At this point it's been fairly well documented that the 2024 "Highland" Model 3 Performance hits current limiting in a very short period of time. Even on a stock vehicle this happens in three to four minutes. On a modified vehicle with a middling driver (it's me), current limiting came in less than 70 seconds. No, that's not a typo. This is obviously not great, and considerably worse when we compare it to the 2018-2023.
But before we dig into the data, let's try to get a better understanding as to the reasons why an incremental increase in power on the 2024 leads to considerably worse current limiting. Simply put, the reason comes down to the fact that heat is directly proportional to the square of electric current flowing - or Joule's Law. What this tells us is that even an average increase in power of 20% will lead to 44% more heat. In contrast, limiting power by 20% will decrease heat by 36%. Understanding this will give a lot more context to the rest of this article.
In looking at the upper graph we can see current limiting starts to come in on the 2024 at about 70 seconds. It is, to be fair, a minor drop initially, cutting down only about 10kW. However, by about the two-minute mark we're starting to see a drop of around 25kW. It of course does not improve from there as the three minute mark shows a staggering drop of about 100kW.
When looking at the lower graph from the 2021, we don't see any current limiting until nearly the six-minute mark, where the power drops off dramatically.
It's important to remember that the High Voltage Battery on both vehicles are virtually the same. So, some of the differences here could be explained by the 2024 proactively trying to pull down the power limit early to extend the runtime. This strategy is unfortunately poor, not only causing limiting to occur very early on (thereby potentially ruining a fast-lap on a 2-minute long track), but still resulting in a massive drop off in only about 3 minutes.
You've probably heard me go on and on already about how enjoyable the outgoing Model 3 was to drive in a power limited state using Mountain Pass Performance's Cooling Party Controller. At a 250kW (335hp) limit, the platform could enjoy roughly 15 minutes of consistent power. For the Model 3 Challenge, we ran closer to 200kW to balance power with the RWD's which suffer from current limiting of the rear motor. On the bright side, this allows for about 20 minutes of consistent driving at nearly any track in an AWD configuration.
That all said, while the feedback while driving power limited was primarily positive, the main pushback that people gave for running in a power-limited state was that you didn't have enough power when you needed it. Hence, work began on push-to-pass.
Push-to-pass is a nifty feature that gives you a short power boost when activated. You can select a lower power limit, an upper (boost) power limit, and a time interval. For the testing I performed at Palmer, I initially selected 250kW/350kW/8-Seconds. Running the car for 12 minutes from 87%-57% SOC with 10 boosts showed no current limiting. Lap Time: 1:46.95
Next, I tried 275kW/400kW/8-Seconds. This time, I ran the car from 82%-54% over 9 minutes with 5 boosts and began to show some limiting at about the 7-minute mark. This is to be expected, as the outgoing Model 3 Performance averaged nearly 300kW on a road-course, surpassing that at lower speeds but dropping under that at higher speeds. The 2024 however is able to pull well over 300kW on straights with the boost activated, dragging the average up. Lap Time: 1:46.3
Finally, I tried 290kW/MAX/11-Seconds. With a starting SOC of 90%, and after 3 boosts, we saw current limiting occur at about the 6 minute mark. Despite running this "limited" mode, I was able to surpass my personal best time at Palmer in the Counter-Clockwise configuration (which had been run in full power in my 2018) by 2/10ths of a second, putting in a Lap Time of 1:45.2.
To provide further context, Model 3 Challenge competitors running 220kW of power (without a boost) have been roughly 4 seconds slower at Laguna Seca over the course of a lap, and roughly 2 seconds slower at Lime Rock Park.
I think the primary take-aways here are what I've been saying for a while now. First, running a lower power limit does not substantially impact lap times (we're talking about a second or two per minute at the power levels I tested), it significantly improves runtime, and allows for a more consistent and enjoyable experience. If you want to get better as a driver, this is the solution. If you want consistent braking points, acceleration, and lap times - this is your solution. The Push-To-Pass feature is a great addition to use either on the straights or when you're trying to pass the C8 Z06 taking corners at 20mph. Enough rambling, enjoy some laps!
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