The power to weight ratio is expressed as the engine torque to vehicle weight
as a base line figure. Yes, the gearbox as a torque multiplier will increase
the torque but the ratio is valid per gear against weight x and lighter
weight y.
So, if the vehicles weight reduces the power to weight ratio improves.
However, if you take 2 cars with identical engines and weight but car A has
closer gear ratios than car B it may well APPEAR to have a better power to
weight ratio when in fact it is simply making better use of the torque. With
car magazine test reports if you look at enough of them you can begin to
understand why the power and weight don't always tell the full story and a
look at detail of the gearbox ratios is the first place I look.
Still, the point you make is valid that perhaps it isn't possible to
calculate an accelerative benefit for a weight saving because gearing is such
a big factor.
Obviously weight reduction shortens braking distances, raises cornering
speeds etc.
Nick
In a message dated 20/12/01 12:19:19 Pacific Standard Time,
sfooshee@clubrx.org writes:
> ).
>
> Right, I wasn't referring to the validity of the thought that power =
> acceleration (torque makes the world go 'round, y'know :). But saying X
> lb. = Y bhp is *exactly* the power to weight ratio. So gaining 1 bhp has
> the *exact* effect as losing 26.667 lb. of weight on the p/w ratio. As
> to the 40 billion variables that determine how the power, torque,
> gearing, and weight effect the acceleration of the car is a matter WAY
> over the simple (and genuinely meaningless, as you said) ratio that all
> the magazines like to list.
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