Tested: Is the Toyota GR Corolla Quicker Than We Thought?

• The limited-edition 2023 Toyota GR Corolla Morizo is the lightest, most powerful, and generally best-performing GR Corolla model we’ve tested.
• However, test results for a new-for-2024 Premium model, which is mechanically identical to lesser GR Corolla trims, are surprisingly close to the Morizo’s.
• Despite a close analysis and discussions with Toyota, a clear explanation remains elusive.

Welcome to Car and Driver’s Testing Hub, where we zoom in on the test numbers. We’ve been pushing vehicles to their limits since 1956 to provide objective data to bolster our subjective impressions (you can see how we test here).

We love a good mystery, and occasionally in our testing of hundreds of vehicles every year we come across anomalous performance data that just doesn’t add up, prompting a deeper investigation. Such is the case with a recent test of an overachieving 2024 Toyota GR Corolla Premium, the test results for which lie beyond the normal vehicle-to-vehicle variances we’ve come to expect from Toyota’s feisty three-cylinder hot hatch. Queue the suspenseful music and the shadowy detective grabbing his hat.

A Clear Hierarchy

Let’s rewind for some context. The 2023 GR Corolla launched with Core, Circuit, and limited-edition Morizo trim levels, all sporting a driver-adjustable all-wheel-drive system, a performance-tuned chassis and suspension, a close-ratio six-speed manual transmission, and a turbocharged 1.6-liter inline-three good for 300 horsepower. The Morizo upped the ante with more torque (295 pound-feet versus the standard 273), shorter gearing, revised suspension tuning, wider Michelin Pilot Sport Cup 2 Connect track-oriented tires in place of the standard Pilot Sport 4 summer rubber, a chassis brace where the rear seats used to be, and a few other weight-saving measures. It also featured the front and rear Torsen limited-slip differentials that are standard on the Circuit and optional on the Core, as well as a hefty starting price of $51,420.

For 2024, the Morizo is no more, and the new $41,455 Premium trim slots between the $37,635 Core and the $46,275 Circuit models, bringing mostly convenience upgrades over the former. The Torsen diffs and brake cooling ducts that are standard on the Circuit also are present, and Toyota says all 2024 GR Corollas receive small aerodynamic improvements plus minor tweaks to the mounting bolts for their steering hardware and rear suspension—revisions aimed more at improving the feel of the car’s chassis than its outright performance.

Upsetting the Established Order

At the test track, the Morizo seemed to justify its price, posting better results than those we’ve recorded for three different Circuit editions of 2023 and 2024 vintage. Compared to the best results from that lot, the Morizo is expectedly lighter (3185 pounds to 3252), quicker (4.4 seconds to 60 mph and 13.0 seconds at 106 mph through the quarter-mile versus the Circuit’s best of 4.8 and 13.3 seconds at 105 mph), grippier (1.02 to 0.97 g), and better under braking (152- and 301-foot stops from 70 and 100 mph, respectively, compared to 156 and 312 feet).

Here’s where it gets interesting: Although our Premium test car, which is mechanically identical to the Circuit, was the heaviest GR Corolla we’ve sampled at 3273 pounds, it tied the Morizo to 60 mph (4.4 seconds) and actually edged it out through the quarter-mile, turning a 12.9-second pass at 107 mph. Its 1.00-g skidpad orbit also is nearly as good, and its stopping performance is virtually the same, coming to a halt in 151 and 301 feet from 70 and 100 mph, respectively. This is despite its more street-friendly tires, plus its greater mass from the retention of functional niceties such as rear seats and a rear wiper.

The Mystery Deepens

So, what gives? The short answer is this particular Premium test car may be a freak, as even the GR Corolla’s chief engineer in Japan, Naoyuki Sakamoto, struggled to wrap his head around how a non-Morizo-spec model could be this quick and capable. Unfortunately, a closer analysis doesn’t shed much light on the matter. You see, the GR Corolla is super easy to launch—just hold the revs around 6700 rpm and quickly yet smoothly let out the clutch—and the Premium, Morizo, and one of the Circuit models all were tested on the same track by the same driver using the same standardized procedures. This eliminates several significant variables from the equation.

Given the Premium was tested in a relatively cool 53 degrees compared to our other hot-weather Michigan tests, our initial thought was that ambient air temperature may be a factor, specifically regarding the GR Corolla’s possible sensitivity to intake air temperature. This thinking was compounded by the known heat-related issue with the GR Corolla’s rear differential, which can overheat during extended hard use and temporarily deactivate the car’s all-wheel-drive system. Toyota is aware of this, and the car issues a warning message in its instrument cluster when it happens, prompting the driver to stop and let the system cool off. This message briefly appeared during multiple Michigan tests, and the quickness with which it both came and went away seemed to be related to how hot it was outside. The Premium was the least affected by this problem.

However, we tested a 2023 Circuit model in California in even cooler temperatures, which in theory should further reduce any heat-related issues, yet it performed on par with other Circuit models, as expected. Granted, that car was running on 91-octane premium fuel, rather than the 93-octane juice we use in Michigan, and we can’t say definitively how much of a difference that makes in the GR Corolla. But that car’s grip and braking results also were in line with other tests of Circuit models, which doesn’t explain the Premium’s seemingly heightened adhesion to the pavement.

Who Dunnit?

Sadly, this is a mystery that likely will go unsolved, as none of the evidence provides a compelling explanation for our observations. While it’s not impossible that this Premium model was freakishly gifted, a more plausible theory is that a combination of factors related to the car, the track, and the conditions aligned just right to produce the above-average results, and that’s where we’ll have to leave it for now—an intriguing facet of one of our favorite driver’s cars.

Source: Motor - aranddriver.com