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Grumpy and Cynical
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Discussion Starter · #1 ·
In this month's BMWcar, there was an article about a supercharged M-Coupe. An interested read, but what caught my eye was a statement that the mod'd M-Coupe's lightweight flywheel, which weights about 1 lbs less than stock, may have hurt its rolling acceleration. I don't understand. Why would a lightweight flywheel hurt acceleration times? I would time the opposite would be true. I have also hear that lightweight flywheels would decrease hill climbing power. Why would that be?

Ed
 

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Rest in peace, Coach
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Ed328Ci said:
In this month's BMWcar, there was an article about a supercharged M-Coupe. An interested read, but what caught my eye was a statement that the mod'd M-Coupe's lightweight flywheel, which weights about 1 lbs less than stock, may have hurt its rolling acceleration. I don't understand. Why would a lightweight flywheel hurt acceleration times? I would time the opposite would be true. I have also hear that lightweight flywheels would decrease hill climbing power. Why would that be?

Ed
Lightweight flywheel = less momentum from the engine = less MOMENTUM going to the wheel.
 

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Double Bimmers
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Re: Re: Light flywheel decrease rolling acceleration power??!?!?

The HACK said:


Lightweight flywheel = less momentum from the engine = less MOMENTUM going to the wheel.
Yeah, should be quicker reving.
 

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Grumpy and Cynical
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Discussion Starter · #4 ·
Re: Re: Light flywheel decrease rolling acceleration power??!?!?

The HACK said:


Lightweight flywheel = less momentum from the engine = less MOMENTUM going to the wheel.
I understand that. Less mass on the flywheel makes it EASIER to spin by the engine, resulting in more effecient transfer of power to the drive train. Why would that make the car slower? Should the car be FASTER than? Are you saying that the car would be slower at lower RPMs, but will picking RPMs faster, and therefore will be faster overall? Why then, would the car's hill climbing ablity be negatively affected? I am very curious. Thanks.

Ed
 

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Rest in peace, Coach
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9,106 Posts
Re: Re: Re: Light flywheel decrease rolling acceleration power??!?!?

Ed328Ci said:


I understand that. Less mass on the flywheel makes it EASIER to spin by the engine, resulting in more effecient transfer of power to the drive train. Why would that make the car slower? Should the car be FASTER than? Are you saying that the car would be slower at lower RPMs, but will picking RPMs faster, and therefore will be faster overall? Why then, would the car's hill climbing ablity be negatively affected? I am very curious. Thanks.

Ed
Rolling start = low RPM = bad with Lightweight Flywheels.

Hill climbing = more load on engine = Not good with Lightweight Flywheels.

Basically, when you get a lightweight flywheel your entire powerband gets shifted up the RPM range, and you rob low end torque to satisfy high end HP. Power transfer is more efficient but power loss/resistence/wheel momentum will overcome the engine momentum easier.
 

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Rest in peace, Coach
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Ed328Ci said:
Thanks. Makes sense now. So much for THAT mod. :)

Ed
It's a great mod if you track your car. For daily driving, it's not something I would recommend.

Hopefully I can get my hands on a set from someone (Rob L., you listening?) and give y'all some objective reviews on it. ;)
 

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Registered
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The HACK said:


It's a great mod if you track your car. For daily driving, it's not something I would recommend.
I agree with that. Street driving, the rattles associated with it get kinda annoying. I didnt notice any significant improvement with the addition of a LW flywheel.
 

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M Mad
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Re: Re: Re: Re: Light flywheel decrease rolling acceleration power??!?!?

The HACK said:


Rolling start = low RPM = bad with Lightweight Flywheels.

Hill climbing = more load on engine = Not good with Lightweight Flywheels.

Basically, when you get a lightweight flywheel your entire powerband gets shifted up the RPM range, and you rob low end torque to satisfy high end HP. Power transfer is more efficient but power loss/resistence/wheel momentum will overcome the engine momentum easier.
So that's why everyone runs out and buys heavy wheels?

The only place a lightwieght flywheel hurts is from a standing start. All other places the reduction in rotating mass makes for better performance.

Drag racers use heavy flywheels. Road racers use lightweight flywheels.
 

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Grumpy and Cynical
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Discussion Starter · #10 ·
Re: Re: Re: Re: Re: Light flywheel decrease rolling acceleration power??!?!?

Pinecone said:


So that's why everyone runs out and buys heavy wheels?

The only place a lightwieght flywheel hurts is from a standing start. All other places the reduction in rotating mass makes for better performance.

Drag racers use heavy flywheels. Road racers use lightweight flywheels.
What about going up hills?

Ed
 
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