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Discussion Starter · #1 ·
Hey guys, just doin the sr20 swap to my b14 sentra gxe and need to get a new flywheel. I was just wondering if it's worth getting a lightened aluminum flywheel, or should i just stick with the stock one?
 

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Some say its one of the best mods. It will probably make your car a bit quicker. But it might decrease street driveability if its too light.
Be careful, or you gonna get flamed and rudely told to search
 

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Devil's Advocate
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b14guy said:
Hey guys, just doin the sr20 swap to my b14 sentra gxe and need to get a new flywheel. I was just wondering if it's worth getting a lightened aluminum flywheel, or should i just stick with the stock one?
It drops rotational weight from the motor, therefore allowing the engine to rev faster, in theory improving acceleration and throttle response. Just like lightened wheels and pulleys would improve acceleration.
 

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employment whiplash, NC
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Simply knocking 2 pounds of rotoating mass with the aluminum underdrive pullies made an AMAZING difference. I just can't imagine how much better it would be to lose another 4-5 pounds off the crank. I really wish they were legal in STX.....
 

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Discussion Starter · #5 ·
thanks guys.
 

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I love how people make everything theoretical and so on when it comes to flywheels and such. It's no different than a lightweight pulley or a lightweight crank. You reduce rotational mass, you reduce the power lost on the drive train.

People consider bolt-ons like intake and exhaust to increase hp, while mods like pulleys and flywheels "free up" hp. Well whatever the case may be, it equates to more power to the wheels and quicker acceleration, so call it what you want, there's no real sience to it.

BTW, Has anyone ACTUALLY experienced less drivability by switching to a lighter flywheel, b/c IMO, that's also BS. Possibly b/c when you did the install, you prolly installed an incredibly insane stage 25 clutch with an on/off switch for a pressure plate. I installed an 8lb fidanza flywheel along with an ACT HDSS clutch and the car has never been easier to drive. Took me a few days to get used to the feel, but rev matching is almost instant it engages very smooth, and so long as I'm not driving like a jackass, I can make it much smoother than I could with my stock setup.
 

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Discussion Starter · #7 ·
Now, whats the difference between a flywheel for an automatic tranny and a manual tranny?
 

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Um, Probably the fact that automatics don't technically have flywheels
 

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Hostile Aberration
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You got some good information in the thread.

Check out that search button in the toolbar deal. It doesn't bite and will serve you well. Folks usually miss the "Advanced Search" thing that comes down if you click on search. I did, it helps narrow down your search responses. The search button really, no kidding, is the key to knowledge on the forum. Once you get good with it you will be able to find out answers to questions extremely quickly. You'll be stunned at the wealth of knowledge you have stumbled across on this site.

Check this out. I just typed in "lightweight+flywheel" into the search engine for grins and chuckles. On the very first page was this thread:

http://www.sr20forum.com/showthread.php?t=128634&highlight=lightweight+flywheel

Ignore all hits in Members Rides, New Members, Classifieds, etc....those are worthless for knowledge hunting.

That is seriously how easy it is to utilize the search engine.

You're new. No flame fest, just a friendly heads up and a couple of helpful pointers. :)

Welcome to the forum! :biggthump
 

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SR20DEEP N.Y.C.
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i have searched this topic before, and they are mixed reviews. some say that lightened flywheels don't make power. and some say that they do. my question is how is it that ur pullies make hp (6 whp) why is it that a flywheel doesn't? isn't it the same concept?
 

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Hostile Aberration
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DEAD SE-RIOUS said:
i have searched this topic before, and they are mixed reviews. some say that lightened flywheels don't make power. and some say that they do. my question is how is it that ur pullies make hp (6 whp) why is it that a flywheel doesn't? isn't it the same concept?
It depends on the dyno used. One type of dyno records the horsepower freed by lowering rotational mass. One type does not.

Someone with a bigger brain please elaborate and provide details, but I am pretty postive on my statement above. I'm just not very mechanically inclined. :tongue:

Either way, you are putting more "oomph" to the wheels any way you dyno the car.
 

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Primera Nut
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It doesn't free anything up. It just reduces inertia so things can accelerate faster. Would you say putting lighter wheels on would free up power ???

Due to the faster acceleration an inertia dyno will show a power increase, a brake dyno will also show an increase if it is used in a spin up test. A brake dyno used in a steady state mode will not register an increase....
 

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Ninety-Nine SE-L said:
BTW, Has anyone ACTUALLY experienced less drivability by switching to a lighter flywheel, b/c IMO, that's also BS. Possibly b/c when you did the install, you prolly installed an incredibly insane stage 25 clutch with an on/off switch for a pressure plate. I installed an 8lb fidanza flywheel along with an ACT HDSS clutch and the car has never been easier to drive. Took me a few days to get used to the feel, but rev matching is almost instant it engages very smooth, and so long as I'm not driving like a jackass, I can make it much smoother than I could with my stock setup.
]

Not actually less driveability, but going from a quick acceleration to a very quick stop you car can cut off and stall. Happened to me a few times and I've known a couple others that have had it happen to them also. Not a big deal though. Not word from word, but a tech. at a local performance shop was telling me under hard deceleration, because of the flywheel being lighter, it causes the rpm's to drop quicker also and sometimes drop too low and stall.
 

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yea, I guess that can happen, most of the problem I have with the stalling is b/c of my cams though.
 

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I have a stillen flywheel with ur ultra ss pullies, feels good and ddriveabliity isnt affected at all. BTW, you shave way more than 2 lbs on the pulleys and more than 5 lbs on the flywheel. My stock crank pulley was heavy as hell and my UR one was like a feather.
 

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Drinking The H Juice Now
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as i stated long ago in a thread far far away that was resurrected.. what you are talking about is parasitic drivetrain loss.

most FWD experience about a 17% loss of crank or brake horsepower, so, if your engine is rated at 145 Brake HorsePower (BHP) - 17% = 120 Wheel HP. Adding lighter weight components such as a flywheel and pullies will reduce that percentage of loss from 17% to roughly 10% or an increase of 7% TO THE WHEELS, 130WHP

but

the crank output will still be 145 BHP.

does this make sense to you?
 

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sleeper
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eh... it's not a parasitic loss at all, just a mass. Here's an analogy; take a shopping cart that is empty and one that has a keg in it. You can accelerate/decelerate the empty one a hell of a lot faster right? But you're not any stronger.

So it's all power to weight. Less weight means faster acceleration, simple as that. It just happens that since the dynojet is the most commonly used dyno over here, and it's an inertial dyno, that people say it 'frees' up HP.
 

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They're just cones!
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Also, it's not just the actual lighter weight that makes it better, it's the inertia. Inertia is a function of mass times distance from the axis.

That's why a flywheel helps a lot more than pullies, because the diameter is greater.

This is also why 12.5lb 17" wheels are worse for acceleration than 17lb stock 15" ones.
 
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