Torque????

[Locust43]

My friend says my Prius has only 82 lb/ft, but I say 377 lb/ft because of the MG2 and the ICE. I know my Prius has at least 295 lb/ft torque from the electric engine alone because I can feel it has power when it takes off. How much total torque does it have and how can I prove it to him?

[priusenvy]

http://priuschat.com/index.php?showtopic=25704

[Tideland Prius]

~100lb-ft net if I remembered correct

[David Beale]

From the Toyota Canada website under "specifications" - electric 67 ft-lb, gas engine - 82 ft-lb. That would be a max. of 149 ft-lb. I believe I read somewhere the electric torque is limited however, to protect various components (it's capable of delivering a lot of torque).

[narf]

Odd,
From the Toyota USA web site:

Gasoline Engine
Power output 76 hp @ 5000 rpm (57 kW @ 5000 rpm)
Torque 82 lb.-ft. @ 4200 rpm (111 N m @ 4200 rpm)

Electric Motor

Power output 67 hp @ 1200-1540 rpm (50 kW @ 1200-1540 rpm)
Torque 295 lb.-ft. @ 0-1200 rpm (400 Nm @ 0-1200 rpm)

Of course, those numbers are before the PSD so what reaches the wheels is much lower, and wouldn't the torque at the wheels be divided by the gear ratio?. I'd believe the 113 ft/lb numbers to the wheels that the dyno runs listed, but note that it's a very flat line. All that electric torque is available right from startup. Too bad the graph doesn't begin until about 3000 rpm.

[David Beale]

Yup, just went back and double checked. They list it as I posted. And thanks, narf, my memory says you're correct. Which is why it's limited, as I recall. 295 ft-lbs would break things on a small car like the Prius. Heck, it breaks things on "performance" cars. I recall reading it is limited also to protect the battery, as torque would be directly related to current draw.

The tires couldn't put down 295 lb-ft of torque either. Even my RX-7, with 225 width tires spins the wheels, and it has less than that.

[Tideland Prius]

<div class='quotetop'>QUOTE(David Beale @ Nov 1 2006, 08:52 AM) [snapback]341947[/snapback]</div>

From the Toyota Canada website under "specifications" - electric 67 ft-lb, gas engine - 82 ft-lb. That would be a max. of 149 ft-lb. I believe I read somewhere the electric torque is limited however, to protect various components (it's capable of delivering a lot of torque).
[/b]

Yes and just like hp, you can't add them up.

on the dyno, the highest reading was 115lb-ft (Brian's dyno) so that's how much torque at the wheels. Toyota says 110hp but at the wheels on the dyno, it's 100hp.

[ekpolk]

Just one more thing to add -- and don't worry, I'm not laboring under the delusional idea that this car is laying down the full 295 ft-lbs. That said, I'm pretty well convinced that traditional dyno results don't well reflect the Prius' capability. In particular, as noted above, most of the curves you see plotted don't begin until roughly around 2500-3000 rpm. This may make sense for a more traditional gas-only car, but how is it reflective of the capability of a car whose torque generation is so radically biased toward the low end?

Experience seems to bear out my suspicion here -- if you try, the Prius will leap off the line like a startled greyhound. Unfortunately, the performance rapidly drops off from there.

I don't think normal dyno readouts do this car justice. Any thoughts from the more seasoned experts? Oh yeah, the graphs do show nicely the advantage of the CVT -- the plots are nice and smoothly level.

[kevinwhite]

<div class='quotetop'>QUOTE(David Beale @ Nov 1 2006, 01:58 PM) [snapback]342147[/snapback]</div>

Yup, just went back and double checked. They list it as I posted. And thanks, narf, my memory says you're correct. Which is why it's limited, as I recall. 295 ft-lbs would break things on a small car like the Prius. Heck, it breaks things on "performance" cars. I recall reading it is limited also to protect the battery, as torque would be directly related to current draw.

The tires couldn't put down 295 lb-ft of torque either. Even my RX-7, with 225 width tires spins the wheels, and it has less than that.
[/b]

Your RX-7 can probably put down 3000-4000 lb-ft maximum at the wheels in first gear.

The rear axle/ final drive usually has a ratio of about 4:1 that multiplies the torque by that amount, the gearbox will also multiply the torque by about 4 times in first gear going down to about 1:1 (or less if it is an overdrive gearbox) in the highest gear. The resulting torque at the wheels will be about 16 times what the engine can produce. (A bit less if the ratios are slightly lower)

The Prius does not have the advantage of a gearbox so the torque of the electric motor only gets multiplied by the final drive ratio together with the torque from the ICE which is reduced by the PSD to about 72% of the 82 lb-ft of the engine. This adds up to about 360 lb-ft going into the final drive and 1400 lb-ft maximum at the wheels. This only applies up to about 18mph when the torque of the electric motor will start reducing.

The Prius does pretty well but this is a very low torque at the wheels compared to most cars - there have been stories of Prius' getting stuck on steep hills, particularly in reverse where the ICE is actually propelling the car forwards in the opposite direction to the electric motor!

kevin

[Bob Addison]

Not sure where you folks are getting your numbers from. The specs provided by Toyota for the THS II are found at:

http://www.toyota.co.jp/en/tech/envi...hs2/speci.html


The max system torque is given as Torque at 22km/h in N-m (kg m) = 478 (48.7). I believe that this converts to 354 ft-lb.