While trying to find information about different tires, I stumbled across this web page:

http://www.fueleconomy.gov/feg/atv.shtml

If you aren't comfortable about where the energy typically goes, this is a good place to start. Remember, our hybrids 'game' the system so the chart covers gas vehicles. Still, it is good to look at the basics from time to time.

Bob Wilson

 

Nice find Bob. I knew it was not an efficient process, but 15%??!!

Before I purchased my TCH I thought the fuel savings were just provided because it's a hybrid. But that graph shows how things like the Atkinson cycle engine and removing the torque converter can provide huge savings too.

 

I'm not buying 4.2 percent for rolling resistance (on top of drive line losses) but only 2.6% for aerodynamic drag. I'm also not buying 17.2% for standby/idle. The aero number seems very low and the idle number seems very, very high. If the idle figures were true than you could more than double the mpg of a car with just idle stop, since only12.6% actually moves the car.....

 

Don't 'ca know that is a Washington DC car . . . sitting on I-66 in the morning, in the evening and Rt. 50 on the weekend.

Bob Wilson

 

Do I feel like a horse's patoot for looking at the numbers and not noticing this. I'm an engineer. That means that I like working with numbers and I'm cynical. Nice catch Lakedude.

 

Not to worry, I sent this note to their POC:

"You might want to have one of your engineers take a look at your web page:

http://www.fueleconomy.gov/feg/atv.shtml

About the only way aerodynamic drag could be less than "Rolling Resistance" and "Braking" would be if the car is driving around in a parking lot. Even the EPA City test gets more aerodynamic drag."

BTW, did you notice how the engine looks like a flat-head with a curious belt to the center mounted pulley? Regardless, I like the graphic because it gets folks thinking about the energy flows.

Bob Wilson

 

I liked it, until I followed a couple of links and go to "How an automatic transmission works." I thought the Prius' PSD was bad. Now my head REALLY hurts.

I also learned a great retort to anyone complaining about CVT's being new...One was sketched out by da Vinci. (So perhaps hybrid owners really are part of a plot to bring down the Christian church.)

 

It's a misleading chart, they mean 2.6 % as a proportion of the 12.6 % that gets to the road. 2.6 + 4.2 + 5.8 = 12.6

So in percentage terms of wheel-power, from their calculations, it breaks down as:

Aerodynamic Drag = 21%
Rolling resistance = 33%
Inertia Braking = 46%

But these numbers and the rest of the chart are still far from accurate, I suspect a summer student may have found the results on wiki or somewhere.