So the ICE is 4- cyclinders?

Look at the specs on Toyota's website. Useful comparisons would be in areas like torque and horsepower. The electric motor is low horsepower but high torque so it's great for assisting off-the-line, and at lower speeds, but it supplements at all speeds.

 

If I'm not mistaken, electric motors have their best torque at low RPMs where ICEs have more torque at higher RPM. The 1.5 L engine in the Prius is 76 HP, whereas MG2 (the bigger electric motor in the car) has something like 67 HP. As Ichabod stated they complement each other well and the electric motor helps the ICE run in its most efficient RPM range and provides the extra power needed to make the car seem responsive. The battery helps out by storing energy that would otherwise be lost but it's really the interplay between the ICE and MG2 that allows the car to get much improved MPG.

 

Toyota rates the hybrid system net horse power at 110. Don't know if "hybrid system" includes the ICE or not, or how they came up with the 110 number.

 

<div class='quotetop'>QUOTE(brandon @ Aug 22 2006, 01:50 PM) [snapback]307774[/snapback]</div>

This number is when both the ICE and MG2 are running - MG2 is limited by the output of the battery to about 28HP rather than its own 67HP limit. This actually adds up tto 104HP but for some reason they quote 110HP!

kevin

 

Hi All,

The ICE and MG2 power maximums does not sum, as the MG2 is also acting as the part of the electric drive for the ICE. The horsepower that does not mechanically go through the Power Sharing Device to the ring gear goes into MG1. From there the electric power circuits guide it into the battery (if not needed for road power) or into MG2. Under full accellerator, all the available electric power from the battery plus the electric power through MG1 from the ICE combine for MG2. The 28 HP is from the battery. I think the Battery and power circuits have a peaking capability beyond 28 HP that makes up the difference between 104 and 110 HP. Once warm, they have to be pulled back to 28 HP.

So, even though its a 67 HP electric motor, approximately 39 of those horses are coming ultimately from the ICE.

The fact the Prius peforms as well as it does with that little of power, points out how poor standard car transmissions are at matching the engine to the wheels at low speeds, and the amout of time that is wasted for shifting. This might be why car manufacturers are now employing many more gears (8 speed transmission is the max I have heard of) and dual clutch automatic transmissions, that can shift very quickly. Of course those things cost money, and only marginally improve fuel economy.

 

DSG is the auto option on VW based cars eg VW, Seat, Audi etc.

My mate's got an A3 with it in. I think you have the option of driving in manual or auto mode.

 

Also worth considering (IMO anyway ), is that what most people perceive as power (as in "horsepower") is really the effect of torque. And when measured against conventional cars of similar configuration, this car is an absolute torque monster, because of the electric motors and their inherent characteristics. For example, even the Camry's I-4 generates only 160 lb-ft of torque, and that's at a relatively "peaky" 4000 rpms. The Prius' MGs alone put out 295 lb-ft of torque, on tap from 0-1200 rpms (the ICE adds only about 80 lb-ft, also up around 4k rpm). This car has the ability to absolutely sling itself off the line from a stop (but of course, compared to most other cars, would quickly lose ground if you were racing). This is largely moot, though, as not many Prius owners own Prii in attempt to "dominate" stoplight drag races. . . Yes, I am chuckling as I type this. My point is that in normal American street use, torque is generally more important than hp, within reasonable bounds.

 

Yep, 295, that's not a typo. See for yourself, click here. That's substantially more torque than a V-6 Camry, and actually, it's pushing into V-8 territory, and it's all on tap right from zero rpm (but only up to 1200 rpm). Alas, it doesn't come with the hp of a gas engine of similar torque-generating ability, but of course, that's not the mission here. Yes, you are thinking about this too much, but hey, fora like this one are for people who do that.

 

<div class='quotetop'>QUOTE(ekpolk @ Aug 23 2006, 04:48 AM) [snapback]308131[/snapback]</div>

But...

Torque at the wheels also depends upon gearing. In a conventional car the engine torque is multiplied by the transmission - by about 4 times in low gear. So the effective torque at the final drive in the conventional Camry will be about 650 lb-ft - double that of the Prius.

Also only about 70% of the ICE torque goes to the wheels, the other 30% goes to MG1 through the PSD So it adds about 60 lb-ft to the final drive giving a total of about 360 lb-ft.

The full torque of the electric motor is only available up to about 20mph, reducing above that. The one advantage that the Prius has is that the electric motor torque is available instantly and without any hesitations.

kevin

 

Obviously, both the trans and the final drive ratio will have a major impact on the final performance "result" of any given car. Now let's wander for a moment into the subjective world of "feel" and "opinion." If you're talking V-6 Camry, sure that car will feel both torqu-ier and more powerful than a Prius. Not so for an I-4, though. Having driven both I-4 and V-6 Camrys (and in fact, owned both), I'd have to say that the Prius is pretty much on par with the I-4 auto trans configuration. They are by no means identical, just roughly in each other's ballparks. Although I'm still "calibrating" myself to the Prius, I'd say that the Prius can initially take off faster than an I-4 Camry, but if the two were actually being "raced" side by side, the Prius would flatten out fairly quiclky, and, haven taken an initial lead, would be overtaken fairly promptly by the Camry. V-6 Camry? Forget about it. . . But back to reality -- that big torque output is real and there for a specific reason. It's a very clever way to "camoflage" the car's true, relatively weak, output. It's like a skillfully done makeup job that transforms an unremarkable face into one that makes people think, "hey, nice, not fashion model pretty, but nice." I hope that makes sense.

EDIT for typo...

 

the prius stays ahead of an i4 camry through a large intersection, then quickly falls behind. we know because we have one of each

oh... and a camry putting out 650 lb ft of torque would probably rip the engine out of the subframe. :blink: manufacturer published torque ratings are at the wheel, while hp is at the engine. usually.

 

Hi All,

Kevin is right. The 295 ft lb of torque is not multiplied by a transmission ratio, only the final drive ratio (which is 4.1). If the Camry transmission has a low gear of 4, and the 4 cylinder has a final drive of 3.39, then the total engine ratio to wheels ratio is 13.56. Additionally, the Prius has 856 revs / mile, and the Camry has 800 revs / mile. Which give the Camry an additional 1.07 torque ratio.

The 295 times 4.1 is 1209.5 ft lbs. The 4 cyl. Camry at low rpm probably has at least 100 ft lbs, for 1356 ft lbs to the wheels, even though its rated for 161 ft lbs at 4000 rpm. Very similar at low speeds. Which matches EKPolk's experience.

My experience with the Prius from a dead stop, is that its slow off the line, kinda like a Dr Jekyl. Then the engine comes on and is up to power by 15 mph. Mr. Hyde is out to play up to about 45 to 55 mph. Hit the throttle on a Prius, as its decellerating between 10 and 50 mph, while keeping some pressure on the throttle petal to keep the engine on, and it will supprise you.

 

<div class='quotetop'>QUOTE(galaxee @ Aug 23 2006, 07:03 PM) [snapback]308603[/snapback]</div>

Galaxee,

Both HP and torque specifications are invariably at the engine.

The 650lb ft I calculated was at the final drive - and assumed a 4:1 low gear ratio - I ignored any effect of the torque converter in an automatic.

kevin