[Warning - long, tech read, continuation of spec data based analysis]
This could be hunkering down the rabbit hole of the spec speculation (pun intended), I am really curious on what TATA could have done to make this seemingly impossible physics happen.
This team-bhp homepage thread on Atto 3 serves as a good reference point.
https://www.team-bhp.com/news/byd-at...hscreen-teased
The Atto 3 is an established car, has real life users, been around and had once even for short period of time outsold the Tesla (when Tesla had a small supply chain hiccup).
In the summary of the thread take a look at the spec.
"Powering the Atto 3 is a permanent magnet synchronous motor that develops 201 BHP and 310 Nm, which is said to propel the car from 0-100 km/h in 7.3 seconds. It is rumoured to come with the larger 60.48 kWh battery pack, which has a maximum claimed range of 420 km (WLTP cycle)."
In contrast, we are looking at 45 ps (bhp numbers are a close good approximation), 110 Nm, 0 - 160 5.7s, ˜20 kWh and ˜250 km.
Weight of Atto 1750, Tigor ˜1200.
If we establish the Atto 3 baseline, and fit that to the downgraded spec and see what variables need to be tweaked to get the tigor numbers.
we all know f = ma. Or force is mass times accelaration. So if we hold the acceleration constant then lesser force is needed to move the same mass or, if the mass is reduced the force needed moves south.
Both the acceleration and force move linearly, until the torque drops. Or as long as the torque is flat or even linearly moving all other parameters move along a linear path driven by y = mx + c (where y is the acceleration point, m is slope of the acceleration graph, x is the rpm and c is the offset from the starting of the acceleration. For a car that starts from idle on a 0 - 60, c = 0) So, its y = mx.
What this helps is to establish the following,
1. We can vary the torque and see what the new 0 - 60 can be
2. Vary the power and see what the numbers are
3. vary the gross weight (which is mass x g where g is 9.8/s square, but its a constant so we can ignore it) and see what the numbers are
4. vary more than one parameter and see how the final numbers should be
From a what should be, to what is, identify what are the other variables that can be changed. In this case, it could be a different drive or gear ratio at different rpm/torque levels or different ampere or current drawn levels to make this graph non-linear, i.e changing the power characteristics of the motor. Since this is a PMS motor you can't vary the power characteristics of the rotor you can only control the flux on the casing.
1. Match the weight
Starting at the Atto baseline, if we lighten the car from 1750 to 1200 all other params being the same the 0 - 100 would be 5.00s
2. Match 0 - 60 spec
Now we get to 0 - 60 (still the flat torque range for idle start) is 3.00s
3. Match torque
Now we get to the 110 Nm, the 0 - 60 will e 8.45s. However, the spec says 5.7s which is 48% deviation. So we have to now introduce a variable here, else the physics will fail. It can be one or a combo of the following (A) change the current characterstics (B) change gear ratio dynamically/electronically at different rotor rpm values (C)some innovatite engg technique that is not pubically known.
Both A and B will lead to a higher battery drain or amphere flow so the claimed range on WLTP cycle is not possible.
Now, we look at more realistic 30% start to stop, 70% 30 - 70km cycle, city like drive. Let first convert the bhp and kw into a single UoM so its easy to understand. 1 BHP ˜= 0.75 kw.
So the ATTO 3 has a 60.kwh or 81 bhpHour battery.
Tigor has 20 kwH or ˜27 bhpHour battery.
f = m X a (we revisit this)
So if both cars are doing the same city like drives (and lets assume thier ranges are defined so) so the 'a' is constant (we still have to figure out how that 'a' is same with that huge 48% gap, let's assume its happening somehow)
Total force applied (or in other words drawn from a source a.k.a the battery over constant time, which is the definition of kwh or our new metric bhpHour) the mass or m matters. 1200 kg (removing constant g) is 70% of 1750 kg, so if they both had the same source strenght or kwh, the rage should be atleast 30% (100 - 70) more. Which is 450 * 1.3 = 585 km. Since we have 27 bhpHour and not 81, we should be looking at 195 km v/s 250(a little close to spec), but at 30% the torque levels (110 v/s 310 Nm), again there is some variable which is difficult to explain. Unless the battery tech is something innovative (atlest its not claimed)
Its seems to be tuned to juice out a usable city range extremly senstive to speed, drive style, start-stops, temperature, gross load (every passenger might start to matter), gradient, cruise time, over all friction (hence 65/ r14) etc.
One does not want so much variability. All this matters when you are eaking out every ounce since you are running close to rated spec on all parameters majority of the time.
I am reminded of an analogy (a far shot but drives the pattern), while Apple had stuck to 12 MP camera until 2020 on a 599$ phone and the world was flooded with 50, even 100 MP at less than 100$ phones, the outcomes were so very different. In a skewed feature to price ratio in the absence of disruptive input, the compromises are not always apparent. I am usully a little vary of "itna zyda itne mai" campaigns.
Often the whole is more than sum of parts, and finally how the car might be put together might trash all these assumptions. Knowing that there are no innovatively engineered parts either on the drive train or the battery how could this have been made? I am not negative on this launch, I am just not able to get euphoric on it.