Automotive in BLOG

In pursuit of better fuel economy, carmakers have created various forms of hybrids. In pursuit of a childhood dream, Chris Lentz created a wild hybrid.

The fifty-five-year-old electrical foreman from Jackson, Michigan, had longed for a jet-powered truck for decades. Two years ago, Lentz discovered a way to realize his dream when he met a pilot from New York who imported used turbojet engines. After watching an example run on a test stand, Lentz paid $10,000 for one. Obtaining a rolling platform for his new toy was a bit easier. Lentz bought a used 2005 Ford F-150 STX on eBay for $12,000.

Lentz's jet engine was designed in the mid-1950s by the Czechoslovakian company Motorlet to power the L-29 Delfin jet trainer. The Motorlet M-701 turbojet has a centrifugal compressor, seven combustion chambers, and a single-stage turbine. According to Jane's All the World's Aircraft, the powerplant weighs 728 pounds and produces 1962 pounds of thrust at 15,500 rpm.

To install the jet in the truck, Lentz fabricated a sturdy mounting stand, a twenty-gallon kerosene tank, and a control console from aluminum and stainless steel. His decorative touches include a red, white, and blue nose cone and a 2700 HP badge (not divulged is the 516-mph velocity needed to achieve that power level).

To light the burner, the pilot advances a red fuel lever and a blue throttle control while operating a two-stage electric starter. There are snapping sounds as ignitors fire in the combustion chambers followed by a muffled explosion and a whine not unlike a 737 taxiing past the lowered tailgate. Viewing the procedure from the rear of the truck reveals a bright orange ball of flame accompanying the muffled explosion upon ignition. With the jet idling at 3500 rpm and during full-throttle acceleration, there are waves of heat but no external flames.

Without jet assist, Lentz's 231-hp V-8 accelerated its 6600-pound burden (truck, jet engine, two occupants) to 60 mph in a sluggish 14.5 seconds. We recorded a quarter-mile speed of 73 mph and a top speed of 85 mph.

The best of three runs in hybrid mode - exploiting both piston and jet propulsion - trimmed six seconds from the sprint to 60 mph. The quarter-mile speed jumped 30 mph and we achieved 140 mph after 45 seconds of acceleration. Feeding more ram air to the jet engine by moving it aft in the bed and shifting the F-150's transmission to neutral at 100 mph to cut the drag of its speed-limited driveline would likely improve performance.

Lentz occasionally fires his jet while cruising but mainly enjoys the reactions he experiences in parking lots and at car shows. His JET PWR vanity plate helps slow learners grasp the point of the bed apparatus.

The Specs

Construction Cost: $25,000
Engines: 4.6L V-8 231 hp; turbojet with 1962 lb of thrust
Weight: 6221 lb
Weight Dist., F/R: 45.6/54.4%
Acceleration: 0-60 mph in 8.5 sec; 1/4 mile in 16.3 sec @ 103 mph
Top Speed: 140 mph
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Is the Horsepower War Almost Over?
War is hell, unless it's a horsepower war, in which case it's kind of fun. For more than a decade, the cars from AMG have been on the front lines of the horsepower wars, which have seen the top autobahn rockets - most, naturally, from Germany - zoom past 300, then 400, and now 500 horsepower. But all good wars must one day come to an end, and for the horsepower wars, that day is starting to feel very close indeed. The new E63 AMG, for example, uses the same engine as the previous model (AMG's near-ubiquitous 6.2-liter V-8) and pushes its headline figure ahead by only 11 hp.

Still, we're talking about 518 horsepower here, easily enough to send this luxurious four-door sedan down the autobahn at (a governed) 186 mph. The thing is, the previous E63 AMG, with only 507 hp, was also capable of 186 mph. Evidently, at the peak of the super-sedan pyramid, there simply isn't much more performance to be had.

The goal: Better driving dynamics
Where, then, did the AMG folks hope to move the needle with this new car? "We wanted a sharper car - better driving dynamics," says Tobias Moers, head of overall vehicle development at AMG. Here again, though, we'd argue that AMG's high-volume mid-liner already made its big move in the chassis department with the switch from the old E55 AMG to the new-for-2007 E63.

Nonetheless, in the quest for even better driving dynamics, AMG engineers tossed out the front air springs (still used on the standard E-class) in favor of steel springs and struts. Air springs are retained at the rear, because of their ability to manage the widely varying loads on the rear axle. As before, the dampers are adjustable, this time in three steps: Comfort, Sport, and Sport+. An available performance package - a seemingly redundant option on a fire-breather like the E63 - makes the three settings a bit firmer still. When we sampled both versions on the beautifully maintained roads around Stuttgart, the standard car in its mellowest setting delivered a pretty comfortable ride, but when we cranked it up a notch to Sport or two notches to Sport-plus, the E63 telegraphed every slight bump or bit of creased pavement we could find. In the performance-package car, Comfort is the equivalent of the standard car's Sport setting, so your choices are Stiff, Stiffer, and Stiffest. Combine that with the 30/35-series tires (front/rear) and that is likely to feel pretty harsh over the crumbling highways that plague so much of America.

Unfortunately, those seeking ultimate bragging rights will want to opt for the performance package anyway, as it includes the reprogrammed electronics that allow for that 186-mph top speed, rather than the standard 155 mph. Otherwise, though, the stiffer spec is hardly necessary. Despite tipping the scales at a shade over two tons (about the same as before), with either setup, the E63 turns in aggressively, remains deliciously balanced through fast corners, and emits barely a peep from its Pirelli PZero tires. A new, fixed-ratio steering rack is quicker than before at 14:1 but is perfectly weighted and never nervous. For those eager to explore the handling limits, the stability control includes a more liberal Sport mode and also can be switched off completely.

A new transmission grabs the powertrain spotlight
The same 6.2-liter V-8 that powered the previous E63 is under the 2010 E63 AMG's hood. AMG engineers were able to boost peak horsepower to 518 hp, chiefly by lowering the exhaust backpressure. The engine's surprisingly sharp, aggressive bark and deep rumble have been preserved. Overall, though, the more significant powertrain change is the adaptation of the Speedshift DCT seven-speed automatic transmission from the SL63 AMG, which replaces the old car's seven-speed automatic. The Speedshift box uses a wet clutch in place of a torque converter and provides faster shift times and very sweet, rev-matched downshifts. Surprisingly, despite the absence of the torque converter, the transmission still beats any automated manual - including BMW's M-DCT - and most dual-clutch setups with its smoothness both in take-off from a stop and in its automatic shifts. And yet its shift speed effectively gives away nothing to those supposedly sportier gearboxes.

As you'd expect, the driver can tailor the transmission's behavior via a choice of modes. The mellowest, C (for Controlled Efficiency, says Mercedes) is really too mellow for a car like this. It's the economizer setting, starting off in second gear, upshifting as soon as possible, and even relaxing the throttle response. Controlled Efficiency might be great for squeezing out the best-possible mpg rating on the EPA test cycle (expected to be 13 city/19 highway, though official figures aren't yet available), and it's the chief reason AMG is able to boast of a 12 percent improvement in the E63's fuel economy. But, really, who on earth is going to hypermile their nearly-$100,000 German super-sedan?

The next two modes, Sport and Sport+, are subtly different in their programming but virtually indistinguishable on the road. Happily, both seem to intuitively understand the enthusiast driver, unfailingly anticipating gear choices, downshifting under braking, snapping off upshifts with lightning speed, and beautifully matching revs on every downshift, whether automatic or manual. Speaking of manual, if the driver calls up his own shifts via the steering-wheel-mounted paddles, after a few moments of inactivity, the box will resume giving its own orders. Turn the control knob to Manual, however, and the transmission will defer almost totally to the driver; the gearbox will not upshift even at the 7200-rpm redline nor will it kick down in response to a booted throttle.

A final, fifth, position on the transmission control knob is RS, for Race Start (or should that be valet mode?). It's a bit fussy to deal with, though. With the stability control in Sport, you hold your left foot on the brake, choose Race Start, when prompted quickly tap the upshift paddle once to confirm, then immediately floor the accelerator (if you're not fast enough the whole sequence is cancelled and you have to start over), and let off the brake. The E63 effects a wheelspin-free blast that should have you to 60 mph in 4.1 seconds.

The buttons to select the transmission, ESP, and damping modes are alongside the gear selector, which is a console-mounted lever rather than the wimpy column shift in the standard E-class. Sitting next to them is a fourth button, labeled AMG, which - like a BMW's M button - can program and store a driver's preferred settings for transmission, stability control, and damping.

As you'd expect from a car with 518 hp, the E63 is a always ready to drop a couple of gears, let out a deep bellow, and tear ahead down the highway. The massive V-8 makes this car a star of the quick, two-lane pass. A new option for hauling it back down again is carbon-ceramic brakes, although they won't be available in the U.S. market until next year. Like all carbon-ceramic brakes, these offer fade-free, racetrack-ready performance, at a price (expect to be $8000 to $10,000), but unlike most they're - almost - squeal-free and fairly easy to modulate.

For AMG: typically subtle appearance changes inside and out
Compared with the standard E-class, the AMG version has a unique front-end design, with a wider, deeper front fascia with functional side slits (they extract air from the engine oil cooler). Wider front fenders make way for the increased front track and ultrawide rubber - 255-series up front; while the rear tires are 285, whether on standard eighteen-inch or optional nineteen-inch wheels. There is also AMG-specific lower bodywork on the sides and at the rear. Inside, there's the aforementioned center console buttons, a unique gauge cluster, sport seats, and available carbon-fiber trim. As before, the overall affect is muscular but refined.

Rumbling into dealerships this fall
The new E63 goes on sale this November, at a price that should come in below the outgoing car's upper-$80,000 base sticker. The wagon version again will be available, but only by special order. The new E63 does not offer a great leap in horsepower over the outgoing car, but it makes measurable progress in chassis dynamics and it offers a more entertaining transmission, even if it's not a stick-and-clutch manual. Its already spectacular predecessor was already arguably at the peak of the performance-sedan mountain. The new model marks only incremental progress, but when you're starting at this level, there's only so much higher you can go.

2010 Mercedes-Benz AMG

Price: $87,000 (estimated)

Powertrain
Engine: DOHC V-8
Displacement: 6.2 liters
Horsepower: 518 hp @ 6800 rpm
Torque: 465 lb-ft @ 5200 rpm
Transmission: 7-speed automatic

Chassis
Steering: Rack-and-pinion with power assist
Suspension, front: Damper struts, electronic damping
Suspension, rear: Air springs, electronic damping
Brakes: Vented discs, front and rear, ABS
Tires: Pirellit PZero, 255/35 ZR19 front, 285/30 ZR19 rear

L x W x H: 192.6 x 75.9 x 56.8 in
Wheelbase: 113.2 in
Track F/R: 66.2/62.8 in
Weight: 4058 lbs
Fuel Mileage: 13/19 mpg (estimated)

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