Real world hwy P&G mpg for 250-650cc cycles?

[MPG_Plus]

I noticed that the option to import using cut and paste does not work, at least for me on my computer using firefox or MS explorer. Also the lifetime average and the three last tanks and last 90 days is off by a few miles per gallon. When shooting for triple digits this make a difference to me. The current mileage is fine and each of the individual data points. I can't see entering a bunch of previous data until that is fixed.

[Honda100]

250 Nighthawk gets around 71-80 mpg for me, very soft cruising. 55-67 ish when getting on it.

[P-hack]

most of my riding is around town, so less aero penalty. P&g helps me get into triple digit mpgs on small bikes. My v65 sabre is just a pig no matter how you drive it. But per the OP, hiway is going to see reduced returns certainly (excepting large hills)

[jkv357]

I guess I haven't chimed-in on this thread yet, so to answer the initial question -

My 2006 Suzuki SV650 N (F.I., no fairing) that's geared-up 1T on the countershaft gets about 55 MPG on the Interstate at 70-75 MPH. Best its done is 62 MPG during some moderate back road riding in the 50-70 MPH range.

That's on ethanol-free 87 octane.

I don't P&G with it, as it's a V-Twin and slows immediately/drastically when you roll off the throttle. It will return 50 MPG in town also, using moderately quick acceleration then a smooth cruise at lower RPMs with minimal throttle opening.

[alvaro84]

Originally Posted by jkv357

I don't P&G with it, as it's a V-Twin and slows immediately/drastically when you roll off the throttle.

Haven't you forgotten about something? Like the clutch lever

[jkv357]

Originally Posted by alvaro84

Haven't you forgotten about something? Like the clutch lever

Nope.

I don't coast with the clutch in on a cycle.

[P-hack]

I would say Yes. It isn't G (as in P&G) if you aren't in neutral or holding the clutch in. You are engine braking which is still braking.

[renault_megane_dci]

With my car, I don't P&G anymore because since it is able to cut off fuel when pedal is depressed, it seems more rewarding.

No use on carbed engine obviously

[serialk11r]

Originally Posted by stillsearching

Most of all I would LOVE to have SFC figures for modern bikes. For instance on cars it's pretty much a given that they'll be the most efficient fuel use, per HP used, maybe around 2000rpm or so. At 1000rpm it will suck. At 5000rpm it will suck. But bikes have such an incredibly wide range, like the Ninja 250 with what, 13,000rpm redline?? I don't know where the ideal part of the curve is for such an engine. I would like to have something with enough power and gear, to put it in that sweet spot of the curve for 55-75mph range approximately. If a 500 is more efficient putting out a 15-20hp load than a 250 is (being run too hard) the 500 will probably get better mileage under those conditions - this i've finally understood.

Bikes have no variable valve timing, so there is considerable (undesirable) EGR at lower loads for quite a chunk of the rev range, and this is probably the main thing that robs efficiency. In car engines the low rpm combustion characteristics are better, but the proportion of friction power increases a lot faster. Looking at a dyno chart of a CBR600RR, the torque seems to pick up a lot at 3000, going to 30 lb-ft or ~45Nm by 4000rpm, and 75Nm/L is around what "Atkinson cycle" engines with a similar intake valve closing point pump out, which is a good sign. So maybe like 4000-7000 is a decently efficient range for applying heavy throttle and you could get away with cruising at 3000 efficiently. For other bikes maybe try to observe where the torque has a similar steep ascent, that probably indicates combustion efficiency picking up. I would guess that it scales mostly with the stroke, since bike engines tend to be designed with the highest possible rev limit and are given cams to suit, though obviously an FZR600 that's basically a detuned R6 probably will be efficient at a considerably lower rpm.

[renault_megane_dci]

A FZR600 as detuned as it is, is still with a very high peak torque rpm required for its 170 hp per litre (100hp variant) or 130 HP per litre in the 79hp version ...

The more I think about it, the more I believe peaky engines are better for bikes because it will be less prone to rear wheel lock on throttle closing.