English opening exchange-sacrifice compensation Evaluation of exchange sacrifice: How good is White's compensation after the exchange sacrifice on move 19?  Seems the position is about even to me but Black might have more issues to solve.  I am thinking it is Whites best winning chance as opposed to having just liquidated the queen-side pawns.

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1.c4 Nf6 2.Nc3 g6 3.g3 Bg7 4.Bg2 O-O 5.e4 d6 6.Nge2 c5 7.O-O Nc6 8.d3 a6 9.h3 Rb8 10.a4 Ne8 11.Be3 Nd4 12.Rb1 Bd7 13.b4 Ne2 14.Nxe2 cxb4 15.Rxb4 b5 16.cxb5 axb5 17.Qb1 Nc7 18.Rc1 Na6 19.Rb5 Bb5 20.axb5
This exchange sacrifice would be good if you could coordonate your pieces in order to support the passed b-pawn. In this given position, however, it looks like you are one tempo short and the pawn will be a target: 20...Qa5 and then 

21.Nd4 [21.Nc3 is quite the same] Bxd4 22.Bxd4 Rxb5 and Black should win.

21.b6 Nc5 22.Bxc5 dc5 23.b7 [I see nothing else to hold on the pawn] Qa7 [or 23...e5 to prevent the opening of the g2-b7 diagonal] 24.e5 Bxe5 and the big passer gives practical chances but Black is clearly for choice.

Probably White would have reached a much better version of the game with 18.Nd4!? instead of 18.Rc1.