mods for better mpg
 

I own a honda valkyrie, not known for good mpg. however, I average 45 mpg . some mods I have done: cut down the windshield, tilted the windshield back, run the rear shocks on the lowest setting I can without dragging parts in the turns. changed thermostat from stock 180 degree to 195 degree, k&n air filter,advanced the cam timing a few degrees, added air wings to direct wind to the side, rather than over the carbs. hopefully this will reduce drag, and also allow the intakes to run hotter. now I am considering rerouting the fuel tank vent, which vents out under the bike, to have it dump into the air cleaner box. any one have any opinions on this idea?

Most of what you've done will increase fe pretty much not at all. Tank vent might be an alright idea though.

??? most people get around 33 mpg on the valk, I get 45mpg, so why would you think my mods would not effect mpg ? cutting down windshield, and tilting it back reduces frontal area. softer shock setting lowers back of bike, which further tilts windshield, warmer thermostat allows engine to operate more eficiently, advancing cams increases lowend torque, allowing me to run in higher gear at low speeds. one question I have though, is do I run the vent before, or after the air cleaner?

I don't know why he would say that your mods won't help FE, but I don't know much about motorcycles. The one thing I do know, or thought I knew, was that a larger windshield is better because the smooth aerodynamically shaped windshield cuts wind easier than the exposed rider.

1. Cutting down the windshield doesn't automatically make for better or worse aero. Not only is it a case-by-case basis, the size of the rider figures in too.

2. It can't be tilted back all that much before it smacks you in the face. So the frontal area change is negligible.

3. Shock setting = nothing on a bike. Distance to ground is a factor on cars, but bikes have no bodywork/ground aero interference to speak of. Windshield angle change due to "rear end being lower" = virtually nothing.

4. Hotter t-stat- that might do something, might not. YMMV

5. K&N- now that definitely won't increase fe.

6. change cam timing- could be helpful, especially if you re-gear higher, but you haven't, so that mainly helps you short shift

7. air wings probably = more drag.

"Most people" ESPECIALLY bikers drive like asses too. Let them ride yours and you ride theirs, and see if they still get 33 and you get 45. Biggest factor of all is probably you driving for fe and nobody else is.

I'd vent after the filter.

lowering a motorcycle is one of the easiest ways to make it faster at the drag strip frontal area is frontal area, regardless if it is a car or a motorcycle you have obviously not sat on a valkyrie, the windshield is several feet in front of my face .when cutting down a wind shield on a motorcycle, the object is to be able to see over the windshield, and yet still have the wind blast shoot over your head. even after cutting it down 4 " I am still well covered. the lowering the rear by itself might not make much of a difference, but in combination with the windshield mods, it all adds up.motorcycles ,by design are not very aerodynamic, so little improvements can make a difference. my driving style does make the biggest difference, though. the k&n , along with my custom built exhaust, definitely makes the valk run leaner. I really don't want to debate the mods I have made, but I want to be clear on where to route the fuel vent. when you say after the air cleaner, do you mean between the air cleaner and the carbs?

Yes - before the air cleaner does no good, after the carbs is just a bad idea period. Closer you get to the filter while still being inside the tract the better off you'll be for even mixing between the cylinders.

thanks, I will give it a try

Also if you get the impression that it's exposed to too much vacuum there and is drawing too much through, add a restriction to the line.

P.S. I've never done it but it seems to be a sensible mod.

thanks again,going to the motorcycle forums and even mentioning mpg usually gets me the ''who cares about mpg, ride it like you stole it" OR "if you want better mpg, buy a moped" responses, so getting a straight answer is kind of refreshing

This may be off-topic, IMO, riding a motorcycle is mostly about being more fuel efficient. All the performance add-ons in the world doesn't make much of a difference if the rider does not have the skill to ride a moto to its capabilities in stock form.
Besides, most (street legal) motos have plenty of capability to perform beyong street legal status.. where can one safely operate a moto to its full capabilities? on the track? on salt lake beds? both of those locals are likely to be expensive to operate, even for short amount of time.

Valkyrie wants to be fuel efficient.. get a different moto with half the engine displacement, 1/3 or 1/6 number of cylinders.

It's tough getting taken seriously when talking about fuel economy at a forum that's not specifically about fuel economy.

riding a motorcycle has very little to do with being more fuel efficient. some motorcycles get less mpg than cars, I ride a honda valkyrie because I like the look, feel, and more importantly, how it makes me feel. I also enjoy getting better mpg out of the motorcycle that I choose to ride. it is like owning a muscle car, that as long as you don't use the power, you can get decent mpg, but you have the satisfaction of knowing that power is on tap if you want to use it. little bikes get blown around by trucks, are not comfortable for long distances, and certainly not comfortable with a passenger. I am getting sick and tired of peolple telling me that I should get rid of my valkyrie just because I want to make it more efficient. if everybody sold their cars, and bought mopeds, we would all be getting great mpg, but I doubt you will get many people to go along with that.

There's nothing wrong with trying to improve your fuel economy in whatever you want to drive/ride. If FE was your only big priority then it would make sense to revisit your vehicle choice, but for some people, other stuff is more important (which is why I drive what I drive instead of something like a Civic VX).

Then perhalps you should realize that trying to get a Valkyrie to be fuel efficient is a moot point, like trying to make a race car fuel efficient. Try putting 60 psi. in the tires if that make it more fuel efficient.


Just wait until gas prices goes (and stays) up to $4 a gallon (or above)..

I have made my valkyrie more efficient. I average 45 mpg, but have gotten as high as 54 mpg. but if my mileage dropped to 33mpg, I would not get rid of my valkyrie, it is the best motorcycle I have ever owned. if I owned owned a race car, I would probably try to figure ouy a way to improve mpg.

Improving fuel economy in race cars is a very important part of race strategy. The guy in 2nd place who has to pit for fuel 3 laps before the end of the race ends the race in 27th place.

54mpg (370 mile range) on a Valkyrie seems unrealistic, even at 45 mpg (310 mile range).
Valkyrie has displacement of 1520cc, 6 cylinder engine, 6.9 gal. tank, weighs over 720 lb., with 3000 rpm cruising at 60 mph in top gear.. that should yeild about 36-39 mpg being generous.

Not so important when the whole drag race is less than a mile.

I only accomplished 54 mpg once, while sedately cruising the back roads with two old couples ,riding a goldwing and a boss hoss trike. but I consistently get 45 mpg, 55 mph, 2500 rpm. riding in the mountains. oh, I also run a 205 60 16 general altimax car tire on the rear. by the way your specs are for an interstate, I run a tourer, which is lighter. I also noticed that my mileage is better than all your vehicles except your scooter, so my efforts of obtaining better mpg from my valk may not be a moot point after all

I call BS, fuel economy good or bad, at least I keep a record of the gaslogs, show some gaslog of your Valkyrie make it more believable.

A standard Valkyrie has a 5.3 gal tank, 682 lb. dry according to Honda, add fuel alone is over 700 lb., not to mention oil. 55mpg that means you travelled 291 miles per tank, 45 mpg means 238 miles per tank.

So how many miles do you get on a full tank?

How much does your Valkyrie weigh?

Does riding two up make any difference?

Car tire with wider and flat profile would have larger contact patch than a motorcycle tire, more rolling resistance, that shouldn't contribute to fuel economy increase.

Contact patch size probably depends mainly on pressure, not tire size. Contact patch shape is what changes when you change tire size. If there's 450 pounds on a tire with 45psi (pounds per square inch), it's going to have 10 square inches of contact patch. On a ten inch wide tire, that's a 1 inch long contact patch. On a 5 inch wide tire, it would be 2 inches long. On a 2 inch wide tire it would be 5 inches long.

Assuming the same pressure and a significantly larger tire, rolling resistance is reduced significantly. Oversizing while keeping the same inflation is effectively overinflating.

my valkyrie holds 5.3 gallons, but 1.14 gallons is reserve.I fill up as soon as possible when I hit reserve, I switch to reserve between 180 and 200 miles , usually takes 4 gallons to top off. mpg drops a couple of miles when carrying a passenger. I came to this site to get some info, I am grateful for that info by the way, but I am tired of having to defend my mods and my ride, and having my honesty questioned, so I am out of here.

By pressure, do you mean the weight that the tire carries?

2-up on a 700+ lb. moto with 205 60 16 car tire vs 180 70 16 standard Valkyrie rear tire.. which do you think might have larger contact patch?

I'm sorry you feel that way, there are many here hypermiling with non-conventional vehicles not known for mileage. For example, my primary vehicle is a V-8 4x4 pickup truck that I can get the EPA highway rating driving in city traffic. Holy Cow also has a 4wd pickup that he hypermiles with as well. Phillip hypermiles with a stationwagon. This is a great site for information on hypermiling with vehicles that people don't usually hypermile. Other sites generally have the attitude that if you're not hypermiling a Prius or a Geo Metro then you're wasting their time.

-Jay

No. "Pressure" in a tire discussion is always about tire inflation pressure, the pressure of the air inside the tire. That's why I was talking about overinflation and such.

Tell me the weight on the tire and the pressure in the tire, I'll tell you the contact patch. I don't need to know the tire size.

Let's say 400 pounds of those 700 are on the tire, and there's 30psi in it...there would be a 13.3 square inch contact patch. The 205-60-16 is 8 inches wide so the contact patch will be 8 inches wide by 1.66 inches long. The 180-70-16 tire is 7 inches wide so the contact patch will be 7 inches wide by 1.9 inches long.

I assume that a motorcycle tire is generally rounder in profile than the square-shaped profile of a car tire, which would mean that the motorcycle tire may not effectively be as wide; I'd guess that the width measurement is at the sidewall, not where the tread meets the road. The motorcycle tire will have to do a lot more flexing and deforming to make that contact patch, which would increase rolling resistance. OTOH, the motorcycle tire is probably a fraction of the thickness of the car tire, so that would probably reduce rolling resistance.

My estimate: Valkyrie 700-720 lb., rider 200-220 lb., passenger 160-180 lb., total approx. 1060-1120 lb. 36 psi in tire. What's the contact patch size?

All that weight is on one tire? I would expect the front tire to carry some of the weight too.

1060-1120lb at 36psi is 30-31 square inches.

You didn't specify the front and rear weight ratio..

Contact patch is 30-31 square inches for all sizes of tires?

I asked how much weight was on the tire, not how much weight was on both tires.

Given the weight (on that single tire) and the inflation pressures I worked with, yes. The math is pretty simple. You have pounds, and you have PSI (Pounds per Square Inch). Divide out the pounds and you're left with square inches.

Different tire rubber/silica/material compound does not effect the contact patch size?

Well, the stiffness of the sidewall could have a small effect on contact patch...but not much.

"The motorcycle tire will have to do a lot more flexing and deforming to make that contact patch, which would increase rolling resistance."

I think you are correct and IMHO chances are good the car tire has lower rr than the bike tire.

Bikes really don't coast well at all and I think it goes beyond the low weight and awful aero.

I wonder how much of a difference the tire material would have in contact patch and rolling resistance.. would car tire have more rolling resistance because of thicker tread/stiffer carcas?
Seem to me unlikely that a Valkyrie would get better fuel efficiency with a car rear tire vs moto rear tire.

Your statement seems to imply that no matter what size of tire, given the same weight carried on the tire and same air pressure in the tire, the contact patches would be the same on different tires... which seems to me grossly incorrect.

I don't know which tire would have less rolling resistance. The motorcycle tire may have to do more flexing because of its round profile, while the car tire may have thicker sidewalls.

How does one corner effectively when using a car tire on a motorcycle?

The size would be the same. The shape would change.

as long as you are talking tires, I will join in, and hopefuly learn something. I can tell you this, the altima is one of the lightest tires out there, so I don't think there was any difference weight wise. definitely more tread on the ground, wouldn't probably work on a sport bike, but on a cruiser, you run out of clearance before you run out of tread. leaned all the way over, I still have about an inch of tread to spare. less tread on the ground leaned over of course, but still more than a motorcycle tire. don't think I gained any mpg with the car tire, but didn't lose any either. friend of mine went with a 65 series tire, and seems to be getting better mpg, possibly gearing? motorcycle tread compound is actually harder than a car tire, so much better traction with car tire. my motorcycle tires were wearing out between 5 and 6 thousand miles. at 200.00 a piece, it was getting kind of spendy. the car tire cost 100.00, and should last at least 20,000 miles. after trying both, the car tire is the more comfortable ride. currently running 36 psi. they call this riding on the darkside, if you want to google it.

Sounds interesting. Do you have any pics of your bike with car tires on it?

sorry, I have no pictures with the car tire. I would have to get my daughter or son in law to take a picture with their phone, and see if they could figure out how to post them.

I wrote up detailed instructions for posting pictures. The writeup is on another forum; don't mind the rowdy, bawdy crowd there...
https://allofftopic.com/showthread.php?t=269

thanks, when my kids get back in town I will use their phone for a camera, and give it a try

Funny, greeted kinda poorly...left the forum...and now the discussion gets informative ;-)