Poll the owners of 964-generation Porsche 911s about how they would improve their cars and answers would likely include fewer oil leaks on their driveways and HVAC systems able to add actual heat or chill. We suspect very few would choose to rip out their car's air-cooled flat-six engine and replace it with a pair of electric motors.
But this is exactly what a new United Kingdom-based startup called Everrati is offering to do in return for the small matter of about $360,000 plus a donor 964 (1989 through 1993 911 models). The conversion is designed to be reversible, although it seems unlikely anyone spending so much money would ever do so. The upshot is a car that promises to be as quick as the mighty Turbo 3.6 was while weighing less than the contemporary Carrera 2. Everrati claims a weight of 3090 pounds.
Let's leave the contentious question of why until later because the what is certainly impressive. The Signature is considerably more than just a powerplant transplant; it's been rebuilt to a standard that doesn't feel far removed from one of Singer's pieces of rolling rear-engined art. Everrati's demonstrator uses a Turbo-style wide body, but it will also perform conversions on lesser 964s. There are some modern details but not too many—LED headlights being the most obvious. The paint finish is impressively crisp, and fat Michelin Pilot Sport Cup 2 tires sit on period-appropriate aluminum alloys. It even has exhaust tailpipes, but we'll get to those later.
While the 964's core structure hasn't suffered radical change, the demonstrator's doors, roof, hood, and duckbill spoiler are made of carbon fiber to help save weight. Fitting the electrical powertrain wasn't easy. Many (if not most) cars from the 1980s would be easier to convert, given the packaging constraints of the Porsche's tight-fitting engine.
In the demonstrator, two Tesla-sourced AC induction motors drive the rear axle, which is fitted with a limited-slip differential, through a common input shaft. (Everrati plans to switch customer cars to a pair of compact modular permanent-magnet synchronous motors from Integral Powertrain from the same family that will power the Lotus Evija.) The space remaining in the rear wasn't sufficient to accommodate an appropriately sized battery, so there are two packs—the larger one in the back with a smaller one in front of the passenger compartment. These run at 400 volts, have a usable capacity of 50.0 kWh, and are connected by a cable that passes through the former transmission tunnel. (There is still room up front for a small frunk.)
Unusually for an aftermarket EV conversion, the Signature supports fast charging through a port located under its vestigial fuel-filler cap. This can support DC fast charging up to 80 kW, allowing the battery to be taken from 20 percent to 80 percent in about 45 minutes. Everrati doesn't quote an official range yet, but it says the car has managed more than 150 miles between charges in real-world conditions.
The Signature's cabin has been retrimmed to a high standard that corresponds to its external finish and features Porsche's own touchscreen infotainment system for older cars. From the driver's seat, the obvious change is with the repurposed analog instruments, with the tachometer turned to a flow/charge meter and the supplemental dials now reporting on battery voltage and charge plus the temperatures of packs and motors.
Turning the key in an elderly Porsche and being rewarded by the sound of silence is far from an unusual experience, the difference with the Everrati being that it can still move away without the busy clatter of an air-cooled flat-six. The experience of a near-noiseless 964 is a deeply incongruous one, something that barely diminishes after an hour in the car. There are other small aural distractions: The 12-volt pumps for the hydraulic power steering and vacuum brake booster can be heard when the car is stationary, road and suspension noise are more obvious when moving, and the rear-mounted motors produce a distant accelerative hum under harder use. That's where the difference between this 964 and an original is clearest.
Even the sportiest sports cars suffer from relative performance deflation over the span of three decades—the basic Carrera of this generation made just 247 horsepower—but the Everrati feels impressively muscular by 2021 standards. The company claims it will be able to go from zero to 60 mph in less than four seconds, which is what we figured for the 964 Turbo in 1994, and performance would likely be similar until at least 100 mph. Beyond that, the Everrati's acceleration diminishes quickly. Top speed is governed to around 130 mph.
There is a very slight delay in the Signature's throttle response, but apart from that, acceleration feels both seamless and relentless. The lack of gearchanges is routine for an EV, but it feels especially strange in a 911. Combined with the absence of any engine note, this made it hard to gauge velocity by ear and meant the figures on the speedometer often seemed surprisingly high.
The Everrati's left pedal operates pads on discs in the normal fashion, but the motors also give powerful regenerative retardation when the accelerator is lifted. There isn't a coast function. The regen is more than strong enough to regulate speed in everyday driving, but it isn't a true one-pedal system, as there is no way for the car to automatically apply its friction brakes (which use Porsche's period ABS logic) without line pressure from the driver's foot. So, it needs positive braking to be brought to a complete halt or to be held on a hill.
Traction felt impressive. The demonstrator is still using Tesla's control algorithm to prevent slip, and the combined torque output of the two motors has also been limited to no more than 368 pound-feet. Even under full bore starts on dry asphalt, there was no obvious sense of the system intervening, although there was the unmistakable sensation of power output diminishing after repeated bursts of hard acceleration. (That's very much a Tesla habit, to be fair.) Full capability returned once the powertrain had the chance to cool.
Beyond the lack of combustion noise and the elimination of spark-plug and oil-change bills, the Signature's driving experience is significantly different from a normal 964. Steering remains full of feedback—the decision to stick with hydraulic power assistance rather than use an electrically assisted rack is entirely justified—and front-end bite felt impressive. The ride is pliant and composed, too, with the demonstrator using adaptive dampers from aftermarket supplier Tractive. But the responses at the rear felt wrong when compared to our memories of the original 964, the Everrati exhibiting only a limited part of the ass-led cornering sensation that comes standard in an air-cooled 911.
While the Signature's static weight distribution is deliberately close to the donor car, with only 40 percent of the mass on the front axle. (We measured 41 percent on the front axle of a 964 Carrera 4.) The weight of motors and battery pack are further inboard than the engine and transmission of a regular 964, and that placement may contribute to less on-throttle understeer and a reduced ability to influence the cornering line through small changes in accelerator position. The result is a car that behaves more like a Cayman than an old-fashioned 911, lacking the thrown-hammer sensation that has both thrilled and occasionally terrified fans of the air-cooled car. To Porsche's credit, the 964 solved most of the lift-throttle scaries of the 911. For those craving an original driving experience, this isn't it.
It's a point made by the continued presence of the exhaust. The Everrati boasts an exterior sound system that can produce appropriately Porsche-like noises through a speaker that will use the vestigial tailpipes as resonators. This demonstrator car wasn't able to do anything more than synthesize a (convincing) idle, but the company promises the full version will be able to replicate the full rev range under different load conditions. (It even might be able to substitute the flat-six noise for something else, like a big-cube V-8.) The company is also working on a virtual gearbox, which it says will use a manual lever to deliver different maps to replicate the torque characteristics of the original engine. All of which seems a complex and expensive alternative to sticking with a combustion version. Even Europe isn't proposing an outright ban on hydrocarbon-fueled classics.
There's something undeniably cool about the idea of an electric Porsche 911, but the reality is noticeably short on soul. Everrati's car is a hugely impressive piece of engineering and also a hugely expensive one. Spending all that money will bring you a car that looks like a 964 and maybe even sounds like one, but it will deliver a driving experience that also feels like a simulation of the real thing. It's proof of how much of the classic 911's appeal comes from both its old-fashioned air-cooled engine and its archaic location.
Frankly, we'd take the oil stains.