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Location:
Lismore, NSW
Registered:
February 2003
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Lightened flywheels
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Mon, 11 August 2003 10:43
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Whats the advantages and disadvantages of getting flywheels lightened? Would it be worth getting my flywheel lightened on my 7MGTE supra?
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: Lightened flywheels
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Mon, 11 August 2003 11:21
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With a lighter flywheel the engine will rev quicker but will loose revs quicker when going up hills 
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Lightened flywheels
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Mon, 11 August 2003 11:36
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if it loses revs quicker when going up hills, it doesn't have enough power  heh heh.
but seriously tho, i'm looking at a lighter flywheel too, either alloy with metal insert or a steel/moly with insert.
a lighter flywheel reduces the rotational inertia. thsi alloys your motor to change it's rotational speed faster (as there is less inertial mass to accelerate/decelerate). you will notice this when accelerating in lower gears, where the inertial mass is a larger percentage of the total vehicle mass. in higher gears the proportion is lower, so it won't affect car acceleration as much.
the main issues with lighter flywheels are idle quality, and starting from stationary.
your motor needs enough stored energy (from the flywheel), when idling, to be able to get thru each compression stroke without stalling. if it's too light, the retarding force of compressing the air/fuel will be large enough to slow or stop the engine.
with low overlap cams, this can be a big problem, but with higher overlap cams (ie lower dynamic compression at idle speeds) the retarding force is lower (less compression force) and a lighter flywheel can be tolerated, as long as the long overlap doesn't cause too much misfiring (and thus lack of power strokes).
when you start from stationary, the inertial momentum stored in the flywheel is transferred in to forward motion when you slip the clutch. with a lighter flywheel, there is less inertia, so you need to put in more energy with your right foot, and be more careful with the clutch to get going without stalling.
the next thing is the danger of lightening a stock cast flywheel, or getting a new one made up. it's your legs and your choice 
another factor is the difference between the inertia stored in a big crank (like the 7M's) and the flywheel. you are trying to lighten the whole rotating mass (pistons and rods included), so 25% off the flywheel may only be a 10% gain overall....
there are plenty of good sites around that deal with lightened flywheels.
Cya, Stewart
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Location:
Brisbane
Registered:
May 2002
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Re: Lightened flywheels
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Mon, 11 August 2003 14:12
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| Cool1 wrote on Mon, 11 August 2003 21:21 |
With a lighter flywheel the engine will rev quicker but will loose revs quicker when going up hills
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Common misconception: engines lose torque with a lighter flywheel.
Fact: flywheels don't create torque. As a matter of fact, as soon as you engage the clutch the flywheel does nothing useful at all.
The flywheel exists to make standing starts easier, and that's all it does. A super-light flywheel will make it harder to get your car rolling from the lights, but once the car is moving you won't even notice the difference... except for the slightly quicker acceleration of course. 
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: Lightened flywheels
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Mon, 11 August 2003 20:44
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A double counterweighted crank in a 7MGTE will weigh upwards of 30 kg. Add another 8 kg of flywheel, another 3-4 for pressure plate and harmonic balancer, plus rods and pistons and you have a rotating assembly mass approaching 45 kg. Other than endangering your limbs, reducing the mass of a cast flywheel by a kilo will have a minor effect.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Lightened flywheels
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Mon, 11 August 2003 23:34
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'Maaate... I can bench press 2 7M cranks maaaate....' I can really see this taking off in gyms around the Western Suburbs... 'Maaaaate... Supra motor crank maaaaate...'
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Lightened flywheels
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Tue, 12 August 2003 01:31
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hehehe - dont laugh...
tie two double counterweighted 7m cranks to a standard bar, and i we'll see how many reps you can get out of it .... heavy heavy fuckers they are
single counterweight 7m cranks arent 'that' much lighter either.
what was it we figured out with the cranks weight and tourque curve? heavier somehow shifted the curve to the left?
theres not really much scope for removing weight on the 7m flywheel as it is anyway. and have you weighed your pressure plate lately, theyre not light. makes spending $$ on a lighter flywheel look kinda silly. (not that i'd do it anyway...)
and GT - pistons and small ends count as reciprocating weight, not rotating... 
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: Lightened flywheels
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Tue, 12 August 2003 05:07
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Pfft....pedant......
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