2001 Chevy Camaro Z28 Sunset Orange Metallic on 2040-cars

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CNG Chevy Impala launch delay grows to a year

The 2015 Chevrolet Impala Bi-Fuel was announced in Washington D.C. in late 2013 by Dan Akerson and was supposed to be on sale by the summer of 2014. Capable of running on gasoline and compressed natural gas, the sedan was said to offer a novel solution at a time when gas prices were high. The vehicles still haven't arrived at dealers, though, and according to Automotive News, a quality issue has set back the launch even a few months more. Using a modified 3.6-liter V6 with hardened valves and valve seats, the Bi-Fuel Impala has separate tanks for gasoline and CNG that it can switch between on the fly. When running on the cheaper natural gas, the sedan was estimated to get 19 miles per gallon in the city and offer 150 miles of range, and the total driving distance was predicted at around 500 miles. The base price was set at $38,210, after the $825 destination charge. The only other major tradeoff was a smaller trunk to accommodate the extra fuel. However, the first shipments of the bi-fuel models now aren't expected until mid-July – about a year later than the scheduled launch. A memo to dealers obtained by Automotive News said the sedan "has been delayed by a second quality hold" to look at the CNG system. The exact details surrounding this problem haven't been released. "We have identified a solution to the delay and are working hard to implement it within the next few months," General Motors spokesperson Chad Lyons said to Automotive News. Around 200 Bi-Fuel Impalas have been made, but none are yet in the hands of customers. Dealers should be able to order 2016 model year examples starting in the third quarter of this year.

Is the skill of rev matching being lost to computers?

If the ability to drive a vehicle equipped with a manual gearbox is becoming a lost art, then the skill of being able to match revs on downshifts is the stuff they would teach at the automotive equivalent of the Shaolin Temple. The usefulness of rev matching in street driving is limited most of the time – aside from sounding cool and impressing your friends. But out on a race track or the occasional fast, windy road, its benefits are abundantly clear. While in motion, the engine speed and wheel speed of a vehicle with a manual transmission are kept in sync when the clutch is engaged (i.e. when the clutch pedal is not being pressed down). However, when changing gear, that mechanical link is severed briefly, and the synchronization between the motor and wheels is broken. When upshifting during acceleration, this isn't much of an issue, as there's typically not a huge disparity between engine speed and wheel speed as a car accelerates. Rev-matching downshifts is the stuff they would teach at the automotive equivalent of the Shaolin Temple. But when slowing down and downshifting – as you might do when approaching a corner at a high rate of speed – that gap of time caused by the disengagement of the clutch from the engine causes the revs to drop. Without bringing up the revs somehow to help the engine speed match the wheel speed in the gear you're about to use, you'll typically get a sudden jolt when re-engaging the clutch as physics brings everything back into sync. That jolt can be a big problem when you're moving along swiftly, causing instability or even a loss of traction, particularly in rear-wheel-drive cars. So the point of rev matching is to blip the throttle simultaneously as you downshift gears in order to bring the engine speed to a closer match with the wheel speed before you re-engage the clutch in that lower gear, in turn providing a much smoother downshift. When braking is thrown in, you get heel-toe downshifting, which involves some dexterity to use all three pedals at the same time with just two feet – clutch in, slow the car while revving, clutch out. However, even if you're aware of heel-toe technique and the basic elements of how to perform a rev match, perfecting it to the point of making it useful can be difficult.

2015 Chevrolet Corvette Z06 Beauty Roll

For those of you paying attention, we've really ramped up the old Autoblog video game these days. Our new series Car Club USA joins Translogic and The List, and there are more Daily Drivers and Short Cuts than ever. But sometimes, all you care about is the car. The Autoblog Beauty-Roll video series has one goal: bring you glossy video of cars, and nothing but. We're collecting moving pictures of all the cars we test, inside and out. Each episode comes with a hit of engine sound – start-up and with a few revs – to round out the package. Set your resolution to max, kick it into full-screen, turn up the sound, and enjoy today's subject, the 2015 Chevrolet Corvette Z06. Oh, and if you'd like more Beauty-Roll, click here to see the back catalog.