| Author | Message | |||||||||||||||||||||||||||
     Mikej |
Not that it helps move the discussion along any (not that that's ever stopped me before  ), but yesterday on the S&S factory tour I saw more different kinds of dynos than I even knew existed. That was one interesting tour. Off to tour the Buell plant today, got invited as a guest on the special limited tour. The Homecoming isn't nearly as well attended as it was last year, but still a nice time, and not any where near as many Hogs here this year either. I'll have to see how the traffic is today since this is the official start of the holiday weekend. Bye. MikeJ (Two eyes, two ears, one mouth, using them in proportion today and yesterday.) | |||||||||||||||||||||||||||
| Bull |
Guys, I'm thinking on giving the engine in my M2'99 the following mods: A moderate porting job on my Thunderstorm heads A new set of forged pistons (slightly increased compresion) S1 cams for mid-high end Mikuni HSR 42 and a K'N airfilter White'bros e-series muffler Will this be enough for let's say 100 rwhp or do I have to make more radical mods. If more, what?? Do I have any weak points in my suggested mods, have I forgotten something?? Id rather not go for big bore or stroker... Please feel free to give me suggestions on how to reach the magic 100 rwhp! Thanks in advance /Jojje | |||||||||||||||||||||||||||
| Aaron |
Bull: look here for the results from a similar setup. 10.5:1 compression, S1 cams, stage 1 head work. He has a race kit exhaust is all, and you're planning on a Mikuni where he's kept the CV. AW | |||||||||||||||||||||||||||
| Hans |
Blake, you robbed me from freewheeling mind time last days. You mingled two systems in your "proof" that the power needed for higher speed is proportional with the cubic of speed. It is only quadrated. De speed plays no part in the equity anymore except for the amount of drag. The speed keeps constant if the trust equals the drag. If there was no drag any speed would be maintained without any power. The power is only used to overcome the drag at given speed. If higher speed is asked the drag becomes quadrated with the (air) speed higher and so needs the trust needed to be higher proportional to the quadrated air speed. With other words: If a rocket gives a certain trust the speed is not part of the equity. It burns exactly the same amount of fuel with high or very high speed of the rocket. It delivers the same trust (= POWER) at various speeds of the rocket burning the same amount of fuel. (For a bike there is of course power needed to bring it to higher speed and to overcome the linear growing roll resistance.) Hans-freewheeling-again. | |||||||||||||||||||||||||||
| Aaron |
Hans: the proportionality of speed increase to the cube of the horsepower increase is a textbook formula, I found it in a book. I was just trying to understand why it's a cube function instead of a square function, and Blake helped me with that. At least mathematically. I can assure you, that relationship is real, I used it extensively in figuring out the LSR bike and it always came out dead nuts on. Here's a quick example ... a typical Japanese 600 sport bike makes what, 95hp, and can go roughly 160, right? Let's see how much power it would take to go 190 with the same bike (or on a bike with similar aerodynamics) ... 190/160 = 1.1875 (18.75% faster) 1.1875 cubed = 1.675 (67.5% more power required) 1.675 * 95 = 159hp. Hmm. I remember reading a test on a Hayabusa when they first came out. Seems it was 156hp and 192mph. Pretty damn close. A little better than the math says, but then again, a 'busa is a little cleaner aerodynamically than a 600 sport bike. This is just one of many data points I have that support this relationship. Most I can't share with the world  But ... using this basic relationship, I had calculated the RR should've been able to go 158.7. Until the last day, we had done 158.5 several times. How Richard got 161 out of it on the last day is still a mystery to me. Rule of thumb: it takes 33% more power to go 10% faster. AW | |||||||||||||||||||||||||||
| Hans |
Aaron, You did sure a very precise and good job and thanks for your explanation and patience. BUT I took as an example a light Cessna with an 100 HP engine making 100 knots and a modern fighter, airodynamical much slicker but with more surface and much heavier making 1000 knots and not needing 100*100*100 Hp but maybe more around 100*100 HP. Following your thumb rule it would need 297.000 HP At the other side of the spectre I made estimations for a "trekschuit": a ship for passengers that was pulled, two centuries ago, by one horse through the Dutch canals. Estimated that the easy going horse made 1 horsepower good for a speed of 4 MPH. Roughest estimation let me think that an 8 HP Diesel could double the speed. Nah. Found on Internet http://www.analyticcycling.com/ForcesSpeed_Page.html a program for cyclists. Results pretty close to the thumb rule. I was just wrong. Got that out of my throat. Phew. Gooood luck. Hans. | |||||||||||||||||||||||||||
| Aaron |
Hans: your mistake is that you're cubing the horsepower. You should be cubing the speed increase and applying that to the horsepower ... 1000 knots / 100 knots = 10.00 (10x the speed) 10 cubed = 1000.00 (requires 1000x the horsepower) 1000 * 100hp = 100,000hp (100 cubed would be 1,000,000hp) My apologies for the commas where y'all use periods, and vice versa. It's an American thing. It's very non-intuitive, I agree! But it's true. The 33% more hp required to go 10% faster comes from cubing 10% ... 1.10 cubed is 1.33 AW | |||||||||||||||||||||||||||
| Hans |
Aaron, There came some light in my confused mind. Thanks again. The delimiter thing: Almost accustomed to the American/English way using periods and commas there is still a tendency to swap them and sometimes that is done one time too much. However: The constant C in the equity P=C*Vcubic is influencable and you knew that also very well. Good luck again. Hans. | |||||||||||||||||||||||||||
| Bobby |
Hi Guys, I am new to your group but have good contacts with the many years I have with Harley-Davidson dealership as a parts manager. A good friend of mine whom run a shop in Ventura, CA. The shop name is Shakedown Street. They have a kit in the works to get 130 HP out of your twin buell, not Blasts. Fuzzy is the guys name, and his number is (559) 644-5001. Have a good ride, Bobby. | |||||||||||||||||||||||||||
| Rashomon |
It does make a difference what gear you run in on a Dynojet or other inertial dyno, for two different reasons. The first has been pointed out; the Buell/Harley transmission is noticably more efficient in fifth, where the power passes through no gear pairs, than in other gears, where it passes through two. That's probably a 3 percent difference right there. Secondly is the effect of flywheel inertia on the overall inertia load of the system. Dynojet fudges flywheel inertia in its software, and over reports rear wheel horsepower to compensate, so the numbers are closer to a brake dyno. Rotary inertias sum proportionally with the square of the gear ratio connecting them, so the effective inertia of the bike (crankshaft) and dyno drum vary with gear ratio. (In designing complex systems, this square function in rotary inertias can lead to situations where a little high-speed electric motor weighing a few ounces powering a massive piece of equipment may be the dominant inertia in the system). As for Dynojets, with good repeatability, you should be able to back calculate the crank inertia by looking at the variation in power output in different runs in different gears, given that you know the gear ratios. In practice, crank inertias are far more dominant than wheel inertias on motorcycle performance in a quarter mile run. Evo Big Twins were slowed by about 0.3 seconds in a quarter by their truly massive flywheels (compared to Japanese levels of crank inertia), while current Japanese motorcycles have chopped flywheel weight to the point where the returns are minor for further crank inertia decreases. | |||||||||||||||||||||||||||
| Aaron |
"Dynojet fudges flywheel inertia in its software, and over reports rear wheel horsepower to compensate, so the numbers are closer to a brake dyno." It must take some huge assumptions to do that, particularly since it can give horsepower without even knowing the engine rpm. So it has no real information about gear ratio in that case. "Rotary inertias sum proportionally with the square of the gear ratio connecting them ..." Now THERE'S a non-intuitive concept. Seems like gear ratio would just change the mechanical advantage on the rotating mass, which would wash out since the rpm also changes and in the opposite direction. But if it's a squared function, that changes everything! So if I'm reading you correctly, the faster the drum is spinning, the more the dyno software fudges numbers upwards because it's assuming a taller gear ratio must be in use, and therefore it's assuming more effective inertia in the drivetrain due to the squared relationship with gearing? If that's true, you're saying there's a whole bunch of guessing going on. 'Course, as long as the guessing follows consistent rules, and the results are only used for comparing similar bikes, maybe that's okay. AW | |||||||||||||||||||||||||||
| Blake |
Great discussion; sorry for skipping out for a few days. To the questions and hot debate... Aaron: Let me rephrase my poorly worded question/scenario concerning power loss on an inertial dyno run. I may have confused the issue with mention of "higher gear" when I meant to address the effective power loss due to inertias of the engine/drivetrain prior to clutch output. A flywheel (like the engine's and primary's inertia) is akin to a capacitor in a simple electrical circuit; like you said it's stored energy (work stored as kinetic energy). It's the rate at which we store that energy where the power loss get's affected. I'm saying that the slower spin-up of the engine's own inertia (including the primary drive) in a high gear dyno run results in more power getting to the tranny input and ultimately the rear wheel (less is being used to accelerate the engine's rotational inertia). A simple mental experiment to illustrate... Given a flywheel (the basic real world example of rotational inertia), does it take more power to accelerate the same flywheel, from 0 to 8000 rpm in 5 seconds versus 10 seconds? I think you'll agree the answer is "yes." And in fact it takes twice as much power to accelerate at twice the rate. Note that in both cases, we've done the same amount of work (W), and have stored the same amount of energy (e). So in the first case we have P1=W/5sec=W/5 where in the second case we have P2=W/10 and we see that P1=2*P2. Accelerating the engine's own inertia at twice the rate would likewise take twice the power. That lost power never reaches the rear wheel of an inertial dyno. Recall the rotational (actually "angular") system equivalents to the linear parameters and equations. Parameters with metric units
Equations of Mechanics, Dynamics, Kinematics
Rashoman: Thanks for the info. I had assumed that the dyno did nothing to correct for inertial losses of the drivetrain. Come to think of it now though, the operator on a Dynojet usually selects the engine model/year from the computer's listings; that must pull in the proper inertias. | |||||||||||||||||||||||||||
| Blake |
The above is still in-work, check back later for the complete sickening work of silliness. | |||||||||||||||||||||||||||
| Aaron |
Blake: my Dynojet software (which I believe is the latest) has no knowledge of bike brands and models. Yes, it forces you to create a directory structure for the results in which they suggest you build around the make, model, and owner's name, but you can type in anything you want, it certainly doesn't recognize it and act on the data. | |||||||||||||||||||||||||||
| Jmartz |
The one and only... /{image} | |||||||||||||||||||||||||||
| Jmartz |
/image (S&S 4x4} | |||||||||||||||||||||||||||
| Jmartz |
\image {S&S 4x4} | |||||||||||||||||||||||||||
| Jmartz |
Last attempt...  | |||||||||||||||||||||||||||
| Rocketman |
Blakey : I'm beggining to think you don't have a woman at home Rocket in England | |||||||||||||||||||||||||||
| Rashomon |
I'm not intimate with Dynojet source code, I just know they fudge from some long ago conversations with Mike Kreikemeir who largely came up with the current Dynojet dyno from the uninstrumented inertia drum that Mark Dobeck at Dynojet used to use for transient carb tuning. I'm fairly sure the fudge factors amount to some standardized assumptions on wheel and crank inertias that likely mean that a Dynojet: 1) Generally overreports actual rear wheel delivered horespower (generalized fudge to match brake dynos) 2) Relatively underreports power of very heavily flywheeled machines such as Big Twins 3) perhaps really overreports delivered power for very lightly flywheeled machines such as GSX-R750s, etc. But as pointed out above, for tuning purposes, where you're comparing set-up A on the dyno to set-up B, this matters not a whit. As for the square effect of the gear ratio, think of in terms of energy. For a rotary system, kinetic energy is proportional to the square of rotary speed (rpm or w), just as its proportional to velocity squared in a linear system. Thus, with a two equal flywheel system connected by a 2:1 gear ratio, the twice speed flywheel will always hold 4 times the energy. But if you apply this to an overall 10:1 first gear ratio on a motorcycle, the effect of the crank inertia is 100 times that of the wheels -- which is why reducing wheel inertia doesn't buy you much at a dragstrip (though it helps with both weight loss "m" and inertia "I"), and why all purpose-built racing machines have no more flywheel than necessary for rider control and reasonably smooth running. And doesn't Dynojet operation require an engine speed sensor on a sparkplug lead? Thus the software always knows the actual overall gear ratio, because it also knows drum speed, and thus can apply standardized factors for crank and wheel inertia that have differing effects in different gears. It would be interesting to look at the differences in Dynojet-indicated peak power for the same machine with and without the speed sensor attached, and in different gears, to get a hint of what the underlying code actually does! | |||||||||||||||||||||||||||
| Aaron |
Rashoman: what you're saying makes sense and it has me thinking ... not concluding yet, but definitely thinking. The Dynojet can take power measurements without the tach pickup lead (which can go to either the promary or secondary side of the coil). If you take power that way, it will only plot it against speed, not rpm for obvious reasons, and you get no torque curve. The torque it's showing is engine torque and to know that it has to know rpm (or rear wheel torque and gear reduction, and gear reduction is extrapolated from engine rpm), so it kind of makes sense. I've gone back and forth, tach pickup and no tach pickup, and there's no difference in the power readings, or at least no difference outside the normal range of repeatability. AW | |||||||||||||||||||||||||||
| Schemky |
Jmartz, Christ man, this is awesome (you can't see it but I am bowing to you as I keyboard this message). Keep everyone posted on how this 4x4 works out. I hope you get a dyno run and share your recipe. | |||||||||||||||||||||||||||
| Jmartz |
Schemky: Its S&S display motor not mine. Sorry | |||||||||||||||||||||||||||
| Blake |
Rocket: I arrived home at 6am on August 26th. I thought I broke her. She laughed at the idea. See you on the Salt. I'll try to round up some real beer for you. | |||||||||||||||||||||||||||
| Schemky |
JMARTZ, Well. . . . . pooot!! | |||||||||||||||||||||||||||
| Pammy |
Jmartz...that's not the one and only...Cycle-Rama built 2 100" motors a few months ago. Pammy | |||||||||||||||||||||||||||
| Tripper |
Pammy, did u sell motor #2? If not, any plans to put it in your X1? | |||||||||||||||||||||||||||
| Jmartz |
Pammy: You were the only person unaffected by rain on the ride back from S&S. Was disapponted to discover a 3.5 stroke is not possible due to interference between the rods and the nuts on the shafts. Maybe S & S will adopt the current monolithic design of HD soon. They have on their higher volume BT units. Guess my 4 x 3.5 motor with titanium rods will remain a just a thought. Jose | |||||||||||||||||||||||||||
| Rocketman |
Blake : Never mind the beer, what about the Florida weed Rocket in England | |||||||||||||||||||||||||||
| Blake |
You silly bloke, I live in Texas. You want I should bring some cactus juice (aka tequilla). |
