Vetter Fuel Challenges

[Grant-53]

This is a well designed tail and should be stable. It is rounded at the top and the Kamm end plate helps as well. The only problem might occur if there is too much weight in the back. An aspect ratio of between 3:1 and 5:1 with a 75% Kamm length is optimum.

[gregsfc]

Good discussion. Thanks for the input everyone.

I'd like to get some others' input on one other topic regarding this event. How small can one go ride wise, for this particular challenge; the mid-Ohio, and finish without getting passed or being in real danger on the interstate stretch? And also, if there are those out there with experience regarding specific smaller rides that can maintain a little over 70, even on grades, fairly safely, please give those examples. I'm not referring to only valid grocery carriers that can actually win a class or the overall crown, but rides that meet all other conditions of the ride, but can finish the ride. For example, are there any 125 class or 150 class? Are there other 200 class? Just wondering how capable some smaller class engine rides can be and if more, smaller vehicles could cut the mustard if they were fully streamlined?

2014 Craig Vetter Fuel Economy Challenge, Vintage Days

At the 2014 event, I was surprised a little that there were two, 200 cc class rides; one dual-purpose motorcycle and one Vespa scooter. Both finished; they finished 2nd and 3rd as a measure of cost/mile and mpg if we look only at non-streamlined and only liquid-fueled bikes; and in fact, the scooter actually gained ground on the front half of the group where the full group had gotten split during the ride due to logistics. I know this, because I was at the tail of the front group, and once on the interstate, I began to see a single headlight behind me that over time, got closer behind me. My speed was pretty constant in behind the next rider for quite a time (at least a few minutes) at 72-73 mph. My speedometer is very accurate, and our group was being slowly caught up with by a Vespa 200 rider while traveling at or about 73 mph, which I found out after we got off the interstate and the Vespa caught all the way up. Later, I went to that rider and spoke with him. He said that his scooter will register at or about 83 running WOT, but that he thinks it's optimistic considerably, and that, when running top speed, it becomes unstable and a little unnerving.

That year at the mid-Ohio, we did not have any of the CBR250R guys there that generally show up these days. For stock or stock-like bikes, there were basically only five that were serious fuel savers in the group that probably thought they had a chance to out do the other stock machines. There were several 1 liter plus bikes; most all of them finished in low-to-mid fifties. Below is how the best stock like rides came in that year which is also on the link above under "results". For some reason, someone decided to include the Hayes machine in the top tier list that year, so they were giving preference to a grocery carrier over finishers. That's a complaint for another day, but results are not being published that way lately anyway, so it doesn't much matter.


1. Hayes Diesel AT (KTR650) 138.48 / $.0274 DNF-only 46 miles
2. CTX700 (2014) 101.85 / $.0330 Could not carry
3. DR200 (2004) 81.78 / $.0410 Could not carry
4. GT200 (2005) 71.20 / $.0472 Could not carry
5. FT500 Ascot (198--something) 68.29 / $.0492 Could not carry

Any respectful and thoughtful comments are welcome regarding displacement, horsepower capability, wheel size, etc. I'm posting this to learn things, so please give your opinion about these matters. Is there a perfect size for a highway capable ride? Or are there several ways to accomplish the same goal? Or many variables to consider?

[gregsfc]

A Fuelly member from IL who recently acquired a Honda NC700X with no fuelly data as of yet; messaged me on Fuelly and said that he will likely come to the event. He may or may not ride. I've encouraged him to ride and used the fact that only one NC700X has participated with published numbers and came in only at 71 mpg. This guy from IL knows Craig. I'm going to encourage him to contact Kraig at his site and get added to the participation list. I don't know the exact model, but I think if someone who is not too large and/or heavy comes in with an NC700X without saddle cases or bags (like that first one did, but couldn't carry groceries anyway); and tucks some during the ride, and especially if its a straight shift model; he or she could easily achieve above 80 and thereby not making me and my bike look like an anomaly. I'd like that!

[sendler]

There isn't really any pre-registration or anything that needs to be done. They are happy to take your name at the morning of the event.. But they do ask that you are accustomed to riding in a group and understand how to keep up. So far the groups have been pretty small. But as you can imagine if 40 bikes or more start to join in, it gets pretty hard to keep the tail end from getting lost.
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One change that would help make the results more accurate would be if we had some observation of the fill ups. It seems there may be some wishful filling going on, with some bikes even using the click method which is totally inaccurate for events with a total use of 1 gallon.

[gregsfc]

I don't think we have to worry at all about 40 or more bikes. I'm just pushing for a few and expect less than that. Maybe one or two more besides the two CBR guys and a few more that would have shown up anyway before I started promoting it. I wish I could bring in about ten different models and such, but I've had only two positive responses, and only one that I know of is going to try and make it.

I know its not required to pre register, but Kraig wants to put more names on his participation list over on his website, or at least I think he does. He encouraged me to send him photos and asked if he could publish my name.

The way I do fillups is to get it as full as I can each time within reason, and I have very consistent results except that one tank on the mid-Ohio run in 2014 where I beat my best ever by 14 mpg. But since the tank before and the tank after that great run were right at what I would have expected (mid 70s), I don't see how my score in 2014 could have been anything but valid. There was a mechanical issue with my windshield that occurred immediately before the ride started where the mount holders broke and it dropped down, and maybe that, combined with my tucking, combined with the big Dewalt box may have given me great mpg. I guess we'll find out this year if that accidental setup had anything to do with my great score. I'm shooting for 88. Anyone can watch my fillups, but I don't have any kind of precise method for filling. For me its mostly art.

I know that truly topping off can be a problem with gas-power and those evap systems, but I've not had any problem. I just ease the level up to the tippy top four times at the same approximate velocity, and I get very consistent results. I like as much range as possible, and that's why I do it this way.

When the air turns cold or my chain gets very loose, my mpg will drop, but other than that, when I'm on a long ride, I get mid 80s in warm weather if it's not windy. When I commute, I get upper 70s. This late Spring, my mpg did not rise back up as much as it normally does for warm weather. I looked at the chain and it had nearly no tension. The tank I'm on now, after taking the slack out, is putting me back up to upper 70s. I saw this happen one other time; had three or four tanks that dropped 5-6 mpg; and then noticed slack in the chain. Fixed it, and I was back to normal. If it gets below freezing, I'll lose ten mpg or more. But luckily, this ride is in July, although the early morning start worries me some, because my bike will use more fuel at even 65 degrees compared to 85 degrees air temperature.

[sendler]

That's odd. I would have expected the looser the chain, the better.

[Grant-53]

The main point Craig stresses is that less air drag means less power is needed which means less fuel burned. The compression ratio is a key to thermodynamic engine efficiency. Mass rate of flow of air/fuel mixture is a function of displacement and rpm. The light high rpm engines are favored for racing and may have a slight advantage with less overall weight. A long stroke, lower rpm engine may burn less fuel and have a broader torque band for street riding. A well designed shell will reduce drag, provide ample cargo capacity, and offer more crash protection. The bulkheads on my tail box are 9mm aluminum honeycomb to protect the back.

[gregsfc]

Originally Posted by Grant-53

The main point Craig stresses is that less air drag means less power is needed which means less fuel burned. The compression ratio is a key to thermodynamic engine efficiency. Mass rate of flow of air/fuel mixture is a function of displacement and rpm. The light high rpm engines are favored for racing and may have a slight advantage with less overall weight. A long stroke, lower rpm engine may burn less fuel and have a broader torque band for street riding. A well designed shell will reduce drag, provide ample cargo capacity, and offer more crash protection. The bulkheads on my tail box are 9mm aluminum honeycomb to protect the back.

That's way over my head but thanks for it. I've got a theory in my more primitive mind that my bike has less potential for improvement with respect to optimizing mpg via weight reduction, higher gearing, and being more slippery at highway speeds than an equally-well-engineered engine with displacement that's just a little more than one-third the size of mine, like the Kawasaki twin 250 or the Honda single. However, I'd guess that there is still lots of room for improvement through gearing optimization and drag reduction even though it may not be to the same level.

I Would love to see Honda's 670 cc twin and Honda's 471 cc twin and the single 250 or 300 with the full streamlining effect just to see the potential of all of these engines when given the maximum effect like are the Vetter-designed bikes; mainly because they are so amazingly efficient already in stock form. Comparing the 670 to the other two would be very interesting to me since it's sort of a total different engine strategy for motorcycle propulsion; more like Fred's diesel strategy, but with spark ignition instead of compression ignition; or we may say it's more of an automobile approach; instead of a traditional motorcycle approach. It's not so important really to show that larger displaced engines can reach the same level as the amazing Honda 250 or 300 single (which we also don't know), because I don't think it can; but I think that there are others besides me who prefer the broader torque band and prefer that engine character, and so it would be interesting to see what the penalty would be for driving a lower-revving, more torquey bike.

[gregsfc]

Originally Posted by sendler

That's odd. I would have expected the looser the chain, the better.

Yeah you guys would know more than me. I came to riding for the first time at age 45 and started on a really great scooter; a Piaggio BV350. I originally thought and worried a lot about choosing a chain-driven bike when trading the BV that averaged 10 mpg less on the same commute at the same approximate speeds but with half the engine displacement. Thought it would be a lot of hassle adjusting and worrying about oiling and cleaning, but soon learned that there is really not that much to maintaining it; still on the original chain/sprocket and only two adjustments so far; quit worrying about cleaning it and just use a waxy lube and don't worry about it; and it has lasted a good, long time. Additionally, there will be much less to replacing or repairing it when that time comes compared to a typical scooter drive system.

It may be, even though I've not noticed it, that I'm letting it get so loose that it's slipping just a bit now and then. When it happened the first time, it was cooler weather, and my mpg dropped from around 70 to 65; I thought it was just due to the colder weather dropping my mpg more; but I starting noticing a slip now and then; adjusted it; and the mileage came back up to around 70. This time around, It didn't get so loose that I noticed any slippage. The need for adjustment seems to happen in a short time period, so maybe I need to make this like a weekly check; instead of about every two months. Soon after the event, I think it'll be time for a new chain and sprockets anyway. I'm at about 14K miles and the bike is coming up on 4 yrs old, everything still looks decent but there is just a tad of wear on the chain, so I'd say it's about time.

[bschloop]

I've missed a couple of years now, but I just confirmed that I will be there this year with my just finished cbr 250 streamliner. I wasn't sure that I'd make the grocery requirement, but it looks like they will fit.

In answer to the engine size question, my last bike was a 185, and I kept up just fine. Properly streamlined, a 125 would be more than fast enough.