Hello people,

I've got some questions for engine gurus. I apologise in advance if the answers are rather obvious. Also, I do not intend this to be a 'if it's so good, why doesn't mitsu do it' or 'stock is all you'll ever need' threads.

For sometime I've seen people upgrading cylinders and rods etc. in their engines. In fact, when I used to race Civics, I too had Jun/Toda pistions, rods and crank shafts. As I was not really responsible for tuning the car when it came to engines, I didn't really know what they were for, except that I could rev higher, quicker and a little more safely.

So here are my questions:

1. At which point (in terms of boost, compression or hp) do the stock pistons/rods/crankshaft become inadequate?
2. Are there any gains to be expected from just changing pistons and rods? Obviously, lighter moving parts are better, but any figures?
3. Are there any other advantages, other than more power (if that) to be had from aftermarket pistons, rods etc.?
4. This might be a little stupid - how does the piston design affect compression ratio?
5. Why does the Cosworth website show two piston sizes? Is it common to make your engine a larger bore?

I'm not exactly planning on getting aftermarket rods and pistons, but mainly curious. I plan to keep my 8MR for a while yet and I'm looking at modding it l extensively also. While I will get (very competent) local machanics to do it if the time comes, I'd like some background to upgrading engine internals so I can see if I'll ever need to do it.

Thanks in advance.