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Discussion Starter #1
I have been wondering about gas milage and RPM's. All conditions being equal (level road, no wind, etc) at what RPM's do you think the 400 will get the highest MPG?
 

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A lot goes into MPG besides engine speed. Wind resistance is the big one. In my experience, the best mileage happens on long steady rides between 45-50mph, Having the wind at your back helps a surprising amount.
 

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I was getting 60 miles per gallon at about 65mph in the warmer months. Like chip said, 40-50.. I'm sure if you ride 40 mph that would be better I just know I wouldn't want a ride anywhere 40 mph if it was a distance run!

Once you get past the registered 70 mph, The MPG start drop off, I know she has a very sweet spot 60-65 mph actual speed, that will be 6000-6500 rpm's if it's a stock unit 400cc
 

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I'm happy to trade a loss of 4 mpg for my Givi Airflow windshield another 3-4 mpg to able to travel a GPS 75 mph.

If you want 60+ MPG then stick to 60 mph or less. I'm not sure anyone really rides 40 mph or less. Do they?
 

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My best mileage, believe it or not, is riding twisties. Sure I'm flogging it uphill, but there's little gas used on the downhill. Considering the average speed is 40 mph, I get almost 70 mpg. So I'd agree with Chip, 40-45 mph gives the best mileage.

But mine is completely worn in stock bike. Swoopy, albeit buffeting, windscreen and all. I like it!
 

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I push my "Wife's' 400 as hard as I can when I ride it. We live at 7000 Ft and I still get 56 to 58 mpg average city/highway. It's a fun bike to ride and at that kind of mileage, just enjoy the ride. The smiles per gallon can't be beat.

"Ride more Worry Less". Life is to short to sweat the small stuff!
 

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Some engines get their best fuel mileage right around the same rpm's as max torque produced at full throttle. At least this is true for my VW diesel which produces max torque at 1750 rpms. Max HP is 4000 rpms.

By playing around with the cruise control on a clear stretch of flat (GPA checked) freeway I saw the best economy number at 1700 rpms (max torque) which is about 52mpg and 60mph. With no other factors being changed the car's computer shows a drop in mileage to about 45mpg if I put the trans in 5th gear which boosted the rpms to ~2200. Dropping to forth gear reduced it even more. At slower speeds and under the 1750 rpm mark dropping the rpms to 1200 (doesn't lug but very little power available) increases fuel used. I don't remember those numbers since I tried that only once. Best to stay around the 1600-2000 rpms for best mileage.

I still can't believe the Jetta weighing 6x the Burgman gets better fuel mileage at certain speeds with a motor 3x the size. Best mileage with the Burgman has been just under 50mpg. Overall mileage of in town and out with the Jetta runs around 39-42mpg. Since it only has 3500 miles on it and most of those were winter driving it should improve some in warmer weather and as the running gear fully breaks in.
 

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I get my best mpg at around 50mph. My engine revs on standard rollers are pretty much the same at 40mph or 50mph. This indicates the variator doesn't kick the bike into it's higher gear until around 50mph. It may vary slightly from bike to bike depending on the wear to the belt etc as that affects the gear ratios as you guys know. On a Uk gallon (4.54 litres) I easily get between 88-90mpg at 50mph. In fact, it does that everytime I cruise at that speed. Yeah...I know, amazing isn't it! However, I rarely ride at 50mph, it's just too much fun to not go faster...:)
 

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I push my "Wife's' 400 as hard as I can when I ride it. We live at 7000 Ft and I still get 56 to 58 mpg average city/highway. It's a fun bike to ride and at that kind of mileage, just enjoy the ride. The smiles per gallon can't be beat.

"Ride more Worry Less". Life is to short to sweat the small stuff!
That's very good indeed. I think the Burgman is one of the best mid size scooters for fuel efficiency and performance.
 

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Discussion Starter #10
I am not really concerned about getting the best mpg, more concerned about enjoying the ride. But when I am cruising on the highway sometimes I think about what the most efficient RPM's for our motor. Seems like there would be a rpm band where our engine would be in the sweet spot of fuel usage. In the real world (with sliders) I find that if I cruise much above 6k RPM's the mpg really drops off. Of course sometimes I just want to cruise at a higher speed and I sure don't let the lower mpg slow me down.
 

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Limited expereince on the 2011 400 I bought in Dec and did not get registered until a week or two in Jan. (about 2000 miels) I also had a week messing with getting a Car Tire installed on the rear.

Anyway, I was seeing 60mpg just riding around East TN curves and hills (backroads mostly) at say 45 to 55 most of the time and a few Interstate runs as high as 80 mph.

I have not worried about trrying to optimize mpg. I get on it most of the time and some are steep curvy roads. Also, a lot of it until the last three rides has been cold weather (30s to 45s) - allow a little more warm up time at start up.

The last three rides (warmer weather of 45s to 70s and longer rides of 180 mile range), I have 66mpg for those three day rides of the 180 mile variety. Average over the last 750 miles is 63 mpg.

Three of the recent rides have been in very steep curvy areas (Newfound Gap between Cherokee, NC and Gatlinburg, TN over the Smokies, Bluff Mtn one of the steepest rides around here, Summit Mtn the ridge part of it which did not involve a lot of steep, Homestead Mtn also very steep and curvy) -- I got right at 66mpg +/- on all of those three rides.

I have just under 2000 miles since early Jan. About 1000 on the OEM tire that came with it at (5200 miles and replaced at 6200 with the car tire) and about 1000 on the Car Tire.

All this based on the oddometer -- I have not compared the odometer with the GPS trip summary. The speedometer error reduced from near 10% to near 6% when I switched to the car tire (based on GPS speed readings vs speedometer).
 

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I do mostly freeway driving (commuting) to and from work. I am usually going 80MPH by the speedo @ 6K RPM. If I can get behind someone to reduce the wind resistance, I get 60MPG. I average 52MPG with the wind resistance going the same speed. I usually try to sneak up behind a motor home or box truck going 70-75 but they are hard to find. When you do that, you still have to deal with the side to side winds
 

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My best mileage, believe it or not, is riding twisties. Sure I'm flogging it uphill, but there's little gas used on the downhill. Considering the average speed is 40 mph, I get almost 70 mpg. So I'd agree with Chip, 40-45 mph gives the best mileage.

But mine is completely worn in stock bike. Swoopy, albeit buffeting, windscreen and all. I like it!
I had not thought about it but you're right. l live in the mountains and most of my riding is crooked mountain roads. I had a 08 400 last summer and riding hard on crooked mountain roads averaged 68 MPG and interstate riding dropped it to just under 60. I rode it 4,000+ miles before the 83 year old guy totaled it when he hit me in the rear.
 

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As has been stated above most engines' maximum efficiency is coincident with their torque peak, 5800 rpm for your 2008 400. This would be about 58 mph indicated (52 or so actual) with the stock CVT components.

Using some "back of a napkin" calculations to guesstimate a 400's coefficient of drag I come up with 0.90¹, I.e. not all that great.

This means that riding at 60 mph would require 60% more power that riding at 52, and traveling 70 would require 220% more than at 52.

Here are the numbers my How Much HP Does It Take To Go How Fast? online calculator comes up with (I just changed the default values to reflect the Burgman 400s characteristics):



The napkin exercise was pretty close, note that the calculator says it takes 25.1 HP (at the rear wheel) to push a 400 (with a 200 pound load) to 90 mph--this coincides with the few dynamometer numbers I have seen, and with the actual top speed of a typical 400...


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¹ - I once heard the aerodynamics of a Harley dresser described as being like "a brick with a parachute on top of it". The "brick" is the bike itself, the "parachute" the rider.
 

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For the 650 the best I have got is 59.5mpg (47miles) at 50-52mph (flat-indicated) in OD where rpm is just above 3,000.
I going to try to reduce the aerodynamic drag and see how high I can get it. According to cliffys' chart most of the hp required is from aero drag above 30mph.


I still can't believe the Jetta weighing 6x the Burgman gets better fuel mileage at certain speeds with a motor 3x the size. Best mileage with the Burgman has been just under 50mpg. Overall mileage of in town and out with the Jetta runs around 39-42mpg. Since it only has 3500 miles on it and most of those were winter driving it should improve some in warmer weather and as the running gear fully breaks in.
This is mostly due to the added wind resistance on the burgman. Was looking at my reflection last time I rode and realized that my back was creating a huge vacuum behind it.
 

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Discussion Starter #16
Thanks Cliff, that is a great response. I think you nailed it. My only question is if the sliders would make any difference at all? If the most efficient RPM's are coincident with torque peak, wouldn't the most efficient rpm remain a constant irregardless of what is going on with the CVT? Or do CVT modifications impact peak torque?
 

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Thanks Cliff, that is a great response. I think you nailed it. My only question is if the sliders would make any difference at all? If the most efficient RPM's are coincident with torque peak, wouldn't the most efficient rpm remain a constant irregardless of what is going on with the CVT? Or do CVT modifications impact peak torque?
Nothing done to the CVT will affect the engine's output, or for any practical consideration impact the CVT's efficiency--which is not all that great. The few Burgman 400 dyno charts I have seen show the rwHP (rear wheel HP) at 24 to 26, Suzuki claims 34 fwHP (flywheel HP).

So that makes the CVT and final drive loss between -24 and -29 percent. In comparison the rule-of-thumb used for manual transmission cars is -15%, -18% for automatics.

Note: below I will be referencing vehicle speeds; these all represent actual mph as I use a DRDSpeedo speedometer correction device, calibrated against a GPS unit. Uncorrected the speedometer on our scoots displays speeds 10% faster than actual speed, so add 11.1% (the reciprocal of 90.0%) to convert them to indicated speeds.

What sliders can affect is what vehicle speed coincides with the engine's torque peak.

For example on my '03 400 (torque peaks @ 6k rpm) and running four 15g and four 18g sliders, 6000 = 62 mph;

When I was running eight 18g sliders 6000 rpm = 65 mph;

With the stock rollers 6k rpm = 60 mph.

One last comment. Traveling at whatever speed coincides with the engine's peak torque will in theory provide the best fuel economy--but only at "that" speed. Because of the complex interrelationships of vehicle speed, drag, required engine output (as drag changes), etc. that speed may not (and likely will not) be the speed at which fuel economy is maximised. The best and easiest way to determine that is experimentally...
 

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I once saw a picture of a chart online that had the percentage of fuel being sent vs the RPM and the amount of throttle opening.
It was from a power commander thread of some kind somewhere.
I copied it down so I could email it if you want to see it.
 

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First of all, I calibrated my AN400-K8 with a GPS and found the speedometer to read high at about 18% at 45mph reading and at 90mph reading meaning my top speed is ~78mph actually and I'm only doing ~38mph actually when it reads 45, with about 10% error on the high side in between. These % errors might also apply to the MpG readings on the dash as well, though I haven't validated that with further testing.
So when my speedometer reads between 40 and 50 mpg on a fairly level road I have been getting my BEST MPG READINGS, up to 67mpg (on a full tank of gas), recently up to 60.2 mpg reading after 100 miles, indicating my Best REAL MPG is at ~37-47 mph actually. My BEST ENGINE RPM are at 4400-5500 for these best mpg readings!
Incidentally, My mpg reading drops to ~30 mpg reading at 80-90mph reading, for the WORST mpg!
Good luck with your gas economy!
 
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