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Toyota Prius (First Generation)
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___I believe the 04 Prius is using GY Integrity’s? I cannot speak for over inflation but the GY Integrity’s are rated for 44 #’s per the manufactures specifications. The question about what the differences are between braking and cornering is a good one but at what point are the tires pressures to high? Above the manufacturers spec? To low? Below the manufacturers spec? Just right? Toyota’s spec? I do know that 37 to 40 #’s in the GY Integrity’s as well as Mobil1 Synthetic in the 03 Corolla has given me an almost 20% increase in hwy mpg over and above what the EPA says the Corolla is rated for on the Hwy. Many Prius, HCH, and Insight owners have found similar pressures and higher works great for them as well with the OEM equipped LRR Bridgestone’s. The going tire pressure for the LRR Bridgestone’s from the Insighter's is 50 #’s and many swear by that pressure in the Insight forums. In fact, some have received 80,000 miles out of them at that pressure and have not received the outer edge wear problem many have experienced at 35 – 36 #’s or a more normal 30,000 miles before replacement as many Insight and former Prius owners have had to endure.
___Again, I can’t speak for safety or cornering because those 50 # Insighter’s are running well beyond the 44 # maximums of those particular LRR tires ratings but it works for them. 40 #’s in a set of GY Integrity’s is 10% below its rated maximum and most certainly helps as far as mileage is concerned ...
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
Unless it's Ford trying to avoid high rollover calculations and thereby murder their Exporer owners.
You can't. It's at the heart of the system, not an add-on. The power-split device will always do something electrically as a result.
Most of the time while cruising, it is uses the excess torque created by running the engine at optimum RPM (which saves gas in itself) to recharge the battery-pack (which ultimately also saves gas). So disabling that would cause a loss in efficiency.
JOHN
It appeared to me that one of the causes of poor highway fuel economy vs city was that the system used the batteries for even slight power "boosts" at highway cruising speeds. And of course eventually had to recharge them the inefficient ICE method.
It seemed to me that at cruising speeds the batteries should be brought "on", ONLY at WOT, when there is a clear(er) need for more HP than can be provided by the ICE alone.
Running the engine at the desired road speed would actually require the use of more gas, so that suggestion causes an efficiency loss.
To achieve optimum RPM, the engine will actually increase spinning speed. Obviously you don't want that to result in an increase road speed, so the extra thrust is instead used to generate electricity for recharging.
Also note that there is a clear MPG increase when you use the motor to maintain speed on a decline of any kind (not even enough to call a hill). Fuel is cut entirely from the engine and thrust is temporarily provided exclusive by electricity. So not taking advantage of that ability is an efficiency loss too.
JOHN
Using gasoline to charge batteries and then using those batteries to drive the wheels doubles the losses.
Toyota is selling the public a "load of poles".
For freeway use a supercharger or even a turbocharger would be a much more efficient method for getting more "go" from a small lightweight ICE such as the one in the Prius.
Look at the Saab SVC, for instance.
The use of batteries to store the energy recovered via regenerative braking for later use is an absolutely excellent idea, and Toyota should be applauded for bringing the Prius design to market.
But using the batteries to boost HP at a time when the only recharge capability is the ICE is rather stupid IMMHO!
And yes, the "system" has no way to predict when this circumstance exists, but I do!
Give me an "electrics" OFF switch on my Prius that is automatically over-ridden at WOT and I'll give you better hwy MPG.
batteries, no charged pulled from the batteries.
Then again, no power coming from the engine goes
to the wheels either! ;-)
what's to say that the most efficient (and least
polluting) engine RPM isn't one that provides more
power than the vehicle needs at that moment? The
extra power is diverted to the batteries, for later
use. (it's the only explanation I've seen for people
who drive the hilly/mountainous route who get higher
MPG than if they were to drive the flat route to
the same place...)
> at typical road speeds.
The factor you seem to be overlooking is that a highway is not perfectly flat, without any wind or turns, and has no other traffic. The constant influence of ever-changing small external factors isn't something that a CVT alone can rapidly respond to. But with an electric motor attached, it can.
The optimum RPM takes those influences into account. And since the motor is spinning anyway, the responsiveness is nearly instananeous. Power can be diverted or created much faster than an engine-only design. So it is able to react to those numerous & frequent small changes, which results in a savings.
JOHN
One could argue that at different throttle openings, power settings, the engine has differing optimum RPMs. In that case I'd still adjust the CVT rather than take the doubling of losses from the use of the batteries.
For the pilots out there CVT is nothing more than a form of constant speed prop.
Many years ago I got a speeding ticket going downhill on the eastside of Snoqualmie pass because I had wanted to see how high the MPG would indicate on the mileage computer. Placed the transmission in neutral and just as the computer reached 147MPG the radar tagged me at 77MPH. Limit was 55 then.
In the Prius on cruise control much of that downhill (FREE) energy would have gone into the batteries in order to keep me closer to the cruise set speed.
Again, regenerative power, power otherwise wasted, is the name of the game.
That is a very DIRTY choice. And since reducing emissions is the primary purpose of Prius, not maximum efficiency, it gets put lower on the priority list.
By the way... disabling the "electrics" would require the sacrifice of having Electric A/C, which provides a big boost in city efficiency... something many wouldn't be willing to give up.
JOHN
DIRTY choice....???
I said that if a different throttle opening resulted in a different RPM need for optimum engine operation then I would adjust the CVT "gear ratio" such that the engine RPM could change without changing roadbed speed.
Assuming your definition of optimum means lowest pollution level without unduly(~??) sacrificing MPG.
Oh, I just realized that to my mind "optimum" means bringing all parameters into BALANCE.
One way to make it real clear which board is covering what car is to call this one "Toyota Prius 1997-2003" and the one in the Hatchbacks topic "Toyota Prius 2004+". Just a suggestion.
___In many cases, once the EGR valve starts to go, fuel mileage and performance will drop hard. Just a thought as to what could be causing your lower mileage possibly? Cold weather shouldn’t hit your Prius that hard as this as you have probably already surmised.
___Good Luck
___Wayne R. Gerdes
I'm considering buying a 2001 Prius for my lengthy daily commute. Five days a week I drive 120 miles round trip to my place of employment. The miles are all on the interstate and it is not an exceptionally hilly route. My speed of travel is generally 70 mph. Would you Prius owners recommend at 2001 Prius for this commute? Any idea what sort of gas mileage I might expect under these conditions?
Any advice or opinions appreciated.
Allen
Ed Headington
Leaving the car without the charger, I just can't make any comment. We've never tried that, however I would doubt if it would be a serious problem.
Ed Headington
Not quite. The 12 Volt battery keeps the computers alive while the car is off, so it can respond to your request for the Traction Battery to start the motor. The 12V cannot start the ICE, because one of the MGs is really the starter, and the 12V can't spin it, and isn't connected to it anyway.
>Because once you start up the car via the hybrid battery it will recharge any drainage of the 12 volt back-up battery.
Correct, if you can get the car started. If not you have to jump the 12V.
>If you don't believe me disconnect your 12 volt battery and voila you car will still start.
If you disconnect the 12V battery, the car is dead as a doornail. Plus, you lose all your history and pre-sets.
>What do you do about the discharge of your nickel-metal-hydride battery ? If they are so discahrged they won't start the car, then they are probably into the "deep discharge" state that significantly shortens their life.
Correct, if the NIMH battery is really drained, the life may be shortened, but they can possibly be recharged. However, it takes a special Traction Battery Recharger that the Service Centers have.
If you're going to leave the car for a long time you can:
1) Disconnect the 12V, but you must reconnect it before starting the car, and you lose all your settings/history.
2) Have someone come by every week or so and just turn the car on for a half hour. The Traction Battery and ICE will top off the 12V. Have to make sure it's really "Ready" on - not just IGN on.
3) Hook up a maintenance charger. This is NOT a trickle charger. A trickle charger runs all the time, and can (risk, not certainty) overcharge and damage the 12V. a maintenance charger monitors the voltage across the battery and only charges when it begins to get low, and only as much as needed. They cost a bit more than trickle chargers, but not exorbitant. If you have a maintenance charger running, you can leave the 12V connected and not lose any puter settings. Some people have even wired in connectors to allow them to just plug it in.
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Anyway not sure if this is related, but there were times when ice froze on my rims. The resulting imbalance caused the car to shudder at higher speeds (removing all the ice/snow between the spokes fixed the problem), at lower speeds it prolly felt similar to what you discribe.
If cleaning your rims won't take care of the problem, try to have them balanced. Hopefully they won't discover something more serious with your tires or rims.
Btw, just so people don't think Prius is prone to ice freezing on its rims, the ice on the rims were caused by my having to drive thru snow as deep as the underside of my '01 Prius. As long as you keep a good momentum and the tires touch the road, snow can't seem to stop this car.
I am on the 2nd set of front Toyota Bridgestone EL on my 2003 Pruis, the first time I heard the noise they gave my new front tires. The second time the up the psi to 45. So far no noise.
But here is a true parallel "full" hybrid.
- Electric Motor at highway speed (>65mph)
- -or- Combustion Engine at highway speed
- -and- has a plug for recharging, so people can drive to work every day without burning a single drop of mideast oil
http://www.evworld.com/view.cfm?section=article&storyid=312
troy
Please respond to jfallon@edmunds.com with your daytime contact info by 12pm Friday, May 27, 2005.
Thanks,
Jeannine Fallon
Corporate Communications
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debi
AFAIK there are only 2 XL rated tires in the size the Prius uses, the RE92 and the Dunlop SP10. Both are claimed to be OE fitments according to Tire Rack...
It's not worth the tradeoff for a few more mpg.
The original poster said the tires "wore evenly". Could he elaborate: Did the tires wear in the center first, or did they wear all the way across the tire?
"There were no costs identified that were specific to the hybrid components of the vehicles."
http://www.hybridexperience.ca/Reliability.htm
Battery Life
A few Prius owners have commented that the vehicle’s 12 V battery has died when the car hasn’t been driven for a few days. Note: The 2001 Prius owners manual specifically states that the vehicle should be driven for 30 consecutive minutes at least once a week to ensure the battery remains properly charged.
For many consumers the life and replacement cost of the hybrid battery pack has been of concern. Toyota has issued the following statement about battery life:
"The Prius battery (and the battery-power management system) has been designed to maximize battery life. In part this is done by keeping the battery at an optimum charge level - never fully draining it and never fully recharging it. As a result, the Prius battery leads a pretty easy life. We have lab data showing the equivalent of 180,000 miles with no deterioration and expect it to last the life of the vehicle. We also expect battery technology to continue to improve: the second-generation model battery is 15% smaller, 25% lighter, and has 35% more specific power than the first. This is true of price as well. Between the 2003 and 2004 models, service battery costs came down 36% and we expect them to continue to drop so that by the time replacements may be needed it won't be a much of an issue. Since the car went on sale in 2000, Toyota has not replaced a single battery for wear and tear.”
http://www.hybridexperience.ca/Reliability.htm
Canada’s highest mileage Prius, a 2001 model, has operated for over 366,182 kilometres with only a few maintenance repair issues. Jatinder Parhar, owner of a Empress Taxi in Victoria, British Columbia, operates this vehicle.
That's 227,535 miles for those counting at home....
It looks like he made the grade with that first Prius. Taxi cabs are expected to have a 200k-300k mile life cycle without major repair. Passenger shuttle vans are expected to last 250k to 400k miles. If he can get 250k miles out of the 2004 Prius that will be a good test.
The second set of tires ran their whole life at 44/42 PSI and wore evenly across the entire tread surface. To me that says 37/35 is too low.
Car makers often choose the lowest pressure that will allow a tire to meet the weight requirements for the vehicle, to promote a "softer" ride. Sometimes they choose a pressure that's too low (Explorer/Firestone debacle, anyone?). I believe the 37/35 pressure for the Prius was too low and the tire wear seems to bear that out.
Ironically, the boneheads that installed the new tires horribly under inflated them (they said they would only inflate to the factory reccomendation, but the highest pressure I found on their "work" was 30 PSI and the lowest 26PSI) This after making a big deal of using "pure nitrogen" to inflate the tires...
YMMV of course.
Does the nitrogen add any life to the tires? If you add air doesn't that kind of pollute the nitrogen? You bring up some interesting points. I assume when I tell the tire guy what pressure I want in my tires that is what he does.
Just my $.02
BTW, many places will not go over the manufacturer's recomendations as corporate culture has dictated that it opens the place up to customer complaints about uneven tire wear due to pressures that are not in manufacturer specs, and of course the dredded lawsuit if anything does happen and tire pressure is found to be a contributing cause.
Toyota Ken
Part of the problem in this particular case may have been that the tire installers were very busy, it was pouring down rain, and we'd been sitting there waiting more or less patiently for about 2 hours...
I'm withholding judgement for the time being, as the price was right, but I'll wait to see what they do at the rotate/rebalance visit.
Nitrogen IS more "stable" in that it has two characteristics that help - it varies less as the temperature goes up and down [normal variation is 1 psi for every 10 degrees F - nitrogen reduces the variance], and it seems to bleed less over time through the carcass and valve - all tires lose a certain amount of pressure over time, even if they are not driven.
None of this is revolutionary, either postively or negatively. It can hardly be a "marketing gimmick" when Costco does little or no marketing to sell their tire service. Most of their clientele couldn't pass a quiz on this topic to save their lives, either before or after their tires are installed.