HP and torque curves nice website

[twocool]

http://mota.no.sapo.pt/bikes/GS500E/gs500e.html

http://mota.no.sapo.pt/bikes/GS500E/dyno1_big.jpg

Just for interesting info...a couple of nice dyno runs on GS500 stock and modified....

Power is flat from 8000 to 10000


Rest of the website is nice too.....makes you think the GS 500 is best motorcycle ever!

Cookie

[Phil B]

Nice. but do note the separate torque graph. Most definitely NOT flat between 8-10k



And, for why people care:

http://www.vettenet.org/torquehp.html

"Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve "


presumably, you can exactly substitute "motorcycle" for "car", and the same applies.

[burning1]

Yeah, the GS is really cammed for good midrange performance. Torque falls on it's face above 8K RPM.

I have a dyno chart with AF/Torque/HP for my stock GS500. Was slowly dieing when it was taken, but really shows how bad torque suffers up top. Will post it up.

[twocool]

Nice. but do note the separate torque graph. Most definitely NOT flat between 8-10k



And, for why people care:

http://www.vettenet.org/torquehp.html

"Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve "


presumably, you can exactly substitute "motorcycle" for "car", and the same applies.

well...ya gotta read that whole website...and the follow ups.........basically the conclustion is HP is the KING........torque is handled by gearing..
ya also gotta figure where the torque goes when you shift form one gear to the next higher gear.

Another conclusion is the further up the rpm for the max torque the better...this makes sense...but makes a hard bike to ride.......needs close range gears, and always high RPM....


The guy on the other website points out, that even as the torque starts to drop off  as RPM go higher in a cetrain gear...it is still better to take that gear all the way to redline before shifting...because the torque at the next higher gear is lower than even that....

Cookie

[twocool]

http://www.allpar.com/eek/hp-vs-torque.html

Here's the guy who kind of disputes the torque deal..........

The thing about he GS500 is we have more gears...and a pretty wide operatining range of RPM....and a petty flat power curve......

Cookie

[twocool]

http://www.datsuns.com/Tech/whentoshift.htm

Here's a guy who is big on the torque curve deal...but ends up contraticting himself at the end....

He starts off saying you have to shift so as to bracket the max torque...but ends up saying you have to bracket the max HP...

Hmmmmmmmmmmm.

Cookie

[twocool]

http://www.welltall.com/ymc/discovery/car/shiftpt.html

Yet another site......

Everybody seems to agree on two major points

1. acceleration follows the torque curve (i.e. the Most torque gives the greatest acceleration)
2.  The optimal shift point is redline..........because it puts you at the highest posible torque on average.

Cookie

[burning1]

And every single one of those articles come to the wrong conclusion, especially when applied to motorcycles. If you map the torque curve of the GS to the gear ratios, you'll find that the optimal shift point (the point where the next gear delivers more driving force to the wheel) comes well before redline. This is true on most RR bikes, nevermind the GS500.

http://www.sportrider.com/tech/146_0402_art/index.html

On most bikes, the optimal shift-point for acceleration out of 1st is at the rev limiter. For each gear beyond that, the shift point moves closer and closer to torque peak.

Generally, torque comes a few thousand RPM before redline on most street tuned bikes. Horsepower peak comes between redline and torque peak, and power falls off a cliff before you reach redline. The purpose of redline is not to act as a shift point, but to warn you that you are reaching an engine speed that is likely to result in engine damage. A little over-rev is typically provided above peak power, for situations where a shift is not desirable, but the driver needs to stay on the throttle E.g. extreme cornering, especially on a motorcycle where leaning lowers the effective gearing ratio of the bike.

[burning1]

Edit: Post is in error, updated post available below.

[twocool]

And every single one of those articles come to the wrong conclusion, especially when applied to motorcycles. If you map the torque curve of the GS to the gear ratios, you'll find that the optimal shift point (the point where the next gear delivers more driving force to the wheel) comes well before redline. This is true on most RR bikes, nevermind the GS500.

http://www.sportrider.com/tech/146_0402_art/index.html

On most bikes, the optimal shift-point for acceleration out of 1st is at the rev limiter. For each gear beyond that, the shift point moves closer and closer to torque peak.


Generally, torque comes a few thousand RPM before redline on most street tuned bikes. Horsepower peak comes between redline and torque peak, and power falls off a cliff before you reach redline. The purpose of redline is not to act as a shift point, but to warn you that you are reaching an engine speed that is likely to result in engine damage. A little over-rev is typically provided above peak power, for situations where a shift is not desirable, but the driver needs to stay on the throttle E.g. extreme cornering, especially on a motorcycle where leaning lowers the effective gearing ratio of the bike.

Best article so far......takes some factors which are particular to motorcycles (comapred to cars) into account..........

Cookie

[twocool]

I just ran the numbers using the Sport Rider spreadsheet, using the dyno chart posted above for a stock GS500, stock gearing, 140/70/17 rear tire.

The GS has a very midrange heavy power curve, and a big jump in gearing ratios between 4th and 5th. It results in some interesting shift points.

1st > 2nd - Shift at redline - Typical, 1st is much much lower than 2nd.
2nd > 3rd - Ideal shift is 9850RPM - this one is pretty important, a little over-rev is okay, but you suffer above 10500.
3rd > 4th - Ideal shift is anywhere between 8500 and 10250 - it doesn't make much of a difference, but you suffer above 10250.
4th > 5th - Ideal shift point is 10,100RPM - There isn't much room for over-rev, and as typical you suffer above 10500 or so.
5th > 6th - Ideal shift point is anywhere between 9050 & redline.



This more or less mirrors my experience racing the GS - in stock form, it *really* doesn't benefit from being revved to the moon... Though had I charted this out, I probably would have modified my 4th to 5th strategy a little.

Nice!!

Interesting findings...like sort of uneven gear spacing....lot of revs available beyond peak HP...not necessarily useful.....

But...shift points seam to bridge the max HP point (plateau on GS500) or even to the high side of the HP max(9000 to 10,000), but way above the the max torque point (7500).

Again its the "driving force" at the rear wheel not the engine torque...

Cookie

[burning1]

You'll notice in the chart... The ideal shift point almost always lands you at torque peak in the next gear up. So, when shifting, think less about where you are in the power band, and more about where you're going to end up.

Shift points will always be above max torque peak, and will typically be a little above maximum horsepower. Remember, with a flat torque curve horsepower increases with RPM, and for horsepower to fall as revs increase, torque has to be falling off so fast that with each RPM, any increase in engine speed reduces torque more than it increases horsepower.

The ideal shift point typically occurs when torque has fallen off so much, that the reduction in driving force by shifting up a gear is more than compensated for by the reduction in engine speed moving us back towards torque peak. As you can see from the above chart, the crossover point typically occurs well past torque peak, but what you'll also notice is that in each gear, the ideal shift point almost always puts you at or near torque peak in the *next* gear up.

Another perspective of torque and horsepower.

Humans make surprisingly large amounts of torque; a typical 140lb rider will produce something on the order of 80ft lbs of force at the crank of a bicycle during the strongest part of their stroke. However, we can't really pedal so fast... Our ideal cadence (RPM) is about 90 in most cases, and a typical maximum is often around 150 or so. So, despite producing gobs of torque, we don't produce huge amounts of power... Our example rider here, only makes about 1.3 HP at 90RPM.

Because we really can't spin the crank so fast, we have to significantly gear up the output of the rider. So, for example, at 30MPH, we might only produce 15lbs of driving force at the rear wheel, vs the GS500s 550lbs (using a calculated gain ratio of 9.4 and a 140lb rider standing on the pedal.)

Torque peak it's self isn't so important - what's most interesting is the torque curve, because that shows how much power is produced over the entire range of engine speeds.

Think about it this way: If you have a bullet and a rock and you've got to throw something, choose the rock. If you have a rock and a loaded gun, always choose the gun.

[twocool]

You'll notice in the chart... The ideal shift point almost always lands you at torque peak in the next gear up. So, when shifting, think less about where you are in the power band, and more about where you're going to end up.

Shift points will always be above max torque peak, and will typically be a little above maximum horsepower. Remember, with a flat torque curve horsepower increases with RPM, and for horsepower to fall as revs increase, torque has to be falling off so fast that with each RPM, any increase in engine speed reduces torque more than it increases horsepower.

The ideal shift point typically occurs when torque has fallen off so much, that the reduction in driving force by shifting up a gear is more than compensated for by the reduction in engine speed moving us back towards torque peak. As you can see from the above chart, the crossover point typically occurs well past torque peak, but what you'll also notice is that in each gear, the ideal shift point almost always puts you at or near torque peak in the *next* gear up.

Another perspective of torque and horsepower.

Humans make surprisingly large amounts of torque; a typical 140lb rider will produce something on the order of 80ft lbs of force at the crank of a bicycle during the strongest part of their stroke. However, we can't really pedal so fast... Our ideal cadence (RPM) is about 90 in most cases, and a typical maximum is often around 150 or so. So, despite producing gobs of torque, we don't produce huge amounts of power... Our example rider here, only makes about 1.3 HP at 90RPM.

Because we really can't spin the crank so fast, we have to significantly gear up the output of the rider. So, for example, at 30MPH, we might only produce 15lbs of driving force at the rear wheel, vs the GS500s 550lbs (using a calculated gain ratio of 9.4 and a 140lb rider standing on the pedal.)

Torque peak it's self isn't so important - what's most interesting is the torque curve, because that shows how much power is produced over the entire range of engine speeds.

Think about it this way: If you have a bullet and a rock and you've got to throw something, choose the rock. If you have a rock and a loaded gun, always choose the gun.

all good points...a little optimsitic for the bike rider....1.3 HP would probably be World champion...most novice riders are at about 1/4 Hp....most good riders in the 1/2 HP range ....1Hp only possible for short bursts or champions...

Little HP means need for lots of gears...like 21 speeds for modern Bicycleses...(little HP but fairly big speed range...certainly from 0 to 40 MPH and higher down hill...........

Motorcycles get by  with 5 or 6 gears

cars with 4 or 5

Old cars: three speeds

Old V8 often had two speed automatic trans....(plenty of Hp and torque and who cared about economy back then?)

Cookie

[burning1]

BTW... It looks like there is some parts compatibility between the GS500 transmission, and the SV650/DL650 (and probably 1000) transmission. Could be useful for racers, especially combined with a high output engine to even out the 4th gear spacing. I'll do some more research and see if one of those bikes has a suitable cog that might be swapped in place of ours.

[Phil B]

I just ran the numbers using the Sport Rider spreadsheet, using the dyno chart posted above for a stock GS500, stock gearing, 140/70/17 rear tire.

Awesome chart, thanks!

but might you rework it, for a fully stock 130/70/17 rear tire?

[Phil B]

PS:

1st > 2nd - Shift at redline - Typical, 1st is much much lower than 2nd.
2nd > 3rd - Ideal shift is 9850RPM - this one is pretty important, a little over-rev is okay, but you suffer above 10500.
3rd > 4th - Ideal shift is anywhere between 8500 and 10250 - it doesn't make much of a difference, but you suffer above 10250.
4th > 5th - Ideal shift point is 10,100RPM - There isn't much room for over-rev, and as typical you suffer above 10500 or so.
5th > 6th - Ideal shift point is anywhere between 9050 & redline.

Looking at that chart, it rather seems that, depending on your top speed target, either 4th gear is irrelevant, or 3rd is. Seems like if you're heading for 100mph+, you may as well just redline 3rd, and then go straight to 5th?

[burning1]

I'll run the numbers tomorrow for a 130/70/17, but I expect that while it will change the speed you shift at, it won't actually affect the RPM, and even then, I wouldn't expect it to make a major difference.

You could shift straight from 3rd to 5th, but I think you'd benefit more from a good speed shift through fourth than you would a double clutched shift from 3rd to 5th, since there really doesn't seem to be a real benefit from skipping 4th.

One obvious conclusion from this chart is that if you are going for top speed, it probably doesn't make sense to shift into 6th with stock gearing. IIRC, the GS won't do more than 115 or so stock, anyway.

[the mole]

The thing that looks interesting to me is that from a pure performance perspective, you could leave out 3rd and 5th. What little you'd lose would (I think) be more than compensated for by two less shifts. This is assuming a re-worked shift drum so that you'd only have four gears.
This actually reinforces my pet hate with the GS, the 6-speed box. Its obvious from the chart that 5 well-chosen ratios would be more than enough for a stock GS (and probably a lot of other bikes).
Extra gear ratios are just a fashion thing...race bikes have more gears, so its 'cool' to do the same on a road bike, except that the race engine has a narrow torque band and might actually need them.

[twocool]

Lots of good stuff coming out of the chart and this discussion!

The torque/shift point chart, of course represents a (racer) rider in a drag race or on a long straight after a tight (slow) corner.....

If we were to look at the shift points I use in recreational riding...or (worse) the upshifts recommended in the manual..

1 to 2 @ 12 MPH
2 to 3 @ 19 MPH
3 to 4 @ 25 MPH
4 to 5 @ 31 MPH
5 to 6 @ 37 MPH

We're already in 6th and not even past the first gear speed on the chart!!!  (but I guess that would be driving like Grandma)

I notice also that the chart begins at 20 MPH........I think the idea of going to a lower overall ratio  (15 th) would benefit at speeds lower than 20...like zero to 5 or zero to 10MPH..(I would think that for drag racing, that first 0 to 20 would be almost as improtant as the rest of the curves)

I am too dumb to figure how to do these plots.....But I would like to see one with the standard tires and gearing, and one with a 15 th .......to see if it really makes any significant difference......and then to consider recreational riding vs racing.......

I think for recreational riding you can pretty much pick (almost) any gear at any time!

1st goes from 0 to 48
2nd goes from 12 to 67
3rd goes from  19 to 86
4th goes from  25 to 95
5th goes from 31 to 125 (theoretical)
6th goes from  37 to 141 (theoretical or down hill, down wind)


I would say that most of us ride somewhere in between the "granny shifts" shown in the owners manual, and the "all out race shifts" shown in the torque curve shift point chart.  For recreational riders,  don't think the actual gear ratios, nor the actual shift points make a bit of difference. (The most I'm ever gonna do is downshift and rev up to like 8500 to pass somebody, or get out of somebody's way...........Or just once in a while for fun.......

Cookie

[gsJack]

Mmmm, first of all a change to a 15T front sprocket with stock tire sizes puts your top gear ratio about half way between stock 6th and 5th gear ratios and might just suit your everyday riding needs best or it might just correct for a larger rear tire size like it presently does for me.  A change to a 14T front sprocket gives a 6th gear ratio approx equal to the stock 5th gear and you might just as well drop a gear and roll on.  Back when I rode with some big twin friends a lot I would just leave my GS in 5th gear on the freeways to match their roll on speeds, worked nicely.

Those graphs of burning1 showing optimal rpm ranges are very interesting but a lot to remember.  Back in the mountain years I would just keep my stock GS between 7-9k rpm sometimes for hours on end and found that to give best GS performance, with a modified GS maybe 7-10k rpm would work nicely.  Contrary to some of the GS dyno graphs published here all of the ones I've seen over the years show stock GS HP peaking at about 8500 rpm and dropping sharply after that  Shifting a GS at 10% over peak, about 9-9.5k rpm, will drop you down right on top of the torque curve around it's 7k rpm peak.  Best you can do with a stock GS I think, get a 600 if you need more.



I can't imagine shifting at the speeds shown in the owner's manuals, my 97 wouldn't even start to pull below the 4k rpm needed for a smooth launch, the 02 pulled from 3k with it's 3 circuit carbs.