What gear is best - torque/speed

[witgen]

I'm amazed to notice that no one has stated the most obvious fact yet.

 

In practice torque on the rear wheel is always greater with smaller gear than it is with bigger gear no matter the rpm or engine torque. It's a physics fact. No matter what are the gear ratios and no matter how big is the dyno hump on the low end.

 

HP and torque measure totally different things and statements like "Torque is the mother of all", is just blatantly incorrect. High HP on high revs produces high torque on rear wheel and low HP on low revs does the opposite, unless you want to rewrite the physics.

 

How you perceive or feel the power is a totally different issue that is not to be confused with physics facts and actual measurable power/torque. It has nothing to do with it. For me it seems that @MGG is trying to rationalize these feelings with dynographs. In many cases our highly tuned and calibrated butt dyno tells us that torquey engine feels more powerful which it is not. It just feels like it because of lugging, sparse power pulses and all the other things fool our brains to think so. Comparing them in dyno will tell a different story.

 

Everyone who loves engine with "torque" is prone shift early. It has nothing to do with humps and bumps of measured torque. It's mostly about the fact that power pulses fuse together and you lose all the rumble and distinguishable power pulses that engine creates when revs get higher. When that happens you lose the sensation of power. It starts to run smoothly so the engine feels tamed and boring. It loses its feeling of "torque". This is especially noticeable in cross plane CP2 where power pulse characteristics are similar with V2 (that is another engine type usually perceived as torquey). 

 

So when people talk about torque they usually don't talk about it in the way it's measured. It's mostly a description about the characteristics on how the engine actually delivers power to rear wheel and how their brains interpret the sensation. So when you feel the urge to compare butt dyno "torque" with dynograph torque, keep in mind that you are comparing oranges and apples. 

[MGG]

12 hours ago, witgen said:

... @MGG is trying to rationalize these feelings with dynographs ... 

You bet, ... at least I shared data so that everyone can make their own decisions, and I put some nice colorful graphs for everyone to enjoy  

 

There is no question that running the motor at high RPM will move you faster but that is exactly the problem for me.  I do not want to move faster, I want to enjoy the ride without going over the speed limit or alarming every passerby. Taking it slower will not infuriate the police standing on the corner waiting for me to f***-up with one wheel in the air or the exhaust screammmmming past them. I am not on a racetrack to shift at redline no matter how much better those HPs might be.  Yes I will rev it up when needed, but not all the time, not even most of time.

 

My "butt dyno" is exactly why I love the T7.

With all the tips, opinions, and experience sharing in this thread, I found a target RPM/gear I will aim to be at next time I ride, and maybe I will be a better rider, and maybe I will be in a better position when I make mistakes.

 

Keep in mind that we did not talk about grip in this thread and we all know it plays a huge role. This is true especially on gravel roads and off-road trails. So all those HPs in the high RPM range will yet again be limited (just like the electronic nanny on other bikes). There is a balance to be found and the grip/RPM/gear/speed/skills is where it starts. For me this balance is closer to the low end RPM but for others it will elsewhere.

 

13 hours ago, witgen said:

In practice torque on the rear wheel is always greater with smaller gear than it is with bigger gear no matter the rpm or engine torque.

I will agree with the fact that I did not account for gear ratios for torque graphs and simply applied the curve I had to all gears, and this is wrong, I know. I am missing a proper dyno with gear details. Keep in mind that we do not know if the Cycle World graphs are take with deflated tire, at what altitude, using what fuel, etc.

So dynos are usually run in the gear that is closest to 1:1, excluding the primary drive ratio and sprockets. For the T7 this is probably the 5th speed. (5th Gear Ratio 24/22 = 1.0909)

Maybe I will crunch some numbers, maybe I will not, but it does bring in a nice aspect.

[MGG]

... Yes ... I could not resist.

 

Assuming dyno was run in 5th gear, ... I added the ratio of each gear without the primary drive and sprockets ... 

Funny thing is that I used the ratios to calculate speed and RPM. I should have used it for torque as well.

At least now there is a more complete picture. 

Interesting, much more interesting. ... 

 

 

[witgen]

@MGG I think you're slightly missing the difference of Power (HP) and Torque. Like I said in my first post, these two things describe two totally different things, but are of course interlinked. High torque means high horse power and vice versa. High HP doesn't mean high speed. You can have a 500 hp engine on a vehicle that has top speed 50 km/h (30mph).  Those things are called tractors and they are all about torque. 

 

Torque itself doesn't do a thing. It's just a force without any time reference attached to it. Power on the other hand is much more relevant, because knowing power we can calculate everything else, for example acceleration that we are mostly interested. Power ( kW or HPs, I'll use SI units because it's easier to understand sorry imperial unit users ) can be calculated with easy formula: Power (kW) = Torque (N⋅m) / Time (seconds). By looking at this you could easily think that the proof has been given that torque is actually mother of all. But it's not like that. For some reason people seem to think that engine torque is a constant and defines everything. And that's where everything goes wrong. People don't seem to realize that gearbox and final drive are essentially torque manipulators. With gearing we can create as much torque we want if we are willing to sacrifice speed. Lower the gear ratio and you have more torque on a rear wheel. Power on the other hand is "constant". There is no gearing that could create more HP. 

 

When we discuss the optimal gearing we should first define what we think is optimal. If it's torque on a rear wheel @110km/h that's easy. Just use gearing that is @9000rpm and you are golden. That of course would make the bike horrifying to drive. If we on the other hand are looking for best fuel efficiency we would need to know how driver is accelerating etc. If we want most pleasant bike to drive we would need to know what is your personal preference. If we try to create the best compromise between all these, well I think Yamaha did a very good job with this, unless you are driving mostly on pavement. In that case I'd say change a bigger front sprocket as suggested. 

 

When we start talking about a grip and other stuff, we open another pandoras box. Youtube channel Mike on Bikes has many good videos about tyre traction and what needs to be factored in (and loads of technical stuff on bikes in general). Getting those in to mix requires a lot more than just few graphs on Excel. And you are forgetting how suspension factors in? How about riding style? Problem on simplifying complicated issues is that you always end up making false assumptions. When you are ending up with questions like "why isn't data supporting my premises", you are in 99.9% of the cases using wrong premises or doing faulty conclusions. This case you aren't actually learning new things. You are doing the opposite. You are actually making your self a worse driver, because you base your learning on half truths and over simplified models. 

[Ray Ride4life]

2 hours ago, witgen said:

think you're slightly missing the difference of Power (HP) and Torque

May i give a short version?

Torque is to get moving, horse power is for speed.

KW is just a different kind of measurement that also applies to electric power.

[BikeBrother]

The sky is blue, like my bike, and the sun is shining through my visor. I'm following a meandering river. Birds feeding on the banks. I'm in a flow, cruizing. Then a biker appears in my mirror. He passes me. Its a CBR600, guy in full leathers. I follow him. He speeds up, but i stay on his tail. He thinks WTF... A sharp curve is coming, he shifts down 2 gears. I close the throttle a little, hang in the curve and accelerate. Enjoying the rumble from the exhaust.

On my way home i take a shortcut over a dusty gravel road. Standing up, steering on throttle, a long curtain of dust leaving behind. After 130 km back home, i did not think even one second about HP or torque. I'm just enjoying the full concept of my T7...

[Hibobb]

@BikeBrother Finally.... Riding is what it is all about.

T7 or TW200.... be happy!!

 

[witgen]

3 hours ago, Ray Ride4life said:

May i give a short version?

Torque is to get moving, horse power is for speed.

KW is just a different kind of measurement that also applies to electric power.

In a way, yes if we are talking about engine without gears. But that isn't the case as long as we don't have electric motorcycles and even then it's misleading because torque and HP are relative to RPM.

 

In practice high rev engines are more usable when trying to achieve maximum power. Thats mainly because torque and HP can't live without each other. More RPM means that we can push more fuel to a cylinder. More fuel, more bang. More bang, more power.  More power, more torque. Wide RPM range with torque max near red line also gives engineers possibility to use long first gear and close ratio gearboxes to keep inside optimal narrow power band which in the end makes things go quick. On regular roads you don't need to be quick. You need wide power band.

 

If we look at what is actually speed, it's basically just acceleration. At some point negative acceleration that is friction (= mainly air resistance) will match the torque generated by engine and final drive and acceleration will stop (or the engine hits max rpms). Then we have achieved top speed. So saying that HP is just for speed is not really very accurate, because without torque we can't build up speed. They are linked together. No torque, high HP, no speed. High torque, no HP, still no speed. 

 

Comparing torque (or energy in general) and power (HP, kW, V⋅A or what ever unit you want to use, they are all representations of energy used in specific timeframe) is in general bit strange. There is no power without torque so its like comparing kilometers to kilometers per hour ( or miles to miles per hour). It won't make any sense of telling people that my bike goes 100km. Or at least it would create a more questions than it would answer. On the other hand saying my bike goes 100 km/h would be much more descriptive. Torque without reference frame just doesn't make any sense. Combined with RPM and HP gives us much more relevant idea what torque actually means in that specific engine. Just by looking torque or HP not both together, you are concentrating only on one side of a same coin.

[Wintersdark]

6 hours ago, Ray Ride4life said:

Torque is to get moving, horse power is for speed.

KW is just a different kind of measurement that also applies to electric power.

The first statement is wildly incorrect.  It fits in some circumstances which makes it popular, but it's correlation not causation and it's an oft-repeated line that is very misleading.  It's coming off thinking as HP as only peak horsepower, and that's problematic.  Horsepower is always what matters; it's just what matters is the horsepower available at your current RPM and what you're pushing against (drag, rolling friction, and mass to accelerate).   A 1800cc 107ci Harley engine is hugely powerful (it's an 1800cc engine!) and it feels like it off the line because it's producing 40hp off idle, vs say an R6 producing ~13HP off idle.   Still, despite that feeling of power, the Harley has to contend with accelerating two to three times the mass, with higher rolling resistance, so while you can "feel the power" it doesn't actually accelerate fast for a motorcycle, and definitely doesn't accelerate faster than an R6 as the R6 very quickly starts generating way more power.    

 

The only real source of that idiom is that high torque (that is, simply powerful engines) while still generating a fraction of their normal output at idle are generating more power than small engines do at an equal RPM.   More boom = more power.  But *acceleration* - your ability to get moving and rate of speed change, when starting from either idle or low speed - is entirely based on horsepower vs. weight at that rpm as rolling resistance is pretty similar and drag is negligible at low speed.  Proof in pudding: Get on a "low torque" R6.  Spin it up to 8000rpm, and let the clutch out as fast as you can while keeping the front wheel down.  See how fast you accelerate from a stop with that low torque engine.  HP is what gets you moving, and (opposed by max engine RPM as a hard limit and HP vs. drag+friction as a practical limit) what determines your max speed.  

 

KW isn't a different kind of measurement really, it's just a different unit to measure work - and one that's much more practical and informative.  1HP = (roughly) 0.75KW.  Doesn't matter which you use though, as the end result is the same.

Edited April 28, 2022 by Wintersdark

[TexasT700]

51 minutes ago, Hogan said:

Close but not quite.

Torque is what causes the moving.

power is the relationship between torque and time.

Therefore power is what describes the performance of the vehicle because everything is related to time. ie miles per hour, seconds to 60.

Thus if all things are equal other then power, the vehicle with the higher power number will be faster with respect to top speed and acceleration.

 

Power is power and it doesn't matter if it's electrical or mechanical.  The standard SI unit is the Watt. Horsepower was used as a more intuitive measure to compare engine output to working horses in the olden days.

1Hp = 0.745 watts.

 

 

Oops, typo.

Decimal wrong.

1hp = 745 watts

[MGG]

Here is an article that does not answer the question of this post but clarifies some of the interesting aspects.

 

Power and Torque Explained — Math for Motorcycles

---

All about power (horsepower) and torque in motorcycles, and how they relate to top speed and thrust.

 

[MGG]

I had the chance to ride a bit off-road over the weekend and I tried to keep my engine RPMs higher.

For my type of riding I think I have started a small change, for the better.

• I think that the T7 became more pleasant when I keep it in 5th gear, 5-6K RPM  on flat terrain, and usually I would always be in 6th gear. Now I think that I will use 6th gear for highways and straight roads.
• On the more difficult uphill gravel roads  I tried to rev higher and kept it on 3rd gear, 5-7K RPM.
• On the trails and difficult terrain I kept it in 2nd gear without worrying about RPM and since clutch was used more often. This has been good for me since I can take my time going uphill or downhill and have plenty of power.
• So I only use 1st gear for taking off and going downhill where I would leverage compression to slow me down and not get into trouble.

 

There is also an aspect I did not consider in the graphs: throttle position. 

The dynos are run using full throttle, but in real life I am very rarely at full throttle so the actual power the T7 puts on the ground is greatly reduced.

This is some interesting read: https://optimumg.com/it-is-all-about-horsepower-or-is-it/

 

I think that a ride recorder would be good for me to understand more. Looking at GPS map, throttle position, RPM, gear would be nice.

I am just trying to be better at what I'm doing.

Your mileage might vary. 

 

Edited May 9, 2022 by MGG
added info about throttle position.

[Wintersdark]

23 hours ago, MGG said:

Here is an article that does not answer the question of this post but clarifies some of the interesting aspects.

 

Power and Torque Explained — Math for Motorcycles

---

All about power (horsepower) and torque in motorcycles, and how they relate to top speed and thrust.

 

 

A really, really important part of this article to note is that it's targetted directly at Harley riders.  That is, this:
 

Quote

The reason torque tells you more of the story is that if you assume a few things, torque translates to “pulling power below high speeds”. Let me justify this.

Here are the assumptions to make:

1. Assume a fairly “normal” gearing ratio on the bike, no matter the drivetrain, including front and rear sprockets, gear ratios, and wheel sizes.
2. Assume a “normal” RPM range. For any given size or class of engine, this is also a safe assumption (e.g. big bore bikes rev less, small bore bikes rev higher, assuming same number of cylinders)
3. Maybe even assume all the bikes are V-twins (which they mostly are for cruisers, which Harley-Davidson riders are mostly shopping for)

So with those assumptions, for most road bikes, you have to operate in the first four gears until you’re on the highway, when you can relax in fifth or sixth gear.

If you assume those things, and then I tell you “This V-twin road bike makes a peak of 120 ft-lb, whereas this V-twin cruiser makes a peak of 80 ft-lb”, you know that the 120 ft-lb one is going to be more arm-wrenching when you crack the throttle.

 

As soon as you're comparing dissimilar bikes, torque becomes a worthless value.  Gear ratios and wheel sizes are not "normal".  RPM ranges dramatically between different types of bikes.  And we're generally not talking about big bore V-twins at all.  When he says "road bikes" he doesn't mean generally all street bikes, but very specifically HD style cruisers.  Fun fact, with the new Pan America and the Nightster, this applies.  While they're also big v-twins, they've very different engines and bike weights.  Comparing torque between a Nightster and a Road King is silly. 

 

What he's saying really is that when everything else is very similar, you can use torque to compare power.  Oddly, he says "pulling power below high speeds" but that's both not really correct and completely useless in this specific case.  Got a Harley with a 108ci engine, and another with a 113ci engine?  Sure, you can compare torque values and extrapolate from there, and the differences will be largely the same at the low end and at the high end (wind resistance notwithstanding).   As he says, this is why HD uses torque.  Well, this and because it's a big number for a Harley, despite actually making laughably low actual power per displacement.   But you can for sure compare otherwise identical bikes just using torque, given that crazy list of assumptions.

 

Peak HP is more useful in all cases, but is also not all the picture.  He fails to really explain why - I can't help but feel this is mostly an apology as to why HD just uses torque without admitting to the rest of the reason HD just uses torque - but it's very simple.  What matters is the HP curve over the RPM range.  That graph is the only graph that has any impact at all.  You can see how much power the bike is able to make at any RPM level.  Then it's just a matter of comparing power output at RPM vs. weight (and drag at high speed).  

 

[Hibobb]

My only wish is that I could get a "Screaming Eagle Kit" for my T7

 

 

[Wintersdark]

3 hours ago, Hibobb said:

My only wish is that I could get a "Screaming Eagle Kit" for my T7

 

 

I'll pull your airbox snorkel out, swap the stock muffler for an open slip-on, scream out eagle noises, and charge you $1200 for the work - it's basically the same thing!

[Wintersdark]

4 hours ago, Hogan said:

Harley uses torque because it's easier to persuade customers that it means something, than it is to explain basic physics

It frustrates me, because it lends to people not really understanding what it means.  Used within Harley's context, it does allow you to make informed guesses about how two Harley's will perform relative to each other, but it also leads to people drawing a lot of very incorrect assumptions about it and comparisons about other bikes using torque specs.  It's my big pet peeve as is probably evident by this thread.  I just can't let it go, as we end up with the endless circle of incorrect assumptions repeated leading to other people assuming that's how it works because everyone else says it.  

[MGG]

Everyone has their own ideas about the power vs torque vs harley vs other bikes vs "you don't get it" vs "...add your sassy comment here..." ... and I am sure that these can be argued at length with good points on one side or the other.

 

I am just trying to improve my skills, and understanding what I can change to get there.

This analysis did help me get a better idea where the power is (or can be) and what speed/RPM I should target.

 

There is nothing like real life practice and that is where I am taking my next steps.

Next step will be an ODB2 tool to record my own usage to draw my own conclusions.

 

Thanks to all for your contributions.

[Wintersdark]

12 hours ago, MGG said:

Everyone has their own ideas about the power vs torque vs harley vs other bikes vs "you don't get it" vs "...add your sassy comment here..." ... and I am sure that these can be argued at length with good points on one side or the other.

 

I can't.  I just can't.

 

Power vs torque is hard fact, not opinion.  It isn't up for debate.  You can debate the value of people's easily packaged analogies, sure, but not what the two things fundamentally are.  This is why this frustrates me so much, as I said above.  There's nothing wrong with not understanding what they are - nobody knows everything after all - but this is isn't something that is fundamentally unknowable or vague.  They are very clearly defined values, and it's only confusing because there have been so many generally well meaning and plausible but wrong or incomplete attempts to package it up in a way that seems easier to understand.   There aren't good points on both sides of that, just people who understand what the terms actually mean and people who don't.  Fortunately, unlike so many things, there actually are hard, unambiguous answers because these are very well defined terms. It's not a mystery.

[Tenerider]

14 minutes ago, Wintersdark said:

 

I can't.  I just can't.

 

Power vs torque is hard fact, not opinion.  It isn't up for debate.  You can debate the value of people's easily packaged analogies, sure, but not what the two things fundamentally are.  This is why this frustrates me so much, as I said above.  There's nothing wrong with not understanding what they are - nobody knows everything after all - but this is isn't something that is fundamentally unknowable or vague.  They are very clearly defined values, and it's only confusing because there have been so many generally well meaning and plausible but wrong or incomplete attempts to package it up in a way that seems easier to understand.   There aren't good points on both sides of that, just people who understand what the terms actually mean and people who don't.  Fortunately, unlike so many things, there actually are hard, unambiguous answers because these are very well defined terms. It's not a mystery.

As long as people keep mixing up speed, acceleration, force, torque and power, topping it with rpm, this discussion will go on forever

 

You are complete right. This is not about opinions or common sense or handy explanations.

In this case, 4-5 simple equations are enough.