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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
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06-05-2018, 01:37 PM | #43 | |
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06-05-2018, 01:40 PM | #44 |
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For everything that spins in the drivetrain, the amount of horsepower released from inertia changes is a result of the difference in power that it takes to accelerate that part from rpm 1 to rpm 2 in time t. The time it takes for the car to accelerate itself usually makes the amount of freed power from rotating part inertia changes a negligible amount. For the driveshaft it is essentially 0. It could be weightless and the biggest benefit to acceleration would still be the static weight loss.
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06-05-2018, 02:02 PM | #45 | |
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06-05-2018, 08:34 PM | #47 | |
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06-05-2018, 08:55 PM | #48 | |
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06-05-2018, 09:49 PM | #49 |
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I found an in depth article explaining the physics and doing the math on everything. It was specifically for mustangs but principals still stands.
A 30lb shaft dropping to 15lbs with same diameter on a 13sec car would avg an extra 1/4hp for the run. However a flywheel going from 25 to 12.5 bcs of the larger diameter would net about 3.5hp over a 13second run. I guess I need to find something else to throw money at. |
06-05-2018, 09:52 PM | #50 | |
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Also, those estimates sound about right. |
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06-06-2018, 12:53 AM | #51 | |
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And by the way, the gains of a flywheel weight reduction are more. You remove most of this weight from the outside part of the flywheel , so it has a much less inertia. |
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06-06-2018, 01:33 AM | #52 |
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There are three bits important to rotational kinetic energy.Mass, it's distance from rotating center, and rpms. For engine flywheel it's all three. For driveshaft, only first to some extent with little left of later two. For wheels mostly first two.
It's not location pre or post transmission that increase or decrease need of energy spent to spin up some part. In this case it's difference of rpms that by chance are different for engine or post gearbox tranny parts, that affects that. Though drifeshaft also lacks diameter in addition to lower rpms it's spun at, for lightening to be very effective. If driveshaft had been spun at 10x faster rpms due different gearing from gearbox / final drive, results would be different. Rpms (and diameter), not location. Think all of them as flywheels of different shapes/masses/spinning speeds and think what impacts energy needed to spin up flywheels in general and which each of them have of those properties. Last edited by churchx; 06-06-2018 at 01:46 AM. |
06-06-2018, 02:28 AM | #54 |
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It's not as lighter drive shafts don't make sense at all though, as due their sheer size/length there they still weight noticeably .. just that lightening them serve more like lightening car/it's sprung/unrotational weights in general, not so much vs lightening rotational weight of other parts that spin much faster and/or that have weights located further from rotation center, and for general car lightening there are better ways of better returns per buck or lightening by much larger weight if within limited budget, then buying expensive shaft. Interior ripping, removal of misc comfort items like AC/audio/noise insulation, lighter battery, lighter seats, rear seat removal, lighter exhaust, removal of crap in trunk, lighter wheels & brakes, lighter flywheel, removal of washing liquid tank and so on ..
If budget is unlimited and there are no class limits on that, shaft can also be one of many things to be installed for lighter weight too. But otherwise main purpose why someone should look at aftermarket driveshafts is their ability to transfer more torque of more powerful forced induction engines without breaking, lesser weight being just slight bonus of little importance, insufficient to justify the price if lightening being sole reason. Due a shape/small diameter that lightening being for rotational mass also doesn't make much difference in this particular case. Last edited by churchx; 06-06-2018 at 02:39 AM. |
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06-06-2018, 03:35 AM | #55 |
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06-06-2018, 01:15 PM | #56 | |
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I'm afraid that I would "win" the pill consumption per day contest …… Besides, ol @Tcoat wouldn't fess up to taking ANY medications; @Ultramaroon has no idea of how many pills mrs Ultramaroon slips into his morning coffee, just to keep him level and ol @Sapphireho wouldn't fess up …. cause that would confirm our suspicions about his "condition(s)" ……. humfrz |
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carbon fiber, driveshaft, dss, fluidampr, pulley |
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