igdrasil

the problem is...our cars does not have constant force:


dyno in pdf

tonkabui

let me clarify what i mean by constant force: although the force exerted by the engine is varied throughout the range, it is constant at any particular RPM. so if you were to accelerate with the engine at 3000 RPM, it will ideally be at that particular horsepower & torque level every single time you accelerate, which leads to a certain rate of acceleration. now if you were to have lowered your weight/mass, then when you accelerate with the engine speed at 3000 RPM, your rate of acceleration will be greater than when the car was heavier. perhaps at the wheel, the horsepower changed (due to inertia change from the change in mass), but the ENGINE is still putting out the same amount of power regardless. does this make sense? let me know if it doesn't.

Mashi Maro

I read in a reputable magazine, can't remember which, that cutting weight from a car will yield increasing returns, by that I mean take 1 pound off at 2800 lbs. will not have as great an effect as taking 1 pound off at 2400 lbs. I don't want to say it is exponentially beneficial, but you'll get bigger and bigger "gains" the more you take off, until you get to the weight of a motorcycle, and we all know how fast bikes go with less horsepower than our cars have already. So if you shave everything away, i think you'll do faster than 14.2 seconds. It is the opposite of engine modification, which yield diminishing returns. You add 10 HP to a 100 HP engine, and it makes a big difference. Add 10 HP to a 500 HP engine and it hardly matters.

tonkabui

it's all about F=ma. with the same Force, if you reduce mass you will increase your acceleration. if you increase force (turbo), keep the same mass, then your acceleration increases. if you increase force and decrease mass, then your acceleration goes up even more. if you add mass (heavy wheels or giant ICE system), then your acceleration goes down unless you add force to counteract that.

stealthscotty

you're killin me people.....

goldstar

The indicated HP (IHP) of an engine is the theoretical HP derived from the energy contained in the expanding gases in the cylinders. It is calculated from the pressures developed in the cylinders and is measured by a device called an engine indicator which produces a diagram of the pressure cycle in the engine.

The brake HP (BHP) or crank HP of an engine = IHP - the HP consumed in overcoming internal engine friction (also known as the friction HP). Thus, BHP = IHP - friction HP. The only way to increase BHP is to increase the IHP (by the usual methods of increasing thermal or volumetric efficiency) or reducing the friction HP (by, for example, switching from a mineral to a synthetic engine oil).

With this in mind and remembering that torque is a function of HP and rpm, there is absolutely no way to increase HP or torque by lightening flywheels or pulleys or by reducing vehicle weight. The effect of lightening these elements will be to increase the power to weight ratio of the vehicle which will increase its acceleration (and maybe its top speed by a slight amount) but will have NO effect on the power output of the engine.

Incidently, reducing the rotational mass of elements such as flywheels, pulleys and road wheels will increase acceleration quite apart from whether or not you lighten the chassis.

Finally you're all aware of the discrepancy between brake or crank HP and wheel HP (WHP). As before, anything you can do to reduce friction between the engine and the front wheels will increase the WHP. For example, switch from a mineral to a synthetic gear oil. This may give a barely noticeable improvement but is offered as an example of the kind of thing to do.

LoudRacer

It's pretty simple a concept, or so I thought. Reducing your weight does NOT result in more power, it results in less work the engine has to do to spin the tires. This is very good for an engine, anything you can do to make the engine work less will result in a longer lifespan.
On the contrary, adding weight to your car or generally pushing the engine to perform harder will do nothing but hurt it. I.E. : racing, towing, climbing hills, etc.. Climbing hills is similar to loading weight onto the car, going up a steep hill is not "technically" putting weight on your vehicle per-say, but your engine will not know the difference. As you car rises in elevation it is fighting gravity even more so than riding on level ground, were this not a true physical fact, there would be no need for cars at all.
As for switching from mineral to synthetic oils, I was told that the only difference was the increased effectiveness of synthetic at colder temperatures compared to petroleum-based oils. I use synthetic, it rocks, but I don't think it's because it reduces friction as GOLDSTAR had posted earlier.
Loud cars kick-@$$, I hate stock mufflers.

TaiMaiShu

so less weight = more power?


........
...just kidding.

midnightblue97

no

VagaBond-X

oh my god, the dead is ALIVE... lol my post in this thread is from back in 2002.... like a year and a half ago... damn

k lets clear this up

reducing weight DOES NOT give u more power...
it just betters ure power to weight ratio (lol that probably confused some of u more hehe)

k think of it like this

lifting weights....

say you can lift 30lbs....

now you go down to 15lbs....

you didn't gain any power from going to the lower weight....

but u can lift the 15lbs faster, more times, more further....

its the power to weight ratio.... with the 15lbs your power to weight ratio is higher,,,, but with the 30lbs your power to weight ratio is lower....

hope that helped....

TaiMaiShu

so if i take out the spare tire thats 25 pounds, that means I'll have 25 more horsepower?
ok i get it now.

Mashi Maro

Reducing your vehicle's weight does not result in a gain in horsepower or torque.
It does result in better power to weight ratio, as Vagabond stated, which improves performance. The most noticeable improvement is acceleration, but there are other things such as less stress on tires, suspension, etc.
Reducing vehicle weight will "feel," and only "feel," like gaining power, but you are simply putting what power you already have to better use.
So better acceleration does not necessarily mean you gained horsepower.
People will tell you that cutting X amount of pounds results in X amount of power, but it is only a gauge, or estimate, of the improvement in your performance. What they often forget to say is, losing X amount of weight is "LIKE" (as in "similar to, but not really") gaining X amount of power.

I don't know if this clears up any confusion. If not, I look forward to checking up on this thread next year.

goldstar

In fact, along with their other advantages, synthetic oils do reduce internal engine friction resulting in higher HP output and better fuel mileage, compared with mineral oils.

The main reason that synthetic oils reduce friction is because of their uniform molecular structure. The uniform diameter of synthetic oil polymers allows them to more easily slide over one another imparting an added slipperiness to the oil that is absent in mineral oils.

A second reason is the greater shear strength of synthetics. This is the ability to maintain a thin film of oil between moving parts under severe shock and impact loads. If the oil film is ever sheared away, however briefly, this will increase friction in the engine at that instant, to say nothing of increased wear.

There are many websites that you can go to to get a more detailed explanation of the benefits of synthetics but to get a more objective explanation, stay away from the sites associated with a specific manufacturer.

I am not commenting on the extent of difference you will notice between synthetic and mineral oils, but on the basis of every little bit helps, synthetics are clearly the way to go for increased performance.

VagaBond-X

yup exatcly... you got it right on!!!!

now imagine you strip the car, ... damn you woulda added like 500hp+

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...



......

....... just joking, its NOT like adding 25hp....which i know that you know, ure just giving everyone a little run for their money....

TaiMaiShu

lol. nobody picked up on my sarcasm. I was joking.