under different conditions.

A) City streets, limit 25/35/45

1. uphill - ??
2. slightly uphill - ??
3. flat - ??
4. slightly downhill - just don't get a ticket
5. down hill - again no ticket.

B) Interstate, 55-75.

or would it be better to just use the grade as the chart? I assume that someone has run the test? And lets say the battery is 80% or better (or 60%+) and It's a downhill run of a mile - "N"? or "D"?

Tks

It is vehicle specific.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

In my case, HCH2

In a regular car, the optimum speed for mpg is the lowest speed in the highest gear -- getting the most forward propulsion with the lowest engine rpm.

But in the HCH2, the CVT makes optimum speed more difficult to find. It varies based on road grade and wind conditions. You can generally assume that low rpm is the priority. And since wind resistance quadruples whenever speed doubles, low speed also means high mpg.

So it comes down to how much your time spent driving is worth relative to your money spent on gas ..... or, sometimes, your bragging rights to a high mpg number on your dashboard display. After 23,000 miles, my "trip B" that I left running since the day I bought the HCH displays just over 47 mpg. That's not particularly high, but it's what I accept in order to cruise along with traffic @ 65 miles per hour and get where I'm going in reasonable time. Those 500 mile road trips would get awfully tedious if I stuck to the old "double nickel," even though doing so would get my average mpg up to the magic 50.

Around town, I find that 25 miles per hour is the optimum speed, because it's the lowest speed at which I can activate the cruise control. The mpg really goes up when you take your foot off the gas and let the computer regulate the speed.

However, on the highway, you can improve mpg with little sacrifice in speed by DE-activating cruise control on uphill grades. The cruise will rev the engine thousands of rpm to maintain speed, while your foot can let rpm rev only slightly, maintain a slightly lower speed, and save some gas.

That's one area with room for improvement on future HCHs -- if the driver could set a rev limit on cruise control, or if Honda could program the car to use up battery boost before increasing rpm, that would boost mpg.

This is all quite a long answer to a simple question. So I'll give you a simpler answer; After a year of ownership, I'd say that the optimum speeds for the HCH are 25 miles per hour in the city, and 50 miles per hour on the highway.

Those speeds will get you stellar lifetime mpg numbers. You'll just have to spend extra time in your car going places, and ignore the obscene gestures from your fellow motorists.
.

Sorry,

I don't have the specific numbers for your vehicle but I can help explain an approach to figuring it out. But first, understand that going up or down a hill entails increasing or decreasing your potential energy. The only efficiency option is to minimize trying to accelerate when going up a hill as this puts the greatest load on the engine and can drive it into high power, inefficient modes:
Ultimately your vehicle has to generate enough energy to overcome drag:

• rolling - treated as a constant force
• air drag - a force that varies as the square of velocity
• "on" load - the energy needed if car is just "on"

If you can get a formula for your vehicle that shows these values, you can plot a curve that shows on a flat surface on a 'standard' day for a fixed engine efficiency, the MPG vs miles per hour:

The "red" line shows how much energy is needed to move the car, an NHW11 model Prius, based upon just the rolling and aerodynamic drag. The "blue" line shows how many miles per gallon we get assuming the engine runs at 31% efficiency. The "gray" line includes the "ON" load, the electric power consumed by the control computers and other electrical loads that are there all the time. This is the 'practical' line.

Now you will notice that there have been benchmarks that are above the "gray" line. This occurs because some cars have been "tuned" so the drag is lower, radiator blocks, and the engine more efficient. Also, some tests are on warmer days when the air and rolling resistance are less. So we can 'game' the system by tweaking our cars, driving them to maximize efficiency and choosing favorable weather conditions.

Ultimately the drag and vehicle overhead dictates how much energy is needed to move down the road. The sole source of this power is the engine as the batteries are just a means for efficient engine operation, not sustained motive power.

Now if you want to start with the NHW11 Prius formula, our coefficient of drag is .29 and the the .42 is the product of the the coefficient of drag times the maximum cross-section area. If you can get the equivalent values for the Honda Civic, you can determine what matches the ".42" value. Then you can also scale the rolling drag as a function of relative vehicle weight. These are first order approximations. Finally, you have to figure out the engine efficiency to the wheel (not just the shaft!). Although the Prius engine can achieve 38% efficiency on a test stand, it has to pass the power through the transmission and differential and there are losses.

Does this help?

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Thanks all. Kind of confirmed what I've thinking and seeing. Here is how I'm driving. I try to find a route has 10% steep up, 90% slight grade down. When I hit a hill I try to get as many assist bars as possible up to 3000 rpm. Flat and level never over 2000. Downhill, 1200 - and 100 on instant. I got to work the other day with 72.2 showing and then 52.3 when I got home. But then there's a 1000 ft difference.

There was the comment "bragging rights". But BR = $$. Home-work-home is 40 miles. The other day my commute cost me $2.55. Vs say $5.36 (or $7.88 for her blazer). So that MPG number is a 1:1 in my mind with my wallet. So if I could get 100 mpg it would leave more $$ in pocket

cal
PS: That VVVVVVVV 48.1 is my 4th tank.

What you are describing is what I call "terrain driving." You are selecting a route that allows you to efficiently achieve enough altitude that the subsequent descent takes little or no fuel burn. The trick is to climb the hill in the most fuel efficient power range and then control your speed on the descent for the least fuel burn, none if possible.

I'm impressed by the 1,000 ft. altitude change but some parts of the country are that way. In North Alabama, I'm close to the Piedmont plateau and most of the near-by hills are well under 1,000 ft.

GOOD LUCK!
Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

I went from around 36mpg to 42mpg on my commute by driving the terrain. But something happened today I didn't expect. My Altima can go up to 43mph on battery alone, and today I was in a line of traffic for miles that stayed under my optimum speed. I was also at a section of road that was relatively flat. Well, I ran my battery down to nothing, or at least to a point where the ice had to run. There I was at a stop light and the ice was running! Arrrggg, ruined the entire commute (WRT mileage gains).

It gets late early out there. - Yogi

That has been my find too. The slower you keep it, the better, but there has got to be a point of diminishing returns somewhere. I drove to Denver yesterday (1,000 feet up and then 2,000 feet down) at ~58mph and managed my best ever 72.5mpg for 79 miles. The mileage really starts to climb on those slight downhills when you glide, and that drive is just about perfect for the slight gliding downhills. Of course, I'll only manage mid 50s on the way home. Still, an average of 72.5 and 52 is 60mpg....I love hills!

Commuter car, grocery getter, and summer road tripper--average 10k miles per year.


Winter road trips and ski trips, bad weather commuter and my wife's "daily" driver--expected average 4k miles per year.

aren't you glad you don't live in the good ole days where it was uphill both ways? ;o)