V8 LS1 flywheel racing weight 4

[sierra4000]

Hello,

exist recommendation for minimum flywheel weight?
how way is harmony ballancer improtant?

we build racing engine and try minimize engine inertia

thank for all comments,

Radek

 

[enginesrus]

There are some that have run drag race type engines with out the harmonic balancer, those engines don't run too long like seconds per run. The cranks usually end up with cracks too.
Light weight flywheels? Just look at a standard flex plate, they are pretty light, yeah most though have a heavy torque converter attached. There are trade offs.
You get one thing for the loss of something else. Your best bet is to contact an outfit that manufactures the aftermarket engine rotating parts and ask them. They have done the tests and studies and can best advise you on what you need for
your specific engine and its specific use.

 

[Lou Scannon]

Good advice. Crankshaft harmonics is a tricky business. Trial and error is the usual path to success. Build on the work of others. Key point: factory harmonic dampers have been validated for stock boundary conditions, i.e. rotating/reciprocating masses and peak rpm. If you change these boundary conditions, don't expect the factory harmonic damper to save your crankshaft.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[sierra4000]

OK,
Because we still use OEM internals, we expect RPM range up to 6800
so OEM harmonic balancer could be more or less good for our application.
With flywheel in the past experience always had acceleration gains with minimize inertia(Our V6 flywheel is 3,5 kg only) and again with low inertia twinplate clutch on V6 engines.

but no have any experience with V8 engines

 

[LionelHutz]

Asking for a flywheel weight recommendation will get almost as many differing opinions as asking which oil is the best to use.

There is no minimum weight required. Run what works for your car and driver combinations, whichever weight that is.

 

[SwinnyGG]

OEM harmonic balancer could be more or less good for our application.

This is only the case, for sure, if the entire rotating assembly is unaltered; 'entire rotating assembly' includes the OEM flywheel.

 

[sierra4000]

For clarification:
LS1 V8 engine
OEM crankshaft,OEM conrods,OEM pistons...........RPM max around 6800
with lightened pulley, flywheel,clutch can easy improve engine (car) acceleration abilities
driveability on slow speeds is secondary,important is road course laptime gain

i worries about engine fail and crankshaft fatigue

 

[SwinnyGG]

i worries about engine fail and crankshaft fatigue

As you should.

What's you're intended service life for the engine? Is it short? Buy one of the myriad of aftermarket LSx balancer options available on the market, and call it good.

Is it hundreds (thousands) of hours at high load? You may need something custom; designing a custom balancer is one of those things that is very, very difficult to do yourself unless you have a very large budget in both money and time, but is VERY easy for someone like ATI to do for you at relatively low cost, if you call them and tell them what you want.

 

[sierra4000]

OK,
Thanks
ATI seems like good idea,
but tell me please, what hapen there, why is need balancer?
i want understand this

car go only short runs under full load.........is european hill climb racing.............one run lenght between 2-10 km

 

[SwinnyGG]

but tell me please, what hapen there, why is need balancer?

Balancers are generally good because they protect things like crankshafts from rapid unplanned disassembly

Short runs are good, but if you plan to do 10,000 short runs between engine rebuilds, then short runs are no different than long runs

 

[GregLocock]

I see the LS1 has the same oil pump placement as the LT5 - a gear pump on the nose of the crank. The bending tune of the harmonic damper is vital, otherwise the gear pump will fail, shortly followed by the engine. The torsional tune is mostly to keep the crankshaft in one piece as it accelerates through its first resonance.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[sierra4000]

Thank you gentlemen!
I will try to summarize

a new original OEM balancer will be good for my RPM range,

for flywheel+clutch inertia is important required car driveability and idle

 

[TugboatEng]

Also, lightening the flywheel does little to improve the acceleration capability of the car. The amount of energy required to spin up the flywheel mass is miniscule compared to the work requires to accelerate the car.

The principle benefit of a lightened flywheel is that it does accommodate faster shifting as the driver can rev-match more quickly.

 

[Lou Scannon]

The inertia of the flywheel is typically significant in the lowest and maybe second lowest gear.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[gruntguru]

Yep. For road cars in first gear, each kg of flywheel at the radius of gyration is typically equivalent to 20 - 30 kg of vehicle mass.

je suis charlie

 

[LionelHutz]

Also, lightening the flywheel does little to improve the acceleration capability of the car. The amount of energy required to spin up the flywheel mass is miniscule compared to the work requires to accelerate the car.

That goes against every test and practical use I've seen. The more HP, the greater effect the flywheel lightening has on acceleration. If the OP has found a lighter flywheel benefits acceleration on their V6 engines then it'll be even more so on a higher power V8 engine.

 

[GregLocock]

I wonder if some maths might help?


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[gruntguru]

OMG - maths?
Lets say final drive ratio is 3:1 and first gear is 3.333, the overall ratio becomes 10:1
If tyre radius is 300 mm and flywheel radius of gyration is 150 mm, the flywheel average mass is travelling at 10 x 150/300 = 5x the velocity of the car. So 1 kg of flywheel has 25 times the kinetic energy of 1kg of (purely translating) car.

je suis charlie

 

[TugboatEng]

I can't tell if serious or not.

I can't take it seriously without any mention of moment of inertia.

 

[GregLocock]

radius of gyration does it for me.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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