Advice for using Hybrid in Hilly Town

[broski499]

Hey Guys, so I'm still on my first tank with my 2008 Prius and I'm noticing my town's landscape is not optimized for great fuel economy.

My commute to work every day is 8 miles both way. The way there is more down hill and the way home has a slight incline. I have two choices in routes to take. One is on the Freeway and the other is side streets. With the Prius's strength in city driving I'm wondering if taking the side streets will be more efficient. Although it is more hilly then taking the freeway which is a gradual decline incline.

Any advice in how to maximize my fuel economy in a hilly area is greatly appreciated.

I'm currently averaging 43MPG, so I'm really close to the EPA but I want to blow past that!

[user removed]

I would take the freeway, unless there are no forced stops on the local route. On the uphill leg find a big rig to break the wind for you, 3-4 stripes behind the truck (126-160 feet). Same thing on the downhill leg except find the spot on your accelerator where the car is truly coasting, no engine or battery use (instruments will tell you). Maximize your coasting at 99+ MPG.

If you can not maintain your target speed without having to use regeneration then approach that spot with lower intiial speed. If you can pick up a vehicle in the right lane that offers you a wind break, it's good for an additional 10 MPG average.

I would think 60 MPG would be possible.

regards
mech

[gone-ot]

MEASUREMENTS (ie: data numbers) of MPG over each path will tell you the "tale" of which is better.

[Cobb]

I think you should read up on some prius mods like one to fool the temp sensor so the car cuts off sooner in the warming cycle, adding a switch for ev mode to use the power stored from the down grade and playing with speed limits.

The prius electric drivetrain is best for coasting and recharging the battery. The gas motor is best for accelerating.

Otherwise do all the other eco stuff, block grill, fully inflate tires and such.

[redpoint5]

I would take the route that gets you to where you want to be the quickest.

That said, the only reason the Prius has a better city EPA rating is because the speeds are lower than those on the highway. If you drove slowly on the highway, then that rating would be higher since there is less stopping. Stopping is detrimental to fuel economy regardless of what powers the car.

Lastly, fuel economy (MPG) is not important. Amount of fuel consumed to get to your destination is the important factor. If you could take a 10 mile route that gets you 50mpg, or a 5 mile route that gets you 40mpg, it would still be better to take the 5 mile route. What I'm saying is that you need to zero your fuel use gauge (you do have a SG, right?) and drive both routes several times to see how the average fuel consumption compares.

[MetroMPG]

Originally Posted by redpoint5

That said, the only reason the Prius has a better city EPA rating is because the speeds are lower than those on the highway.

Not exactly. The reason the car gets such great city MPG is mostly due to the amount of time the engine shuts itself off (which is every time you release the accelerator, once it's warmed up). EOC for the win.

For that reason, I think you should investigate the hilly side street route. (Though the other concerns are valid: time spent driving & total fuel burn.)

Provided the route isn't infested with stop signs/lights (worst ones are at the bottoms of hills) it could work out very well. You want to lift the accelerator at the summits (which stops the engine) and coast the descents (feather the throttle to cancel regen to maintain speed if necessary). Drive up the next climb. This equals pulse & glide. Equals fantastic MPG.

Generally also avoid using "EV mode" to propel the car, except for low speed futzing around (parking lots, etc. ).

Let us know what you find out!

[broski499]

Originally Posted by MetroMPG

Generally also avoid using "EV mode" to propel the car, except for low speed futzing around (parking lots, etc. ).

Thanks for the advice! I will defiantly have to take the different routes and see which uses the least amount of fuel. You mentioned not to use the EV mode except when in a parking lot. Why don't I want to use it to maintain a coast longer?

[broski499]

Originally Posted by redpoint5

What I'm saying is that you need to zero your fuel use gauge (you do have a SG, right?) and drive both routes several times to see how the average fuel consumption compares.

I have an Ultragauge, I will have to see if I have that gauge. I can always just subtract my starting fuel point and my ending and find out how much I used. Thanks for the advice. Didn't think about how the quickest could be the best because when you aren't driving you aren't using any fuel!

[MetroMPG]

Extending a coast can be a good use of EV mode.

But you have to keep in mind that juice you take out of the big battery has to be replaced, and if you're being a good eco-driver by minimizing braking, then you're not going to be replacing much via regen.

Which means you're recharging the pack by burning gasoline, which isn't very efficient.

How much you use EV mode should depend on how much you use regen.

[user removed]

His commute is 8 miles either way. I would guess it probably depends on the elevation changes he experiences. In either scenario, freeway, or local, the differences will be freeways tend to have less steep grades uphill and downhill. In his location how heavy is the traffic? How many stops especially those that are at the bottom of hills as Metro stated in his post.

The perfect hill allows you to climb at best bsfc, then maintain the same speed downhill, with the least disruption of traffic flow. The climb would be more steep than the downhill, with the downhill being the perfect slope to maintain your speed target, probably close to the speed limit.

The Prius is good aero wise, but wheel to wheel regen efficiency is not as high as best engine efficiency.

Without more information it's hard to choose the best route. If the hills are coastable within a close range of your desired average speed. The that would be the better choice, but that is ass-uming you dont have stop and go situations on the local route.

regards
mech