Determining Redline

[kingmoochr]

for each gear, you calculate your rev drop based on your gearing for a certain speed, and aim for your shift to land you right at the beginning of your peak power, so that your following shift doesnt come so late that the next gear is missing the powerband. it really isnt that complicated, as your bike is usually configured to use a certain rpm via cam profile related to gearing. most high strung narrow banded motors arent bolted to a tall ratio trans. basically, if you feel you arent gaining anything by winding it past those last 2k rpm, you probably arent. just because theres a little red line on your tach doesnt mean its a target, just the point where the motor will likely experience catastrophic damage.

 

[Sidewalk]

Can a guy look at the Dyno print-out of his bike, study where the torque curve goes in relationship to the hp curve..... then determine what rpm point is the BEST for shifting for the most/best performance?

Not really, for a few reasons. Two of them being that on the street you are rarely at WOT (especially with a Bandit!) which is where a dyno is done. The power curve at WOT is different at half throttle (for example). For WOT performance, gearing is important. If you shift too late you are not taking full advantage because you are past the power peak, if you shift too early you will have even less power available to you because of where the next gear leaves you in the rev range. That is why on the track you are setting up your gearing all the time, trying to find the combination that lets you get the best performance through the majority of the turns, because you will be at a different RPM as you are rolling on each time.

 

[FickleBiker]

Okay.....
So if I'm willing to pay for a Dyno run, and I like to ride my bagger Bandit at a spirited pace through the foothills.... and catch up to the faster bikes and better riders outa the corners onto the straights,

what do I ask the Dyno operator to do for the most 'real world' information I can use to my advantage?

Do I ask for individual print outs for EACH gear,
and only at HALF THROTTLE,
and look for the range of max torque -or- max hp???

All that I have done in the past was put a pair of white pinstripes on my tach indicating the range where max' torque was to be found (@ WOT).

 

[kingmoochr]

well, you arent redlining and shifting in the corner, id imagine youre only doing that on straights, and if you are trying to go fast on a straight, you are wot. so id say wot. but unless you have other motives for the dyno run, you are throwing money away. just do some experimenting by changing your shift point a few hundred rpms from redline and see what feels the fastest. you probably know when your bike is pulling and when its not. theres no science to be had on the street like the track.

 

[gixxerboy55]

Okay.....
So if I'm willing to pay for a Dyno run, and I like to ride my bagger Bandit at a spirited pace through the foothills.... and catch up to the faster bikes and better riders outa the corners onto the straights,

what do I ask the Dyno operator to do for the most 'real world' information I can use to my advantage?

Do I ask for individual print outs for EACH gear,
and only at HALF THROTTLE,
and look for the range of max torque -or- max hp???

All that I have done in the past was put a pair of white pinstripes on my tach indicating the range where max' torque was to be found (@ WOT).

You really don't need to take your bike to the dyno, just shift slightly past peak horsepower. On your bike peak power is around 100 hp at 7650 rpm, so i would shift at around 8000 rpm.

 

[Sidewalk]

Okay.....
So if I'm willing to pay for a Dyno run, and I like to ride my bagger Bandit at a spirited pace through the foothills.... and catch up to the faster bikes and better riders outa the corners onto the straights,

So many variable there is no where to begin. The biggest being is you never know what is going to be right unless you are running the exact same corners over and over again, to precision. Odds are if you are doing that, you are racing professionally and you can try and communicate with your engineer on what gearing you prefer for each individual gear and your final ratio.

Or, just ride in the real world and enjoy the massive torque attack of your Bandit.

Only reason for you to get a dyno run is to see if you need to consider tuning out flat spots. But for choosing the right gear, you are not going to get that information from a dyno.

How often do you ride at half-throttle? Odds are you are rolling on from closed to neutral thottle all the way up to 80% to full throttle, Not much time spent at 50%.

 

[Burning1]

You really don't need to take your bike to the dyno, just shift slightly past peak horsepower. On your bike peak power is around 100 hp at 7650 rpm, so i would shift at around 8000 rpm.

That's not technically correct. Ideally, the best time to shift is when the next gear up will provide more drive than the previous gear.

Sport rider has an excellent article on shift points and power.

The short answer is that while horsepower is the best way to measure the peak power of an engine, ultimately acceleration is about how much torque is being delivered to the rear wheel. Rear wheel torque can be measured in foot pounds, just like engine torque. However, unlike engine torque, rear wheel torque is greatly effected by the transmission. An engine that produces a lot of horsepower but not much torque can be geared much lower than an engine that produces a lot of torque but not much horsepower. For any two given engines, the engine with higher peak horsepower can always be geared to provide more rear wheel torque.

When actually calculating rear wheel torque, you need to use the torque dyno graph from the engine, and compare that to your gearing, from engine through to the rubber. As we know, peak torque usually falls off before peak horsepower. However, because a lower gear provides more power to the rear wheel than a taller gear, it usually makes sense to stay in the same gear well past this point. Eventually torque falls off so much that shifting up a gear will actually provide more thrust at the than staying in the current gear. The steep part of this descent often happens near peak horsepower output, but not always.

On most bikes, maximum acceleration occurs by redlining first and second gear, then shifting progressively closer to the torque drop off point in each subsequent gear.

Of course, it depends heavily on the bike. A 600cc sport bike rider will usually do well to shift near redline in the first 4 gears. A 1000 rider will usually benefit from redlining almost every gear (liter bikes use tall gearing, often good for 100mph in first.) My BMW R1150R Rockster seems to prefer short shifting, often 1-2K before red line (at about 6K RPM.) The Rockster has both a torquey engine, and a short ratio gearbox.

Side notes: It's best not to hit the rev-limiter on any bike; avoid it if at all possible, because it sure as hell isn't a shift warning. Besides being bad for the bike, it usually doesn't provide a lot of power. Also remember that shifting isn't nearly as important as proper line selection. It's better to be off by 500-1000RPMs than it is to waste attention needed for other tasks.

 

[gixxerboy55]

That's not technically correct. Ideally, the best time to shift is when the next gear up will provide more drive than the previous gear.

Sport rider has an excellent article on shift points and power.

The short answer is that while horsepower is the best way to measure the peak power of an engine, ultimately acceleration is about how much torque is being delivered to the rear wheel. Rear wheel torque can be measured in foot pounds, just like engine torque. However, unlike engine torque, rear wheel torque is greatly effected by the transmission. An engine that produces a lot of horsepower but not much torque can be geared much lower than an engine that produces a lot of torque but not much horsepower. For any two given engines, the engine with higher peak horsepower can always be geared to provide more rear wheel torque.

When actually calculating rear wheel torque, you need to use the torque dyno graph from the engine, and compare that to your gearing, from engine through to the rubber. As we know, peak torque usually falls off before peak horsepower. However, because a lower gear provides more power to the rear wheel than a taller gear, it usually makes sense to stay in the same gear well past this point. Eventually torque falls off so much that shifting up a gear will actually provide more thrust at the than staying in the current gear. The steep part of this descent often happens near peak horsepower output, but not always.

On most bikes, maximum acceleration occurs by redlining first and second gear, then shifting progressively closer to the torque drop off point in each subsequent gear.

Of course, it depends heavily on the bike. A 600cc sport bike rider will usually do well to shift near redline in the first 4 gears. A 1000 rider will usually benefit from redlining almost every gear (liter bikes use tall gearing, often good for 100mph in first.) My BMW R1150R Rockster seems to prefer short shifting, often 1-2K before red line (at about 6K RPM.) The Rockster has both a torquey engine, and a short ratio gearbox.

Side notes: It's best not to hit the rev-limiter on any bike; avoid it if at all possible, because it sure as hell isn't a shift warning. Besides being bad for the bike, it usually doesn't provide a lot of power. Also remember that shifting isn't nearly as important as proper line selection. It's better to be off by 500-1000RPMs than it is to waste attention needed for other tasks.

No need to worry about hitting the rev limiter, redline is 9500rpm on the 1250. Interesting article, simply put you want to keep it in the meat of the powerband when in drag race mode, and you can feel it in the seat of your pants, in most cases you will shift a little past peak power.

 

[Burning1]

No need to worry about hitting the rev limiter, redline is 9500rpm on the 1250. Interesting article, simply put you want to keep it in the meat of the powerband when in drag race mode, and you can feel it in the seat of your pants, in most cases you will shift a little past peak power.

At track days, I do hear a lot of riders hitting the rev limiter. At the rev limiter, there is zero thrust at the rear wheel, little power below the limiter, and serious upset of the chasis. In first, over-revving the bike can provide useful power. In second and beyond, redline is where the engine usually starts seeing massive drops in power. It almost always makes sense to shift before the engine hits the red, both for reliability and for performance.

That's why I silently laugh at the rice boys who think they look cool bouncing off the limiter.

Knowing shift points is useful down the front and back straights of most race tracks. Usually, there's nothing to worry about other than tucking, shifting, and making sure you don't do anything stupid, like cutting off the guy on a Hayabusa who's planning to fly past you, and then park it going into the next corner.

On the street, I rarely ride my bike that hard. The 600 typically spends it's time in the 6K-8K range, unless I'm planning to pass someone.

 

[gixxerboy55]

At track days, I do hear a lot of riders hitting the rev limiter. At the rev limiter, there is zero thrust at the rear wheel, little power below the limiter, and serious upset of the chasis. In first, over-revving the bike can provide useful power. In second and beyond, redline is where the engine usually starts seeing massive drops in power. It almost always makes sense to shift before the engine hits the red, both for reliability and for performance.

That's why I silently laugh at the rice boys who think they look cool bouncing off the limiter.

Knowing shift points is useful down the front and back straights of most race tracks. Usually, there's nothing to worry about other than tucking, shifting, and making sure you don't do anything stupid, like cutting off the guy on a Hayabusa who's planning to fly past you, and then park it going into the next corner.

On the street, I rarely ride my bike that hard. The 600 typically spends it's time in the 6K-8K range, unless I'm planning to pass someone.

Yea it's funny new sportbikes have a lot of overrev, just wasting time and your motor trying to hit redline. And whats with the newbie riders bouncing off the rev limiter in neutral, i always feel sorry for the poor motor.

 

[Joebar4000]

Yes, it limits engine RPM. Longer stroke means more FPM which limits RPM.

No appreciable difference. In theory a longer stroke has more leverage at the crank. In practice it has far more to do with valve timing, intake runners and plenum volume.

Great post, and to elaborate on the above misconception - for a given displacement, torque doesn't change for a given combustion pressure, regardless of the stroke length.

As stroke increases, piston area decreases. So, sure, the longer lever exerts more torque, IF you have the same force acting on the piston. But you don't, cos it's smaller.

The reverse is obviously true - short-stroke motors have relatively huge pistons, so the net result is less leverage on the crank, but with much more force on the piston.

The results are a tie, as it turns out.

But longer-stroke motors tend to offer better cyclinder filling, and offer themselves better to providing a good burn, at lower rpm. To do this, cam timing, plenum shape and size, port length, blah blah is all geared to make the most of that, and by the reverse, for short-stroke motors, they're all about best overlap/intake length/cam timing for max filling at higher rpm.

If you look at torque numbers for same capacity bikes, you'll find the torque figures are frequently similar (as long as they aren't artificially limited by regulations or something), but the rpm at which they occur is dramatically different. Same torque at twice the rpm=twice the power.

 

[Sidewalk]

Yea it's funny new sportbikes have a lot of overrev, just wasting time and your motor trying to hit redline. And whats with the newbie riders bouncing off the rev limiter in neutral, i always feel sorry for the poor motor.

That over rev is nice when you don't have enough time to upshift for the next corner though, but at least have some propulsion left.

I don't get that option with a 2-stroke

 

[afm199]

It's not unusual at all for racers to bring a bike to redline momentarily and leave it there, rather than shifting up and immediately back down again. At corners such as T1-2 at Sears Point or 7-8 at Thunderhill. The upshift in this case can slow you down.

 

[Burning1]

It's not unusual at all for racers to bring a bike to redline momentarily and leave it there, rather than shifting up and immediately back down again. At corners such as T1-2 at Sears Point or 7-8 at Thunderhill. The upshift in this case can slow you down.

Great point and well understood. My complaint was about track day riders hitting the limiter on the back straight of Thunder Hill.