Eliminate the rev limiter?

[670cc]

Ok. That all makes sense.

Now, on a flat road - (Florida is all flat roads it seems) I can accelerate faster short shifting than if I run to redline in every gear. Why is that?

Well personally, I don't believe that you can. Or there's something wrong with your bike.

If so you may want to tell that secret to the test riders that do the timed runs for the spec sheets. They're on flat ground, and I'm pretty darn sure they don't short shift to get the best 0-60 times!

But, my point about the charts is that if the motorcycle had gobs of torque in a very low RPM range, that would be DIRECTLY reflected in the horsepower curve. You would easily see that the bike had above average power in the lower RPMs by looking at the power curve. There's no need to clutter the chart and confuse some people by showing the torque curve.

 

[bamamate]

Actually it is not unusual for “short shifting” to give better 0-60 times. Many engines, especially non-high performance production engines, the hp curve starts to fall off before redline. Once it starts into the significant fall you are better off to shift to put you back in the fat part of the hp/torque curve where it is quickly climbing. I don’t remember the NCs specific curve……buried in some 2012 post……..

 

[Mojave]

You know, frankly, I wish the people that make these dyno charts would stop putting both the torque and the horsepower curves on them. When the chart shows only horsepower on the vertical axis and RPM on the horizontal, it tells you everything you need to know. Then people might stop saying torque does this but horsepower does that. The bottom line is that power does everything.

Work is done by power (energy transfer). Agree that HP is the important info, and the torque plot can be inferred from the HP plot. Full throttle dyno run HP don't tell much about the bike in the real world, but the torque value kind of does.

Bigjeff, all flat it seems? No doubt about it -it's a flat place! I don't know what to say except that I think if you somehow measured the accelerations you'd find your SOTP impressions to be wrong.

A while back before I bought my NC a fellow at work traded in his Honda Superhawk VTR1000 on a standard NC700X. When I found this out and asked him how he liked it he shrugged and said he could only go 65 up the highway grade out of town (Ridgecrest is the name but we are in a Valley!). On his Superhawk he'd just put her in high and roll up at whatever speed he wanted. I asked if he downshifted and he said "no, it's a special engine and it's best to be in the middle of the range". I said no, you are bogging and have to downshift! We had this exact argument out in the parking lot. This engine may be special but it doesn't have special physics applied.

 

[670cc]

Actually it is not unusual for “short shifting” to give better 0-60 times. Many engines, especially non-high performance production engines, the hp curve starts to fall off before redline. Once it starts into the significant fall you are better off to shift to put you back in the fat part of the hp/torque curve where it is quickly climbing. I don’t remember the NCs specific curve……buried in some 2012 post……..

Totally agree. Shift when the power peak starts to fall off, which on the NC700 is just past 6200 RPM per the plot in this thread, post #44. So you would pretty much 'short shift' right about redline on this bike.

Again, I don't ride this way at all. My NC probably hasn't been past 4000 RPM in the last 5000 miles. But, the discussion was about methods for best acceleration.

Something that would be interesting is if they did a dyno run at half throttle and another one at a quarter throttle. Then we could see the horsepower plot as it applies more to real world riding. It's not like we ride around at WOT all the time like their dynomometer test does.

 

[dduelin]

Think you are right.......and suspect it is not a coincidence the rev limiter is placed right above this max acceleration rpm...

That is the rub. Because the peak is so close to the hard limiter it's very difficult to time the shift without hitting the limiter. If the power band had the usual taper after peak hp the engine would give more warning "it's time to shift" but the 700 has virtually no headroom from peak to shutoff plus the gearing is such the bike spins up so fast in the first three gears. I think I probably shift between 5800 and 6200 under WOT because if I wait until the rpm rise begins to fade I'm guaranteed to hit the limiter. If you watch the tach and try and shift at 6250 it's seemingly impossible to shift in time. On the other hand shifting under WOT close to 5500-6000 yields close to maximum acceleration without risk of the loss of momentum hitting the limiter does.

 

[bamamate]

I agree with dduelin. I shift in the 5500-6k range. With the gearing it doesn’t drop you too low in the RPMs so you are still in the “power band”.

 

[SergeantChuck]

At WOT I usually find myself shifting at 5000rpms. To me it seem to flatten out right in that range so I shift. My opinion. Regardless, this bike just doesn't have the power no matter where you shift. If that is what someone was looking for they should have bought something else. What this bike does great is commute and 1up toruing and that is why I switched although I may need to buy a second bike (CBR) to have the other side of things. Don't get me wrong, I really like this bike but I would not waste anytime on trying to figure out where to shift to accelerate the best because it just isn't there. No offense to anyone. Just my opinion.

 

[malony]

Last month in German forum someone has raised NC700X rev limiter to 7200 rpm.
That's the crazy guy with the top speed video in youtube.

 

[NCer]

Anyone seen this? Thoughts?
Amazon.com: MAGNUM Programmable REV LIMITER Ignition Controller Honda NC700X: Automotive

 

[anglachel]

You know, frankly, I wish the people that make these dyno charts would stop putting both the torque and the horsepower curves on them. When the chart shows only horsepower on the vertical axis and RPM on the horizontal, it tells you everything you need to know. Then people might stop saying torque does this but horsepower does that. The bottom line is that power does everything.

My understanding is that the constant in that first derivative I mentioned earlier becomes the problem.

Now if we published either curve and the max numbers, then we'd be ok, it's give us the constant to use on the derivative or integral to calculate (or estimate) what the other curve looks like.

Not sure how much of the difference there is just gearing (Honda geared this bike for gas mileage, high rpm and high hp aren't a recipe for high mpg)

Sent from my SAMSUNG-SGH-I537 using Tapatalk

 

[Mojave]

Waaa,,, no calculus nece. The constant came from Watt himself after measuring what a horse could lift. Dynameters measure power against RPM, from which the torque values are trivially calculated.

Back to dduelin's comments about the peak power and redline - Exactly, the engine is merrily just starting to sing when WHAM! Lights out. If it's any consolation Ducati 2V's are like this too. If I'm not watching the tach and going by ear when I shift ( if I take a peek) I'm in the 6000-6200 range. If I watch the tach it's easy to shift right near the limit without detecting any cutout, but I don't usually watch the tach when I'm riding. I'm slowly getting used to the bike - if seems hard to judge that last few hundred revs by feel. Lately, I've only hit the limiter when I've been tired and kind of spacing out.

Something that would be interesting is if they did a dyno run at half throttle and another one at a quarter throttle. Then we could see the horsepower plot as it applies more to real world riding. It's not like we ride around at WOT all the time like their dynomometer test does.

Indeed. Some kind of 3D waterfall chart? For a while I had a Ducati S4R that seemed unusually stout at light throttle in the midrange. In the high range it was off the hook, but you expect that from an opened up Ducati 996 4V. One day a neighbor was visited by a fellow with a 06 Speed Triple. On paper the bikes are identical - same torque and horsepower curves. We swapped bikes for a little ride. On the road it was ridiculously lopsided - the Monster was a raging bull and the Triple was smooth and kind of gutless. Personally I was a little jaded with the Ducati surging and getting my ears rung by the Arrow exhaust, so I kind of liked the Triple. The Triple rider thought the Monster felt half again as powerful.

Anyone seen this? Thoughts?

"Two nasty lookin' switches over there, but I'm not going to be the first" Egor (Igor)

I'm interested but I not going to be the intrepid explorer.

 

[showkey]

An interesting comparison........the small turbo clean diesel RV guys discuss topic of power vs torque, climbing hills at peak torque or peak HP RPM, shifting early or late and dyno curves. The NC and diesel dyno charts have a lot in common like flat tongue curve starting from a low rpm and a relatively low rpm limit but much higher that a the old big diesels.

There is no consensus over there...........either...........but nobody want to raise the rpm limiter

 

[Mi_ka]

Well, I am a bit late to the party…
I read through the past 4 pages with the intention to answer most of misconceptions or misunderstanding spread across various posts but I gave up since it is too much typing and the discussion evolved in an obscurely half-wrong-half-right way.
Let me clarify I am no college educated guy so I cannot deeply use math and calculus since my (then unbeknown to me) peculiar gluten related chronic fatigue problem was messing my memory in a way I missed the chance to learn most of these basic math tools back in high school (if you know folks that have unexplained fatigue problems tell them to try some gluten free diet for ten days before jumping right into Prozak etc chemical mess therapies that doctors prescribe too easily these days).
However, I have been deeply interested in engine stuff since kid and I have a good understanding of how things work and in these internet days it is easy to google around for the math tools needed, thank god. I had been a dyno local support guy for a euro firm for 7 years and did a lot of thinking on the matter besides basics "WOT pull-printout" stuff that unfortunately most people only care about.
Anybody properly educated is welcome at shooting my thoughts down since I have always found this is the best way to better myself, through people properly in-the-know of stuff proving me wrong.

==

So, things are quite simple:
At any given moment our engines put out just one kinetically useful thing:
FORCE in the form of TORQUE which for us means force applied on an rotating medium (since our force originating medium is a rotating crankshaft, upon which it is based the core engine system that performs a sustained harmonic oscillation driven by thermal expansion forces of burning gasses in the cylinders).
By leveraging the generated Torque through gearing and wheels we apply the aforementioned Force on the bottom edge of our rear tyre to propel us into space over time by acting on the road surface.
Changing the lever used, in our case shifting gears and by modulating the throttle we alter the magnitude of this propelling force which is the TORQUE the crankshaft puts out on its power take off gear.
The magnitude of this applied force changes our kinetic status
either keeping our velocity steady (while our dynamic energy increases when we climb up a hill or friction increases due to headwind or load)
or accelerating us (when it is greater than needed to just overcome friction absorbing our movement energy/momentum - by the way do not forget that inertia fighting our acceleration also exists in all rotating parts of our machine besides its linearly moving mass through space).

So what accelerates us and keep us moving is our engine’s Torque output multiplied by gearing “levers” in the ‘unit construction’ contained gearbox.
Torque tells us how strong our engine force output is across its rpm functioning spectrum at any given moment at its crankshaft takeout point, not at the vehicle-road propelling interaction point.
Torque is expressed in units of force by lever length. It says nothing of how much Work can be provided in a given time window (as this is the way we comprehend movement, in time windows).
Work (defined as force x distance) is the useful outcome of manipulating our engine’s provided Torque to move us around - since we consider non-Work losses an inherent embedded quality in our moving around activities, we can consider for our case that Work = Energy provided by our engine (much energy is wasted not delivering work).
How much Energy our engine is able to provide loaded at WOT is a derivative of its WOT Torque output over distance it travels (crankshaft rotations) in a given time window. This is POWER, the rate of providing energy in this given time window. It is a derivative of what engines put out, Torque by distance traveled in this given time window which coarsely goes down as [force x revolutions x time x mathematic factors to address the circular nature of this motion] to provide us with these “Horsepower” unit numbers to compare and understand how much different Energy pumping abilities two engines posses.

The constant came from Watt himself after measuring what a horse could lift.

Horsepower tells energy pumping rate ability and not how strong an engine is at its crankshaft output point. For given rear wheel rpm (speed) we can leverage smaller Torque at the crankshaft takeout point (smaller engine) through gearing to come up with similar propelling force at the wheel by sacrificing more travel (higher rpm) as with all lever systems.
This bright guy of the past, Watts, calculated Horsepower as [Work (Energy) provided by a horse] to asses coal unit royalties and not of how strong a horse is since he already knew that a horse is about as strong as a… horse. He was interested in work (energy) output, not force (strength).
A small sturdy short horse is less strong than a tall sturdy one but it normally walks faster with its short legs. If we put it at a longer radius mill wheel than the tall one it will cope with the resulting lesser pulling load and do its full rotation at about the same time as the strong tall but slower walking horse. Result: Each one has a power of 1 hp though they are not of the same strength. This is why small high revving bikes achieve similar top speeds to bigger lower revving ones but have much worse acceleration if gone WOT while rolling at similar rpm and speed: To achieve similar acceleration they must shift down and leverage lower torque output through gearing down higher rpm up to their higher redline (if rotating parts inertia difference is about analogous to the big bike rotating parts which is usually not and in favor of the big bike).

Dynameters measure power against RPM, from which the torque values are trivially calculated.

Brake dynamometers measure applied roller torque directly by braking the drum while the engine is run at a steady state and calculate horsepower out of engine rpm and crankshaft torque after calculating gearing ratios.
Inertial dynamometers calculate “moments of roller inertia” differences to calculate the associated “moments of torque” needed to change the roller’s inertia momentum and come up with torque applied over the acceleration pull time window. Then it is the same gearing/engine rpm story to come up with horsepower and crankshaft torque.

… going up a grade at 83mph in sixth gear pulling 4500 RPM … pinned on the throttle…no "acceleration". By shifting to 5th the engine is now spinning 5600 and is now producing less torque but more power, the bike will accelerate …. We downshift to get more power.

To come to our question of best rolling acceleration provided by the NC the answer is simple: Use the best lever x force combination available.
The lever is the selected gear and the force is the torque output. Moving higher at the rpm spectrum by choosing a lower gear may move us in less torque output rpm territory but the longer lever provided gives a higher force output at the propelling wheel. By doing this we are harvesting many more (weaker) power pulses per distance/time unit travelled so we are putting down more energy in the same time window -> more power harvested from our engine (energy pump).

Now, on a flat road - (Florida is all flat roads it seems) I can accelerate faster short shifting than if I run to redline in every gear. *Why is that?

Best acceleration is provided by the best torque-gear combination product. For the NC, based on the posted graphs and without studying gear ratios it looks like if you span the engine between 5500-6500rpm you get about 4-5% less torque (ruler of the eye) than when using 4500-5500rpm. But you also get about 6/5 of the available lever for this 4-5% less torque output which is 17% bigger leverage at the same vehicle speed-load. But higher gearbox friction losses come into play with higher rpm through a lower gear. My guess is that any gain when accelerating from standstill is small by shifting near the red line and you probably feel that short shifting is faster because it is just much less stressing as an experience. May be wrong however but cannot think it deeper for now. A friend with a stopwatch could help you provide numbers.

Something that would be interesting is if they did a dyno run at half throttle and another one at a quarter throttle. Then we could see the horsepower plot as it applies more to real world riding. It's not like we ride around at WOT all the time like their dynomometer test does.

The quarter and half throttle comparative pulls are much more difficult than initially thought as a little over or under the quarter/half mark means big differences in measurements. If we take into consideration small TPS calibration/voltage differences even on same type bikes things become worse.
What is interesting to study is how well the injection/carburetor system responds to sudden throttle changes like acceleration tests through the gears. I have done something like that on a post here: DR650 on a Marolo Dynamometer : Technical Tips, Tricks & Maintenance
You can see that you can graph much more than just WOT pulls even in inertial only mode.
Even more in braked modes with extra sensors attached...

Some kind of 3D waterfall chart?
For a while I had a Ducati S4R that seemed unusually stout at light throttle in the midrange. In the high range it was off the hook, but you expect that from an opened up Ducati 996 4V. One day a neighbor was visited by a fellow with a 06 Speed Triple. On paper the bikes are identical - same torque and horsepower curves.

Power/Torque output has to accelerate the bike’s mass as well all rotating parts. The crankshaft of the Ducati is much less inertia to accelerate than the triple. Possible higher mass pistons/rods on the twin I guess are less than a match for the 50% more parts of the triple which should have higher friction losses as well.
Even if both engines put out same numbers on a braked dyno test, the less inertia engine would accelerate faster for the same bike mass and rpm/speed throttle opening. But what about the flywheel mass? The wheels mass? The gearing? Aerodynamic differences at higher speeds? It all gets really complicated with no industry wide established tests to asses anything else than WOT pulls to redline. Even with these simple looking WOT tests, different brands employ different ways to asses “losses” and embedded inertia to come up with an HP number which differs between brands/pulls/operators for a gazillion reasons. I have given up trying to educate people there is no such thing as RWHP “proper power”…

, you'd probably get maximum acceleration on this bike by shifting right before the rev limit cutout. *That way when you row through the gears you're utilizing the most of the hump in the HP curve. *

Think you are right.......and suspect it is not a coincidence the rev limiter is placed right above this max acceleration rpm...

I repeat my previous post yada-yada: Most probably soft valve springs, narrow plain oil bearings to save friction, rods on the skinny side to save reprocitating mass reducing friction even more mandate a low redline - all these to achieve stellar mpg as this engine is tuned for only low-mid optimum rpm breathing while retaining a useful real life engine output (can achieve close to stellar mpg on other modern engines but not at a real-life riding pace). Providing higher strength parts for higher rpm ability is just a waste of friction even if it would help staying in higher gear through canyon corners to be faster than others. This is other bikes territory. The NC seems to be fast enough-stellar mpg, period.

I think there may be a misunderstanding here about the relationships of torque, RPM, and horsepower. *Notice how the torque value for the NC700x is higher than horsepower value when below 5252 RPM? *Notice how the lines cross at 5252 rpm? *Well every engine in the world is the same way (assuming they actually rev as high as 5252). *Check every dyno chart in any motorcycle test and you will see the same thing. *The lines always cross at 5252. *It's simple math. *

5252 is just math magic and is a different number for other unit systems, pushing the cross point out of usual rpm spectrums but I am too tired to look into it again...

Exactly, the engine is merrily just starting to sing when WHAM! Lights out. If it's any consolation Ducati 2V's are like this too.*

All the 2V Ducatis are like this?
I had a week long travel experience 15 years ago on a Cagiva Elefant 750 and remember this granular-to-redline progression too even though I never hit the limiter, if it existed on that bike. I really want to know if all 2 Valvers are like this and how different are the 4 Valvers in comparison. Is the desmo (while great breathing at high rpm) any responsible for snatchy behavior under 3K or just the fueling?

the peak is so close to the hard limiter ... the 700 has virtually no headroom from peak to shutoff

Pretty digital bike? I want soft tape compression!

 

[showkey]

Just we you think the thread dies of natural causes....................it gets back up and starts walkin and talkin......

 

[ziggie]

Kind of like the walking dead lol.

 

[L.B.S.]

With the kind of generous effort spent on a post like that from Mi_ka, though, I'd happily read zombie threads all day long.

So many threads and posts are just shy of drivel, (all mine included, lol ) that it sure is refreshing to see one where the person bothered to articulate their thoughts in such a fashion.

 

[bigjeff]

, that it sure is refreshing to see one where the person bothered to articulate their thoughts in such a fashion.

Hey - I said the same thing - just without all the words. (jk lol)

 

[Mi_ka]

I am glad someone finds my mind burbling useful - I really hope someone properly educated will jump in refining the whole thing sharply distilling it down to 5-6 sentences that fully clarify all this I put down in a rather crude way.

Oups, forgot:

Last month in German forum someone has raised NC700X rev limiter to 7200 rpm.
That's the crazy guy with the top speed video in youtube.

Any links? Is his NC a manual one or a DCT? Any problems reported?

 

[bigjeff]

Any links?

https://www.youtube.com/watch?v=TcW7jzkuBmg

He hit about 121 mph at the best. Good run. I have had mine to 119. My CB to 135. Both on a GPS.

 

[wozza]

Hahaha....most of conversations on the subject of horse power is above my head.... Ah at least I'm honest about it I suppose....