what strategy do you use when driving uphill?

[drewllbrb]

What strategy do you use to maximize mpg while driving uphill? Do you just floor it and get it over with? Or, do you go terribly slow and try to conserve? I drive downhill to school about 25 miles, and the return drive kills my mpg. What does everybody do in this type of situation?

[Neicy]

Assuming you were in a good glide all the way down, you probably got phenomenal mpg, so you are just averaging it out going the other way. Just drive at a reasonable steady pace back again. A lot depends on the speed limit you have to deal with, and how many lanes you have to work with. In the end you should still end up with something reasonable for mpg. It just looks bad because coming down looked soooooo good.

[AussieOwner]

I try to keep a steady speed, but also watch that MFD to limit the amount of power back into the battery. I feel that if I can keep the power such that the ICE is only powering the wheels and electric motor, I am not wasting any excess fuel. This is, of course, on the basis that you can fill up the battery with regen braking on the downhill segments.

[jiepsie]

I moved to a country that has no hills

[efusco]

Depends, if it's on a highway with traffic I don't adjust too much. I often try to 'pre-accelerate' when I'm 1/4-1/2 mile away from the base of the incline I'll bring my ICE rpm up to around 2300 (depending upon how steep and tall the hill is I may get up to 3000 rpm before I hit the base).

I use that momentum and maintain the 2300-3000rpm range for as long as I can without impeding traffic...more often than not, even in the hilly Ozarks, I can make it up and over the hill w/o exceeding 3000rpm.

Now, without the ability to monitor that rpm you just have to shoot for moderate acceleration and avoid the High rpm Wide open Throttle (WOT) condition which is terrible on your FE.

Sometimes, though, you just have to push it if the hill is particularly tall and/or steep.

With rural roads where I'm not impeding traffic if I get slower I will still pre-accelerate, but will avoid WOT and try my best to keep the rpm at or below 2300 even if it means a significant drop in speed.

[Devil's Advocate]

If you can set the cruise control and let the computer do the thinking. I used this method for a 2400lb cargo load this past weekend (3 adults, three motorcycles a trailer and all the gear for a weekend of racing from Anaheim to Las Vegas, avg 29 MPG there 27 MPG back @ 55 mph) and it worked great. The computer switches back and forth between the traction battery/ICE/and MIGs I & II a little more efficiently than when not using the Cruise control.

Only with the huge load and drained traction battery was there any issue with the cruise control. Going from Vegas to Anaheim (up the big hill just past state line) the traction battery gave out around 3100 foot elevation and the ICE went into generator mode running at full throttle (or almost, I judged this by the MPG reading which the lowest was 9.8 but averaged about 11.8 at full throttle).

The car slowed to about 45 MPH but no slower, so I think that MIG2 was doing most of the work, as all the electricity/power from the ICE was going straight to the MIG. Was worried about load on the MIG, but the temp was around 60 outside so not to extreme.

[usbseawolf2000]

My strategy is similar to Evan's. I gain more momentum before the hill and while climbing the hill, I watch the arrow between the ICE and the battery. My goal is not to have that arrow.

If there is arrow going to and from the battery that means, the ICE is making too much or too little power. I also maintain Ignition Timing Advance value around 17-20 depending on the hill.

For those without OBD-II reader, do not go below 25 MPG mark when climbing hills. If you use no fuel on your way down (using warp stealth), that means you'll average 50 MPG for that hill. If you are aiming to average 60 MPG, climb at 30 MPG.

[bwilson4web]

My experimental data with a 2003 Prius going up a 6% grade:

• 55 mph - ICE reaches 4,150 rpm, climb entails 2,400-4,150 rpm in which efficiency decreases
• 60 mph - ICE rpm includes excursions to 4,500 rpm when ICE efficiency significantly falls off
• 65 mph - ICE rpm spends more time at 4,500 rpm and battery drain is more significant
• 70 mph+ - ICE rpm reaches significant 4,500 rpm and the battery drain is negitive
• 80 mph - battery drains when reaching 525 ft., 160 m.

On the highway, I prefer to follow, not tailgate, heavy trucks in their climb lane, which often hovers around 55 mph. A perfect solution in the mountains.

NOTE, the potential energy gained is available during the subsequent descent. Just don't go nuts and waste it all at high speeds.

Bob Wilson