Originally Posted by Fabrik8

Just out of curiosity, where do people come up with these specs? Where does the magic 18 pounds of boost come from? Is 17 pounds too little, or is 19 pounds too much, but how do you know because the engine isn't built yet...

Originally Posted by Fabrik8

I just think it's a little backwards. You don't know what you're going to actually make at 18 psi, unless you have an identical build and tune to someone else. If you have a different turbo, different compression ratio, different cams, different intercooler, etc., you don't know what you're going to get at 18psi. You and some buddy could both do a B18 build, shooting for 18psi, and you could get a HUGE difference in power at 18psi compared to what your buddy got. It just seems like a completely arbitrary way to do an engine build and a turbo setup.

So if you were shooting for 500HP (just pulling a number out of the air) and one engine/turbo setup made 500HP at 15psi, and another engine/turbo setup made 500HP at 21psi, would you still build the engine off of an arbitrary boost pressure number?

Along the same lines, if you can make a much better torque curve at a different boost pressure with a certain engine/turbo setup, would you still shoot for some particular boost pressure number?

I'm just saying that you're going to be putting a lot of time and money into an engine build, and you're basing the entire thing around something arbitrary that doesn't have a lot of correlation to actual power numbers.