Instant Torque

"youshiftem" (torinosport302) 02/05/2015 at 12:44 • Filed to: None

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A lot of articles mention the instant torque of the electric motors in a Tesla. How does this compare to the torque curve of a clutch dump?

HammerheadFistpunch > youshiftem 02/05/2015 at 12:47

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Well...the torque is there, but no so well managed. speaking of instant torque, if you look at the torque curve for my lowely 1FZ-FE, I have 240 ft-lbs at 1000 rpms, before the torque converter is even in play (about 1500 stall) which is pretty great considering it peaks at only 275 ft-lbs. So its pretty much a flat and instant torque curve.

crowmolly > youshiftem 02/05/2015 at 12:57

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Based on the mountains of parts that have been broken over the years I'd say pretty close. LOL.

Aaron M - MasoFiST > youshiftem 02/05/2015 at 12:59

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An electric motor has peak torque at 0rpm. This doesn't practically feel all that much different than a Land Cruiser (as cited in an above comment), but it does mean that the motor makes so much power it doesn't need a multi-speed transmission, and can start and cruise in the same gear.

As far as the clutch dump goes, your foot is the limiting factor in both cases. The electric car will always deliver more of its net torque though, because there's no power shunted out in the form of driveline shock (i.e. the reason clutch dumps are bad for transmissions).

youshiftem > Aaron M - MasoFiST 02/05/2015 at 13:10

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I agree the efficiency and lack of transmission is interesting news, I just don't know why the "instant acceleration" is anything new. Any V8 with a muncie and slicks will get a better 60' time than a Tesla.

Aaron M - MasoFiST > youshiftem 02/05/2015 at 13:14

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I'd disagree. The 60' time is going to be 100% up to the driver, and I'd be willing to bet that if the two cars had the same tires and the same driver the Tesla would post a better 60' every time. If that isn't the case it likely has a lot more to do with the fact that the Tesla weighs 2.5 tons than the torque curve.

Snuze: Needs another Swede > youshiftem 02/05/2015 at 13:15

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I don't follow Tesla super closely, but it seems like the cars just plant and launch. It doesn't actually take all that much torque to break tires loose, I can do it in my Cruze and it makes a peak of 200ft-lbs, so I suspect they have some torque management in the software. It will ramp in the torque absolutely as fast as the tires can handle it.

TJDMAX > youshiftem 02/05/2015 at 15:06

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Even when you do a boosted launch or a clutch drop in a muscle car, the instant your clutch engages and starts moving the tires your RPMs drop and you are no longer at whatever RPM you started at.

In an electric car, like a Tesla, you have max torque from 0 rpm all the way to max rpm. Even the flattest torque curve for a gas engine still has a peak rpm where the torque is greatest and will be less on either side of that number.

youshiftem > TJDMAX 02/05/2015 at 15:10

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Not true, the inertia of the spinning engine can exert a higher force than the the engine at peak torque.

Cigar-shelf Jones > youshiftem 02/05/2015 at 15:20

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The three things that make it different are (two mentioned by other posters):

1. Max torque is delivered at 0 rpm by a DC motor, ideal for launches because...

2. No clutch/complicated transmission, so you really are at 0rpm on the motor at launch and don't waste nearly as much of that torque in mechanical losses as you would in a conventional car

3. Computer management of the motor: That torque can be managed to within an inch of its life to max out vehicle acceleration, while preventing wheel spin.

TJDMAX > youshiftem 02/05/2015 at 16:22

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But its not an instantaneous transfer of force. You have clutch discs slipping before the gears start moving and then the tires start rotating.

Sure the Tesla has gears but it doesn't have clutches. As soon as you apply voltage to the motors you're off. That's where the instantaneous feeling comes from. Not to say you can't get that in a muscle car, just not a muscle car that is street legal or capable of being driven very easily on the streets. You would need a lot more power and a very strong clutch.

Distraxi's idea of perfection is a Jagroen > youshiftem 02/05/2015 at 16:55

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One of the advantages of electric that doesn't get a lot of publicity is superior traction control.

With a clutch dump you're relying on the clutch engaging at just the right pace to keep the tyres at max effort until the car catches up with the engine rpms. If it engages too slowly you don't deploy all the torque you could, if it engages too fast you break traction and lose acceleration because spinning tyres deliver less thrust than gripping ones.

The reason the Tesla is so fast is because it can keep those tyres working to the max, all the way from zero to 60. Rather than relying on modulating the clutch, throttle, and brakes, all of which adjust only a couple of times a second, it can adjust engine torque at the chopping frequency of the inverter, which is around 20kHz. And because it doesn't have a clutch in the system it can do it right from zero speed. So if Tesla's engineers know that this particular tyre gives maximum traction at 5.5% slip, they just program in 5.5% max slip and that's what you get, from the first few degrees of rotation.

Old-Busted-Hotness > youshiftem 02/06/2015 at 06:23

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Do a clutch dump in 4th gear and you'll see how it compares.