- #1
scotzur
- 5
- 0
This may be a question better suited for the mech/aero engineering section, but I figure I'll start here.
MY question relates to a phenomenon that I just can't seem to figure out.
It has to do with a flywheel in a car.
With a lighter flywheel i would expect to see more horsepower at the wheels at ANY RPM. Although i personally have never seen this phenomenon firsthand, oftentimes on a dynometer (device for measuring horsepower and torque) a heavier flywheel will result in HIGHER power at low RPM's and eventually a lighter flywheel will yield higher results at higher RPM's.
I mean it would just stand to reason that a heavier flywheel would have more inertia than a lighter flywheel and would therefore need more energy to accelerate from (for examples sake) 1000 to 3000 RPM. The same "extra energy" would be required to accelerate the flywheel from 5000 to 7000 RPM. I don't see any reason why a heavier flywheel would show more power at lower RPM's.
The ONLY explanation I can think of is that with a heavier flywheel the individual "pulses" of force created during each combustion stroke of the motor are "smoothed out" and stored in the flywheel and released to the drive train over time. If this is the correct explanation, can anyone explain that in more mathematical terminology?
And if this is correct, is the car TRULY putting more power to the ground with a heavier flywheel, or is it just "tricking" the dynometer into seeing more power.
Here is a link to a website that discusses just this phenomenon, but does not go into any explanation:
the article is interesting, but more importantly, for a visual, you can click on the 6th picture down on the right hand side (it's a dyno chart) to enlarge it; then click on the image once it loads to zoom. This is a chart of a dyno pull done in first gear; Interestingly the dyno pull in second gear reveals that the phenomenon is almost completely gone.
http://www.europeancarweb.com/projectcars/0109ec_bmw_m3_clutch_flywheel/
MY question relates to a phenomenon that I just can't seem to figure out.
It has to do with a flywheel in a car.
With a lighter flywheel i would expect to see more horsepower at the wheels at ANY RPM. Although i personally have never seen this phenomenon firsthand, oftentimes on a dynometer (device for measuring horsepower and torque) a heavier flywheel will result in HIGHER power at low RPM's and eventually a lighter flywheel will yield higher results at higher RPM's.
I mean it would just stand to reason that a heavier flywheel would have more inertia than a lighter flywheel and would therefore need more energy to accelerate from (for examples sake) 1000 to 3000 RPM. The same "extra energy" would be required to accelerate the flywheel from 5000 to 7000 RPM. I don't see any reason why a heavier flywheel would show more power at lower RPM's.
The ONLY explanation I can think of is that with a heavier flywheel the individual "pulses" of force created during each combustion stroke of the motor are "smoothed out" and stored in the flywheel and released to the drive train over time. If this is the correct explanation, can anyone explain that in more mathematical terminology?
And if this is correct, is the car TRULY putting more power to the ground with a heavier flywheel, or is it just "tricking" the dynometer into seeing more power.
Here is a link to a website that discusses just this phenomenon, but does not go into any explanation:
the article is interesting, but more importantly, for a visual, you can click on the 6th picture down on the right hand side (it's a dyno chart) to enlarge it; then click on the image once it loads to zoom. This is a chart of a dyno pull done in first gear; Interestingly the dyno pull in second gear reveals that the phenomenon is almost completely gone.
http://www.europeancarweb.com/projectcars/0109ec_bmw_m3_clutch_flywheel/