wozzah1975 wrote:Head flow has everything to do with boost (amongst alot of other things). See what happens to the boost when you reach the limit of your cylinder head flow......Boost goes up, power stays the same......
Sure, when taken to extremes yes.
I see this conversation going in circles... and a few posters seem hardfast focussed on making boost a function of head flow as being the only reason why a person with a M45 on a 1.8 can't get beyond 6psi.
I'm trying to help the OP by saying that he a) might have a boost leak, b) could have options to further reduce the pulley size/increase boost, or c) have a timing/cam problem that is limiting the captive postive pressure due to blow-through (intake -> exhaust).
All this debate over how much a 1.6 vs 1.8 head actually influences this discussion seems to be largely irrelevant as when we get into details, people are introducing extreme scenarios (like comparing a turbocharged vs S2000, or when you max out the head flow as being the top line limit) - all true points, but not relevant for the OP issue.
I don't disagree that at the limit, head design can impact max boost seen, but in the context of the OP's question I don't believe it has any relevance.
Afterall, if the 1.8 engine is only 15% better than the 1.6 (in terms of max power) then how can you explain that the head is 2x better at flowing air if the NA engine can only produce 15% more power, and note that displacement is mostly the reason for the power difference here.. (1.8 is 12.5% more displacement than 1.6).
Nobody yet has been able to explain how it can in the context of the OP's question.