I can solve a rubiks cube, and an arrow cube, but I have 2 questions on the arrow cube to make me faster.

Is there a more efficient way to twist a center only 90 degrees?

And is there a more efficient way to turn a center 180, I curently do R U R' U(X5)

More efficient than what?

To rotate the U center 180°: (ULRU2L'R')*2

Hi Marcom & CS2011,
This is probably a google translate issue or language issue .
I think he means `can you` and the answer is more complex:
You can't twist a centre piece 90 deg without affecting other pieces: A 90 deg turn changes the parity of the puzzle so you would get 2 edges needing to be swapped, etc. So if you turn one centre by 90 deg, you need to turn another centre by 90 deg to correct the parity. If one centre has no orientation and the others do, it would be possible to have this `hidden` (depends on the order you are solving the cube, the method or if it has arrows on all faces).

EDIT: Maybe I'm making this too complicated:
I usually solve a supercube by taking into account the orientation of centres proactively, and using sequences that don't disrupt them. This for me is a philosophical thing, because I believe that is the challenge of the puzzle, rather than adding a fix in hindsight.
But:
RU' RU RU RU' R'U' R2 will turn the U centre (U') and the R centre (R) and not disrupt many pieces. This might be what you are after because I assume you want to fix side centres as part of a layers method? Combined with Marcom's pure algo for U, I think it is OK?

Cheers,
Burgo.

Let me add a small comment to that (i could not resist).
The cube can be solved by turning only 5 layers out of the 6. One can emulate D by for example this sequence: R L' F2 B2 R L' U R' L F2 B2 R' L.

The first 6 turns move the whole D layer to the U layer and then U effectively does the D turn (after reversing the first 6 turns. So this is one longish conjugate sequence.

Obviously there is no way to reduce the number of layers for solving the cube centers as well...

Per

This doesn't perfectly simulate a D turn because it also twists the center on the U face by 90 degrees.

I think the original poster is not asking about a super cube but a Sheperd's Cube:

On this puzzle a single center can be twisted by 90 degrees. The reason this is allowed is that there are two identical corners and a few identical edges. To resolve a single twisted center, first swap the two identical corners (they are diagonally opposite each other on a line through the center of the cube). Then swap two identical edges. This will have changed the overall twist of the centers by 90 degrees.

I was talking about a super cube, I didn't know it was impossible to turn just one center 90 degrees.

U (MEM'E') U' (EME'M')

That's switch the U center orientation by 90° clockwise and the R orientation by 90° counterclockwise, then ou can adapt with other cases, it's really easy.

Yes i mentioned it does not perfectly simulate a D turn. But i did think the original post was a bout a supercube (or picturecube). Shepherd's cube is indeed different - and confusing.

Per