Efficient hill climbs

I think its best to just maintain on the way up the hill and when you are about to reach the peak back off just a bit.
If I am on the downside on the highway I will press the pedal just enough to bring up the yellow arrows to eliminate regen (at highway speeds).

 

Testing has shown 55 mph is a an excellent speed to maintain climbing a hill. Anything over 60 mph is not so good and please don't try to accelerate ... that will just deplete the battery sooner. But 55 mph can be maintained up just about any 6% grade hill.

As for the descent, it tends to work better if you can use "B" versus using "D" and the brake. The reason is your battery will still get a nice charge but it won't be so harsh in terms to raising the battery temperature.

As a suggestion, try resetting your trip meter at the base of each hill (or a point of your choosing) and then climb at different speeds and record the MPG and distance at some fixed point near the crest. You can use this method to figure out 'fuel burn to climb' and plot which speed gives the best performance.

GOOD LUCK!
Bob Wilson

 

Dan,

How many miles is your daily commute?

 

I like to maintain 30 MPG and warp stealth down the hill. This way, I would average about 60 MPG.

In summary, climb at half the MPG you want to get.

 

Huh? Maintain 30 mpg? How does maintaining 30 mpg help you average 60 mpg? What do you mean by this?

 

Use the Energy screen on the MFD to maintain 30 instantaneous MPG. The speed may increase or decrease depending on the hills. On the way down, you won't use any gas so it should average 60 MPG right?

 

Are you saying that if I maintain 30 mpg on the climb (at 10, 20, 30 or 40 mph) that when I crest the hill when coasting down I will average 60 mpg for the entire up/down segment?

Just wondering what you meant by maintaining 30 mpg and warp stealth "down" the hill. Wouldn't you get much better than 30 mpg when warp stealthing down the hill?

 

Yes. 30 MPG uphill and infinite MPG downhill so average should be 60 MPG.

Prius can climb pretty a steep hill at 55 MPH @30MPG.

 

I understand what you are saying...thank you.

But I have a question about your math.

If uphill is 1000 feet at 30 mpg and downhill is 1000 feet at infinite mpg how does that average 60 mpg for the entire up/down segment? For arguments sake lets assign an mpg value lower than infinite mpg on the downhill...say 120 mpg over the 1000 downhill segment.

So 30 mpg on the uphill 1000 foot distance and 120 mpg on the downhill 1000 foot distance. Wouldn't that be 75 mpg for the total 2000 foot segment?

 

I do not think it possible to get 30 mpg on some of the hills I climb. The grade is too steep and too long.

 

I also commute over many hills although at freeway speed (65 mph limit). When I tried it as if I were riding a bike (accelerating on the downhill to generate speed to get up the hill) it felt like I was using the car efficiently but my first fill up showed that I was only getting 44 mpg. I have since used the instantaneous FE gauge to maintain over 40 mpg in the climbs, which results in sometimes slowing to 50 mph. So can't practically do that in traffic. I don't think pulse and glide would work on an uphill as you don't want to be accelerating at all, so I'll pick a new lower instant mpg target like the previous post of 30 mpg. I guess bottom line, if no one's behind you let it slow down on the uphill. Otherwise keep it within 10 mph of the limit I'd say. Why can't we all be in Priuses, hey what's the plural of Prius anyway? Prii?

 

MPG target driving is a good way to zero in on the most efficient way to drive a car up a hill...especially if you don't have instrumentation to give you a visual representation of your sweet spots.

If you drive the same route every day and go over the same hills you might want to hit the reset button on your trip mpg at a specific point at the bottom of a hill and record your mpg at a specific point at the bottom of a hill. This will give you the mpg over that segment of your commute.

Doing this over and over for the same segment should tell you what the most efficient way to attack that specific segment is for you. Outside of that, I highly recommend purchasing a Scanguage II to see other performance indicators that will help you maximize your fuel economy for your entire commute.

 

Averaging rates is often confusing. Consider instead this example using amounts: Imagine a hill 30 miles up and 30 miles back down. Drive such that you burn 1 gallon going up (30 miles, so 30 MPG), and stealth all the way back down (assume 120 MPG, which would consume 30/120 = 1/4 gallon). You will have gone 60 miles on 1.25 gallons = 48 MPG.

For the original question: Drive as slowly as you can stand while going up and minimize the use of the brakes, and that will be pretty close to ideal. It would be hard to do better without a ScanGauge or detailed analysis of the exact route.

 

According to numbers from the ScanGauge my 20 mile commute averages about 70 MPG if I minimize acceleration and climbing speed. It quickly drops down to about 60 MPG even with moderate acceleration and climbing speed.

 

B mode throws away energy, so I would avoid that until the battery was full on downhills, which doesn't sound like a problem for your situation. This averaging of "mileage" is a bit more obvious for those of us with a MFD in litres/100 km, imo.

 

In your example I agree with your math. You used gallons instead of mpg as the standard to figure mpg. The original scenario did not measure the up and down segments in gallons...it was measured in mpg up and mpg down to get an average mpg for the segment.

In the original example of 1000 feet up at 30 mpg and 1000 feet down at 120 mpg (or infinite mpg as the OP put it) it's an average mpg of 75 mpg...correct?

In the OP's example he said 30 mpg up and infinite mpg down (I added the 120 mpg for the sake of having numbers). I don't see how an equal up and an equal down cant be the up mpg plus down mpg divided by two to get the average. Two mpg numbers of equal distance traveled added together and then divided by two is the average of those two numbers mpg...no?

 

I think you get confused by the use of MPG instead of gallons per mile. As a non US citizen, I still have to think the other way arround to use MPG (the less gas you use, the higher MPG you get, zero fuel consumption being infinite MPG, ... kind of counter intuitive when you're not used to it).

See it this way: to climb the hill, you maintain 8L/100km. As you go downhill, you go in stealth and your fuel consumption drops to 0L/100km. Your average will then be 4L/100km, or half of going uphill.

 

Matt,

I had this in mind... Imagine a 30 miles uphill and 30 miles downhill. If I use one gallon uphill (30 MPG) and use no gas downhill, I would get 60 miles for gallon of gas.

 

No and No.

Average mpg == (total miles) / (total gallons). Any other answer is garbage.

Ratio items cannot be averaged when the denominators do not match. When the hill takes 1 gallon on the way up and 0 gallons on the way down, the denominators do not match.

This is one of the reasons the U.S. MPG scale is stupid. Figures expressed in Liters/100km or Gallons/100miles could be averaged by your method.