Quote:
Originally Posted by Goingnowherefast
I'll try to tackle this. Worth noting that I'm not specialized in transmissions per say, but there is a lot of overlap with my area of engineering. From a technical standpoint, there two main reason why a traditional planetary automatic transmission will always have some efficiency losses even when it's locked:
1. In order to lubricate and to create sufficient hydraulic line pressure to energize the clutches and brakes, an oil pump is required. This is usually driven off the torque converter which is driven off the engine, and thus will have inherit losses, just as any accessory driven off the engine does.
2. Transmissions that use wet clutches (like the automatic in the twins) will have drag losses caused by the shearing of oil between rotating (but open) clutch plates. In this sense, DCT's have the advantage in that they only have one open clutch at a time, where as a traditional automatic could have 2-4 open at any given time depending on the gear selection.
Additionally, in practice AT's aren't truly "locked" a whole lot. This is to improve shift quality, durability, and NVH. Of course, any slippage will result in a power loss and it generates a considerable amount of heat. Tell me if you guys have any questions or something is unclear.
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This doesn’t answer the question. We know why the AT has an extra 2% drivetrain loss across the entire powerband, we don’t know why it has a much steeper/quicker drop off in power after 6900rpm vs an MT but an almost identical (but 2%) lower powerband all the way up to 6900rpm.
I have a feeling this may intentional in the ECU tune and/or TCU programming to help smooth out the shift and/or help save the clutch packs.
And I think based on personal experience how my car feels that this can be entirely tuned out as my car continues to pull hard all the way to redline (7500rpm now) with no noticeable drop off and my tuner has done many things to change how the AT works in the tune.