The first digit of the code relates to the emissions regs the engine meets.
Z = euro 4
Y = euro 3
X = euro 2
C = euro 1
Cars made before the emissions regulations have no letter at the start of the code.
The next 2 digits are the capacity.
For example, the 22 in Z22 SE means 2.2 litre.
The next letter is the compression ratio.
G = 8 to 8.5:1
L = 8.5 to 9:1
N = 9 to 9.5:1
S = 9.5 to 10:1
X = 10 to 11.5:1
Y = 11.5+:1
The next digit relates to the fuelling.
D = diesel
E = multi-point injection
Z = single-point injection
V = carburettor
Some engines have an extra code at the end, if they are different from normal
For example:
H = high output
R = increase output
T = turbo
V = volume model