Brand new front page! Click the Front Page button directly below and check it out!
0 Members and 1 Guest are viewing this topic.
December 1, 2008, 4:53 pm Launch Party Is Over for Nissan GT-RBy Ezra DyerWe Americans just can’t have nice things.Nissan GT-R, soon without launch control.As Exhibit A, I give you the Nissan GT-R and its soon-to-be-discontinued launch control feature: A bunch of people bought GT-Rs and fried their transmissions using launch control. Said customers then hit Nissan with warranty claims, at which point Nissan took its toy and went home. Thus the 2009 GT-R will be the only vintage of the car with the factory-sanctioned ability to perform a high-r.p.m. clutch drop from a standstill. I’m not sure whether that will make 2009 GT-Rs more valuable on the used-car market, or less. With the proliferation of dual-clutch sequential manual transmissions comes a thorny issue for car companies — whether or not to include launch control, and how to design the system if they do. Launch control systems address a major performance issue inherent to sequential manual transmissions, which don’t have clutch pedals to drop: namely, how does the driver execute an aggressive takeoff from a standing start? Usually, through an arcane button-pushing routine to initiate launch control.Nissan’s system was the real deal, an automated version of the sort of machinery-abusing takeoff that a human driver might attempt on a drag strip. There’s a certain video-game-cheat quality to setting up the system, like the button-pushing sequence you’d use to get 30 lives in the old Nintendo game Contra. Set the suspension to “R” mode, set the transmission to “R,” turn off the stability control, left foot on the brake, right foot hard on the gas, pop the left foot off the brake … and hold on. The motor would wail, followed by a violent clutch engagement and all four tires clawing frantically under maximum power.Now, I don’t know the specifics of the warranty claims that caused Nissan to discontinue the GT-R’s launch control system. For instance, were people doing right-angle burnouts while running over manhole covers? (I include that example because an engineer at a car company once told me that he had to duplicate that exact scenario to figure out how customers were causing a certain drivetrain part to fail.) Were people just doing occasional drag strip runs? And at what point does responsibility shift from the customer to the automaker when something breaks? That’s the question plaguing the growing number of companies who offer some form of launch control. If you own a manual-transmission performance car and you abuse the clutch and transmission to the point of failure, you as the owner have a pretty direct responsibility for what happened. If you take, say, your Subaru WRX STI into the dealer for a new clutch, and they take it apart and discover that you’ve inflicted 90,000 miles worth of wear in 5,000 miles, well, your left foot is the obvious culprit. But in a car with launch control, there’s a philosophical difference. Sure, you may have initiated the launch control sequence 20 times in a row and fried the clutch, but ultimately the car itself was the one doing the dirty work. So if something breaks, why is it your fault simply for using a feature that’s built into the car? It’s an argument that Nissan, at least, has decided it doesn’t want to get into. Launch control systems in the United States have a history of either being omitted entirely (as in the United States-market Ferrari F430) or dumbed down. For instance, the launch control function on BMW’s single-clutch sequential-manual gearbox, SMG, was a modified version of the system used in Europe. The European SMG would slip the clutch to provide the fastest takeoff possible, at the expense of clutch wear. The American system would quickly — but completely — engage the clutch, which tended to spin the tires and probably cost a few tenths of a second on zero-to-60 time. The rear tires were the circuit breaker of the system, the place where excess energy could be dissipated in a manner conducive to avoiding warranty claims. But all-wheel-drive cars like the GT-R, Mitsubishi Evolution and Porsche 911 C4, which usually have too much traction to generate significant wheel spin, put the stress on the clutch. And that’s an expensive circuit breaker.There are different ways of handling that stress. With Mitsubishi’s twin-clutch Sportronic transmission in the latest Evo, the launch control mode restricts full engine power until the car is rolling and the clutch can fully engage. The system also monitors clutch temperature and will call a timeout — forcing the driver to pull over to let things cool down — if multiple launches raise clutch temperature too high (the launch control feature on BMW’s new DCT dual-clutch transmission also keeps a careful eye on temperatures and will take a hiatus if it gets too hot). The Evo with Sportronic does 0 to 60 in 5.2 seconds, while the five-speed manual version is a few tenths of a second faster. The difference is purely down to the violence of the launch and can be traced to the first 60 feet of an acceleration run, where the manual Evo’s launch r.p.m. and clutch slip are restrained by nothing more than the driver’s penchant for mechanical sadism. In the case of the dual-clutch Evo, the programming is calibrated to err toward longterm drivetrain survival rather than ultimate drag-strip heroics. Mitsubishi points out that, while the dual-clutch car is slower than the five-speed from rest, the Sportronic car’s quicker shifts and extra gear ratio make it faster around a road course. So the virtues of either transmission and the relevance of launch control depends on whether the word “track” conjures in your mind a drag strip or the Nürburgring.Then there’s Porsche’s new PDK dual-clutch transmission. A base Porsche 911 Carrera with a six-speed manual can go from 0 to 60 miles per hour in 4.7 seconds. The same car with PDK and launch control is actually four-tenths of a second faster. There are no restrictions on how often you can use launch control, and the warranty is identical to that of non-PDK cars. I suppose time will tell whether Porsche, unlike Nissan, has designed a transmission tough enough that launch control doesn’t lead directly to legal damage control.
Have the computer in the car track if LC is used. Inform buyers, if LC is used the warranty on the transmission is voided.Voila, problem solved.
