unsprung weight

[GG300]

Does anybody know the relationship between unsprung weight and horsepower? I heard that sheding 10 lbs. of pork = 1hp is this correct? regards, GG300

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[andy31144]

I've always heard one pound of unsprung weight relates to about twenty pounds off the car itself. I don't know about horsepower.

[Verde]

I don't believe that there is a difference between sprung or unsprung weight re horsepower (or torque for that matter). The comment about the value of unsprung weight typically relates to handling. That is, the reduced inertia of lowered unsprung weight allows more accurate tracking over bumps and changes in direction. And does so more efficiently than lowering sprung weight.
When it comes to power (other than the inertia of the powered wheels) weight is weight.

[Q8_TwinTurbo]

Less unsprung weight always helps in accelleration, braking & handling.

When you loose unsprung weight from a car, you are actually minimizing the HP loss. The main parts that help in aiding the unsprung weight of a car are lighter wheels, lighter tires, lighter brake rotors. The engine related parts that help the tachometer rev up faster are lighter connecting rods, pistons, valves, retainers and springs. One more part that helps free up a few extra hp would be a lighter set of pulleys (oil pump and alternator) as well as a lighter crank pulley. I would not advise anyone using their car as a daily driver to go with underdrive pulleys, since they lower the voltage/charge as well as the oil pump drive. I would rather go with lighter stock diameter pulleys. You would benefit from the less rotational mass with stock like voltage and oil pump drive.

Loosing unsprung weight ie lighter wheels, Lighter rotors etc. has it's advantages over loosing fixed weight ie doors, engine bonnet etc.

Example; A car that weighs 3000lb and has 300hp (3000lb divided by 300hp) would equal to having 10lb of weight for every 1hp or 0.1 hp for every 1 lb of weight

That same car, after having -500 lb of weight removed would change that ratio to 8.33 lb for every 1 hp or 0.12 hp to every 1 lb of weight.

Some peoples conservatively quote that the effect of loosing unsprung weight as opposed to loosing sprung weight would come at a ratio of 1 to 4 being conservative ;
example: (The removal 1 lb of unsprung weight equates to the removal of 4 to 5lbs of sprung weight).

As a conclusion, loosing weight from a vehicle helps it's performance. Taking to affect the total weight distibution of the car not getting affected much. Corner balancing after loosing weight would help greatly.

[landjet]

Didn't you forget about the LWFW in the quicker revving equation?

[GT3Ranger]

Q8_TT reading your post I agree with some points and not others.
First unsprung weight has to do with and is relavent to rotational mass. It has nothing to do with horsepower in a direct manner.
True that lightening of components will enhance the effectiveness of the horsepower.
Lighter internal engine components enhance making of HP in a manner of efficiency. Like a LWFW enhances revs but does not make HP.

The equation is 3 to 1. Meaning for every 1 lb. loss of the rotating mass (ie. a wheel or rotor) you save 3 lbs. that is needed to rotor (work) the mass.
Example: If you get wheels that are 5 lbs lighter all around you save 15 lbs. per corner in unsprung weight. Meaning it will require your car 15 lbs less effort to rotate the mass (wheel, rotor, flywheel, crank). You do not save 60 lbs. in raw weight but in efficiency in rotating the mass (wheel).
As Q8_TT stated this translates to better acceleration, braking and handling.

btw Q8 I disagree with the comment about using a smaller lightweight pulley in a DD. Pulleys have been designed that do not distort the engine harmonics. I've had an Evosport pulley in my E60 M5 for over 30K miles and zero problems. Not only myself but hundreds of other M5/M6 owners.

Anyway my 2 cents.

Ranger

[Q8_TwinTurbo]

Originally Posted by landjet

Didn't you forget about the LWFW in the quicker revving equation?

landjet,

good catch, you caught me on that one. Thanks for bringing it up.

[Q8_TwinTurbo]

Originally Posted by GT3Ranger

Q8_TT reading your post I agree with some points and not others.
First unsprung weight has to do with and is relavent to rotational mass. It has nothing to do with horsepower in a direct manner.
True that lightening of components will enhance the effectiveness of the horsepower.
Lighter internal engine components enhance making of HP in a manner of efficiency. Like a LWFW enhances revs but does not make HP.

The equation is 3 to 1. Meaning for every 1 lb. loss of the rotating mass (ie. a wheel or rotor) you save 3 lbs. that is needed to rotor (work) the mass.
Example: If you get wheels that are 5 lbs lighter all around you save 15 lbs. per corner in unsprung weight. Meaning it will require your car 15 lbs less effort to rotate the mass (wheel, rotor, flywheel, crank). You do not save 60 lbs. in raw weight but in efficiency in rotating the mass (wheel).
As Q8_TT stated this translates to better acceleration, braking and handling.

btw Q8 I disagree with the comment about using a smaller lightweight pulley in a DD. Pulleys have been designed that do not distort the engine harmonics. I've had an Evosport pulley in my E60 M5 for over 30K miles and zero problems. Not only myself but hundreds of other M5/M6 owners.

Anyway my 2 cents.

Ranger

GT3Ranger,

I was saying what i thought i understood. Thanks for the verifications. This is a reason i am on such forum. We live and learn. Thanks again.