Rep Power: 222

Okay so the 7th Gen Civic Si's (2003-2005) have 2.0 liter engines.The 8th Gen Civic Si's (2006-) also have a 2.0 Liter engine.But why does the 7th Gen Si only produce about 160 hp while the the 8th Gen produces about 200 hp?Why is there a 40 hp gap?They both have 2.0 liter engines.I'm not good with this in depth stuff so does anyone know why?

 
Rep Power: 512

compression ratio differences. 7thgen Si has a compression ratio of 9.5:1, 8thgen has an 11:1

 
Rep Power: 215

There is actually alot of differences. The ep3 has the k20a3 that has the economy ivtec where only the intake lob engages vtec with 2 lobs. The a3 has a low compresion ratio as well. It is also hooked up to a 5 speed tranni. The newer si fg2/fa5 has the k20z3. It is better built than the a3 is. The z3 has the real ivtec where vtec is kicked in with both the intake and exhaust cams with 3 lobs. It has a higher compression and is hooked up to a 6 speed tranni with lsd. There are quite abit more things but it is lengthy.

The k20a3 is the cheapest k20 there is and can be built to that power and still have alot of money left. The newer k motors can do something that the other motors cant. Its called vtec killer setup. And cost loke 300 for the setup and the k20a3 will be running almost the same amount of hp to the wheels as the z3 with bolt ons. The z3 may have bout 10-15 hp more but the z3,s respond well to bolt ons. So the a3 is actually a good motor. The a3 though is alot better to boost cause of the compression. The a3 has proven to uphold 12 psi with stock internals for a daily bases with a good tune. But all together the z3 is alot better.