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Discussion Starter #1
Hello,

I just got a 04 Prius for test drive. My questions is:

1) When coasting with foot off the gas padel, the car is in regenerate mode right?. So when I start touch the brake it should go into more deeper, harder regerate right?. What I am not so sure is when hard regenerat begin. When I press a little more, just a little bit more, it seem the hydralic is kicking and grabing the disk. Is that seem like what you veteran Prius feel like ?. The grabbing of the wheel seem like mechnical grab rather than electrical grab.

2) What is B mode drive for ?. Is it more harder regenerating or just mechnical drag via engine freewheeling?.

3) From what I experience so far, to drive a Prius and achieve 50 mpg and beyond, would require a complete overhaul of how you drive. From accelleration, coasting , speed modulating, trip planing, look a head, etc. etc. Is that seem sound like what you veteran feel too or am I just nerves.I only drive it for about 25 minute in heavy traffic all by myself.

I like the concept of regenertive, the design of the Prius propulsion system such as shutdown the engine, how it restart the engine, power split device, cvt, electric motor, cleaner. But I am not sure if it enough to change driving habbit. Now if I change my driving habbit and it give me 100 plug mpg that would be something I would surely do. I guess it's pretty easy to for get that Prius is a very clean car and that most people, myself included would over look it easily and just focus solely on mpg.

Comments are real welcome.
 

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There are others much more qualified to address the questions you ask about regeneration...however, I CAN tell you that I have made a few minor adjustments to driving style - but nothing drastic! I am much more likely to pay MORE attention to road conditions/traffic patterns so that I don't have to rapidly decelerate (brake hard)...and i admit to coasting through a few more neighborhood stop signs ... but other than that I haven't changed my driving habits a lot. And I get 48 to 52 mpg. I live in the Maryland suburbs of WashingtonDC and drive 14 miles to work each day in stop and go local traffic, so I'm both impressed and pleased with my car's performance! BTW on interstates I'm more likely to be driving at 70 with occasional drifts to 80, so I don't baby the car for performance.
 

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Knguyen said:
Hello,

I just got a 04 Prius for test drive. My questions is:

1) When coasting with foot off the gas padel, the car is in regenerate mode right?.
As long as you are going faster than 7 MPH, yes.

Knguyen said:
So when I start touch the brake it should go into more deeper, harder regerate right?.
Again, yes, as long as you're over 7 MPH. There is another limitation here. If the Antilock Braking System (ABS) senses a difference in wheel speed, the harder regeneration will be shut off and it will rely on hydraulic brakes.

Knguyen said:
What I am not so sure is when hard regenerat begin.
Regeneration increases with pedal pressure. It takes a fair amount of pressure to maximize regeneration.

Knguyen said:
When I press a little more, just a little bit more, it seem the hydralic is kicking and grabing the disk.
The hydraulic brakes kick in from the start on the rear wheels since regeneration can't affect them. Perhaps that's what you feel. This is important because you don't want the rear wheels drifting around in front of you when you brake.

Knguyen said:
Is that seem like what you veteran Prius feel like ?. The grabbing of the wheel seem like mechnical grab rather than electrical grab.
I don't have 2004 experience. The 2001 does apply both front and rear hydraulic brakes throughout. Regeneration is more of a brake assist.

Knguyen said:
2) What is B mode drive for ?. Is it more harder regenerating or just mechnical drag via engine freewheeling?.
B mode is there for the same reasons that conventional automatics have 2 and 1 in addition to D. Use it when decending a long hill to reduce the load on the brakes. It's primarily mechanical drag from the engine, but it does tend to a higher recharge current to the battery than the simulated engine drag of D mode. The recharge current is significantly lower than when doing an equivalent amount of braking using the brake pedal in D mode.

Knguyen said:
3) From what I experience so far, to drive a Prius and achieve 50 mpg and beyond, would require a complete overhaul of how you drive. From accelleration, coasting , speed modulating, trip planing, look a head, etc. etc. Is that seem sound like what you veteran feel too or am I just nerves.I only drive it for about 25 minute in heavy traffic all by myself.
The general advice is to "just drive it". You'll eventually learn to fine tune your driving via feedback from the MPG screen. There are some things to be aware of though. Tire pressure is very important. Low pressure kills mileage. Many service departments set it low. You won't achieve anywhere close to 50 MPG if you mostly do short trips (5 minutes or less).

If your heavy traffic was "stop and go" traffic, you also didn't have a chance to get 50 MPG. In that situation you'll get around 5 MPG in a regular car and around 20-25 MPG in the Prius. Not bad.

Knguyen said:
I like the concept of regenertive, the design of the Prius propulsion system such as shutdown the engine, how it restart the engine, power split device, cvt, electric motor, cleaner. But I am not sure if it enough to change driving habbit. Now if I change my driving habbit and it give me 100 plug mpg that would be something I would surely do. I guess it's pretty easy to for get that Prius is a very clean car and that most people, myself included would over look it easily and just focus solely on mpg.
Don't drive like a maniac and you'll be fine. See John's site for lots of driving hints you might want to consider.

Knguyen said:
Comments are real welcome.
Congratulations on your test drive. Let us know what you decide.
 

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You can get as involved as you want to as far as driving style goes. I personally use the mileage info screen as a sort of biofeedback station. I'm in no hurry so I can pamper the car and I get rewarded with higher MPG.
 

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Discussion Starter #5
Hi guys,

Ok let me be clear about what happen. Today the dealer let me do an overnight test of a 04 Prius. Picking it up at noon and drove it back to work. I was nerves and not sure about driving it so the original comment is no longer valid:
Here is some of my though:
I understand the EPA rating. Its mean the car is capable of but not fixed at . So when the EPA rating for the Prius is 60 city and 50 HWY I understand it rating. Its understandable for a hybrid. A lot of people do not understand that. For example my coworker today pointing out at the EPA sheet on that car and said see its funy. Its hould be the other way around. Now Rober S. you say if in a stop and go I would get around 20 to 25 mpg for the Prius. I do not understand why would you say so ( no flaming or other wise intended just simple discussing here). Before I test drive the car today I understand why EPA would rate the Prius 60 in city. In a stop and go situation the Prius would shine like a sun. Its where the hybrid propulsion work best by using regenerative, battery and ICU as a whole to save gas. The control system would maximize regenerative and battery use and minimize ICU use. And that seem to be exactly what happen to me today on a trip home from work.
Eden Prairie to Brooklyn Park via 169 is 18 miles of traffic jam on a nice and sunny day and 18 miles of 2 car length parking lot when ever a single flake of snow hit the ground. (John 1701A would know what I am talking about. 169 jams up is the worse if not worse than 35W and 494 intersections. John, back up me on this wills you).
For most of the time the traffic would creep up at 15mph for 5 cars length then stop, or 20mph for 10 cars length then stop. The ICU runs seldom and battery usage was more. The ICU would run when climbing hill but would shutdown as soon as accelerator lifted. And while the ICU run it would recharge or when traffic stops ahead, the generator regenerate. It keeps at it until I got home and the MFD show 65mpg for 18 miles drove. Thats a great mileage. That is 3 times more than my current cargo class transportation machine which get about 20mpg hwy (Dodge caravan 3.3 V6). So I took a picture just in case some one wants proof.
When I got home I drove my kid to my mom and comeback for a round trip of 36 miles. When I got home the MFD show 52mpg for 56miles drove. So I guess hwy drive does lower the mileage a bit since the ICU is use more.

So I do think that EPA is achievable fairly, dare I say, easy. In city specially stop and go a 60 plus mpg is achievable and in HWY a 55 mpg is bit harder to achieve but can be there nonetheless.

When I got home again, my wife hop in and took command . I advice her how to activate the ship. She, then proceed to clear it from docking. All the time I keep commenting her that she is not a candidate for driving a hybrid ( I have a hidden agenda for this so please understand).I told her that she drive a hybrid car like she would drive a normal car, she get close and brake hard instead of coast to regenerate. I, then, proceed to explaining to her about the concept of regenerative, the modern automotive technology such hybrid. But to my surprise, she got more turtle that I did when I drove it. So even though I am a very technical minded ( B.S. in Computer Engineering) experience is the second part of knowledge.

In short, I am completely sold on the hybrid concept. Toyota have made a technological advance in automotive technology by combine the ICU and an electric motor via the use of planetary gear; specially how the engine start that made it all possible. The next technological breakthrough would have to be a lot higher battery power density. I wish for a bigger capacity or an option to add on an extra 100kwh battery. When that happen then 100mpg in city will become a very real reality. After today drove home on a real every day condition and achieve 65mpg average for 18 miles without much trying, I feel that were witnessing the dawn of a new age in automotive technology.ok dont hurt me if it seem stretching it a bit.. I am still fresh from the drive experience. Tomorrow returning the car will be hard.. I hope I dont cry.

My hidden agenda is to brainwash her that the Prius were ordering will be my, since she drove a 97 Camry 3.0V6 with 2 miles on the odometer when I pick it up at the dealer for her back then. All the while I was driving an old beater 81 Prelude.

So for now that wait is on. My wife and I agree that we should go ahead a buy the car ( all the while I keep say in ok but this is my new car right.. rightyou had the Camry brand new and now its my turn right)

Were ordering a package 7 any color but a silver or a black is nice.

P.S. If some one would buy me a Prius, Ill mow your lawn for a year.
 

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RSnyder said:
Knguyen said:
When I press a little more, just a little bit more, it seem the hydralic is kicking and grabing the disk.
The hydraulic brakes kick in from the start on the rear wheels since regeneration can't affect them. Perhaps that's what you feel. This is important because you don't want the rear wheels drifting around in front of you when you brake.
I do not believe this is accurate. Regenerative braking takes place unless the deceleration level desired, determined by brake pedal travel, is greater than regeneration can provide. The rear drums do not come into play during light braking. There is a Toyota graph of this in one of their technical presentations. They come into play at the same time the front discs do. Also, dynamically, it is desireable to have less or no braking on the rears. This improves stability and directional control. What would cause the "rear wheels drifting arount in front of you when you brake" is if the rear wheels were locked. Otherwise this cannot happen, even in the absence of front braking.

The amount of regenerative braking available is significant. It feels almost like traditional braking, which was the design intent.
 

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Discussion Starter #7
MD,

I too, have spend time researching the Prius. I too have seen the graph. I was testing what I read and what I should experience. I didn't know how the Prius response. I can only reference my experience from what I know from conventional non regenerative brake and I feel the disk got grab almost as soon as I press down on the brake slightly. But now with a little more drivving experience ( what ever little time I got from overnight testdrive). My feeling is that you are right, the graph is right , that regenerative begin almost right away and as hard as real brake is and I can press down harder. I was gauging how hard I have to press down the brake to slow the car down when needed but at the same time minimize wear on brake and maximize on regenerative effect.
 

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Guess I better defer to those with 2004 specific knowledge. My comments apply to the 2001-03. I left one detail out of the stop and go mileage description. While you still have a decent charge in the battery, it will appear you're getting 100 MPG or so. This lasts for about 10 minutes, then the MPG from that point on is 20-25. But remember, all the other cars around you are getting 5-10 if they're lucky.
 

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Hey! I'm even stilling learning about the truly impressive design of HSD.

At 73 miles, the value on my Multi-Display said 64.3 MPG. (And that's using E10, which holds less energy than 100% gasoline!) That amazing performance wasn't expected. I was just cruising along in the burbs, with only two brief jumps onto the highway. Now at 109 miles, it has dropped to 59.5 MPG. Bummer, eh?

The remarkable engineering will end up surprising lots of people in the end, especially those that try to apply traditional concepts. HSD was built from scratch, with little concern for retooling & retraining needs. The goal was to deliver an product that wasn't bound by the current industry limitations. Being forced to restrain design due to "this is the way it is done" mindsets was really a pain. Thankfully, we are no longer in that realm anymore.

The most difficult aspect I have to deal with when discussing Prius is lack of perspective. Many really don't have a good understanding how their current vehicle actually performs. Most are totally shocked when they see the back of my website-card. That huge dip in MPG during the winter comes as a total shock to them. All this time they have been under the impression that vehicles are immune to the effects of winter, that they perform the same year-round.

Arrgh! Oh well. Time will reveal the fact that HSD is far more capable (and less complex) than the the impression people currently have.
 

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Discussion Starter #10
Robert

What you wrote about the fully charged battery seem very logical and yet how did the Prius achieve high mileage is not quite logical ... but it did happen to me and to other. I recalled my drive to home from work was that, since I am fresh as a daisy in drive the Prius, I mostly eyeball the mileage LCD... so I didn't remember much about the ICU activity. Mostly I remember that it's would run briefly every time there is a small inclinenation on the road and regenerate almost as soon as the paddle lifted.

My guess is, since the ICU never roar when response to high power demand, it mostly run at low load and at maximum efficiency which dictate by engine control system ,and that the battery got recharge from ICU and from regenerate that probably why I got 65mpg all the way.

I notice that every time I jump to freeway or accelerate even in local road, mpg would drop as low as 14mpg until the load demand is drop and I have reach steady state then mpg start to climb until ICU cut out. Then at that point it on battery and mpg shot to max. So my guess is that the battery state drop and then briefly recharge then drop then recharge due to the nature of stop and go and the ICU would only running on low load and cut out ASAP when the gas lift. And that enough to keep the system achieve it purpose and it ratingpretty cool made me wish for a 500KWH battery, a 1000V regenerator on the Prius and a flash charge system. Minimize gas usage, lesser pollution..more power to the disruptor ...wait...nevermind that...the list go on and on.

Normal ICU would keep running at fast idle or normal engine road speed when the gas paddle lift due to transmission couple (except for manual tranny which can be decouple if the driver so wanted). One of the most importance features of the Prius hybrid system is the ICU cut out almost instantly when gas pedal lifted. (My opinion). At almost any road speed the ICU will cut out, this feature save a lot of gas. I guess in the Prius world there is no such word as "idle" in the vocabulary. The Prius ICU run for a very specific purpose when it run: as a primary mechanical power source, battery recharger, heat source. There is no idle state. It's kind of cool to drive this car... I return the 04 Prius back to the dealer yesterday and I already miss it... It's gone be a long wait...

One other thing ...some review still have a mind set of expectation of EPA of the Prius as they would from a normal ICU.. They keep posting a 38 or so for city and 42 or so for highway... I kind of confuse??... did they actually test the Prius mileage or did they pluck the number from the air and fill it in... in the same format of low in city and high in hwy just to discredit the Prius that the Prius is just a hype and would not live up to it expectation..have any one notice that ?.. I mean, there are reviews that would say that ...to achieve the Prius EPA rating, one would drive in such a way that they would endanger other on highway. I honestly didn't not drive below 55 limits nor did I accelerate way too slow during a jump on or jump off freeway.. and I did still get 51mpg or so for 50 miles..how about you guy.. did you guy drive in a way that would endanger other to achieve maxi mpg ?..It's make ya question about the review accuracy and intention...
 

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I have driven my Prius for 4500 miles and consistently get 50-52 mpgs. I have made no big adjustments to my driving style; I just watch out for downgrades and remove my foot as soon as possible from the accelerator to coast downhill, coast to red lights instead braking when close to the light, and accelerate moderately.

The EPA estimate for highway conditions is easy to reach or surpass; I don't drive enough in the city to determine if those 60 mpgs are as easy to obtain.
 

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REGARDING THE QUERY AS TO WHTHER ONE HAS TO CHANGE HIS/HER DRIVING HABITS IN ORDER TO ACHIEVE BETTER MILEAGE: YEA-- YOU DO.BUT I LIKE TWO QUOTES FROM FELLOW PRIOUS OWNERS. (1) "You can get as involved as you want to as far as driving style goes. I personally use the MILEAGE INFO SCREEN (consumption screen)as a sort of biofeedback station. I'm in no hurry so I can pamper the car and I get rewarded with higher MPG."
I ALWAYS USE THE SCREEN THAT SHOWS HOW MUCH POWER YOU ARE REGENERATING AND WHAT YOUR MPG ARE. I LEARN TO BE MUCH LIGHTER ON THE GAS PEDAL-- AND I AM REWARDED WITH GREAT MILEAGE.(2) ANOTHER QUOTE: "I have driven my Prius for 4500 miles and consistently get 50-52 mpgs. I have made no big adjustments to my driving style; I just watch out for downgrades and remove my foot as soon as possible from the accelerator to coast downhill, coast to red lights instead braking when close to the light, and accelerate moderately.
The EPA estimate for highway conditions is easy to reach or surpass; I don't drive enough in the city to determine if those 60 mpgs are as easy to obtain."
LIKE ALL ESTIMATES ON ALL NEW CARS- they are not always realistic. I GET GREAT MILEAGE-- BUT I DO NOT GET 60 MPG -- EVEN WITH A LOT OF COASTING!!! LOVE THE 2004 PRIUS!!!!!
 

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Discussion Starter #13
becky said:
LIKE ALL ESTIMATES ON ALL NEW CARS- they are not always realistic. I GET GREAT MILEAGE-- BUT I DO NOT GET 60 MPG -- EVEN WITH A LOT OF COASTING!!!
I did get 65mpg in that instant of drive from work to home. I know it's only 20 miles oneway trip, one time, but the highway that I took to go to/and from work is the normal route and in normal jame up. I suspect that when I got my Prius I would get close to low 60 mpg as easy as that time. I still think that the Prius is really shine in heavy traffic.
 

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becky said:
LIKE ALL ESTIMATES ON ALL NEW CARS- they are not always realistic. I GET GREAT MILEAGE-- BUT I DO NOT GET 60 MPG -- EVEN WITH A LOT OF COASTING!!!
I once got 64.4 MPG on a 157 mile trip. Yeah, it was a short trip, but valid nonethelss, because it was my typical daily driving (no special "all downhill" trip or anything like that), and because I filled up and calculated the mileage mathematically. Also, there were no temperature changes that might have messed up the calculations by way of "bladder shrinkage," so I'm confident that this was accurate.

My next goal is to get over 60 MPG on more than half a tank's worth of driving. (bragging rights at work - Priceless!)
 

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Knguyen said:
P.S. If some one would buy me a Prius, I’ll mow your lawn for a year.
Sorry, no deal; my lawn service does that now for a LOT less. 8)
 

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BIF said:
My next goal is to get over 60 MPG on more than half a tank's worth of driving. (bragging rights at work - Priceless!)
Have you considered publishing a book on how you achieve those results? I'll buy one. :D
 
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