Getting through the solution in this level in this quick of time can be tough so it will probably take you several tries. You're going to have to make each move really fast and without making any mistakes. Your run will have to basically be flawless so if you happen to make a wrong turn or slow down for a second, don't bother continuing and just restart the puzzle because you won't make it in time. Even if you do everything perfectly you'll still just be finishing at 16 seconds.
There are actually 2 solutions I know of you can use to get through Level 8 in that fast of time. The first one looks it would be faster however when I earned the achievement I used the second one and finished the level right at 16 seconds.
1st solution (quicker):
RURU LDLU LURD RULU LDRU URU
2nd Solution:
UDL URU LDL LUR DRU LUL DRU ULD RUR UU