The ultimate bracket-racer
The large, comfortable, 3858-pound GT coupe shown here happens to be the sixth-quickest production car Motor Trend has tested, catapulting itself to 60 mph in 3.6 seconds and through the quarter mile just eight seconds later at 127.3 mph. To achieve such breathtaking performance in most supercars requires deft toe-work on the pedals and/or expensively traumatic clutch abuse. But anyone who can smash a gas pedal to the floor can drive this new SLR McLaren with nearly the same results and do it over and over again with impunity.
The engine is refreshingly simple. The SOHC 24-valve, 5.4-liter V-8 uses only a Lysholm-type twin-screw supercharger and twin intercoolers to make its power, no variable valve timing or lift, no variable intake geometry, no tricks. Air gets in and out of the engine efficiently, too, entering via the tristar nostril through a huge air cleaner, straight into the supercharger and exiting almost directly into two huge catalysts and mufflers and out four short side pipes. Total exhaust back-pressure is just 5 psi.
ESP switched off, sport-shift mode selected, left foot on brake: Right foot depresses accelerator 30%, electronic signal opens single throttle plate accordingly, electromagnetic clutch engages supercharger, bypass valve closes, pressure builds.
Blower spins at 2.4 times crankshaft speed, reaches peak boost of 13.1 psi. Engine speed stalls at 2500 rpm, crankshaft torque is restricted to 325 lb-ft, torque converter multiplies this to 398 lb-ft, first gear and final drive multiply that torque to a theoretical 2169 lb-ft at each rear brake, not accounting for driveline losses.
Left foot slides off brake, right foot holds accelerator at 30 percent, a force approaching 1900 lb is delivered to each rear-tire contact patch (almost double the weight pressing down on each rear tire), tires spin in unison (equalized by brake intervention, not a limited-slip differential), car launches.
Car crosses one-foot rollout, timing begins, tires still spinning, accelerator still at 30%. Torque rises to unrestricted 550 lb-ft at 2500 rpm.
10 mph, engine producing 250 hp, roughly 70 of which get sufficient grip on the pavement to accelerate the car.
20 mph, tires find sufficient traction to allow driver to feather in throttle, tires approach road speed in first gear, 120 ponies are pulling hard now, providing an average of 0.7g pressure on the driver’s backside.
Full throttle, engine producing peak torque of 575 lb-ft.
Engine produces 617 peak hp, inhales roughly 68 lb of air per minute; fuel rail sprays over 0.75 gal/min of fuel into the engine–about half the flow rate of a modern showerhead. Instant fuel economy measured in fractions of an mpg.
48 mph, Bosch P-Motronic ME 2.8.1 engine controller retards spark, trimming torque 40% during the upshift into second gear.
60 mph. The 1-sq-ft rear deck wing rises to 10* to improve downforce. Roughly 410 hp are accelerating the car now, 10 of which are overcoming the aerodynamic drag.<
127.2 mph, 1/4 mile flashes past in third gear.
130 mph. Of 464 hp making it to the road, over 110 are devoted to wind resistance. Driver brakes, rear wing rises to 65* angle, drag coefficient increases to 0.43, generating 15 hp worth of aero drag and 167 lb of downforce, distributed 49/51% front/rear.
The SLR also is simple to operate. The steering is far more direct and intuitive than is the Benz norm, and the car’s amidships weight concentration helps it go where it’s pointed quite eagerly. The by-wire brakes take some getting used to, but they smooth out after a half-hour of acclimation. Even the dashboard is elemental: The dual-zone climate control and the radio each gets its own knobs and buttons–no mouse, no TV screen–just as God intended.
But this car’s mostly about delivering urgent forward progress, so let’s zoom in tight on a quarter-mile run.
Switching off the ESP saves time, but requires expert modulation of wheelspin. Leaving ESP on adds just two tenths and 0.6 mph, but makes for incredibly repeatable performance from run to run. Talk about the ultimate bracket racer.
The transmission’s manual mode offers three levels of shift speed and harshness, the quickest of which may shave another tenth off the quarter-mile run, but only after the driver masters the tachometer lag in the lower gears to avoid hitting the rev-limiter.
Sure, rich folks have a choice of supercars priced in the $455,500 range. But not all rich folks are expert drivers. This car does more to make them seem like they are.
Slush vs Clutch
A clutch is a friction disc that clamps against a steel flywheel to transmit engine torque to the transmission, releasing to permit shifts or to idle at a stop. A torque converter is a fluid coupling that works like a fan blowing transmission fluid into a turbine, which causes the turbine to turn. Vanes that direct this fluid back out of the turbine and into the fan again effectively multiply the engine’s torque at low speeds until the two elements are locked together.
Pumping transmission fluid robs some power, but the fluid shoulders the load of accelerating a car from rest. Dry clutches consume no power; but they cannot multiply torque, and they incur considerable wear during an aggressive launch.
|Acceleration, seconds to mph And Quarter mile|
||2 VT 6.0
||5 Saleen S7
||6 SLR McLaren
||8 Turbo S
||9 Mercedes-Benz CL65 AMG
|2005 SLR McLaren|
|Drivetrain layout||Front engine, RWD|
|Engine type||Supercharged 90* V-8, alum block and heads|
|Valve gear||SOHC, 3 valves/cyl|
|Bore x stroke, in/mm||3.81 x 3.62 / 97.0 x 92.0|
|Displacement, ci/cc||331.9 / 5439|
|Max SAE net horsepower||617 @ 6500 rpm|
|Max SAE net torque, lb-ft||575 @ 3250 rpm|
|Specific output, hp/liter||113.4|
|Weight to power, lb/hp||6.3|
|Axle/final-drive ratio:1||3.06 / 2.54|
|Suspension, front; rear||Control arms, one coil-over shock unit, anti-roll bar; control arms, one coil-over shock unit|
|Brakes, f;r||14.6-in vented ceramic disc;14.2-in vented ceramic disc, ABS|
|Wheels, f;r||19 x 9.0; 19 x 11.5 cast/forged aluminum|
|Tires, f;r||255/35ZR19 96Y;295/30ZR19 100YMichelin Pilot Sport PS2|
|Track, f/r, in||64.5 / 61.8|
|Turning circle, ft||40.0|
|Curb weight, lb||3858|
|Weight dist, f/r, %||48 / 52|
|Seating capacity, persons||2|
|Shoulder room, in||54.0|
|Cargo vol, cu ft||9.6|
|Acceleration, sec to mph|
|1/4 mile, sec @ mph||11.6 @ 127.2|
|Braking, 100-0 mph, ft||287|
|Braking, 60-0 mph, ft||103|
|600-ft slalom, mph||68.3|
|200-ft skidpad, avg g||0.97|
|Top-gear rpm @ 60 mph||2050|
|On sale in U.S.||Currently|
|Price as tested||$455,500|
|Stability/traction control||Yes / yes|
|Airbags||Dual front, side, knee|
|Basic warranty||4 yrs/50,000 miles|
|Powertrain warranty||4 yrs/50,000 miles|
|Roadside assist period||Unlimited|
|EPA mpg, city/hwy||13 / 18|
|Fuel capacity, gal||25.8|
|Range, miles, city/hwy||335 / 464|
|Recommended fuel||Unleaded premium|