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Why Do These Similar Cars Feel So Different? – Feature – Auto Reviews – Car and Driver
November 22, 2011 | 
Author The Evo MR and the WRX STi feel very different when evaluated one against the other on the track, so we did a few more handling tests to see if we could gather some data that would shed light on our seat-of-the-pants assessment.
First off, although these cars appear to be quite similar (turbocharged four-cylinder engines, four-door bodies, four-wheel drive, limited-slip front and rear differentials, etc.), there is a major difference in the way the four-wheel-drive systems distribute engine torque.
The Subaru employs an electromagnetic clutch on the center differential. Under normal driving conditions, say you’re just cruising down the interstate, the diff clutch is disengaged, and 65 percent of the engine power is routed to the rear wheels, with the remaining 35 to the front (a 35/65 front-to-rear split). The car’s engine computer adjusts that center-diff clutch, based on information from the yaw-rate and throttle-position sensors, and can send as much as 50 percent of engine torque to the front wheels. So the Subaru varies the torque split between 50/50 and 35/65. The driver can also manually select the torque split via a center-console switch.
The Mitsubishi, on the other hand, never sends the majority of engine torque to the rear axle. Instead, it can send all the engine torque to the front wheels or 50 percent of it (using an electrohydraulic clutch on the center diff). So the Evo varies the front-to-rear torque split between 100/0 and 50/50. In addition to the yaw-rate and throttle-position sensors, the Evo has a steering-wheel-angle sensor that also provides the computer with information.
Now, we’re simplifying things a little because it would take pages to describe exactly when those center-diff clutches operate, but basically, the aim of these systems is to make the car go where the driver wants. For sporty cars like these, four-wheel drive can simply be another tool in the engineer’s box that improves handling, and the computer algorithm that controls these center diffs is tuned in much the same way as the car’s suspension. Four-wheel drive is another interconnected variable—like shocks, springs, anti-roll bars, and tires—that affects vehicle handling.
Judging by the Subaru’s four-wheel-drive system, we initially figured the STi would be better at the racetrack simply because putting more torque to the rear wheels frees the front tires to do their main job, which is turning the car. The Subaru also has better weight distribution (58.2/41.8 versus 60.7/39.3 for the Evo), which should improve its handling.
But despite the STi’s power-to-weight advantage, it wasn’t the faster car at GingerMan, as Swan reports. The STi’s best lap time was 1:39.15 and the Evo’s was 1:38.88.
To dig a little deeper, we decided to perform some tests that go beyond our usual procedures, but before we went back to the track, we put both cars on Kumho Ecsta MX tires to remove that variable from our results. And even though these cars have driver-operated switches that can alter the function of the center diffs, we did all our testing in the automatic mode.
First, let’s talk about the split-traction-surface test. We used Bosch’s proving ground in nearby Flat Rock, Michigan. That facility has lanes of pavement running side by side with tiled surfaces, ideal for measuring varying traction levels. For this test, we put the left-side tires on a tiled lane that simulates driving on packed snow and the right-side tires on dry concrete. Then we accelerated from 5 to 50 mph. We also performed the same test with all four tires on dry concrete.
The Subaru accelerated at the same rate on both the dry section and the split-traction surface, whereas the Mitsubishi was 0.4 second slower on the slippery section than it was on the dry.
That test tells us the Subaru’s four-wheel-drive system is a little better at sending torque to the wheels with traction.
Article source: http://www.caranddriver.com/features/05q1/why_do_these_similar_cars_feel_so_different_-feature
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Tags: engine torque, four wheel, four wheel drive, wheel drive | 
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Honda’s Head of R&D Talks CR-Z, Minivans and Music
MT: And of course you have the new CR-Z now, the first hybrid with a six-speed manual.
KS: Yes, that’s true, but our engines are so good and so fuel-efficient now, that to be honest, that’s why we did not add idle-stop to the Jazz lineup as it just makes things more complicated and you need ten times the battery current capacity with idle-stop.
And it makes the car more expensive, too. That’s why we only offer hybrid. It’s already economical enough.MT: And of course you have the new CR-Z now, the first hybrid with a six-speed manual.KS: Yeah, we do, but I am not a big fan of it. I think its face is too aggressive, too in your face. I wanted it to have a more futuristic design.MT: And what about the power of the car? Is it powerful enough?KS: Hmm, that’s a painful question.
Let’s put it like this. With our next generation of sports cars, we will offer a slightly different definition. Like the CR-Z, they won’t just be cars that offer moderate acceleration, but deliver driving thrills and cornering fun while still giving drivers a feeling of topless and free. Part of our plan was to get the CR-Z on the road and see what the market wants. So we expect to add to this lineup soon.MT: We’ve heard strong rumors of a 2.0 liter naturally aspirated version. Perhaps, we might see a more powerful…KS: Don’t get ahead of yourself.
Yes, we are considering upgrades to the CR-Z, but can’t say what right now of course. We are also thinking about other smaller cars, too.MT: Like a modern-day version of the little Beat from 1991?KS: Well, I won’t say we are not doing it, but if we do, it’ll handle well. We want to promote our environmental technology globally mainly through hybrids. But we will do small cars, too. That’s my area of focus now. The move in the world is towards smaller cars so we must follow that – downsizing.
2010 Acura MDX – First Drive Review – Auto Reviews – Car and Driver
With Acura’s upcoming crossover-coupe-whatever setting the tone for the brand in terms of refinement and technology, its once techno-trendsetting MDX sibling is looking a bit long in the tooth. Indeed, the second-gen MDX—which placed first of eight in our last
—has sat relatively unchanged since its 2007 debut, and this fact, combined with a number of newly engineered goodies also used in the ZDX, makes this year the perfect time for an update.
Six Gears and a Better Ride Perhaps the most notable upgrade is Acura’s first-ever six-speed automatic transmission in place of the previous five-speed. The transmission will proliferate through the company’s V-6 models, with the ZDX, in which the gearbox was first shown, being the next Acura to market so equipped. The company says the new gearbox also will work with four-cylinder vehicles such as the
and base TSX. Unfortunately, many other luxury carmakers already are moving on to seven- and eight-speed units, and the six-speed doesn’t improve fuel economy much in the MDX, which is now estimated at a still-thirsty 16 city mpg and 21 highway mpg versus 15/20 in 2009. The transmission shifts quickly and smoothly, and its ability to perform multiple-gear downshifts nicely augments the Super Handling All-Wheel Drive system during sporty driving. The gearbox’s standard and sport modes are selected via the console-mounted shifter, and all trim levels get steering-wheel-mounted paddle shifters as standard.
Also new are retuned active dampers that come as part of the Advance package, which takes the place of last year’s Sport package. Despite the MDX’s handling prowess and all-wheel-drive grip, we’ve criticized its ride for being a bit harsh and unyielding, particularly in the sportiest suspension setting. And although it remains firm, our brief jaunt north of Detroit revealed the new version to be far more compliant in both sport and comfort settings while maintaining good body control.
The 300-hp, 3.7-liter V-6 has been retuned for more flexible power delivery, while nineteen-inch wheels are now a factory option; 18-inchers remain standard, although they’re now lighter than before and have a new design. All of this serves to bolster the MDX’s already surprising agility, but we were taken aback by the ultra-light steering—at all speeds—that felt much more artificial and over-boosted than we remember.
More Gizmos and Driver Assistance As with the six-speed automatic, Acura has been somewhat slow to adopt advanced driver aids such as active cruise control, blind-spot detection, and automatic collision-mitigation braking to the MDX. But all the above debuts on the 2010 model as part of the aforementioned Advance package, along with the larger wheels, climate-controlled seats, and upgraded leather upholstery. Although our brief stint didn’t allow much time to explore the safety stuff, we’re told it operates similarly to competitive systems.
An optional multiview reverse camera with normal, wide-angle, and top-down views is new, and it displays through the eight-inch infotainment screen. The latter view will undoubtedly aid in accurately lining up a trailer with its straight-down look at the rear bumper, but prepare to jump to the Technology package to get it: Settling for the base model means you get a single-view reverse camera with a display integrated into the rearview mirror.
The Technology package also gets a new hard-drive-based navigation and entertainment system fortified with voice recognition, real-time traffic updates with rerouting, and weather updates that overlay Doppler-style radar images on the navigation map. An upgraded 10-speaker, 410-watt audio system that combines USB-port connectivity, Bluetooth streaming audio, and a Ford Sync–style function that allows voice control of your music library is included in the Tech pack. The newly available Entertainment package offers heated second-row seats and a nine-inch motorized screen for rear-seat occupants.
Will Looking the Part Make a Difference?
Although we weren’t enamored of the second-gen MDX when it arrived wearing an early, prepubescent version of Acura’s now-ubiquitous metal-shield grille, passersby will have no problem spotting the 2010 model and its softer metallic nose, revised front fascia, and new rear bumper with more chrome moldings and new exhaust outlets. Although we must say the new look is more glitzy and expressive, especially with the larger 19-inch wheels, the end result is just as funky as most other Acuras.
The interior has been upgraded with a thicker steering wheel, new wood trim, and LED lighting. Acura says it also made the plethora of center-stack buttons easier to understand, but frankly, we didn’t notice—the dash looked as busy and complicated as ever. Fortunately, the leather is sumptuous, the seats are very comfortable, and the navigation system is still one of the best available.
Arriving at dealers late in the year, Acura says pricing will increase by about three percent over 2009 levels, which means well-equipped base models should start below $44,000. Loaded versions with all the driver aids, interior gadgets, and rear-seat entertainment likely will near the $55,000 threshold. We’re anxious to see if the MDX’s measurables have improved with the new transmission and suspension, and it seems Acura has taken one of our favorite luxury SUVs and made it incrementally better.
Article source: http://www.caranddriver.com/reviews/car/09q3/2010_acura_mdx-first_drive_review
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