From the April 2023 situation of Automotive and Driver.
You possibly can’t let some curbing stand in the way in which of a superb lap time, notably at Virginia Worldwide Raceway, the place it is best to clip virtually as many as potential to set a aggressive lap. Snake is one such part, and the Lucid Air Sapphire prototype I am piloting glides over the concrete serrations as if constructed to do nothing else after which rockets towards the Climbing Esses. Extra care and selective curb skimming work higher right here. Subsequent, the tight Oak Tree nook presents one other mild dose of apex clobbering. The best-hand detour into VIR’s internal loop comes up rapidly, however the Sapphire’s humongous 10-piston entrance brake calipers squeeze trackworthy carbon-ceramic rotors to haul this cruise missile neatly right down to turn-in pace with out a trace of squirm or squiggle. The automotive bends by way of the low-speed horseshoe easily with maybe a hiccup on the exit. Then it is off to Spiral and the diving left-right mixture that comes simply over a blind crest.
“Whoa! That was an enormous twitch.” There’s one other slight energy interruption after I graze the low curb on the exit of Spiral, however the automotive reasserts itself by way of the remainder of the Infield. The Sapphire appears to like Curler Coaster, however as I exit Hog Pen and set my sights on the Entrance Straight, the automotive walks towards the left fringe of the monitor, robbing me of the arrogance to plant my proper foot. With a full lap underneath my belt, it is time to return to the pits for a debrief. After that, we’ll take into account making some adjustments.
This course of is not completely new territory for me. Earlier than journalism, the work that put meals on my desk was evaluating and tweaking the suspensions of prototypes in growth at proving grounds, racetracks, and even public roads when routine driving character was underneath scrutiny. However my focus was at all times on tuning the {hardware}—springs, dampers, anti-roll bars, tires, bushings, and so forth.—as a result of not one of the suspensions I labored on had a line of software program code related to them.
John Culliton, ace driver and senior technical specialist in Lucid’s chassis and automobile dynamics division, holds a job much like the one I as soon as had. He rode shotgun so we may focus on the automotive’s habits on the fly. As soon as we untangle ourselves from the prototype’s five-point harness and duck underneath the total roll cage, calibration and validation supervisor Esther Unti joins us on the automotive’s trunk, which incorporates a raft of data-logging gear and a port into which she now plugs her laptop computer.
They appear gratified to corroborate my suggestions with their very own, which is necessary as a result of it is essential to distinguish between what the automotive is doing and what a driver is doing. That is the primary time the Sapphire has tackled VIR’s Grand Course, and a take a look at crew should obtain a sure degree of monitor familiarity earlier than driver tuning may give technique to automobile tuning.
However that is removed from the Sapphire’s first tuning session. Fairly the opposite. Chassis and automobile dynamics director David Lickfold and his staff have visited quite a few tracks and proving grounds. They’ve up to now dialed within the specification of the purely mechanical bits—these issues I used to tune—and the inner building of the bespoke Michelin Pilot Sport 4S tires.
Lickfold and firm have additionally settled on a base mechanical valving for the electronically managed Bilstein dampers, which largely operate with none digital valve adjustment within the base Clean driving mode. Software program-controlled rebound and compression-damping valves add supplemental damping throughout excessive occasions on this mode, however they arrive into their very own, robotically adapting with further damping in Swift mode, then kick that up one other notch in Dash. The staff has additionally landed on a power-steering-assist profile for every mode, in addition to the mode-dependent habits of the Bosch electromechanical brake booster that blends the huge friction brakes with the automotive’s excessive potential for regenerative braking.
These primary components really feel properly ironed out, and although Lucid didn’t formally lock them down, they stand at near-production standing. What does that go away for this VIR session? The engineers are nonetheless tweaking the damper software program in Swift mode, however the Sapphire’s capability to shrug off curbs tells me they’re shut. That primarily leaves one thing I by no means needed to cope with in my engineering profession: managing the torque produced by the Sapphire’s insanely highly effective three motors.
A standard Lucid Grand Touring sports activities at every finish a single motor containing a cleverly built-in differential inside an impressively compact coaxial motor housing with outputs on the motor’s centerline. Every motor is able to 670 horsepower, however the GT’s whole 1050 horsepower is lower than the mixed sum of each. That is as a result of the GT’s 112.0-kWh battery cannot put out as a lot energy because the Sapphire’s 118.0-kWh pack. This distinction additionally clears the way in which for uneven high-load torque splits.
Within the Sapphire, the identical 670-hp unit resides up entrance, however the rear finish incorporates a pair of these motors in a shared housing. As a result of every rear wheel is individually managed, the rear axle has a scary 1340-hp potential, and the sum of all three motors is a staggering 2010 horsepower. Lucid will solely cop to a complete mixed output of 1200-plus horsepower, with a definitive quantity some weeks away. However the distinction between no matter that placeholder signifies and 2010 suggests a severe quantity of torque-vectoring potential. That brings us again to Unti’s laptop computer and why Lucid is at VIR.
This powertrain offers Culliton and Unti lots of tuning freedom, however they have to account for a lot of completely different performance-driving eventualities. In a straight line, there may be nothing stopping them from sending all of the battery can muster to the rear axle—besides sanity and physics. You will at all times get a faster and extra secure launch when greater than two tires put torque to the bottom. To that finish, they inform me that about 75 % of launch torque goes to the rear. Even on the drifting finish of the spectrum, they nonetheless ship a little bit of torque to the entrance “to make slides extra predictable and obtain increased sideslip angles.” Cool.
VIR’s Grand Course lies between these two efficiency extremes, with a wide range of corners. That is what makes it such an ideal location for our annual Lightning Lap take a look at and a helpful place to type out the Sapphire’s complicated torque vectoring, which works approach past simulating the differential motion that comes naturally to a single-motor drivetrain. Torque vectoring in an EV with two motors on one axle can generate drive extra rapidly, exactly, and easily than commonplace brake-based torque vectoring. And the diploma of break up is very variable as a result of one motor can regenerate energy whereas the opposite drives ahead.
Unti’s laptop computer, loaded with Lucid-developed management packages, manages all of those settings. Actually, some 90 % of the traces of code throughout the Sapphire had been written in-house. The applying Unti is working with at the moment permits her and Culliton to change parameters that subsequently rewrite underlying code accordingly. For instance, the wheelbase module reallocates torque to imitate the sensation of a bodily shorter or longer wheelbase, relying on circumstances.
Culliton and Unti punch in just a few tweaks to handle points I encountered. For prime-speed exits, akin to when popping out of Hog Pen, they up the extent of rear torque vectoring so as to add a little bit of rotation as I transition from half throttle (they use the phrase “throttle” versus “accelerator” or another unsatisfying time period, so I’ll too—this as soon as) to Entrance Straight acceleration, so I get previous the sensation that including extra will enhance understeer. Within the dramatic Spiral transition, they soften vectoring and reduce the turn-in second in order to not overwhelm the rear tires. And within the eventualities the place the again finish twitched on nook exit, they add a bit extra entrance torque bias for rear stability.
They did not inform me any of this earlier than I went out within the Sapphire once more, lest I anticipate the consequences. However the changes labored a deal with. The 2 minor corner-exit wiggles disappeared, and the automotive was way more secure after I crested the low-speed transition in Spiral. Better of all, I used to be higher capable of feed on the facility as I exited the ultimate flip. The phrase “insecurity” disappeared, changed by “my God, this factor is fast.”
There was a aspect impact, although. As is usually the case in tuning, while you enhance one factor, you lose out elsewhere. That occurred in Curler Coaster, the place the Sapphire turned a bit twitchier. A mistake on my half might need introduced that about as I sailed just a few ft previous my traditional turn-in level and tried to deliver it again. The automotive appeared to attempt to assist, however right here two wrongs didn’t make a proper. Again to the pits for an additional assume and software program tweak.
At this level, my time was up, however Culliton, Unti, and Lickfold had been going to stay at VIR for an additional spherical or two earlier than packing up and shifting on to a different testing locale. It’s going to be nice to see the place the Lucid Air Sapphire finally ends up once they’re completed, however issues look very promising certainly. Let’s hope we are able to get our palms on one for the following Lightning Lap.
Sapphire vs. Plaid
It is tempting to have a look at the Tesla Mannequin S Plaid and the Lucid Air Sapphire by way of the identical lens. In any case, every has a tri-motor powertrain that produces upward of 1000 horsepower. However there are basic variations.
For one, the Sapphire was a part of the Lucid Air recreation plan from the beginning and can seem within the mannequin’s second yr of manufacturing. David Lickfold instructed us his staff knew of the necessity to put down all that huge energy and torque once they initially conceived the suspension. The identical is true of the objective to make the automotive completely trackworthy, which implies its 10-piston entrance calipers and carbon-ceramic brake rotors aren’t any afterthought.
In the meantime, the Plaid emerged within the Mannequin S’s tenth mannequin yr. It is uncertain that Tesla deliberate the Plaid’s existence that far out, particularly because the firm constructed its model across the induction motor that Nikola Tesla invented, a stylized cross part of which is Tesla’s emblem. However in 2019, Tesla quietly began abandoning induction motors within the Mannequin S, switching to permanent-magnet synchronous ones, and the Plaid would not have been possible if that hadn’t occurred.
What’s extra, the Mannequin S Plaid shares tires and brakes with the much less highly effective variant. All- season 19-inch tires stay customary, with 21-inch summer season rubber an possibility. The Plaid is principally a motor swap. A $20,000 carbon-ceramic brake improve package is deliberate for later this yr, however it ought to have been a part of the Plaid package deal from the start.
Technical Editor
Dan Edmunds was born into the world of vehicles, however not the way you would possibly assume. His father was a retired racing driver who opened Autoresearch, a race-car-building store, the place Dan lower his enamel as a steel fabricator. Engineering faculty adopted, then SCCA Showroom Inventory racing, and that mixture landed him suspension growth jobs at two completely different automakers. His writing profession started when he was picked up by Edmunds.com (no relation) to construct a testing division.