ktegra said:
From John at Team Integra
Differences between a z1 and a1 are...
-cams are different on ALL motors. K20a has itr cams (obivously) K20z1 has their own cams that are better then k20a2 cams but not as good as ITR cams and k20a2 cames have Type-S cams (obivously).
The cams in a k20z1 are in between a a1 and a2...but a1 cams are SO mild of a upgrade over a2 cams that z1 cams are even less. They're better cams then the a2 motor but by a extremely SMALL amount, ITR cams z1. They're different cams...they have different part #'s.
-Bolt ons: K20z1 has a ITR snorkel and catback...that's it. It does NOT have a ITR intake manifold which everyone seems to think they do, nor does it have the header, downpipe and cat. K20a,a2,z1 all have the same throttle body. The k20a3 found in the 02-05 EP3 has a z1/a2 Intake manifold and throttle body. The base RSX which shares the same motor has a dual runner setup like the 3rd gen GS-R and a slightly smaller TB.
-Compression: k20a has .5 more compression due to more material on the k20a pistons vs k20z1 and a2. Rods, crank, bearings, head, block, pan, everything else is the same/identical.