Hello everyone and welcome! In this video
we're gonna be talking about Tesla's claim that the new Tesla Roadster is going to have 10,000 Nm of torque
and the reason why we're going to talk about this is because I think there's a lot of confusion online as
far as what this number actually means and let me just preface this by saying what Tesla's doing is actually super cool
so in the last video
I think some people got the wrong idea and we're under the impression that I was somehow
just trying to hate on Tesla for no reason about their 1.9 0 to 60 claim
that wasn't the point I was trying to make I think what they're doing is incredible
I think from an objective standpoint
there is no performance measure
that an electric car can't be better at than an internal combustion car
aside from weight. Weight is really the only thing that's currently holding back electric cars
because they can't match the energy density of gasoline or diesel fuel at this time
once battery weights go down and performance can go up and range can go up with lower weight
then there's really not going to be any future for internal combustion engines from a logical objective standpoint
so I welcome the future of electric cars. I think what Tesla's doing is supercool. Great, glad
we've cleared that up now getting into this 10,000 Nm of torque number in the presentation
Elon said if you know what this means, it's just stupid and
that's very accurate if if a car were to have 10,000 Nm of engine torque or motor torque. That is just stupid
it's magnitudes ahead of what is currently available on the market in production cars
but if you look at Tesla's website it says 10,000 Nm of wheel torque.
Now this is a very important distinction because wheel torque alone is a pretty meaningless
number to know and I'm going to demonstrate why here with a one horsepower electric motor
So we've got our one horsepower electric motor
and it has a gear at the end of it with a hundred teeth and that gear is
rotating a much larger gear which has a million teeth on it, so this one horsepower motor produces that one horsepower at
5252 rpm so we know that at
5252 rpm based on the equation for horsepower
it's going to be producing 1 pound-feet of torque as well, so we have an electric motor produces one horsepower 1 pound-feet of torque at
5,252 rpm now it's multiplied
10,000 that's the gear ratio from this small gear to the larger gear so we now have a
motor that is going to have an output of
1 lb-ft times our gear ratio of 10,000 so at the wheel or whatever would be attached to this it would be producing
10,000 lb-ft of torque an insane huge stupid number, but the unfortunate news is that that would be at a speed of
5252 divided by 10,000 or about half an RPM
so extremely slow. Boatloads of torque, very slow.
So this is why a torque number alone without knowing the horsepower without knowing the RPM is truly a meaningless thing to know.
Now an example we're going to use a
real world example where we know all of the numbers behind is the Dodge Demon also because it's a car that you know is super
fast as far as 0 to 60 and
for the quarter mile holding the production record for those at this time so the Dodge Demon with 91 octane gas has
972 Nm of torque at the engine
that is then going through a torque converter if we are in first gear that is then multiplied by
4.7:1 that's the first gear ratio
and then that finally goes through the final drive which is a gear ratio of 3.09:1
so our example with first gear using 91 octane
972 x 4.71 x 3.09 and that will give us about
14,000 Nm of torque at the wheels that's the wheel torque so as you can see certainly higher than the Tesla roadsters claim,
the wheel torque being
14,000 in first gear and that's with no torque multiplication
from the torque converter now a second example if we were in 2nd gear using 100 octane fuel the engine actually makes
more torque with that hundred octane fuel, 1044 Nm, second gear is
3.14 x 3.09, our final drive and that gives us still over
10,000 Nm so the Dodge Demon in second gear using high-octane fuel
can actually make more wheel torque than this Tesla claim here,
and that's in second gear so again context is super important because gearing matters gearing is what gives you these
stupid crazy huge numbers
and that's why most engine manufactures when they quote torque or when you measure
torque on the dyno it gives you that torque back at the engine, so you know you're measuring at the wheels
but then you're calculating back for what is the engine torque, and that's what manufactures are going to claim,
they're gonna use engine dynos and say what is you know the torque at the engine or the electric motor for this vehicle?
now we haven't yet talked about torque multiplication and for my examples. I just assumed that was one
it's not in fact one, but torque multiplication is not a constant number
it's dependent on the differential between the engine rpm and
the transmission rpm, so your output shaft. So when you're sitting there at a stoplight, and you're revering up your engine
but you're not moving or holding the brakes then you're gonna have the maximum differential in speed between your engine and your transmission so torque
multiplication is going to be very high it could be
2:1 or even higher than 2:1 through that torque converter
versus once you're driving, once you're actually moving, once you're hitting these peak torque numbers
which occur you know 4500 rpm or something along those lines,
the car is actually, the transmission is moving because the wheels are moving and so the speed differential between the engine and the transmission
is much lower, the torque multiplication is much lower. That's why I didn't increase these numbers
it's not going to be these multiplied by two it might be slightly higher
but not a huge amount and then of course once that torque converter actually locks up. You don't have torque multiplication
it's just 1:1 very similar to a manual style transmission.
Now the good news is Tesla didn't leave us completely without context with this 10,000 Nm number.
So we know that the car has to 0 to sixty of about 1.9 seconds,
we know that hits the quarter mile in about 8.8, 8.9 seconds
so we do have some data, and we do know that the car is actually going to be extremely fast
so you know we can use looking at the tires that were on the prototype we can get the diameter of those tires
and you know if we assume a gear ratio of 9.73:1 like is used in the Tesla Model S
then we can do a little bit of math to calculate motor torque to calculate the motor rpm
and if we assume that the peak torque can last all the way to 60 miles per hour
then we can calculate what that motor power might be and in this case it's going to be about 1000 horsepower
now that 1000 horsepower would be how much the motor is
at the RPM that allows the vehicle to hit 60 miles per hour the RPM will of course continue to increase and horsepower
even if torque starts to drop will increase along with it depending on the rate at which torque starts dropping off so it's likely that
it would be even more than a thousand horsepower with all of these assumptions, and you can use some online calculators
there's a bunch out there that help you predict
you know based on how much your car weighs and its quarter-mile time how much horsepower does it have so I plugged in a
bunch of different calculators going with an estimate of about 5000 lbs of weight for the Tesla Roadster again
there are no published numbers for how much the car is going to weigh
I think it is going to be pretty heavy unless there's some serious breakthroughs in battery technology
so assuming it weighs around 5,000 lbs and hits the quarter mile in 8.8 seconds, it's going to be somewhere around
1,400 horsepower now of course if that weight would be less then it's going to have less horsepower
needed in order to do that so it's heavily dependent on the weight of the vehicle which we do not know
but we do have some context,
we can kind of guess around
where the horsepower is going to be and I think it's you know safe to assume that it's going to be over 1000 horsepower.
So thank you all for watching, and if you have any questions or comments feel free to leave them below.
