Technical Analysis: Ferrari FXX

Road and Track, July 1st, 2006

It has been said that money can't buy happiness. But if you happen to have considerable Ferrari juice as well, it can buy involvement in one neat project: the FXX. The Ferrari Enzo carried the internal-Maranello designation FX, so it’s entirely logical that a development project leading to its successor be called FXX. Not so logical, but certainly an interesting business model, is the project’s Clienti-Piloti collaboration. A total of 29 FXX cars were offered to particularly well-connected (and evidently well-heeled)Ferraristi, each of whose €1,600,000 (about$1,920,000) bought the car, a racing kit of helmet, suit, gloves and shoes, and participationin a factory development program. Albeit in a somewhat limited sense, each FXX owner becomes a Ferrari test driver for two years—and gets to keep the car as well.

The FXXs are for circuit use only, though no racing activity is planned. Any road-going homologation would be done solely by the owner, not the factory. Several Ferrari-sponsored training/development sessions are part of the deal. Two of them, at Homestead, Florida, and Mugello, Italy, have already taken place. (In fact, our Patrick Hong attended the first one. On page 82 he reports up-close-and-personal from an FXX cockpit.) Mont Tremblant, Canada, and Spa-Francorchamps, Belgium, have June dates; Nürburgring, Germany, is in September and Vallelunga, Italy, the Ferrari World Finals, is in October.

Just between you and me, I sense a certain element of flim-flam in all this. But certainly not in the car.

FXX: THE CAR

Recently I had opportunity to visit Maranello and chat with Ing. Amedeo Felisa, Ferrari SpA vice general manager and godfather of the FXX. I learned alot about this car’s fascinating technicalities.

But first, I asked, why 29 of them?

“It was originally 20,” he said. “But we had agreat deal of interest. It grew to 21, then 22, 23…We finally decided that ‘more or less 20’ meant ‘not more than 29.’ ”

Are we looking here at the Enzo II?

“Maybe 90 percent of the thinking for the Enzo replacement will evolve from this FXX project,” Felisa said, “but we also have some special ideas, some strange ideas. And the new car will definitely carry a different name; it won’t be an Enzo.”

How much of the FXX is Enzo-derived?

Although Felisa said the carbon-fi ber/aluminum-honeycomb/aluminum substructure layout is related to that of the Enzo, there are major revisions in the engine, gearbox, wheels and tires, electronic control, aerodynamics and a host of other details. Let’s examine these.

Like the Enzo’s, the FXX’s powerplant is a 65-degree naturally aspirated V-12 mounted amidships. Like the Enzo’s, it has double overhead camshafts per bank and four valves per cylinder, these valves with continuously variable timing.

The most telling differences are in displacement, the FXX’s 6262 cc versus the Enzo’s 5998, and resulting output. The FXX produces 789 bhp at 8500 rpm (versus 650 at 7800 for the Enzo) and 506 lb.-ft. of torque at 5750 rpm (versus the Enzo’s 485 at 5500).

As they say over here, there’s no substitute for cubic centimeters. But a little arithmetic also indicates that the FXX’s enhanced output is attributable to more than just a kick in displacement.

Ing. Felisa is justly proud of the FXX’s specific power, 1.26 bhp/liter, quite stunning from an engine with normal aspiration.

“We get this through increased revs,” he notes, “but it presents a real challenge with such a large engine.”

There’s plenty of reciprocating mass in a 6.3-liter powerplant. And frictional losses are notoriously high with a V-12 configuration.

How were these challenges met?

Knowing he’s not saying anything particularly profound, Ing. Felisa smiles and says, “Through design of components, through improvements in lubrication and in protecting surfaces in special ways.”

Details: Solutions delved into mechanical, hydraulic and internal-flow matters. Reduced power losses are attributed to a new crankcase design. Revised combustion-chamber geometry and a low-backpressure exhaust system are cited as well. Let’s also guess that Ferrari Formula 1 technology could be of benefit here, with ultra-mini-skirted piston geometry, strength-optimized connecting rods of titanium and the latest in nanotech surface treatments.

FXX GEARBOX: NEAR-F1 TIMING

The transmission of the FXX is a sequential manual, its underlying gearbox with six forward speeds and reverse. Like the Enzo’s, it’s actuated by steering-column-mounted paddles, the right one for upshifts, the left for downshifts.

Enhancements have reduced shift times by 40 percent compared with the Enzo’s then-state-of-theart 150 milliseconds. An FXX’s shift can take place in as little as 80 millisec., from disengagement, through gearchange, to reengagement.

Two reasons are cited, both related to lessons learned with F1 gearboxes. First, transmission inertia has been reduced by 10 percent (possibly through more efficiently sized gears and synchronizers). Second, and rather more subtle, Felisa hinted at an exploitation of the rotational energy inherent in spinning gears, particularly at the instant of disengagement.

The point of speedy shift times, of course, is to lessen the duration of torque interruption. So why not just fit a twin-clutch layout, à la BorgWarner/VW/Audi Direct Shift Gearbox?

“Such developments take time,” Ing. Felisa admits, and I recall his earlier comment about strange ideas.

The FXX cockpit is more starkly executed than that of the Enzo, quite befitting the car’s R&D nature. Its onboard telemetry tracks as many as 39 different parameters. Buttons on the carbon-fiber-centered steering wheel permit scrolling through data bits, uploading them to the pits and voice contact as well. It’s a two-pedal car, of course, and the oversize brake pedal looks particularly appropriate for dabs of the left foot. Five-point harnesses are part of both custom-size seats—and, yes, the idea of the second seat is so “the Client Test Driver will be able to share the unique track experience with a passenger.…”

Uh, thanks, no. I get to go to my dentist today.

THE ROAD INTERFACE

Suspension of the FXX is derived from the Enzo’s. Front and rear, there are unequal-length A-arms connected via pushrods to horizontally opposed coil springs, with electrically adjustable dampers and an anti-roll bar.

Tires, though, are decidedly different from the Enzo’s exotic street rubber. Ferrari commissioned its partner Bridgestone to develop tires that resemble F1 rubber but for their 19-in. wheels (F1 cars are restricted to 13-inchers.) Like F1 tires, the FXX dry variety are “semi-slick,” with four circumferential grooves. Compounds and structures were optimized in the directions of predictability and driving ease, not all-out performance obtainable only by the Schumachers of this world.

I asked Ing. Felisa about the tradeoff of tire size, tire profile and unsprung weight.

“The choice of size,” he said, “is dictated by two factors. How fast does it run? That is, how often does a tire particle encounter its deformation with the road surface. And how much torque is it asked to transmit in acceleration? The tires designed for the FXX optimize these criteria.”

Brakes are FXX-dedicated as well. Brembo devised composite ceramic discs of truly gargantuan15.7-in. diameter up front, 15.0 in. at the rear. Also cited are six-piston calipers, special pads and dedicatedmeans of cooling this hardware.

Dimensions of the FXX are close to those of the Enzo. They share a 104.3-in. wheelbase, though the FXX’s 190.2 in. overall makes it just a tad longer. Its dry weight is cited as 1155 kg, 2547 lb., a claimed 220-lb. reduction from Ferrari’s Enzo data.

Add an estimated 175 lb. for a full fuel tank (the Enzo’s has a 29.1-gal. capacity), and I get what we’d call curb weight for the FXX of around 2720 lb. By contrast, our pal Richard Losee’s Enzo weighed in at 3230 lb. (See our July 2003 Road Test.)

Needless to say, the FXX is free of airbags, air conditioning and other amenities of a road-dedicated Enzo. Befi tting its R&D nature, though, it does have  built-in pneumatic jacks for pit work. The FXX’s ratio of weight to power is impressive indeed: 3.4lb./bhp. Ferrari cites an estimated 0–60-mph sprint in 2.8 sec., and I’d have no reason to doubt this capability.(Consider: an Enzo’s 5.0 lb./bhp, 3.3 sec. to 60; a Porsche Carrera GT’s 5.8 lb./bhp, 3.6 sec.)

Ferrari uses lap times around its Fiorano test track as a measure of development. The company cites an FXX time of less than 1 minute 18 sec., versus 1 min. 25 sec. for the Enzo. The F2005 Grand Prix car holds the record at 55.9 sec.

AERODYNAMIC CLEVERNESS

As with the Enzo, one of Pininfarina’s goals with the FXX was to produce a highly efficient shape without need of aerodynamic add-ons. And though its exterior is not dramatically different from the Enzo’s, the FXX produces some 40 percent more downforce.

An interesting measure is downforce/weight, and here the FXX is even more impressive. Calculatedfrom wind-tunnel data at 350 km/h (217 mph, the claimed top speed of both cars), the Enzo’s downforce/weight ratio is 0.41. By contrast, generating more downforce—and carrying less weight—the FXX’s value is 1.12. That is, available downforce exceeds the FXX’s weight, making a drive acrossthe ceiling of a tubular track a theoretical posit. A Ferrari F1’s ratio is cited at 2.78.

Downforce is only part of the picture, drag being crucial as well. Here, the FXX embodies a concept that Ferrari calls aerodynamics bleed, essentially trading available downforce in the interest of reduced drag.

As Ing. Felisa explains: "Aerodynamic characteristics increase with velocity. In fact, downforce can increase to the point that it compresses the suspension too much. Also, it is important to maintain the fore/aft balance of aerodynamic forces.”

Most of the FXX’s aerodynamic magic occurs beneath the chassis, in ducting and diffusers. Aerodynamic channels both fore and in the midsection are fitted with adjustable flaps that control the airflow. When road speed exceeds 150 mph, the midsection flaps achieve a “base bleed,” diverting flow into channels that exit on the car’s rearmost surface, just below the twin exhaust outlets on either side.

This achieves several goals: It trades away a bit of unnecessary downforce and concomitant drag. And it reduces drag further by beneficially affecting the car’s wake, that inherently low-pressure region being dragged along at the rear. Flow from the four exhaust outlets also contributes to this wake drag reduction. (Ferrari’s F1 cars used exhaust flow in a similarly beneficial manner, their goal being to optimize flow over the rear wing elements.) Last, smallish winglets atop the rear flanks of the FXX fine-tune the wake control.

At the same time, up front, flaps ahead of the front tires divert the flow to maintain balanced vertical loading and to reduce drag at this end of the car as well.

“The FXX isn’t a car,” Ing. Felisa likes to stress, “it’s a project.” And when we see the eventual replacement for the Enzo, whenever it appears, we’ll know the people—and the process—responsible for it.