stunthanger.com
Engine basics => Engine set up tips => Topic started by: Dick Fowler on September 09, 2007, 09:03:16 PM
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I'm more than a little perturbed by the latest lock down of a thread I started. I presented a logical argument based on know physics principles (I do have a B.S. in Physics so I consider myself somewhat knowledgeable) that were my views on the subject. It contained no personal attacks or rebuttal of any previous comments by any other person.
If these type of post becomes the subject of censorship simply because someone doesn't comprehend what was written or misreads what I posted, then I will not continue to waste my time or the time of others by posting here.
Goodbye!
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I'm more than a little perturbed by the latest lock down of a thread I started. I presented a logical argument based on know physics principles (I do have a B.S. in Physics so I consider myself somewhat knowledgeable) that were my views on the subject. It contained no personal attacks or rebuttal of any previous comments by any other person.
If these type of post becomes the subject of censorship simply because someone doesn't comprehend what was written or misreads what I posted, then I will not continue to waste my time or the time of others by posting here.
Goodbye!
Dick
The thread was shut down because it was going nowhere good, and was not adding anything to this web site except you allowed Phil another opening to continue the "adding heavy parts adds additional horsepower to any engine" This is not true.
As I stated you can change torque to happen lower or higher in an RPM range , but this does not mean adding heavier parts increases horsepower.
If you are taking a shot at me by your statement that "someone doesn't comprehend what was written or misreads what I posted" I did not misread or misunderstand anything you said, and the thread was not locked because of your post.
It is not my wish that you leave but I will not let people tell others that you can add horsepower to any engine by adding heavier parts, which is the reason the thread was locked
Regards
Randy
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Against my better judgment here goes.
Phil, I'm sorry but my premise and presentation didn't demonstrate that heavier is better or "makes" more horsepower. In fact other than four stroke motors, heavier flywheels/cranks are of little benefit in our application. Heavy reciprocating parts are the pits on most engines. The piston is constantly being accelerated and decelerated and F=ma says that's bad. I don't think we see this the same way. The sustainable horsepower of an engine is controlled by the combustion process. Bigger flywheels do not affect the sustainable power output of an engine.
Randy, my comment regarding comprehension was directed to you. Your "rebuttal" was filled with what you thought I said... not what I said. The term inertia was used by the Suzuki guys. Inertia and mass are not the same but are related. If they increased the inertia 20% then it had to be done by either relocation of the mass farther from the center of rotation or adding mass. Either way that increases the kinetic energy of the rotating mass at any given angular velocity. I thought it was interesting but obviously others don't. End of story.
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""" The term inertia was used by the Suzuki guys. Inertia and mass are not the same but are related. If they increased the inertia 20% then it had to be done by either relocation of the mass farther from the center of rotation or adding mass. Either way that increases the kinetic energy of the rotating mass at any given angular velocity. I thought it was interesting but obviously others don't. End of story. """
HI Dick
Maybe you misread my post.
I agree completely with your above statement, and never said anything to the contrary, my point was this.....adding heavy parts to a engine does NOT increase horsepower.....
It can add kinetic energy, providing that the motor can still turn the heavier parts
The Suzuki advertising was interesting but really didn;t say that adding mass...intertia...or heavier parts added to the total horsepower of the motor...which was what the thread you referenced was about, and gave Phil an opening to come in and get it started again. I know it was not you that was pushing the idea that adding weight adds horsepower .
There is no question that adding weight within reason that the motor can turn, will add kinetic energy... That was the whole reason for my sawmill post. I agree with you on what you wrote about that also, Again horsepower and kinetic energy are two differant things, that was my point.
Phil doesn't ,and can't seem to see this.
Randy
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Wondered why I couldn't join in on previous thread!
Knowing commercial hypes and exaggerations and interpretations, "Increased torque delivery" could just mean smoother and more consistent, and due to the increased inertia of the system, i.e. stored energy, takes longer to slow down when a load is applied.
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I personally don't subscribe to increases "measured at the brochure" and would not put stock in what a Suzuki adman dreams up. But why are these discussions taken so seriously????? If YOU believe something, does it diminish your fun if I don't believe it also? Instead of trying to compose a theory based on your physics background, why not just research what's already been tested and proven many times over, many years ago. The S.A.E. has done all this research ad nauseum, and it has published many books worth of reports. Go down to the local university library and see what they have. Many large school libraries have many volumes. I would suggest looking online, but the S.A.E. charges hefty fees for its research material. y1
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I suspect what Suzuki means by "increased torque delivery" is that on a peaky, hi-revving, high-horsepower bike, maybe with a smaller engine like a 250cc or so, the increased inertia in the system(whether from weight or repositioning of balances or what) lets the rider use that extra stored kinetic energy to get a smooth start, instead of killing the engine at every other stop light. I haven't ridden in a long time, but I do remember that the smaller, peaky engines took some real practice with the clutch on the starts to get a smooth take off.
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I went to the website that was referenced in the other post. This part o the page.
1783cc, 4-valve DOHC, 54 degree, liquid-cooled, fuel injected V-twin engine designed for strong throttle response and massive torque output
112mm bore and 90.5mm stroke utilizing forged aluminum alloy pistons with short skirts, and cut away sides riding on chrome moly steel connecting rods
Unique new two-stage cam drive system creates a compact cylinder head design and reduces overall engine height and creates a lower center of gravity.
Crank inertia for the C109R is increased by 20% for increased torque delivery at low speed and for reduced vibration across the rpm range
Not exactly a small bore scooter.
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Some where this whole thing got off kilter, someone forgot that to increase HP or Torque means applying more energy. A flywheel, as used in cars, planes, and most internal combustion engines is a capacitor of sorts. It stores energy produced by the internal combustion process. Torque is a angular measurement of force. Somewhat like a lever. You can increase the force exerted by a lever by either applying more force to the lever or making the lever longer and applying the same force. A flywheel works the same way. Make it heavier and it will store more energy or you can make it a larger diameter and the effect is the same as the moment arm (lever) is longer. However in either case you have to inject more energy at a given RPM for this to happen. In a motorcycle and cars etc, torque multipliers are used, these are the gear boxes usiing the same principal as pully systems, I.E a smaller pully turning a bigger pully in efect multiplies the force (torque) at the larger pully, however the rotational speed is reduced. Heavier flywheels will not increase power unless a proportional amount of additional energy is applied (Burning more fuel or burning it more efficiently, or using a fuel that has a higher energy output / BTU) and of course this also means the HP will also rise.
the short explaination of why the max torque is reached usually at a lower RPM than HP, is because after a certain point the flywheel has stored all the energy it can and then any additonal gains are driven by RPM (you can pump more energy into the flywheel but you can make it spin faster) so the HP will still rise with the RPM increase, until the maximum combustion efficiency of the engine is reached and then HP falls off dramatically. So to keep everything running at the prime points of the RPM band gear boxes are used so the engine is spinning at the RPM where max torque is generated. It is a balancing act, between combustion efficiency, RPM and rotational mass. So if a engine builder wants to get more torque at a lower RPM they add some flywheel weight and for a given displacement, make the engine burn fuel better at a lower RPM, they actually take away from the combustion efficiency at higher RPM and add it lower down. either that or they would have otherwise they would have to increase the size of the bang at all RPM's. In the case of the suzuki it was probably not producing enough power down on the RPM band, because of any number of factors, so by tweaking the gearing, increasing flywheel mass and making the combustion more efficient (bigger bang) in the lower RPM's they got what they were after. But no matter what anyone says, that extra oomph at the bottom had to come from some where. Anyway my 2 cents without the brain numbing math
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Hi Guys. Flywheels are stored energy. They give up their energy in a transient (time averaged) event. Any flywheel represented by rotating mass inside the engine (prime mover) is used up in the transient acceleration and there after must be re - stored so the energy must come from the combustion process. Like Randy has stated, large flywheels can help move a heavy vehicle from rest but after the engine speed has become syncronized to the vehicle gearing the flywheel just becomes and encomberence to positive acceleration. All events relevant to humans are power and not torque oriented. We integrate over time. Human time is not an "instantanious moment of inertia". You don't get "massive low end torque" in any sustainable (steady speed) way from massive rotating mass in the engine. That is totally a product of knock limited BMEP.
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Dave A. - "Hi Guys. Flywheels are stored energy. They give up their energy in a transient (time averaged) event"
Tell us what concept you just described and the units that are used when this energy is "given up" on a time average basis.
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Dave A. - "Hi Guys. Flywheels are stored energy. They give up their energy in a transient (time averaged) event"
Tell us what concept you just described and the units that are used when this energy is "given up" on a time average basis.
Easy. Torque and time. Not just torque. Torque by itself does nothing unless it produces motion at a definable rate. We call the output of this equation power. Engines don't have "low end torque" anywhere but on a graph. A graph that is exactly (less system losses) the same shape as the vol eff or BMEP curve. Engines can have low end power depending on how well they handle high BMEP at low speeds. Any power rotating mass adds while the engine is not producing power came from the last cycle of the engines power stroke. This added power is really subtracted on the next cycle (to "re-spin the flywheel) or we could have perpetual motion in no time. An external flywheel that spins up from braking or some other collection of the product of the motion accomplished by the work (power) of the engine is a totally different discussion.
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I would have said Inject energy to get it spinning. Law of physics "An object that is in motion will tend to stay in motion until it ecnounters an external opposing force" In the weightlessness and vaccum of space that flywheel could spin forever (Stored energy) Another good one is "Energy can not be created or destroyed, it only changes form"
The short answer ;D
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I went to the website that was referenced in the other post. This part o the page.
1783cc, 4-valve DOHC, 54 degree, liquid-cooled, fuel injected V-twin engine designed for strong throttle response and massive torque output
112mm bore and 90.5mm stroke utilizing forged aluminum alloy pistons with short skirts, and cut away sides riding on chrome moly steel connecting rods
Unique new two-stage cam drive system creates a compact cylinder head design and reduces overall engine height and creates a lower center of gravity.
Crank inertia for the C109R is increased by 20% for increased torque delivery at low speed and for reduced vibration across the rpm range
Not exactly a small bore scooter.
I read that ad to mean they took away weight from the pistons. This means less energy is spent moving the pistons and more energy can be applied to the end of the line, in this case the flywheel.
It says nothing about adding weight anywhere, or a larger flywheel. It only talks about lighter pistons. Other than that we have no idea what esle was done to the engine and what they are comparing it to. Arguing over it is pretty pointless.
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I agree with you Doug, senseless to argue about an add that was probably writen by the marketing department, based on what they thought the engineer said at the lunch meeting that they showed up late to.(just my experience in my line of business).
it did say something about crome moly rods. so they probably would be a weight reduction as well.
hey with all those cubes i would say torque isn't going to be a problem.
when that guy with the electric bike gets out of the hospital maybe he should try a burnout with this one as well !
Dave jr.
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I think the discussion was prompted by the line
"Crank inertia for the C109R is increased by 20% for increased torque delivery at low speed and for reduced vibration across the rpm range"
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Just noted Doug's comment about piston weights. I don't agree with it considering that it's the reverse of Phil Bare's theory. Neither are correct.