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Old 03-04-2013, 01:13 PM
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Re: 8 speeds is soooo 2014

Tadge Juechter is the chief engineer for the Corvette C7. He was interviewed by Car and Driver in the March 2013 ediction. Here is a relevant portion of a comment from him: "The number of speeds isn't everything. We introduced the C6 with a four-speed automtic and brought in a six-speed transmission in the second year, and had a hell of a time beating the four-speed on both fuel economy and performance. We operate at high torque, high efficiency across a broad rpm range, so we don't need more gears. That said, we see the market going to more speeds, so we'll keep an eye on that and when we can offer genuine improvement in fuel economy with more speeds, we will."

Naturally, a Corvette has nothing in common with our WK2, except perhaps that the Corvette's engine and WK2's hemi's are both high torque engines.

Perhaps the direction is that a vehicle will benefit more readily from additional gears if it has any of the following traits: low torque, narrow power band, heavy vehicle?
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  #26  
Old 03-04-2013, 01:31 PM
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Re: 8 speeds is soooo 2014

Quote:
Originally Posted by oxman View Post
Tadge Juechter is the chief engineer for the Corvette C7. He was interviewed by Car and Driver in the March 2013 ediction. Here is a relevant portion of a comment from him: "The number of speeds isn't everything. We introduced the C6 with a four-speed automtic and brought in a six-speed transmission in the second year, and had a hell of a time beating the four-speed on both fuel economy and performance. We operate at high torque, high efficiency across a broad rpm range, so we don't need more gears. That said, we see the market going to more speeds, so we'll keep an eye on that and when we can offer genuine improvement in fuel economy with more speeds, we will."

Naturally, a Corvette has nothing in common with our WK2, except perhaps that the Corvette's engine and WK2's hemi's are both high torque engines.

Perhaps the direction is that a vehicle will benefit more readily from additional gears if it has any of the following traits: low torque, narrow power band, heavy vehicle?
What about all the other car companies that use more than 4 gears, are they just not doing it right? There is more to this world than a v8 so we can't compare the gears to just that.
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Old 03-04-2013, 07:45 PM
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Re: 8 speeds is soooo 2014

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Originally Posted by SnoFire View Post
What about all the other car companies that use more than 4 gears, are they just not doing it right? There is more to this world than a v8 so we can't compare the gears to just that.
Basically what he's saying is if you have a powerful engine, you don't need as many gears. Which is entirely true, a powerful engine with a large power band doesn't need to stay in a specific rpm range to make its power, so it doesn't need extra gear ratios to keep it in that range.

Adding those extra gear ratios increases the amount of time you waste shifting. In a vehicle without a lot of power outside of its narrow power band, this is more than made up for by being able to stay in its power band, but in a vehicle with a wide power band (think Hemi and other V8s), it's less of an issue.

Extra gears helps low powered vehicles that have narrow power bands more than it helps vehicles with big V8s. Things like the little Honda VTEC engines need more gears to stay in that narrow band (to a lesser extent, you'll see this with the V6 as well).

Reality is, with a powerful engine, more gears is more of a marketing thing than anything.
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