EOC on motorcycle - Fuel Economy, Hypermiling, EcoModding News and Forum

saunders1313 · 07-22-2008, 06:43 PM

Apparently my motorcycle is not the greatest to EOC on. Although I still do it quite a bit, it takes the most convenient vehicle to EOC or P&G and makes it very inefficient. It still works, but I find that I can’t coast nearly as far as my wife’s Hyundai Elantra. It probably has a lot to do with the momentum.

dcb · 07-22-2008, 06:47 PM

Same here, it got better when I upped my PSI. The cars glide farther at higher speeds (say above 10mph) and the bike glides farther at lower speeds (< ~10mph) , Aero has a lot to do with it I'm pretty sure. I also noticed I don't scrub off as much speed on the corners on the bike it seems.

saunders1313 · 07-22-2008, 07:34 PM

Well with a bike you can take turns at a larger radius than a car (not as wide) and so you don't have to kill the speed as much. The aero of a bike is terrible. Although it is good that I can draft at 3 seconds behind almost anyone and feel a difference.

MechEngVT · 07-23-2008, 11:53 AM

The fact that you can easily feel a difference while drafting means that your aero is awful. The more aero a vehicle is the more extreme draft will be required to detect a perceptible difference.

I think you were initially correct when you mentioned both aero and momentum. I think if you took a look at your CdA/mass ratio it will be the defining factor it how well/how far you can EOC at highway speeds. Higher weight and lower CdA will coast further; higher CdA and lower weight will not coast as far.

Motorcycles have horrific Cd, but low A. Both are rather rider-dependent, as is the running weight. Knowing little about bikes, I'll go with some assumptions that between rider and bike you're looking at 1000 lbs, Cd of .5 and half the area of a car. Your car let's say has a Cd of .35 and a weight of 3000 lbs. Your CdA/mass ratio of the car would be 1.17x*10^-4 (x being your total area of the car) while your motorcycle would be 2.5x*10^-4. Since your bike has the higher CdA/mass ratio it will decelerate more quickly than the car (higher drag per momentum). Even if the bike had only 1/4 the area of the car you are still marginally higher on CdA/mass ratio, which will get even worse with a lighter bike or fewer BigMacs. It's not purely scientific and won't help you calculate your actual deceleration, but it's a good method of determining the trend.

You are correct though that at low speeds the vehicle with less rolling resistance (the bike) should coast better.