It would only be overrated if Lexus claimed a time of 4.5 seconds and not one legitimate media outlet could reproduce that.
And this is exactly what Lexus does and say about a lot of their engines: they overstate and overrate.
That's why I threw out that caveat about C&D et al. testing and used the word LEGITIMATE as I think that's very important as most people who buy these cars research enough to see through Lexus' charades.
As long as the manufacturer can repeatedly demonstrate that the engine can achieve the rated power
within the testing environment they specified, they cannot be sued for false advertising. Different manufacturers rate power under different testing conditions. The SAE standard protocols are purely voluntary and manufacturers are not required to follow it. BMW rate their engines for hot-and-high climates, which results in ~10% underrating. Lexus is not required to rate their engines under the same conditions as BMW. A small portion of TMC engines are also rated for hot-and-high climates such as the truck-based GR and UR.
There is a difference between overrating acceleration performance and engine power. Lexus has historically underrated their FWD vehicles while their recent track record with RWD vehicles are poor. The reason why their RWD products fail to achieve the numbers they claim can be complicated, but it is unlikely the result of engine overrating because it is hard to cheat a dyno. It could just be the official numbers are tested under very ideal conditions.
But even if we take the official numbers out of the picture, Lexus RWD vehicles still seem to underperform compared to competitors with similar power-to-weight ratio. Again, the main culprit is unlikely the raw performance of the engine. One thing to note is that at similar power-to-weight ratio, a Lexus does not lag behind average competitors too much. Audis always have the benefit of the extra traction from Quattro. But the real outlier here is BMW. While everyone attribute BMW's impressive straight line speed to engine underrating, but few appreciate how much can be gained from a well-optimized engine map and transmission tuning. The BMW B48-ZF8HP50 powertrain has widely been considered the golden standard of powertrain calibration. No other manufacturer has been able to get so much potential out of the engine as BMW could.
Real world acceleration is quite different from dyno runs. The power/torque curve we get from manufacturers are steady-state operating points, but acceleration is all about transient performance: how quickly the engine can transit between different operating points. This is when powertrain calibration comes in. During hard acceleration, what the ECU does is following a path on the engine map that gives the greatest amount of power over the rev range, and if that path lines up perfectly with the transmission gear ratio, you can get the optimal acceleration. The fastest way to accelerate is of course keeping the engine at maximum power using an ideal CVT (no slip-induced power loss), but an ideal CVT doesn't exist.
But an engine map that is optimized for performance may not be optimal for efficiency. As an example, the BMW B48 is tuned to more aggressively retard the ignition timing and enrich the mixture to create a hotter exhaust, allowing the turbo to spool up much quicker than competitors (note: in Sport mode only). Effectively, the B48 has a software-based anti-lag system. This is how the engine has a sub-500ms turbo lag while the average competition still have over 1 second of lag. The tradeoff is pretty clear, the engine will have worse fuel efficiency and emissions in Sport mode but to BMW this is a worthy tradeoff. If you gave BMW the 2GR-FSE they could make a sub-5s IS350. TMC, on the other hand, will almost never tune the engine to sacrifice even one bit of efficiency for an extra 0.1s in a straight line (1LR being the sole exception but that's technically a Yamaha engine).
In the end, the difference in philosophy made all the difference. The IS200t/300 is notoriously known to bog in a start. The car almost does nothing during the first second and the turbo picks up very slowly, and the car ends up almost one second slower in 0-60 than the 330i, C300, and A4 45TFSI even though the four are pretty evenly matched in power-to-weight ratio. That's the price they have to pay by stuffing an efficiency-tuned engine in a sports sedan.
I would certainly like to see them changing their approach in the future, and play the hybridization card to their advantage.
