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I decided to take my new Prius #9 on it's first tank of gas up into the mountains to see how she'd do. I didn't do any major climbs, but did go up some serious grades and around some tight curves. For those that are familar with Colorado, I went up Golden Gate Canyon Hwy to 119 to Hwy 72 back to flat land.

First thing that evey new owner should learn: throw out all things you "know" about with respect to engine sounds! Of course, the first thing that freaks you out is when the engine stops at stop lights. Also, since there are no gears, you don't hear the shifting that you're used to either. But when you're going up a serious hill, the engine noise makes no sense to what your used to. First, with the electic motor helping pull the car up the hill, the engine sounds fine. I was surprised how well I was accelerating up the serious incline. Watching the battery, though, I could tell this was going to be short lived. Sure enough, as soon as the battery was "empty", that little four banger was solo in trying to keep us moving up the hill. It was whining and screaming to the point I thought it was going to burst. Now I know why they don't give you a tachometer 'cause it would probably freak you out! (I'm sure that Toyota has it all under control, but what a sound!) Ironic was that for a stretch, I was following a Porshe up the hill, and I thought that his engine probably was making the same noise.

Even though the four cyclinder engine was screaming, she got me up on top without having me be a slow poke, but I sure felt sorry for her. Then came the down hill run... What a thrill to put in the "B" mode and watch that battery charge back up! This was the first time I saw the familar blue battery bars go to one purple bar, to a full set of light green bars - full battery.

In the long run, the gas mileage of the whole trip was above 45 MPG. It was comical to see that at it's worse, when I was going up a steep section on just the ICE, the instantaneous mileage was 15 MPG, which was the "best" that my Dodge pickup would ever hope to get!

As far as handling, I've driven Acura TL's and Integras, as well as my big old Dodge pickup, so as far as handling goes, I felt safe whizzing around the mountain curves, but I wouldn't call it a sports car by any stretch of the imagination. I didn't want to take it to the tire squealing stage yet, but I was approaching it. I also hit some serious wind, and I didn't have any probably dealing with it like some folks report. But I'm also a pilot and I'm used to fighting wind, so it might be second nature to me.

So other than sitting in the most UNcomfortable seat around, and listening to that poor engine just about explode, it was a great drive and I look forward to many more.

Hope this helps prepare folks for when they get their vehicle. Enjoy...
 

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ephrumsirc said:
...What a thrill to put in the "B" mode and watch that battery charge back up...
I'm pretty sure my owner's manual says that regenerative battery charging doesn't occur when the transaxle is in "B" mode. Does anybody have any idea how his battery would get recharged going downhill in "B" mode?
 

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Magic.. yep... didn't ya know? damn car is magical

I must say, it's nice to get a true report from someone. I'm over here in San Jose, California. We have this highway 17 over here that goes over the hill. I keep seeing more and more Priuses going over the hill and i always wonder the same thing. How is that car doing? I see some zoom too. It amazes me. Thanks for the mountain update. I know of areas in colorado. My dad grew up there and we own some property in Manitou Springs. thanks again for the report. :D
 

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classic mileage in mountains

FWIW, I just had my first mountain experience since getting my 02 classic. On the city streets of Savannah and commuter driving, I was up to 58. Driving flat highway from Savannah to Virginia with defrost on I got only 45. After fillup in Southern Virginia I went through the mountains with CC on and no defrost, got 54.8. I am favorably impressed with southern mountain mileage. 8)
 

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BIF said:
I'm pretty sure my owner's manual says that regenerative battery charging doesn't occur when the transaxle is in "B" mode. Does anybody have any idea how his battery would get recharged going downhill in "B" mode?
I think you're getting confused with the word "regenerative," BIF. While it's true that there's no regenerative "braking" going on in B (as I also believe the manual states), that is, the brakes aren't contributing. Regenerative battery charging IS happening because you're coasting, i.e. you're not pressing the gas pedal, but still rolling. Just as it does on the flats when you coast to a stop before touching the brakes. Those of us in mountainous terrain who get long downhill stretches in B see our battery icon go to full all of the time. And let me tell you, with the lack of rolling resistance on these Priuses, you get going like a bat out of hell on those steep grades unless you ride the brakes or switch to B.
 

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BIF said:
ephrumsirc said:
...What a thrill to put in the "B" mode and watch that battery charge back up...
I'm pretty sure my owner's manual says that regenerative battery charging doesn't occur when the transaxle is in "B" mode. Does anybody have any idea how his battery would get recharged going downhill in "B" mode?
You're thinking of Neutral - no charging is taking place.

In "B" mode, you get the same amount of regenerative braking as you would in "D." It's the long descent that charges up the battery. The "B" is for engine braking - the engine spins (fuel not required) to help slow you going downhill so you don't burn out your brake pads.
 

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BIF said:
ephrumsirc said:
...What a thrill to put in the "B" mode and watch that battery charge back up...
I'm pretty sure my owner's manual says that regenerative battery charging doesn't occur when the transaxle is in "B" mode. Does anybody have any idea how his battery would get recharged going downhill in "B" mode?
Sorry, but you are wrong. The "B" mode in the new 2004 Prius does charge the batteries, infact in the owners manual it states this. Perhaps you are relating this statement to your / or an older "classic" prius, which does not recharge marginaly in the "B" mode.
 

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Common people. There is a nice screen in front of you that can answer this for you. For one, B does use the engine to keep you slowed down. I heard someone in here post that the engine isn't actualy on. Very possible. Even so, it's possible to charge the electric system too. Someone do a test (even though someone has done this and we are still questioning this) Go up a hill.. and cruise down using B gear. Look at your display to see if the battery is recharging. If so, Tell us if the engine is handing down some of the B gear power to the generator. The car tells you everything that's happening. I know for me i'll be using B gear a lot when i go over highway 17 from San Jose to Santa Cruz and back again.
 

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Discussion Starter #9
One thing I didn't mention that was interesting about "B" was that not only does the battery get charged (faster than if in "D"?), but unlike when you pop an "normal" car into low when flying down a hill, and you feel like the transmission is going to drop out of the bottom because of the sudden down surge, the Prius gradually eases into an engine braking mode. You can really it feel slow the car down. One bad thing I did do was forget to take it out of "B" for a small stretch, and I've heard that brings down the mileage quite a bit, but it didn't adversly affect the driving. So as you're rolling up and down, you just have to play with that joystick and pop in and out of "B" and "D".

Glad some folks got use of the report. Happy driving!
 

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woodworks said:
BIF said:
I'm pretty sure my owner's manual says that regenerative battery charging doesn't occur when the transaxle is in "B" mode. Does anybody have any idea how his battery would get recharged going downhill in "B" mode?
I think you're getting confused with the word "regenerative," BIF. While it's true that there's no regenerative "braking" going on in B (as I also believe the manual states), that is, the brakes aren't contributing. Regenerative battery charging IS happening because you're coasting, i.e. you're not pressing the gas pedal, but still rolling. Just as it does on the flats when you coast to a stop before touching the brakes. Those of us in mountainous terrain who get long downhill stretches in B see our battery icon go to full all of the time. And let me tell you, with the lack of rolling resistance on these Priuses, you get going like a bat out of hell on those steep grades unless you ride the brakes or switch to B.
Interesting
So it would be better to have it in D and ride the brake but not enough
to use the pads ??
 

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Here's some info about B in the 2001 Prius. I don't know if any of it applies to the 2004.

Every morning on my way to work, within 2 blocks of my house, I go down a steep hill. I usually crest the hill at 20-25 MPH. If I leave Pikachu in D and don't touch the brake, the battery charges at 9-12 amps (higher as it goes faster). I end up going 45-50 MPH at the bottom. Since this is a 35 MPH zone, I don't normally do that. Prior to getting my Mini-Scanner, I used to use the brakes steadily to end up at 35 MPH at the bottom. Since getting the Mini-Scanner, I've learned that I was wasting a lot of potential recharging. It turns out that the antilock braking system is extremely paranoid and will kill regenerative braking back to 9-12 amps at the slightest hint of a bump. By watching the Mini-Scanner, I've learned to feel when regeneration drops out. When it does, I release then reapply the brakes. I can get the recharge current up into the high 50's this way, but it requires heavy use of the brakes, so I must also release them some of the time to maintain speed. With light braking that minimizes the use of the brake pads, it only recharges with about 20 amps.

Finally, in B mode, I reach the bottom at about 35 MPH and get between 10 and 15 amp charging. This is not particularly car speed related, but does seem to vary inversly with engine RPM which is also not particularly steady.

I'm still not completely sure what to make of this, but a few things are evident:

- braking with the brake pedal instead of B could get a lot more regeneration except for the ABS cut-out.

- getting a high regeneration current from braking also requires heavy use of the brake pads, so a lot of energy is still getting thrown away.

- best reclaimation of energy probably occurs under light braking on a very smooth surface, but it takes a longer time to charge the battery this way.

- there is some regeneration occuring in B mode (more than would occur with the brake pedal on a slightly uneven surface), but it will also take a while to charge the battery.

- there's lots of room for improvement. Hopefully Toyota made significant improvement in the 2004 Prius.
 

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artman67 said:
Interesting
So it would be better to have it in D and ride the brake but not enough
to use the pads ??
How could you "ride the brakes" without using the pads? If you're applying any pressure at all to the brakes, the pads are getting worn.

The question I have is whether you're better off wearing your brake pads or using engine braking during a long descent? Brake pads are of course cheaper to replace than engines, but the fact that Toyota gives us the B option would suggest that perhaps they consider that the preferable option. Is a puzzlement. :?:
 

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Sorry, woodworks. But light (and I think moderate as well) pressure on the brake pedal, above about 8 (?) mph engages only the regenerative braking, via the MG. Harder braking, as well as braking below 8 mph, engages the pads. Driving conservatively, the brakes on the Prius should last very considerably longer than those on another car, because you are really making very little use of them. Cool car.
 

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Still some confusion about brakes, "D" and "B" modes here. I'll try to clarify.

First, remember that everything you know about conventional cars will very likely be wrong if you apply it to the Prius. :)
For instance :
If you're applying any pressure at all to the brakes, the pads are getting worn.
The brake pedal on the Prius is just a sensor that is transmitting your requirement to a computer, which will decide what to do in order to slow down the car. If it can without using brake pads, but electric motors instead, it will do it since it's better to charge the battery than just producing heat. So yes, it's possible to brake without using brake pads on a Prius. For more information see here (note that there has been a significant improvement with current generation Prius over the previous one).

Now, in "B" position there are 2 things that change compared to "D" : first, the engine is spinning (without fuel) and as every engine spinning with only air coming into the cylinders it brakes. This braking is not "regenerative", since it only produces heat. Second, there are more amperes coming into the battery than in "D" without applying the brakes, so one can say the regenerative braking through the electric motors is more powerful. However, you can also obtain more battery charging in "D" by slightly depressing the brake pedal, which will produce the same effect except that you don't have engine braking.

In conclusion : both "D" and "B" modes allow regenerative braking, only "N" doesn't. But there's necessarily some non-regenerative braking in "B" because of engine braking; so for maximum efficiency you should only use "B" in the cases where brake pads must be applied to slow down the car. It's rather difficult to tell when for new Prius drivers; as a "Classic" Prius driver I particularly enjoy the Prius Miniscanner which tells me exactly what's going on in the car when I drive. Unfortunately it's not available yet for the 2004 Prius.

PS : Daniel responded while I was writing my (long) post. I agree with him.
 

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How slow, mph, was the car on ICE? Was the gas pedal floored? How far up the grade (minutes?) did it go before ICE only?

TIA
 

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Discussion Starter #17
Rensho said:
How slow, mph, was the car on ICE? Was the gas pedal floored? How far up the grade (minutes?) did it go before ICE only?

TIA
Let's see... I had no problem keeping up to 60 mph, and it wasn't floored at all. It took about 3 minutes (guess) before I was on total ICE. Even though it sounded like the engine was going to blow up, somehow I felt like I could "give it more" and she would keep on going...

I've got another drive up Flagstaff mountain scheduled June 22nd, so I'll pay more attention and let you know if it's dramatic either way.

If I could figure out how to post files here, I was going to post a grade map that shows the elevation profile of the trip (from Topo USA), but I've got to figure it out...

Happy driving.
 

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Mountain Driving in AZ

Ephrumsirc,

That grade up to Sunset Point is pretty bad, but that long hill just before the scenic pullout south of Munds Park really drains the batteries. My 2002 Prius is usually on full ICE before the crest of that hill, but I can still pass a lot of other cars.

I think if everybody would go the speed limit or get out of the way, I could make it to the top with speed and batteries to spare. It's pulling out and passing that really drains the electrons.

I usually get in the mid-30's (mpg) going up, but enjoy the 30+ minutes of 99+ mpg coming back down. The gas savings makes it much more affordable to take to the high country on the weekends, this summer.

Have you checked out that gas station in NE Phoenix? I am only paying $1.649 per gallon (with the rebate).
 
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