So far, Dodge has dribbled out eleven of a planned 14 previewed details on this upcoming drag strip, well, Demon, and these have provided us a bit of information even though we haven’t seen the whole thing yet. They even have a dedicated site with a video from each announcement.
Some basics: the Demon wears 3.5-inch wider bodywork to envelope its fatter 18 x 11-inch wheels and track-gripping 315/40R18 Nitto NT05R drag racing radials tires. And it as we reported previously, it has undergone the automotive equivalent of the Green Juices diet, by discarding the back seat and the front passenger’s seat to cut 200 pounds of weight.
Today’s leak provided an interesting tech tidbit that will fascinate gearheads and thrill drag racers: the Demon will be the first ever, factory production car with a transmission brake to hold the car stationary at full throttle, for maximum possible launch ferocity when the lights go green.
The usual solution is for the driver to hold the car in place with the brakes while revving the engine with the transmission in Drive. A transmission brake does what it sounds like, clamping on the transmission’s output shaft to hold the car from moving rather than braking the wheels.
The driver signals the Demon to unleash Hell on his or her command by squeezing the steering wheel-mounted shift paddle, which provides a 30 percent reaction time advantage over foot-brake launches.
Revving the engine before launch creates a 105 percent increase in launch boost pressure from the supercharger, which contributes to a 120 percent increase engine launch torque.
The Demon’s engine makes maximum power at launch by using an innovative technique that lets the Hemi’s blower spin up to maximum boost without the engine making so much power it overpowers the brakes.
It does this by cutting fuel flow to some of the engine’s cylinders, while retarding ignition timing to also reduce power. This lets the supercharger spin up to higher boost without spinning the rear tires before launch. That lets the engine reach full boost, and full power, that much quicker on takeoff.
Slamming all this power into the driveshaft and axles at the squeeze of the shift paddle sounds like a good way to break things, so to avoid that Dodge has the Demon first pre-load force all the way through the driveline to the rear wheels before locking the transmission.
This takes any slack out of the various joints in the system, which not only reduces the chance of snapping a crucial part on takeoff, it also shaves 150 milliseconds off the time it takes for the power to meet the pavement, yielding faster acceleration times.
Dodge also upgraded many of the drivetrain parts to help them survive the Demon’s launch fury. That means a driveshaft able to withstand 15 percent more torque than the one in the Hellcat thanks to the application of high-strength steel, a 20-percent increase in tube thickness and heat treated stub-shafts.
Engineers also upgraded the differential housing, with 30 percent increased torque capacity. They did this by using heat-treated A383 aluminum alloy for the housing and then applying the traditional racing technique of shot-peening the internal gears to increase durability and reduce residual stresses.
Finally, the axles feature larger 41-spline half shafts that deliver 20 percent increased torque capacity, thanks to thicker-diameter high-strength steel axles and larger constant velocity joints.
The transmission brake is also helpful because Dodge anticipates that customers will fit skinny low-drag front wheels and tires to the Demon for races, and those tires won’t hold the car back very long when using the brakes to hold it at the line.
Why does Dodge expect this to happen? Because one of the goodies included with the purchase of a Demon is a crate containing spare wheels and tire-changing tools to facility trackside wheel swaps. Presumably to narrow front wheels and tires.
The Demon also uses traditional drag tricks like softer springs, shocks and swaybars to help put the power to the pavement
All of these tidbits ensure that the Demon will launch like a bat out of hell at the drag strip. That launch will be much faster than the car’s launch to the market, with Dodge’s Chinese water torture dribble of details before the actual event.
source: maxim.com by DAN CARNEY