Norwood designed the V drive to be as narrow as possible, yet still have enough strength to maintain the team's "bulletproof" requirements. The casing was custom-machined from 6061 aluminum and the four straight-cut gears were machined from heat-treated 8000-series steel. The Lenco feeds the oil into the casing to maintain lubrication. Finally, a custom-built carbon-fiber driveshaft carries the drive from the output of the V drive to the rear-end input flange.
This design will surely raise the bar in FWD transmission technology. It's massively strong, with fast and reliable shifting and unlimited gear-ratio options. Are there any weaknesses?
"I guess the biggest disadvantage of the system is the amount of power the system will absorb," Norwood says. "The Lenco isn't the most efficient transmission in terms of power losses, but we'll have more than enough horsepower to compensate and the durability and idiot-proof shifting makes up for it. I also like that I can tune the shifts to help maintain traction."
But what about the weight of the driveline? The transmission isn't very heavy, but the rear end will be fairly hefty. Norwood believes the weight of the rear end will be an asset rather than a liability, helping to plant the tires and stabilize the launches. The team will still be within 25 pounds of the class weight limit and overall, the advantages far outweigh the disadvantages.
The most important component of the 2004 NORAD Celica's driveline will be the NORAD 'slipper' clutch. "Watching the front-wheel-drive cars at the track is reminiscent of the dragsters of the late '60s," Norwood states. "Most of the teams are relying on wheel spin to launch the cars. The problem is the high-revving, narrow powerband of the four-cylinder cars means you have to spin the tires to stop the car from bogging, or worse, getting into tire shake."
Track conditions change constantly so a car never does exactly the same thing twice. That's why cars are so inconsistent. The only way to control the situation is to slip the clutch in a controlled manner. Norwood is focusing a lot of time on developing a system that will allow the team to control the clutch slip accurately. Other teams are also experimenting with slipper clutch setups, so in the future there'll be much more consistency as they figure it out.
Norwood's clutch system is developed from a Tilton three-plate carbon/carbon race clutch that has seen extensive modification. The biggest change is the addition of adjustable posts in place of the standard cover plate 'fingers'. The adjustable posts are manufactured from titanium to keep the reciprocating weight low; they allow the clutch to be adjusted for wear and to ensure the plates are perfectly in line. A cover on the bell housing can be removed to allow for easy adjustments between rounds. To make the posts work, the original Tilton plates were machined and the fingers were machined off the stock cover.
Lastly, the addition of a fourth aluminum heat sink clutch plate will help to keep the clutch pack from overheating as it slips. A Tilton hydraulic clutch release bearing completes the package.
The control system for the clutch features a pulse width modulation (PWM) valve that's controlled by the Motec ECU. The computer takes into account the engine's rpm as well as the clutch line pressure. A 2000 psi transducer controls the clutch pressure according to a pre-programmed curve, and clutch release can be finely controlled via the ECU.
All of this electronic wizardry boils down to the fact that the clutch release can be accurately controlled according to track conditions, temperature and tire compound.
This system will require a lot of track testing to get an accurate database, but once the information is in the system, the tuning of the clutch on the launch should be fast and reliable and the Celica should be far more predictable from run to run.
"I'm convinced that a controllable clutch is the way forward for the FWD cars," Norwood explains. "My system is just one way to do it and I'm sure the other guys will have some kind of slipper clutch in 2004. Only time will tell if we're going at this from the right direction."
The final aspects of the driveline that we'll examine are the 9-inch center section, the CV, hubs, spindle and brake assemblies. Check out page 126 for the next installment.