Project Scion TC - Tech

About a year ago, we reached the point with Project tC where we thought we had enough to turn the lifestyle-branded wannabe performance car into something worthy of the Sport Compact Car name. By our estimate, the tC should have been tuned well enough to take on a mildly tuned Acura RSX Type-S on identical tires. Bang for the buck and performance-wise, the two were closely matched. So it was off to the racetrack to do a project car shoot-out between the two.

The results were close. So close and (more importantly) uninspiring, we put off posting the results until we could arrange a proper rematch. The bottom line was that while the RSX possessed decent track potential out of the box, our tC struggled to convey the same driving feel, even if the numbers were about the same. We knew the car had more in it. The only question was if it would be a waste to spend more money on our purple coupe. We could have just started with an RSX and called it a day.

So the Scion sat un-tinkered with for a year as we scratched our heads and thought about what to do with it. In the meantime, it held up reliably as our cargo carrier and daily commuter, without any incident or mechanical difficulty. The selection of quality parts from manufacturers like Progress, Hotchkis Tuning and TRD made the car immensely better, but not great. With its supercharged engine, bigger brakes and coilover suspension, our tC was actually pleasant to drive and fast, the way it should have been straight from the factory.

We knew we still had some speed left on the table, so we got ambitious and dug back in. But this time we weren’t going to spend more money and get more parts. We were just going to refine what we already had.

The original Progress suspension was an excellent choice for street performance, firm enough to reduce body roll and quicken transitions to nearly Evo speed, yet also smooth enough to drive your mom around. However, the limitations of the suspension’s street focus became apparent during our shoot-out experience. Major complaints were the not-so communicative ride, appearance of mid-corner understeer and the overall sloppy nature of the econo-box platform. The car had also been set up with too little rear spring rate and suspension travel, causing the dampers to bottom out when going over speed bumps.

Our first task was to eliminate the bushing gush and flex out of the suspension. It’s obvious that the tC was built to ride well and have minimal NVH (geek-speak for noise, vibration and harshness), with crisp handling low on the list of priorities. Gush is bad for handling. For a car to handle well, its suspension should work to keep the alignment true, with the tire’s contact patch consistent and as large as possible. The frictional grip of a car’s tires can transfer over a 1000 pounds of force to the suspension, with suspension arms acting as levers that can multiply this many times over.

All this force is brought to bear on the soft biscuits of rubber known as tC suspension bushings. Rubber is an excellent choice for an average driver, whose idea of taking a fast turn only stresses a car to 40 percent of its maximum lateral capability. For those who like to push the envelope, smooth-riding rubber means a lack of steering precision and a loss of grip, due to shifting alignment.

The rear suspension subframe hangs on four huge, squishy rubber bushings with large-windowed cutouts to add additional shock-absorbing compliance. The lower trailing arm’s main bushing also shares a similar cut-out rubber biscuit design. When moved with a prybar (to simulate tire loading), it was possible to get the rear suspension to move nearly half an inch in either direction. Because 1/16th-inch of movement is something most drivers can feel, one inch is extreme and makes an iffy proposition of precise driving at the limit.

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Orlando Motors Sport üzerinde şu anda okumakta olduğunuz 'Project Scion TC - Tech' isimli yazı 19 Mar 2008 tarihinde, saat: 02:54 'de admin tarafından gönderilmiş.

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