Peak RPM for Max Fuel Economy?

[garyahouse]

It seems to me that no matter what you drive, be it car or truck or bike, you'll get slightly poorer mileage when you travel too slow, and much poorer mileage when you travel too fast. With both the research I've done and the vehicles I've owned, the sweet spot seems to be around 50, give or take a few mph. The easiest way to see the effect that different variables have on mileage is to keep a close eye on the gauge of a newer vehicle that measures instantaneous mileage. My hybrid car has such a gauge. For example, increasing weight decreases mileage. A 10 % gain in gross weight (3 more people) results in a 10 % decrease in mileage. Increased wind resistance will do the same thing. However, the biggest factor has got to be speed. My car gets poorer mileage at say, 38 or 42 than it does at 48. I make my best mileage of 48 mpg between 48 and 52 mph on level ground, 44 mpg at 62, 40 mpg at about 70 and 34 mpg at about 80 and so on. I wish I could measure the actual numbers on my FJR like I can on my car, but here's my point: the same principles apply to all vehicles, though the actual numbers will vary.

Gary

darksider #44

 

[SkooterG]

Oh goody! We haven't had a good mental masturbation thread in quite a while! Woo-freaking-hoo!

 

[HotRodZilla]

Oh goody! We haven't had a good mental masturbation thread in quite a while! Woo-freaking-hoo!

Masturbation?? You getting primed for your meeting with Wheaties??

 

[escapefjrtist]

Keep the bike under 80ish mph and the mileage is fairly constant...unless you're hammering on it. Anything over that and the mileage falls proportional to the speed... or so I've been told!

--G

 

[Denver_FJR]

Ok forum brainiacs, here's a twist (and slight thread hijack)... if maximum distance is your goal and higher speed = reduced MPG & more frequent gas stops, what is the most efficient speed to travel?

 

[HotRodZilla]

Ok forum brainiacs, here's a twist (and slight thread hijack)... if maximum distance is your goal and higher speed = reduced MPG & more frequent gas stops, what is the most efficient speed to travel?

These bikes get the absolute best mileage at ZERO rpm. So, to get the most MPG out if your bike, fill it up, park it on a trailer, and then drive it all over the country. A person could get 10,000 miles per gallon or better.

Or leave it off and push it. You wont use a drop of fuel.

I suggest you start right away.

 

[Bustanut joker]

Oh goody! We haven't had a good mental masturbation thread in quite a while! Woo-freaking-hoo!

Masturbation?? You getting primed for your meeting with Wheaties??

Well, Alan was talking about inches a few posts back....

 

[Fred W]

Ok forum brainiacs, here's a twist (and slight thread hijack)... if maximum distance is your goal and higher speed = reduced MPG & more frequent gas stops, what is the most efficient speed to travel?

Good post. I think I see where you are going with this.

So, is your question really about maximum distance? Because that would be the same answer as maximum mpg.

Or is it the "maximum distance per unit of time"?

I still think that the maximum distance per unit of fuel (time notwithstanding) will occur at the minimum (possible) rpm in top gear.

But if you throw in the time qualifier, then you have to figure out how much time you'll save or waste by going so slow, stopping for refueling, etc. Then the calculation will favor a much higher speed in top gear.

In reality, this is the compromise that most of us would strive for. We all want to get somewhere in a reasonable amount of time with reasonably controlled expense, even if "somewhere" is just a loop back to where we started.

 

[user 213]

There were actually some pretty good answers in this thread, despite the useless question that started it. Real world riding on the FJR means that like Fred said, go slower, you'll get better mpg. At 55 mph, you'll get some great mileage. You'll get run over by a truck, or die of boredom somewhere around Pecos, TX, but other than those downsides, you'll get better range due to the higher mpg. Ditto for running with the screen down. Sucks in the rain though. Not really sure about bags off, never ridden the bike that way. Sort of defeats the point of having a bike with hard luggage, for me.

The difference between 65 and 80 mph in gas mileage is pretty insignificant too, (as was said). You'll still be seeing 42-44 in most cases, except for one little thing. You screwed up all hope of any decent gas mileage when you installed the PCIII. Well, not all hope, but almost certain hope.

PLUS my PCIII tells my display to lie to me....so I dont know the trooof!

The "trooof" is you never needed the PCIII and it's the primary cause of poor mpg on FJRs. Want instant better gas mileage? Unplug the PCIII and plug the O2 sensor back in. Believe it or not, actual real time sensor readings where the ECU has data and can aim for stoichiometric air/fuel ratio will get you the best mpg possible. CLICKY

 

[wfooshee]

I still say, as did UHOH, that riding for "efficiency" is the least economical thing you can do on the bike. You don't save anywhere near enough money to pay for the food and lodging you'll need by being on the road longer.

Quite a while back there was a guy posted here that he proudly replaced his gas-hog truck, which was killing him at the pump, with a new, more efficient vehicle, and was saving 50 to 100 bucks a month in gas. Yee-ha! New vehicle payment was up toward 400 bucks, though, I think, so I'm not really sure why he was bragging about saving money.

Riding for economy is the same backwards thinking. It costs too much to save gas while you ride, so it doesn't pay off.

To address Denver_FJR's challenge, in my previous post I showed that dropping speed to go from 40 to 45 miles per gallon saved 2 fuel stops over the 5339 miles. Is that even significant in that amount of time? Especially considering that the total trip time increased by 22 hours??!??!?! I haven't been able to find a trip calc that made worrying about 1 or 2 stops worth any consideration at all. By the time you've saved enough mileage to drop a stop, you've added way more trip time than the stop would have taken.

Now I need a cleanup rag . . . . .

 

[Bustanut joker]

I'm getting a headache..

 

[not2shabby]

So....if you have a PC3, your real time mpg readout is skewed? Hmmm, first I've heard of this! What's the cause?

I'm getting a headache..

I think I just heard a flock of sheep go "whew"!

 

[Fred W]

So....if you have a PC3, your real time mpg readout is skewed? Hmmm, first I've heard of this! What's the cause?

The second gen mpg readout doesn't know anything about the fuel that is being added (or subtracted) by the PCIII. It assumes that you are running the stock fuel injection map.

 

[Bounce]

Well **** ballz. I thought for SURE one of you guys would have an answer based on factual riding experience.. TominCA stated the obvious, Ionbeam approached an answer, and Ignacio posted the most honest.

Thanks gents. I'll see what turns up. I'll have 5,339 miles to test my hypothesis. :angry:

the hygiene of your ballz aside, i suspect the reason no one knows the answer is because the bike isn't usually bought by hypermilers. a thumper or something in the 250cc class is usually the venue of those looking for high mpg.

folks with FJRs that want to get farther between fill ups tend to add fuel cells.

If you want to minimize travel time, the 'only real way' is to get on the road very early each day.

excellent point. leave at 5am. ride until 11pm. spend an hour getting checked in/out and sundries. no more than 30 minutes at each fuel stop (my preference is no more than 20). pretty good day when "off the clock".

 

[not2shabby]

So....if you have a PC3, your real time mpg readout is skewed? Hmmm, first I've heard of this! What's the cause?

The second gen mpg readout doesn't know anything about the fuel that is being added (or subtracted) by the PCIII. It assumes that you are running the stock fuel injection map.

Ah, didn't think about that. It makes sense though and explains why it's usually on the optimistic side according to my calculations. Thanks Fred!

 

[wheatonFJR]

So....if you have a PC3, your real time mpg readout is skewed? Hmmm, first I've heard of this! What's the cause?

I'm getting a headache..

I think I just heard a flock of sheep go "whew"!

:lol: :lol: :lol:

 

[huron52]

Kay, serious answer time. If your revs go over 5G's you'll take a pretty significant mpg hit. So you good up to about 75mph. After that, you'll be able to hear the sucking noises. It must be the default map for the ECU, if your above 5G it richens the mixture up a lot for performance.

That being said, the best I ever got was a little Sunday afternoon jaunt up the arctic watershed north of here. 65mpg running at a steady 50mph.

... but I sure wouldn't want to ride across the country like that.

Now wait just a minute there bungie.... I recall someone being well over the 5,000 rpm several times on a cross country trip.

 

[Fred W]

Now wait just a minute there bungie.... I recall someone being well over the 5,000 rpm several times on a cross country trip.

I guess Maximum Fuel Economy was not on his mind then.

 

[dcarver]

That is much lower in wind resistance than the bags or a trunk. Just look how these things stick out and catch wind:

Improve the aerodynamics and speed will have much less effect.

and that's why Skooter now wears a full face helmet!

Oh goody! We haven't had a good mental masturbation thread in quite a while! Woo-freaking-hoo!

If we put wings on that fjr then put the fjr on a treadmill would it take off?

 

[Bungie]

Now wait just a minute there bungie.... I recall someone being well over the 5,000 rpm several times on a cross country trip.

True! Do you remember how we were stopping for gas every 200km LOL! Lets see, I distinctly remember running around 7000 in 5th for about an hour and two other guys were so far in front of me I thought they lost me for good

Funny how we all need gas (in the main tank at least) around the same time.

Regardless, good trade. Prairie was made for dispatching. I would've gladly ate a bullet rather doing that at 55mph.