Hypermiling poll: Hills

I don't do anything special on the way up. The car has to burn more fuel to gain elevation.

But pay special attention to the way down. This is where you make or break average round trip MPG by 'recovering' the fuel burned on the way up.

 

Hypermiling...Depending how much regen is expected on the other side, I would try to "glide" up in EV, giving room to "free energy".

"Normal" behaviour...keep up the speed, or slowing a bit up hill.

 

In general, as constant power output as you can manage [allowing
speed to drop] seems way more efficient than ramming it on the
upside. You can get most of it back on the down, often even in
warp-stealth without burning any gas at all. If speed drops too
far, obviously, we have to push harder but I generally don't
take the ICE above 3000 RPM and if that's truck-climbing-lane
territory, so be it.
.
_H*

 

Based upon this chart:

I would try to keep the 1.8L Prius between 2,700-3,800 rpm with 4,000 rpm being an upper limit. This lets the ZVW30 run with maximum, cooled exhaust so the mixture should be about a lean as it can be at high power settings. As a general rule, we like to see the exhaust temperature as low as possible so the left side of this rpm range would be 'less bad' than higher ICE rpm ranges.

Bob Wilson

ps. not voting

 

If it is just me and a strip of pavement (rarely): Pulse down to reach desired maximum speed at the trough and fairly rapid decel on the climbs such that I crest at my desired minimum speed. These uphill 'glides' will pull down SOC, but the big speed delta seems to drive trip mpg ever higher. Not enough results to quantify. In big hills, this might be 70 mph down to 20mph. Not practical generally.

In 2-way traffic or heavy traffic, reverse the above: pulse up and glide down for an almost steady speed. Would use cruise but don't want regen on the glides. Plus, I start the pulse before the trough and ease off near the crest if traffic permits.

In most cases on the freeway where traffic can easily get around: steady throttle so you lose speed slowly on the climbs and recover it on the downs. Small speed delta that does not impede anyone.

The last two methods work fine with passengers who don't notice major differences from 'normal' driving. Not so the first.

 

Since "hypermiling" is the operative word, I will add my input on the basis of my experiences and also on the basis of the available hypermiling toolkit.

The following assumes safe and legal speeds on the right most lane while never exceeding the PSL!!

- If possible, acquire a bit of speed before entering the climb. Typically a gentle increase in speed will help especially if we place the ICE in a low IGN reading (13-16 on the scangauge). When compared to the Gen 2, the Gen 3 Prius is a lot harder to get into this range but seeking a lowered RPM (<1300RPM) usually gets us close to this optimal boundary.
- Lock in a target MPG and monitor the rate of speed loss as you may not want to drive too slow while cresting the hill. If the rate of momentum loss becomes too high then ensure you stay off the pack as much as possible and have the ICE do most of the work. At this point use the DWL technique to get you to the top of the hill.
- Once at the top of the hill, the follow-up strategy will also depend on what's ahead, but it is generally a good opportunity for ICE off and good regen opportunities with some speed gains on the way down.


Think of a hilly topography as a roller-coaster: You loose some speed as you climb and you gain just enough speed on your descents to continue the game in the right-most lane.

Cheers;

MSantos

 

I like taking advantage of slower tractor trailer rigs. Many of them will be in the far right lane going slow, and people understand if THEY go slow. If you're tucked in behing 'em ... no one cares, because folks can see the big truck in front of you. Now, I not only benefit from NOT having to overcome wind drag of higher speeds, I have the added benefit of slip streaming in the truck's wake. Works for me.


.

 

The tactic used to climb a particular hill takes many variables into consideration...

Traffic, steepness of hill, strength of charge, terrain prior to the hill and after the hill, etc, etc, etc.

In general, on a "normal size" hill I would be in the 2000 rpm range climbing up the hill until reaching near the top at which point I would A) ride down the hill in neutral as long as my speeds were at or below the 60 mph range and traffic allowed or option B drop into warp stealth or battery only mode depending on speed as traffic allowed.

The one thing to remember about hills is that there is always a decline after the incline...at some point if you drive far enough. That being said...you always have the opportunity to recapture the mpg lost climbing the hill as you proceed down the hill. Because of this...climbing the hill efficiently is just as important as going down the hill.

One nugget of information that has helped me attain higher mpg is to not view the hill as up and down...rather as resistance and absence of resistance. When going up the hill the goal should be to monitor rpm's and as traffic flow allows decline slightly in speed to keep rpm's low. Then...when cresting the hill...use the entire decline to overcome any mpg losses from the uphill portion (aka absence of resistance). If your overall tank goal is 60 mpg and the uphill and downhill are equal distance an mpg of 30 on the uphill and mpg of 100+ allows you to stay above your tank goal.

For closely bunched small to medium size hills you can employ a reverse pulse and glide technique where you would pulse on the decline...drop into neutral (at 60 mph or slower)...and glide on the incline. To "move" the car you need gas...why not move the car in the most efficient environment...with the least resistance and going downhill. And while you may need a small amount of pulse to reach the top of the next hill during your glide (depending on the size of the hill)...you are pulsing the car during the time of least resistance...on the downhill. That being said...monitor mph when doing this so as to not reach too high of speed over the limit.

 

Neutral doesn't help because the engine idles and continues
to burn fuel. Not a lot, but still burning. That's *why* there
is warp stealth...
.
_H*

 

Chose the wrong one can I rechoose?

 

That's why I gave two options...option A neutral glide and option B warp stealth.

To answer the OP's question on how to efficiently ascend and descend hills you almost need to be in the car with them to be in their environment (traffic, grade, etc). With a car in front of you and an impending stop on the decline...maybe I'd regen instead of warp stealth.

In general terms, I was just giving the options...all of which are more efficient than just using the Go pedal to move the car.

 

That is a great idea...I usually want to go around a large truck in front of me but why not drive like I would ride my bike on a group ride.

 

Can u explain warp stealth? 1st time Prius owner & new to Prius Chat.

 

A dealer told me to put the car in power mode and goose the throttle high enough so that you can glide over. This only works if you have some juice in the battery. Since the elect. Motor is high torque -- it will kick in as soon as you goose the throttle. So you use mostly the elect. Motor on short bursts. You can recover juice on the glide down the hill on the far side.

 

Try and maintain speed, losing 1-2 mph ok, but never let the instant mpg drop below 30 mpg while climbing the hill (or while any driving at hwy speed other than on-ramps or emergencies)

 

I think the trick with hills is to play roller-coaster and gain lots of speed on the way down the previous hill, then use this momentum to get part way up the next hill. On the way up I keep L/100km below 10 for as long as possible (lower if the hill is small) and let the car slow down on the way up. Rolling hills are so good for mileage.

As far as meeting a large hill on an otherwise flat road (or worse, a red light) sometimes you just have to spend a bit of money.

 

I never see any hills. In a 120 mile run from Greenville MS to Tunica MS, you gain 60 feet.