Is power/weight all that matters?

dutta_d1 · 22nd December 2012, 11:17

The power/weight ratio is just like the Ghz of a computer processor. Matters for performance, but it is not the only thing that matters.

In two words, it's marketing strategy that there is so much fuss about power/weight ratio.

Ricci · 23rd December 2012, 22:02

@Accelerate, when you say feels quicker - as in the Verna feeling quicker than the Linea, did you do this comparison starting from rest, giving it all it can acceleration, or was it already on the move - then press pedal (or maybe downshift , then accelerate ) ?

P:W ratio only measures the peak - which you can avail of only at 5 speeds, the shape of the rest of the torque curve is important. A very peaky engine, with a high sudden peak with significant drop in torque above and below that RPM , will show a high power to weight ratio, but an engine with somewhat less peak power/torque but a wider useful RPM range over which it makes over 90% of max torque, will be quicker despite lower power:weight ratio. This is very rare of course, most engines have sufficiently wide band around the peak torque/power to have 1500-3000RPM bands that will make you smile , but I'm talking more out of observation with petrol engines. Diesels tend to have more narrower rev ranges.

So, it would be great to get the power/torque curves of the said cars, the gear ratios and know the effective output (after transmission losses) to get a better understanding of why the Linea was slower even with similar P:W ratio. I might be simply down to turbo-lag, since most engines for general consumer use are not tuned for high performance over narrow powerbands.

22nd December 2012, 11:17	#16
dutta_d1 BHPian Join Date: Oct 2010 Location: Guwahati Posts: 70 Thanked: 55 Times	Re: Is power/weight all that matters? The power/weight ratio is just like the Ghz of a computer processor. Matters for performance, but it is not the only thing that matters. In two words, it's marketing strategy that there is so much fuss about power/weight ratio.
	() Thanks

23rd December 2012, 22:02	#17
Ricci BHPian Join Date: Nov 2008 Location: Pune Posts: 809 Thanked: 1,179 Times	Re: Is power/weight all that matters? @Accelerate, when you say feels quicker - as in the Verna feeling quicker than the Linea, did you do this comparison starting from rest, giving it all it can acceleration, or was it already on the move - then press pedal (or maybe downshift , then accelerate ) ? P:W ratio only measures the peak - which you can avail of only at 5 speeds, the shape of the rest of the torque curve is important. A very peaky engine, with a high sudden peak with significant drop in torque above and below that RPM , will show a high power to weight ratio, but an engine with somewhat less peak power/torque but a wider useful RPM range over which it makes over 90% of max torque, will be quicker despite lower power:weight ratio. This is very rare of course, most engines have sufficiently wide band around the peak torque/power to have 1500-3000RPM bands that will make you smile , but I'm talking more out of observation with petrol engines. Diesels tend to have more narrower rev ranges. So, it would be great to get the power/torque curves of the said cars, the gear ratios and know the effective output (after transmission losses) to get a better understanding of why the Linea was slower even with similar P:W ratio. I might be simply down to turbo-lag, since most engines for general consumer use are not tuned for high performance over narrow powerbands.
	() Thanks