I can't figure this out, I installed a larger downpipe over the weekend went from 2-1/8 to 2-1/2 no big deal : heres the problem with the 2-1/8 I was running 10.25 boost A/F in the 11's at wot with the larger downpipe my boost dropped to 9.00 psi and A/F are richer (of course less boost) I thought the larger downpipe would only cause less backpressure I did'nt think it would effect my boost level ?..................I fixed it by cranking up the mbc, what use to be the setting for 11psi is now the setting for 10psi, any thoughts ?

 

did the new downpipe change anything about the area around your wastegate?

 

i have never heard of anything like that. actually in most cases ( a turbo mr2 comes to mind) the larger turbo back exhaust actually increased boost levels

 

poorly designed downpipes can cause wastegate blockage issues that lead to boost spikes.

 

Found what was causing the boost lost..........................leaking packing on mbc, just assumed it was downpipe related, fixed the leak now it feels like it should ! "You know what happens when you assume" LOL

Thanks