| Author | Message | ||
     Jaimec |
Whenever anyone talks about performance improvements, they almost always jump right to the exhaust, followed by the intake, followed by the microcode in the FI controller. What about lightening the flywheel to get quicker acceleration/deceleration? Or has Buell engineering already made the flywheel as light as feasibly possible? Plusses and minuses, anyone? | ||
| Pariah |
I think it would be great, as long as it wouldn't worsen low RPM (clutch slipping) operation... a lower mass flywheel might be more prone to stalling. But this could be compensated out with a re-map, maybe sacrificing some fuel economy? | ||
| Ccryder |
ANd the 1125r doesn't spin up fast enough for you? You can change things like clutch baskets to reduce the rotating mass. If you reduce the flywheel then you are playing with balance of the engine. Time2Work | ||
| Rfischer |
You can also reduce the torque by doing that and end up with a motor that makes HP "in the corner of the box", but can't get there for lack of grunt. Bin there, dun that..... | ||
| Jaimec |
That's why I ask these questions. Thanks. Might be okay for a competition race bike, though. | ||
| Carbonbigfoot |
It wouldn't surprise me if those factors are already optimized to within a fraction of what's possible. Rotax has a good bit of experience... R | ||
| Ccryder |
I'm sure many, many hours were consumed trying to get the balance just right with the flywheel and the balance shafts. My 25rt is almost as smooth as my 90deg V-4 ST1300. | ||
| Teach |
Probably my old age, but I can't imagine trying to get more power out of this engine for street riding.... But it is fun for me to read about it!!!  | ||
| Jaimec |
Actually, lightening the flywheel wouldn't give it more power... just change the characteristics of the power it already has. I suspect it would rev up quicker, but be harder to launch without stalling. Also, more engine braking on throttle roll-off, and a rougher idle. Most of the negatives would mean nothing on a race bike, as they spend most of their time near redline anyway but it would definitely hurt it as a street bike. | ||
| Rfischer |
My experience with lightened flywheels in the sportster-based lump my race tuber had was that while the motor spun up faster if not under load, it was slower to accelerate on the track. Simply wasn't making the torque it could otherwise make to pull in the mid-range. When I went to Bob Johnson at J.E.T. [badweb sponsor] to build a new motor, first thing he did was throw the cut 'wheels away [along with most everything else the shop I had been using put in..]. When he got done I had a motor putting out 115 ft./lbs at the RW that pulled Ducs off the corners like they had shifted into neutral. Stock-weight S&S flywheels. | ||
| Slypiranna |
The flywheel is the means of torque storage to be unleashed within the next rotational event. Unless you wish to add a fourth counterbalance to this engine, leave it to Rotax/er...alone. Intake, exhaust and...is where the additional powers lie in wait!  | ||
| Ducxl |
Most Ducati guys'(not me) go for swapping out their flywheels for aluminum ones. I don't know about the 1125r but my Duc flywheel can be removed without major engine disassembly.So,it's a cheap mod. From "Nichols" performance site: Nichols Manufacturing was the first to develop and manufacture aluminum flywheels for Ducatis. In order to cover the entire Ducati line, we are the only manufacturer who makes six types of flywheels. Further more, our flywheels increase performance more than any others. Before you spend time and money on increasing your engine's horsepower, why not get the most performance from the stock configuration without sacrificing reliability. Decrease rotating mass and you will increase performance. This also reduces the gyroscopic effect of the components, which means your motorcycle will move from side to side with less effort. Your stock flywheel weighs more than 4 pounds. Our flywheels weigh 9 to 12 ounces(!) depending on the application. They are CNC machined from 6061-T6 aluminum and use steel inserts to trigger the timing sensors. The assemblies are balanced. These flywheels will free up existing horsepower and torque, and increase engine braking. | ||
| Bob_thompson |
Ducxl, if I am not mistaken isn't the Ducati's engines closer to perfect balance being a true 90 degree twin and thus less likely to be out of balance with an aftermarket flywheel? Better yet is the BMW boxers. Does Ducati use any sort of balancers as our Rotax uses? Just wondering, Bob | ||
| Jaimec |
Can't see what flywheels have to do with counter balancers... By the way, the new BMW 1200s have a single counter balancer to cancel out rocking couple vibration. Our engines have three... one for each cylinder to cancel primary and secondary imbalances, and one to cancel the rocking couple. | ||
| Slypiranna |
Rotational "mass"/counter rotating couples/ has a lot to do with all that rotates within a power plant. Stored energy is more so important than anything else herein (or weaken the torque curve)...but if you alter the rotational mass, you will alter the counterbalance. And no, I do not buy the advertisement above, at least for which this engine subject involves. Back to thread... (Message edited by slypiranna on December 05, 2008) (Message edited by slypiranna on December 05, 2008) | ||
| Ducxl |
perfect balance Ahh,life is great...Zen | ||
| Ducxl |
and thus less likely to be out of balance with an aftermarket flywheel? WHOOPS!...I didn't consider that question...Elaborate? | ||
| Ducxl |
THe flywheel helps keep the engine running. Isn't the Harley engine NOT supposed to be able to run? | ||
| Dentguy |
"..but if you alter the rotational mass, you will alter the counterbalance." Not if the rotating mass part is a bolt on flywheel that is not used for engine balance. | ||
| Slypiranna |
 Maybe this will help a little; "When forces are applied to a rotating member in a pulsed manner or in such a manner that the direction of such forces changes during application of the forces, as happens with the crankshaft of an internal combustion engine, such forces have the potential for inducing rotational imbalances in the rotating member even if the member is statically balanced. Crankshaft counterweights, a flywheel, and often a harmonic balancer are affixed to a crankshaft to minimize the vibrations which result from the nature of the forces which act on the crankshaft. In a reciprocating piston engine, the power pulses or firing strokes are pulsed and cyclic. However, the effects of the counterweights, flywheel, and harmonic balancer are continuous. In engines with relatively numerous cylinders, such as six, eight, or more, the power pulses are more evenly spaced over the crankshaft rotation cycle. In engines with relatively fewer cylinders, such as four, two, or one, it is difficult to evenly time the power pulses whereby these engines tend to vibrate more than engines with more cylinders." I'm leaving mine stock but I'd love to read one of you test a lighter one.  | ||
| Dentguy |
My point was that just because a flywheel is part of the rotating mass doesn't mean it is used to balance the engine. Most are balanced as separate units. So changing it out to a lighter one doesn't mean it will definitely throw the engine out of balance, though it will change how it runs. Most modern engines are internally balanced and don't use the flywheel as a balancer. The flywheel weight and inertia are used to get through the next compression stroke. A lighter flywheel has a harder time getting through the compression stroke and will do what Jaimec said "Actually, lightening the flywheel wouldn't give it more power... just change the characteristics of the power it already has. I suspect it would rev up quicker, but be harder to launch without stalling. Also, more engine braking on throttle roll-off, and a rougher idle." I think I would leave the flywheel alone, especially if you are riding it on the streets around town. |
