.

The fairing will make or break the project. You will definitely want to fair the front wheel separately and allow air to flow around it and through the oil cooler/exhaust/engine block. The bottom should be fully faired with slots for stands, and maybe have partial fairings on the sides, starting low near the front of the engine and going up to the back near the seat (kinda triangle shaped). This should transition to the back behind the seat and a fully covered rear wheel. You may not have to enclose the bike completely in order to get good airflow over the top, this trike for instance, doesn't have a center section. The gap in the middle is small enough that most of the air flows over relatively well, and an enclosed center section isn't considered to be worth the hassle. I'm not sure if a faired motorcycle with a gap would behave the same since that trike had a much lower range of speeds, probably ~25-60mph. But considering the hassle completely fairing the bike might be, it's worth a look. Where was I? Oh yes, so you'll wand to have the front fair direct the flow of air over your head, and gradually taper back, so a kinda tall fairing in the rear. Google boat tail and kammback with aerodynamics. Another freebee might be routing the exhaust right behind you like modern sport bikes do. The reason is that any vehicle with the aerodynamics of a motorcycle, such as bricks or dump trucks, punch a tunnel through the air and leave behind a large low pressure area that sucks in air flowing around the vehicle, which creates lots of drag. By putting hot/high pressure air behind the vehicle, the low pressure area is filled up a bit, and the air flow around the vehicle will separate farther back, which means less drag.

I've been looking at the same sort of project from a performance bent, since imo, if I really wanted high efficiency I'd go to a faired/caged version of something like a Quest velomobile with a 2-6kwh li-ion battery pack, a 30hp peak/4hp continuous electric motor/controller for around town/acceleration, and a Honda gx 120 or 160 for highway cruising. It should get at least 250-300mpg@70mph, and run a ~15s qm. Not too quick, but quick enough, and around town I wouldn't even run the gas engine. The best part would be building the steering, the trike I mentioned has really cool steering.

[Cowboy]

Thanks Pinhead!  Those links should keep me occupied until bedtime and beyond.

Here's a photo of the gear arrangement on the CT200 (first generation trail 90)  You could shift from low range to high, but it took a couple wrenches and fifteen minutes!

[Cowboy]

YesPlease,

You and I are thinking along similar lines re: the fairing design.  I want to enclose it as much as possible, while making it easy to get on and off, easy to put my feet down at a stop, and easy to get out in case of an accident. I've gone back and forth in my mind over whether the fairing should enclose the front wheel separately. I've seen designs built both ways, but no information that tells me which design is more efficient.

As for leaning out the mixture, you can be assured that I will do so, without regard to NOx. I live at 7000 feet in the Rocky Mountains in Wyoming. We don't have a smog problem, and even if we did, the wind here would make it Nebraska's problem in short order. I've heard it said that the solution to pollution is dilution. The wind around here provides plenty of dilution!  (I still don't like two-strokes)

I have some leaning toward higher displacements, because in the end, I want a practical vehicle, not just a bike that theoreticaly gets great gas mileage, but is a drag to ride because it's gutless. I want it to be the kind of vehicle I look forward to getting on, and I think slightly higher displacement would help make it more practical, even if the gas maileage is not quite so impressive.

[yesplease]

If you don't mind driving slow, that's the quickest and surest way to increase mileage. A CB650 that gets ~50mpg@70mph may get almost 80mpg@55mph. From there TBs/MS&S will improve power, acceleration, and fuel economy enough to break into the 100mpg@55mph area. I'd go with the front wheel fairing, but in order to test it accurately, you might want to wait until you get your bike into the 100mpg range constantly, so if it's something small, like a five percent difference, it won't get lost in the background. On cars, there have been tests that show a 6% improvement just from blocked rear wheel skirts and grilles, so it'll probably make a difference. But back to speed, in top gear, driving slow can make a big difference.  Check out the gassaver forums for a bunch of FE nuts. 

[crazypj]

CT is pushrod motor and S90 is OHC.
The S90 will do 70mph in third with the right gearing,(on flat road, still air) about 90mph flat out (and some clip ons and rearsets, plus a 110lbs rider )
Those valves look nice and light for a high speed engine dont think you would be close to having enough clearance with any bike engine to allow piston to get past them? Also, with heavier valves you need heavier springs which increases the parasitic drag, your using extra power just to drive the engine. They seem to be designed for low speed emissions, not power or fuel economy ( if you have less fuel burned at lower RPM then emissions have to be lower)
Generally, having a very low idle will stop the valve gear and small end being lubricated properly as it relies mainly on oil splashing around (and on a plain bearing motor the big ends can fail as there may not be enough pressure at very low RPM)
Just my 2 cents
PJ

[Pinhead]

I agree with most of what you're saying PJ. The only thing I object to is "if you have less fuel burned at lower RPM then emissions have to be lower." The very definition of "emissions" includes NO_x and unburned fuel, CO which should be CO₂.

Also, you don't have to lower your idle to 300rpm or anything like that. The 300rpm idle is simply an example. If you read through the site, all those valves do is open a bit quicker as soon as the chamber pressure is lower than atmospheric pressure. They then close as soon as the pressure is above atmospheric. Since our bikes have so much valve overlap and duration, they lose bottom-end torque. You are right, though, that valve clearance would come into effect with those valves. I personally think it'd be worth it to cut some clearance into the piston if "meat" allows.

The other mods, though, have already proven themselves time and time again. Search MPGResearch for PowreLynz, PowreRingz, Edging, and Singh Grooves. All of these mods are excellent detonation deterrents and allow for much higher compression. If you have an engine with any squish, Singh Grooves and Edging will work to your benefit. PowreLynz and PowreRingz will work on any engine.

re: Leaning out fuel mixture

NO_x would be the very last thing I'd worry about if I was running lean. Burned exhaust valves and pistons would be my only concern. Since a lean mixture burns much more slowly than the "perfect" 14.7:1 ratio does, the fuel is still burning when the exhaust valve opens. Since the valve isn't in the seat it can't dissipate that heat into the head, hence burned valves.

NOTE: stiometric ratio of 14.7:1... That's the ratio of air to fuel vapor, by weight.

The afforementioned mods to the intake tract (PowreLynz/PowreRingz) help to vaporize the fuel, and the combustion chamber mods (Edging/Singh Grooves) promote a much faster flame front and deter detonation. Since the fuel can burn much faster, the fuel mixture can be much more safely "leaned out." Also, since a higher ratio of the fuel that you put into the engine is in a burnable vapor state, you can cut back on the liquid fuel put into the cylinder and still have the magic 14.7:1 fuel ratio.

[TomC]

Hi crazypj
     "The S90 will do 70mph in third with the right gearing,(on flat road, still air) about 90mph flat out (and some clip ons and rearsets, plus a 110lbs rider"
     I can see were the crazy part of your screen name comes from.
          TomC

[crazypj]

NOx  increases as combustion temp increases with high compression motors.
 At low engine speeds you are using less fuel per cycle with more time for complete burn so you will have less emissions.
Some form of water injection will increase cylinder pressure a lower speeds and also lower combustion temps
A very mild cam with little or no overlap will keep fuel/air in combustion chamber longer to extract max amount of 'work' from it.
  Stoichiometric  F/A ratio will give complete combustion but for max fuel economy you run lower than stoichiometric, a least 15:1 and as much as 17:1.
Lean burn engines are using between 25:1 to 30:1  F/A ratio's with a rich(er) mix in precombustion chamber.
 Remember, this is being done with whats available on the open market at reasonable cost, not an experimental lab engine.
It may be easier to find a small diesel and modify that, they are designed to work with excess air. A small turbo can double power output and also give a cleaner burn.
The black smoke from diesels is due to incomplete combustion, which is wasting fuel.
The mini excavators use a twin cyl diesel, shouldn't be too difficult to mate to a HD type transmission.
PJ

[crazypj]

Hi crazypj
     "The S90 will do 70mph in third with the right gearing,(on flat road, still air) about 90mph flat out (and some clip ons and rearsets, plus a 110lbs rider"
     I can see were the crazy part of your screen name comes from.
          TomC

I also built a 110mph XL125 ,
Britain used to have a 12bhp learner limit, 120mph on Yamaha RD125's or 125 on Suzuki RG125, both came with full fairings stock (both made MX bikes for 'parts'  as well  )
Honda took it too serious and made it very difficult to modify their motors, everything from the air intake to end of tailpipe had restrictions
Didn't do Kawasaki so I don't know what was done to them, probably the usual, fit a Micron and KX125 top end (or one of the 'cheater' 170cc kits)
PJ

[crazypj]

YesPlease,

You and I are thinking along similar lines re: the fairing design.  I want to enclose it as much as possible, while making it easy to get on and off, easy to put my feet down at a stop, and easy to get out in case of an accident. I've gone back and forth in my mind over whether the fairing should enclose the front wheel separately. I've seen designs built both ways, but no information that tells me which design is more efficient.

As for leaning out the mixture, you can be assured that I will do so, without regard to NOx. I live at 7000 feet in the Rocky Mountains in Wyoming. We don't have a smog problem, and even if we did, the wind here would make it Nebraska's problem in short order. I've heard it said that the solution to pollution is dilution. The wind around here provides plenty of dilution!  (I still don't like two-strokes)

I have some leaning toward higher displacements, because in the end, I want a practical vehicle, not just a bike that theoreticaly gets great gas mileage, but is a drag to ride because it's gutless. I want it to be the kind of vehicle I look forward to getting on, and I think slightly higher displacement would help make it more practical, even if the gas maileage is not quite so impressive.

Might be a good idea to look at Tony Foal's FF designs. It making something of a resurgence and wind resistance is the bigges problem in fuel economy.
PJ

[Cowboy]

The feet forward position works well in aerodynamic designs because it lowers the top of the drivers head so much, and tony Foale's designs lower the driver even more by sinking the seat all the way to the ground. Lowering the overall height of the vehicle cuts wind resistance a lot.  The 477 mpg winner of Vetter's cometition acheived a similar low stance by riding the bike laying down, cafe style.

Because I'm concerned with making my bike practical, I'l adopt a slightly feet-forward design, but probably not so extreme as Tony Foale!

[nickjtc]

CB/CD175 (CD only has one carb so should be more frugal, but the CB has less mass in its body work). Single seat. Ditch anything not essential.

Mine ('72) was good for 65mph cruising whilst getting 70+mpg, in comfort.

[RatBikeRandy]

You may want to check a Suzuki GS500E or possibly a Bandit 400.  My wife got 77 mpg on a road trip on her sporty GS500E with a small fairing.  It is a lightweight and very quick bike. 
Lots of luck, sounds like a great challenge.

[gerhed]

Ultimate Gas Mizer
Pic on left of machine running 48volts-it'll do 50!