Thursday, January 8, 2009

How to: Increase the power to weight ratio on my Ducati

Any vehicle's acceleration, be it a car or motorcycle, is determined by its power to weight ratio. I think its a bit more intuitive to flip the ratio giving weight to power, that is, a number indicating how many pounds each horsepower has to move.

Some examples:
Dodge Viper
  • 10 cylinder engine
  • 450-hp
  • 3500-lbs
  • power-to-weight ratio = 0.129 hp/lbs
  • weight-to-power ratio = 7.8 lbs/hp
So, for the Viper, one hp pushes almost 8 lbs down the road.

Ducati Multistrada
  • 2 cylinder engine
  • 90-hp
  • 500-lbs
  • P-to-W = 0.180 hp/lbs
  • W-to-P = 5.6 lbs/hp
That is, each horsepower on the Multistrada pushes less than 6 lbs down the road.

Now we see why even relatively small-engine size motorcycles blow the doors off nearly any automobile.

But wait...
Neither cars nor motorcycles drive themselves. So, we should factor in the weight of the driver/rider to be a bit more precise. For most cars, the weight of the driver is relatively negligible compared to the weight of the car. For example, for the Viper, a 200-lb driver (yeah, a portly dude) amounts to less than 6% of the car's weight. So, the 7.8 lbs/hp becomes 8.3 lbs/hp...not much change (6% change to be exact).

What about the motorcycle?
The 200-lb rider is a whooping 40% of the weight of the bike. Thus, the most excellent 5.6 lbs/hp raises to a Viper comparable 7.8 lbs/hp. So, now this Ducati won't stomp the omnipotent Viper.

So, how do I increase the W-to-P ratio of my Ducati?

Control portion size.
No late night snacks.

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