I rode my first 600 today

[OB_BusaGeek]

The 'Busa is a monster and I love it, but let's be fair to the 600s.

Kirk,
Let's use your numbers. 45ft lbs of torque @ 10,000 rpm vs. 99 ft lbs of torque @ 6750 rpm. If the two bike were at this condition AT THE SAME SPEED (600 in a lower gear). And the two bikes had tires of the same diameter. The 600 is about 100 lbs lighter. By my calculator, the 600 will pull with 80% of the force that the busa will. Not the same, but closer than the numbers look. It's hard to compare torque number between bikes of different character, that's why we use HP numbers. Torque is raw turning force, HP is a little more abstract. Always remember, you can manufacture torque (change gear ratios), but HP will not change.
Torque is what you are doing now, HP is a measure of what can be done.
A "torquey" bike is not one with high torque numbers (otherwise a 500cc GP bike would be considered a torque monster), it's a bike that makes similar torque across most of the RPM band. Then, it's any speed in any gear.
You can get a lot of enjoyment and performance from a 600, but you have to manage youre RPMs carefully. On a big bike, you can make a few mistakes and get away with it.

 

[OB_Dr Busa]

You can't change torque nor horsepower by changing gear ratios. Torque is (simplyfied) hp/rpm. So no matter which gear you're in the torque and hence the horsepower of the engine at a specific rpm will remain the same.

 

[OB_BarryW.]

Dr.B:
An engine's torque-speed relationship is constant for a given throttle setting, that is not what gear ratios effect, they effect the torque-speed relationship of their
output element (rear wheel on bikes). Shaft power is constant across a gear reduction, torque is not. A gear ratio allows you to trade speed for torque, but the product (torq*speed) is the same value (power) on each side of a gearbox (power in = power out).

B_Geek:
I'll be the first to admit that I could take any 600 at any track (maybe not Daytona) and stomp my Busa's butt. I think the issue on this thread is focused more on the driveability on the street/twisties where you can't memorize the layout or have predetermined brake and throttle markers.
Your calculations are correct, but one thing to bear in mind is the torque-speed relationship at the rear wheel. For your example, because the Busa is "torquey" and is pulling a taller gear than the 600, it has a broader band of speed for that particular gear, whereas the 600 has "short legs" and will require a lot of gearbox activity to hang at 80%-of-Busa acceleration level. On unknown terrain, this is really a hindrance since these gearchanges will be unforeseen. Will a 600 carry more corner speed than a Busa?...you betcha, simple physics. Is the Busa easier to ride fast in unknown terrain?...you betcha, IMHO

[This message has been edited by BarryW. (edited 27 June 2000).]

 

[OB_Dr Busa]

So what you're saying is that you can get different torque graphs on the dyno with different gear ratios ?

 

[OB_BarryW.]

No, that's not what I'm saying if you're referring to getting different ENGINE torque curves. Like I said, the relationship between engine torque and speed is fixed for a given throttle position. If you're interested in the torque curve at the WHEEL (there's no reason to be) then, yes changing gear ratios will change this.

On an inertial dyno (e.g.DynoJet 150) the back tire inputs a torque to accelerate a known rotational inertia (the roller) at some resultant angular acceleration (t=Ia), this is the rotational counterpart to the linear F=ma relationship. The software to calculate the engine's power curve takes the measured engine speed data and roller speed data and calculates the engine's power like this: From the measured roller speed history, the software calculates the acceleration (differentiation of angular velocity with respect to time yields angular acceleration) of the roller. Using the rotational inertia constant for that particular roller, the torque on the roller (not the engine-remember this) is calculated as discussed above. Recall, power is the product of torque and angular velocity, therefore the software now has enough information to calculate power being sent to the roller, which IS the same as the power from the engine (less parasitic losses). It can then output a graph of power vs. engine speed. Since it now knows engine power as a function of engine speed, it backs out the engine torque from the power=torq*speed calculation. This is calculated engine torque, not the torque that the roller experienced.

The effect of different gear ratios is to change the amount of torque AT THE WHEEL and it will manifest itself in an increased or reduced amount of time required to accelerate the roller. Think of the difference you'd experience in conducting an inertial dyno test in first gear as opposed to sixth. Obviously, the first gear run would accelerate the roller rapidly, but not to a very high WHEEL SPEED, even though the engine only knows it went from idle to redline as fast as it could (i.e. full power). Now, a sixth gear test will accelerate the roller slowly, but to a much higher wheel speed, and again, the engine only knows that it went from idle to redline as fast as it could.

Hope this makes sense. I read your profile so I took the liberty of throwing around some equations that may or may not be familiar to you yet.




[This message has been edited by BarryW. (edited 27 June 2000).]

 

[OB_BusaGeek]

BarryW,
I have a degree in Mechanical Engineering, so the equations are old hat to me. I agree with you wholeheartedly. And, yes you can change the torque at the back wheel just by changing gear ratios. But, the dyno wont be fooled because it asks the operator what the gear ratio is so it can factor the gear ratio out of the equation. So the torque curve from the dyno wont change.
Think about this. The dyno calculates rear wheel acceleration. Then converts it to REAR WHEEL TORQUE. Then through some calculations it comes up with what theoretical torque would exist at the crank if no drive train losses existed. If this dyno spits out a number like 99 ft. lbs. of torque, there is actually no place that that torque can be measured, at the crank there is about 115 ft lbs, at the rear wheel there is about 400 ft lbs (in first gear). So, the torque value spit out by a dyno is really just a de-geared version of REAR WHEEL TORQUE so that people can compare two number to each other. But, if you wanted a compareable number, why not just use HP. In my opinion torque number are really just fiction. On the other hand, the shape of the torque curve is incredibly important for tuning purposes.

 

[OB_Hapo]

...hey, the bottom line is, the little girly bikes is gonna LOSE!

 

[OB_BarryW.]

BG:
I really don't think there is a even a provision for gear ratio input in the software, it's simply not needed. For it to be meaningful, you'd also have to know the tire diameter and have some subroutine to estimate the change in diameter as a function of speed, each individual transmission gear ratio (for full sweep testing with upshifts), as well as the primary reduction ratio between the crank and clutch, WAY more information
than a dyno tech. would have for all the bikes they test. And the level of complexity
required to estimate the complete powertrain parasitic torque losses through "some
calculations" would be the subject of multiple doctoral dissertations and is currently leading edge automotive powertrain computer simulation technology, well out of reach of anyone but a major research organization or a large automotive OEM. I've co-authored an SAE Technical Paper on the subject of manual transmission efficiency trends, and there's a lot of things going on.

Even though the power curve you get from a dyno sheet shows power as a function of engine speed, understand that it is REAR WHEEL POWER as a function of engine speed, not CRANKSHAFT POWER, not even an "estimate" of crankshaft horsepower. The torque curve reported on an inertial dyno sheet is calculated off of the "apparent" engine power curve, and as such, it is a derived, not a measured value. On an engine dynamometer (where power absorption is usually taken off the output shaft for a bike engine since there's no clean way to attach a driveshaft to the crankshaft) the measured parameters are engine speed and shaft torque. Power is then calculated. Again, this is not crankshaft horsepower in the same sense as can be measured on automobile engines because the transmission has robbed some power. My personal experience with one of my dragbike engines had it making 175rwhp on an inertial dyno and 183bhp on a water brake engine dyno. Within instrumentation calibration error limits, this said that losses in the chain, wheel bearings, and 15"x26"x10" drag slick accounted for a power loss of 8hp.

Yes, the shape of a torque curve is incredibly important. Remember the torque at the wheel causes the acceleration that you feel. Roadracing engines can trade some peak horsepower for more low end torque and cut faster laps due to driveability issues. And "driveability" in this sense means they actually have more area under their rear wheel torque vs. speed curve for a lap's distance, or put differently, they've put more POWER to the ground. Believe me,
I've spent my entire career dealing with powertrain testing and design and the whole torque vs. speed thing requires a lot of thought.

Cripes, 8pm and I'm still at work instead of drinking beer and putting my centerstand on
the Busa. I'll check the thread tomorrow, but for now I'm outta here!

 

[OB_Hapo]

...not me! I just went down to the Suzuki dealer and wrote a few checks and Ill spank ya! Wheee this thig is a gas! You all run your programs, I'm gonna run some gas through this thing!

 

[OB_Hapo]

That Hapo...gets a bit out of hand some times....I think he is crazy, but don't tell him I said that! And thanks to all the Geeks out there that have made things like the Busa not only possible, but cheap and plentiful as well!

 

[OB_SlowHand]

Best Cycle parts, you are right, but that's not the point. The performance is there on the 600s, but they are basically boring to ride, particularly after riding a Busa.

If I intended to race Willow Springs, I would buy an R-6. I would probably be faster on it than on my Busa. On the street, I wouldn't waste time on one because of the lack of torque. Boring.

 

[Guest]

I went across Deals Gap in 2nd, came back over in 3rd, couldnt tell a diff. It just PULLs.

 

[OB_Ripper^]

There is not much choice in small displacement bikes when purchasing new. I use my sons R-6 at times and find it a very light and very quick but find it uncomfortable to ride and a little to light.I still like my big Suzukis with inline fours. A lot of weight and a ton of power! Still any 600 is a great beginers bike!

 

[OB_cereal_killer]

Kirk, you observations are valid. My experience with 600s riding in packs was that I was always at full throttle or fully on the brakes. If revs fell beloww 8500 RPM I could just kiss the group I was in goodby at the next straight. Feeling for the limits of adhesion on a 600 is stone axe simple compared to a bike like a busa. If I carried in to much speed and my rear end started to step out I could just widen my line a smidge and stay at full throttle.I garauntee that I had at least as much fun duking it out in the pack with other 600s, timidly ridden 900s, and a damn good rider on an EX500. BTW, I owned a crappy FZR 600 with a FOX rear shock, yosh pipe, 150mm rear tire, ignition advancer, jetted carbs, and prabably a real 75-80 horsepower, painted like a marlboro/yamaha YZR 500(matte black frame and wheels, red+white paint, lots of decals, good imposter). Im assuming the laws of physics havent changed too much in 4 years so take it easy on me.