As a driver in NASA's SE-R cup road race series, I'm used to road racing SE-Rs, but this SE-R is unlike any I've ever taken out to the track or driven. Project Phoenix strikes!
Although the Nissan Sentra SE-R is blessed with the nearly indestructible SR20DE engine, its notoriously weak transmission delayed the car's development. Ever wonder why you don't see more hot SE-Rs racing in Quick Class or many big-powered turbo SE-Rs lurking on the streets? It's not the engine that's lacking. It's the transmission. The transmission is the area where Honda has a major advantage over Nissan.
In last month's edition of Project Phoenix, we covered the basics to get the buttery soft gears and transmission case of the SE-R to live under boosted conditions. Since we're planning to take Project Phoenix into serious battle, we had to take another step; we set out to build the strongest, most bulletproof SE-R drivetrain ever concocted.
PAR GearsetThe Australian company Precision Automation and Robotics (PAR) is known for its bulletproof gearsets for the Subaru WRX, another excellent car saddled by a weak transmission. We approached PAR's North American Distributors, JGY Customs, Inc., to help us obtain one of PAR's gearsets for our SE-R.
The PAR gearset has what's known as a constant mesh engagement instead of the common syncromesh engagement used by most production cars. In syncromesh engagment, cones push into cups to match transmission gear speeds so the gears don't grind during shifting. Syncromesh engagement is smooth and quiet-that's good for street cars, but it's not the fastest way to shift.
Constant mesh transmissions use dogs and dog rings to match gear speeds. Dogs are big, beefy tabs on the backsides of gears, and dog rings are rings attached to the adjacent gear with slots in them. When shifting, the dogs grab the dog rings, instantly spinning the adjacent gear up to speed, allowing the gears to engage. Because of this instant positive engagement, constant mesh transmissions can shift very quickly and positively, normally as fast as you can move the lever.
There are disadvantages to constant mesh transmissions. Engagement is rough (there's a bang) and the shifting is notchy and requires more effort. With a constant mesh transmission, you must shift decisively and with some authority, or the dogs will grind, quickly ruining them. If you can shift accurately, you'll be rewarded with lightning-fast shifts both up and down. For these reasons, all motorcycles and nearly all race and rally cars feature constant mesh transmissions.
For full-throttle, clutchless, lightning-fast upshifts, you simply preload the shifter right before you want to shift and back off the throttle slightly. The transmission will go right into the next gear faster than you can blink an eye. This is especially interesting for drag racers and those with turbo cars. You don't have to close the throttle all the way, just quickly reduce the throttle to unload the gears and witness the fastest speed-shifting ever.
Although this might seem scary to those of you conditioned to years of driving syncromesh transmissions, it's easy, and if you shift with a sharp snap, it's harmless to the transmission.
In the case of the SE-R transmission, the constant mesh engagement has a very important feature; unlike bulky syncros, dogs and dog rings don't take up much room or add much thickness to the gears, which frees space, allowing the gears to be much wider and stronger.
PAR also uses a high grade of steel in the gearsets and a special heat-treating process to ensure toughness. Stock transmissions use a small gear tooth profile to reduce noise at the cost of some strength. The gears also use PAR's super tooth profile, a large tooth profile that gives much more engagement area and strength. Durability, not noise, was a consideration when designing the tooth profile. The gearsets feature straight-cut gears that are slightly stronger than stock helical-cut gears, but are slightly noisier. Straight-cut gears transfer power more efficiently because they don't slide across each other as helical gears do. The transmission will run cooler and soak up less wheel power as a result.