Dual clutch vs. standard trans.

[90crvtec]

The only thing I would be worried about would be the extra load on the synchronizers from skip shifting. For some transmissions this is known to be a problem (Honda S2000), while other cars seem to live with it just fine.

You are right that skip shifting is an additional option that helps a good driver with a manual transmission achieve a little bit more economy. However, the fact that a driver would have to resort to skipping gears due to the almost humanly impossible ability to shift as quickly as most DSG transmissions still seems like a drawback to me. It's sort of a 'work around' rather than a solution.

For manual transmissions that have dual or triple cone synchronizers on certain gears, I don't think skip shifting has much of a negative effect due to the ability of the extra cones to synchronize the gear speed. But, on gears that only have a single cone synchronizer set, I try not to make it a habit to skip shift. Honda manual transmissions seem especially sensitive to this, I'm not sure if other makes are also as finicky.

 

[rpn453]

Originally Posted By: 90crvtec
The only thing I would be worried about would be the extra load on the synchronizers from skip shifting. For some transmissions this is known to be a problem (Honda S2000), while other cars seem to live with it just fine.


Just allow an appropriate delay in the shifts for the transmission to spin down and it shouldn't make a difference. As long as you don't have to use any additional force, you probably aren't adding any extra wear. I have to add a delay to my 1-2 shift under normal conditions anyway to get a smooth shift because those gears are spaced so far apart. I can force a quick shift, but it doesn't happen naturally like 2-3 and 3-4 which are appropriately spaced.

I do almost every sort of skip-shift pattern imaginable because I enjoy using the full range of my engine on a regular basis and then shifting softly. 1-4, 1-2-4, 1-2-5, and 1-2-3-5 are probably the most common. The 2-5 shift probably requires a full second delay before it will slip in effortlessly.

 

[Cujet]

I generally prefer manual transmissions. The DCT's upshift into gears I don't want to be in, and they do it even quicker than a regular automatic.

I can't tell you how annoying it is for a "performance" driver (who expects response) to drive a pedestrian DCT. A "U" turn can be a real eye opener.

Hard braking to 15MPH, initiate U-turn, floor it. Wait, wait, wait, wait. Yes, it really is 2.5 seconds before the transmission finds 1st gear and the "throttle by wire" is commanded to open.

It's infuriating for a guy like me, and unsafe.

 

[JHZR2]

Originally Posted By: NateDN10
Originally Posted By: sciphi
A manual driver with a torquey engine can also skip-shift. I find myself going 1-2-3-5 around town in the Cruze, and 3-4-6 accelerating onto the highway. It's not much extra effort to skip-shift when not needing the acceleration from the higher gear. That makes up a little for the inherent efficiency of a dual-clutch automatic since it's saving a shift once at speed.

It all boils down to preference and ability. A dedicated driver in a manual transmission car can wring great fuel economy from it. Likewise with a dual-clutch auto car.

Skipping gears doesn't make sense to me, but maybe I'm missing something. Isn't an engine at its most efficient near its torque peak? And therefore, wouldn't you want to use every gear in order to maximize the amount of time you spend near the torque peak?


Studies from long ago (saab perhaps?) indicated that skip shifting and staying just above lugging was most efficient due to least pumping losses.

 

[rpn453]

Originally Posted By: JHZR2
Originally Posted By: NateDN10
Skipping gears doesn't make sense to me, but maybe I'm missing something. Isn't an engine at its most efficient near its torque peak? And therefore, wouldn't you want to use every gear in order to maximize the amount of time you spend near the torque peak?


Studies from long ago (saab perhaps?) indicated that skip shifting and staying just above lugging was most efficient due to least pumping losses.


Yeah, the torque peak is only the most efficient full-throttle operating point. It is not more efficient to run at half throttle at the torque peak than to run near full throttle at a much lower rpm. For any given speed, the lowest rpm that the engine can run smoothly (and in closed loop mode) will be the most efficient.

 

[SteveSRT8]

Originally Posted By: Cujet
I generally prefer manual transmissions. The DCT's upshift into gears I don't want to be in, and they do it even quicker than a regular automatic.

I can't tell you how annoying it is for a "performance" driver (who expects response) to drive a pedestrian DCT. A "U" turn can be a real eye opener.

Hard braking to 15MPH, initiate U-turn, floor it. Wait, wait, wait, wait. Yes, it really is 2.5 seconds before the transmission finds 1st gear and the "throttle by wire" is commanded to open.

It's infuriating for a guy like me, and unsafe.



Absolutely agreed, but what you're experiencing is programming, not trans design.

When set up properly these are going to be nice. And note that many of these are NOT DCT, some are only automated manuals.

 

[rpn453]

"Once the dealership has its allocation, it starts working to sell you, the customer, a part of that allocation. Sure, dealers can and do trade between themselves, and they’ll also order a car for you if you’re willing to wait, but in general, it’s critical that dealers sell from their own current or immediately incoming inventory. Meanwhile, the manufacturers are dealing with a variety of their own issues: oversupply, undersupply, parts availability, the ever-changing demands of their workforce, and random acts of fate. You see, the lines must keep running at all costs."

"Never forget that the real customer for an automaker isn’t you, and it isn’t me. It’s the dealer. Given enough time, the dealers will move whatever they’re given, whether it’s an Aerostar or an Aztek. We’re just the saps who take ‘em off the lots. So how can you get what you really want? The answer is simple: if you want a particular car, place your order and bide your time. Legitimate customer orders usually take priority over allocation, unless we’re talking about buying a Ferrari. But if you want a deal, then find a dealer who has the car you’re willing to take right there in his inventory. It’s costing him money every day, and he’s about to get two more like it off the truck. That’s how you can get the best deal, every time."

http://www.thetruthaboutcars.com/2012/02/avoidable-contact-dealer-vs-manufacturer/#

 

[artificialist]

Originally Posted By: JHZR2
Originally Posted By: NateDN10
Originally Posted By: sciphi
A manual driver with a torquey engine can also skip-shift. I find myself going 1-2-3-5 around town in the Cruze, and 3-4-6 accelerating onto the highway. It's not much extra effort to skip-shift when not needing the acceleration from the higher gear. That makes up a little for the inherent efficiency of a dual-clutch automatic since it's saving a shift once at speed.

It all boils down to preference and ability. A dedicated driver in a manual transmission car can wring great fuel economy from it. Likewise with a dual-clutch auto car.

Skipping gears doesn't make sense to me, but maybe I'm missing something. Isn't an engine at its most efficient near its torque peak? And therefore, wouldn't you want to use every gear in order to maximize the amount of time you spend near the torque peak?


Studies from long ago (saab perhaps?) indicated that skip shifting and staying just above lugging was most efficient due to least pumping losses.

Certain versions of the Corvette, Camaro, and Firebird had a device that sometimes forced people to shift from 1st to 4th to save enough fuel to meet CAFE standards.