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Discussion Starter #1
I was wondering if the Prius is capable of a sustained criuse ranging from 80-100mph with mild rolling hills. The battery won't run out and leave me with the trucks going 65 will it? Yes I know this speed seems a bit high, but on I-280 it is very normal to see cars going at this pace, even the slowest cars touch 80.

BTW what is the top speed of this car?
 

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I drive an '02, so some of these numbers may have changed for the '04. The top speed is 100 mph, and the car can handle sustained speeds of up to around 85 mph indefinitely. I've only heard a few reports of low batteries when climbing very high, steep mountains at high speeds for extended periods of time.

Unlike the Honda Insight and Civic, the Prius can use the engine to recharge the batteries while simultaneously providing torque to the wheels. Therefore, both the battery and the engine can drive the car under significant load forever (or until you run out of gas). However, above 85 mph, the engine has to do so much pushing that it can't always generate enough electricity to keep up with the depletion. There's plenty of capacity in the battery for excursions into the 85+ mph range (e.g. passing), but you shouldn't expect to cruise uphill indefinitely at those speeds.

To answer your specific question: no, the battery will not run out, letting trucks pass you at 65 mph. If you cruise steadily at 90 mph for a long time, your battery might drop enough that you would be limited to 85 mph for a while, but those "mild rolling hills" you mentioned will allow the engine to use some excess torque to recharge the battery. I don't think you'll have any problems--please post your results.

Douglas (2002 Silver, Wisconsin)
 

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Sounds good to me, it'd just be too embarrising for me to buy a $22k+ car and be beat by a $14k budget mobile on the freeway. This is will be a significant purchase, and for this price I need to know it will handle freeways as well as a Camry. I'll let you know when I finally get the car, looks like it could be a while. :wink:
 

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lasrx said:
Sounds good to me, it'd just be too embarrising for me to buy a $22k+ car and be beat by a $14k budget mobile on the freeway. This is will be a significant purchase, and for this price I need to know it will handle freeways as well as a Camry. I'll let you know when I finally get the car, looks like it could be a while. :wink:
It seems to me that if you're getting a Prius, at any price, your priorities shouldn't be to "better" other drivers as if in a race.

If you have a competitive spirit, and are planning to race your Prius with other highway drivers, I would respectfully suggest that you should consider racing other hybrids or else maybe re-examine your reasons for buying a hybrid. Just my never-to-be-humble opinion.
 

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lasrx said:
Sounds good to me, it'd just be too embarrising for me to buy a $22k+ car and be beat by a $14k budget mobile on the freeway.
The budget mobiles are not necessarily slow. The Toyota Echo's 108hp gives it decent acceleration due to its light weight. And cheap 2004 Ford Focus ZX3s and LXs sold in California come with the 2.3L PZEV engine with 148hp.
 

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Discussion Starter #6
BIF said:
lasrx said:
Sounds good to me, it'd just be too embarrising for me to buy a $22k+ car and be beat by a $14k budget mobile on the freeway. This is will be a significant purchase, and for this price I need to know it will handle freeways as well as a Camry. I'll let you know when I finally get the car, looks like it could be a while. :wink:
It seems to me that if you're getting a Prius, at any price, your priorities shouldn't be to "better" other drivers as if in a race.

If you have a competitive spirit, and are planning to race your Prius with other highway drivers, I would respectfully suggest that you should consider racing other hybrids or else maybe re-examine your reasons for buying a hybrid. Just my never-to-be-humble opinion.
I don't think I'm competitive on the freeway; but I also don't want to be the car that has to move into the slow lane because it can't keep up with traffic. Performance is important because there is a 13 mile stretch of moderate hill climbing at freeway speeds(CA-17). But there is an equally long descent which makes me think of how a Prius can recapture all that energy I used getting up to the peak. The highest gas spike this year was $2.69, its averaging $2.29 now, but summer is coming with the summer hikes sure to follow.

I guess my reasons for a Prius: the super milage, and the fact that I'm not hurting the enviorment as much as a normal car, its reasonable performance, the neat / cool thing factor, and the smart entry system is also a nice bonus. Maybe it would be wise sit and wait for more information more about the Hybrid Accord V6, and the Hybrid Camry.

About the Focus and Echo I doubt I can see myself in either. The Echo in my mind is simply unsafe, it is maybe TOO light(2085lb). One of my friends owned one and a high gust of wind blew his car into the side of the freeway destoying the car. The Ford and its Focus doesn't seem to have the best track record for relaibity, which makes me question its long term value. I own a Camry that bluebooks for double a Taurus of the same model year and equipment level. I guess resell value is important to me too.
 

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Hi, Lasrx:

Okay, I take back what I said. Your earlier comment about paying money and being the slow one kind of lead me down the path that you may be buying a Prius for the wrong reasons.

I don't have my own Prius yet...only about a week to wait. But I have read an awful lot about it, and from what I can tell, if you're going up a hill, the ICE will drive the wheels and possibly recharge the battery too. I guess under certain circumstances (maybe a headwind, heavy payload), an uphill climb may also need help from the electric motor.

I think if you're going downhill on a freeway, the engine keeps turning, but the fuel and spark stop, and the compression is relieved...that way, the engine is already moving when it's time to apply fuel, spark, and compression again (at the bottom of the hill).

If the ICE needs help (usually during acceleration), it will drive the wheels and generate electricity for the electric motor, so both will be moving the car.

If I have misstated anything, I'm sure I'll be corrected. So check back.
 
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Prius at 90

I have no problem maintaining 90 on the interstate. Never had any battery problems either. I also am able to maintain 90 on a 6% hill on interstate 84 for five miles straight. Believe me, take it from someone who owns an '04... you WON'T have a problem.
 

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Re: Prius at 90

I am not talking cruising speed but I talked to a guy that said he took his up to 112 and it wasn't done yet. I want no part of that but I was surprised to hear him say it.

jim
 

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lasrx said:
...

Performance is important because there is a 13 mile stretch of moderate hill climbing at freeway speeds(CA-17). But there is an equally long descent which makes me think of how a Prius can recapture all that energy I used getting up to the peak.
I have not driven a new Prius, but I can tell you that the classic Prius (with less power) chews up Hwy 17 like angel-food cake.

I took one for a day trip to Monterey. I outran everything going up the hills -- SUVs, sports cars, the lot -- but, with the classic's dodgy suspension, got passed on the downhill because of poor handling. (It was a rental -- it may have also been poorly inflated or worn tires.)

Battery meter never budged from 3/4.
 

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Discussion Starter #11
mho said:
lasrx said:
...

Performance is important because there is a 13 mile stretch of moderate hill climbing at freeway speeds(CA-17). But there is an equally long descent which makes me think of how a Prius can recapture all that energy I used getting up to the peak.
I have not driven a new Prius, but I can tell you that the classic Prius (with less power) chews up Hwy 17 like angel-food cake.

I took one for a day trip to Monterey. I outran everything going up the hills -- SUVs, sports cars, the lot -- but, with the classic's dodgy suspension, got passed on the downhill because of poor handling. (It was a rental -- it may have also been poorly inflated or worn tires.)

Battery meter never budged from 3/4.
Ah, thats very reassuring to hear someone whos been on this road before vouch for the car. Passing; I'd never dreamed it could do anything close to that here. I think the B gear would be put to very good use going down as well. I guess I should rent one and go on a roadtrip to see how it handles my commute.

BTW Jimb, 112Mph is just a bit higher than I usually take it, but its nice to know it can do it. I wonder what kind of milage the Prius gets at 112, I'd think the aerodynamics would break down long before that putting a lot of excess drag on the car killing milage.
 

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I think there's a limiter in place to prevent powered speeds of >105 or therabouts.

Remember, your coeficient of drag will double from 50 mph to 70mph. I'm not a mathmagician, but I am under the impression that it's not a linear decrease of cd. Which means that your mileage will degrade even faster at 80, 90, 100 or faster.

In my manual geared BMW Z3, I was able to go almost an extra 100 miles on an 11-gallon tank of gas just by driving between 50 and 55 mph, compared to my typical highway speeds of 80-90 mph. Sounds weird, but it was true.
 

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Discussion Starter #13
BIF said:
I think there's a limiter in place to prevent powered speeds of >105 or therabouts.

Remember, your coeficient of drag will double from 50 mph to 70mph. I'm not a mathmagician, but I am under the impression that it's not a linear decrease of cd. Which means that your mileage will degrade even faster at 80, 90, 100 or faster.

In my manual geared BMW Z3, I was able to go almost an extra 100 miles on an 11-gallon tank of gas just by driving between 50 and 55 mph, compared to my typical highway speeds of 80-90 mph. Sounds weird, but it was true.
I thought most cars were electronically limited to 130mph. Is the low number to protect the Prius from transmission damage? In my car I need close to 4,000 revs at speeds over 100mph, I've read that the Prius redlines at 4,000. Maybe 105+ is pushing it to spin too close to redline?

http://www.findarticles.com/cf_dls/m3012/12_179/58398900/p3/article.jhtml?term= As I see it the ICE must be engaged at speeds above 42mph. Also the Prius engine isn't as heavily reinforced as normal engines. It doesn't have to be for what it was intended. So I guess the engine doesn't like 105+ speeds because it takes it up to redline. Hence the 105 limit?

I'm not sure exactly how aerodynamics is calculated. But I always thought that if you start to hear wind noise your wasting energy (noise is a byproduct of kinetic energy being converted to sound?) it forces the engine to make up for it. I too have noticed that going 55 does save a bit of gas, maybe it could a combination of the lower wind resistance and lower engine RPMs. But the Prius is extreemly aerodynamic so maybe it can hold higher speeds before the wind starts to affect milage?
 

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lasrx said:
I thought most cars were electronically limited to 130mph. Is the low number to protect the Prius from transmission damage?
Many cars are electronically limited to not exceed the speed rating of the tires. Since the Prius comes with tires with the S speed rating, it would not be surprising if it had a limiter at 112mph or less (the S speed rating for tires corresponds to 112mph).

Of course, you can put tires with a different speed rating on the car. There aren't that many summer or all-season car tires for sale with lower than the S speed rating, but many winter tires have lower speed ratings (not that you would want to go 112mph or anywhere close on snow and ice). Many summer or all-season car tires have higher speed ratings like T, H, and V. Usually (though not always) the higher speed rated tires tend to emphasize sportier characteristics (like handling and braking).
 

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Though I'm not completely sure of this, my understanding of the way the electric motor and computer controlled inverter works leads me to believe that the 101 MPH limit on the 2001-2004 Prius is at least in part there because above that speed the motor/inverter will always produce a higher voltage than the battery. This would force the battery to be continuously charged, quickly exceeding it's capacity then overheating it.

It would also be pretty hard for the engine to maintain speeds over 101 MPH since engine power would be unavoidably drained off to this charging current. You'd probably need a downhill run or stiff tailwind.

With the higher motor terminal voltage of the 2004 Prius, this particular limit on speed would be higher.
 

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lasrx,
I have a 2004, and have driven over hiway 17 several times. (I live in Santa Cruz.) You push on the gas, it goes. Fast. I don't go as fast going down the hill (either direction) because I'm used to a smaller car. (I used to drive a Tercel.) The battery never gets below half full on the way up, and usually fills to the top on the way down.
 

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Remember that the '04 Prius has a 76-hp gas engine, which is perfectly adequate to keep it moving at high speed. The electric motor gives you power for acceleration and passing.

On my recent road trip I was generally cruising at 72 or 73 mph. Nearing home and impatient I was going 75 (the speed limit on I-29 in ND and SD). I was able to accelerate to 80 easily for passing. Beyond that I cannot say because I'd be scared to maintain 80 mph. But the car had plenty of power, and even against a fierce headwind driving 73 mph the Prius had no problems at all, and was able to zip up to 80 in no time flat for passing.

My Civic was much more sluggish getting from 75 to 80 for passing. The Prius felt like it was telling me I was a wimp for going so slow.

PLEASE DON'T DRIVE LIKE A MANIAC. The Prius has far more power than anyone but a race driver needs. Unless maybe you are towing something. It's not made for that.

Under conditions that would slow you down, the 18-wheelers are going to be going a lot slower.

A bigger issue is that the Prius does not handle well under strong cross-winds. I had to keep a tight grip on the wheel the whole time. The wind always blows hard here.
 

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Discussion Starter #18
I took a test drive today! I felt so short in the car, I couldnt see over the hood. ;) I was scared weaving out of a tightly packed lot of NEW cars. It was a new experience trying to figure out where the car was without a hood to judge with. It feels like the car can handle its own on a hill. I managed to get it up to 62Mph on an uphill curve, far short of 80mph, but then the VSC kicked in and a warning beep sounded, the salesman said it was normal, but I decided to play it safe and let off the gas. No tire squealing though, the body roll told me it should have, I didn't hear anything! (never owned a VSC asisted car) The acceleration and ride felt very much like a Corolla (good/bad), in fact the engine noise sounded just like one. :? The ride was also a bit harsher than I expected. Is this normal or did I just get a test car that's been through too much abuse? :?: I drove back down the hill in B and it pretty much recharged the battery back to full. :) The fuel consumption screen showed the 25MPG flat the whole way. :| They said that mileage was low because the battery was significantly drained when we sat in the lot (5-10 min) with the A/C on full while he talked about the features. I have a feeling testing the cars uphill capabilities with the A/C blasting isnt good for mileage either. Over all, the performance is respectable, but it drives a bit stiff, steering took a bit of effort and the pedals were overly sensitive.

I decided I liked the car even with all those minor quirks I noticed, and will probably enjoy giveing it a chance to prove its worth. Maybe driving a Prius just takes some getting used to. I put down my deposit today. Hopefully I'll have my package 6/7, in silver, driftwood, or seaside in the next two months or so. I pretty much told them I'd take any color / model so hopefully this speeds it up. They said that they got sold 12 this month and were getting 11 more this month. Is this average?
 

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Remember, your coeficient of drag will double from 50 mph to 70mph. I'm not a mathmagician, but I am under the impression that it's not a linear decrease of cd.
The coefficient of drag (Cd) is a constant and equals 0.26 for the present Prius. The drag force increases as the square of the speed, which means it roughly doubles from 50 to 70 (whatever unit you use :wink: ) and also means the energy required to drive along a given distance is much higher if you drive fast. Everyone who buys a Prius for fuel economy should consider driving at moderate speeds.
Though I'm not completely sure of this, my understanding of the way the electric motor and computer controlled inverter works leads me to believe that the 101 MPH limit on the 2001-2004 Prius is at least in part there because above that speed the motor/inverter will always produce a higher voltage than the battery. This would force the battery to be continuously charged, quickly exceeding it's capacity then overheating it.
Just the opposite, you would discharge the battery. The speed limit in the Prius corresponds to the maximum speed the car can maintain using only the power coming from the engine, on a level road with no wind. Remember the Prius can not deliver its maximum power permanently because part of it comes from the battery, and the only primary source of power is the engine.
 

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If you look at the performance curve for MG2, it shows flat 33 kW output from about 1000 RPM to about 5700 RPM, the curve then quickly drops to zero at 6000 RPM (which corresponds to about 100 MPH). My understanding of this drop off is that above 5700 RPM, the inverter cannot counter the "back EMF" because it remains above the battery voltage for too much of the full cycle.

The inverter contains a simple bridge rectifier which will always pass current back into the battery whenever the voltage from MG2 exceeds the battery voltage. There doesn't seem to be any circuitry to prevent this.

So I conclude that above 100 MPH the inverter doesn't have high enough voltage available from the battery to counter the generated voltage from MG2, so it's no longer able to control MG2 as a motor. The rectifier continues to allow MG2 to operate as a generator (it's free running state). So the inverter can't get power from the battery to MG2, but the rectifier gets power from MG2 to the battery, for a net charge of the battery.

Since at these speeds the battery cannot help provide motive power (except through MG1), you would also need some external assistance to maintain the speed above 100, such as a downhill grade, tailwind, or closely tailgating a semi.
 
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