hi, i have a 91 civic si with the sohc del sol motor in it, i custom built a turbo manifold from an old chikara header, (I fear i may have got lazy on my welds) anyway running a 02-03 vw turbocharger, my car boost 5-7 psi fine until 4000 rpm's then it just drops all boost, when i first finished my kit, before the manifold saw much heat it pulled strong all the way to redline, after a while it started going down hill, dropped all boost at 4500 then at 4000, if you rev it up you can see a little exhaust leaking from my manifold, but it is hard to tell where. a leak from the manifold would make it lose boost when there is a heavy load on the motor wouldn't it? i have the hf manifold and adapter plate, i will probably switch to that, the vw turbo spools super quick though, sucks it cuts out in the funnest part of the motor 4k to 7k. if you have any info on this let me know i would appreciate it. pretty sure it is the manifold though charge piping is fine no leaks there, and wastegate seems to be opening consistantly.
thanks

 

i think you answered your own question, if you r mani is leaking that bad you wont make boost

 

My mani leaks at the external wastegate port, I used some high temp RTV selant but when it starts leaking it just causes the turbo to spool later, I don't loose boost... I still get full boost its just later in the rpm range? Mine is only a little whole, I'd imagine yours must be fairly large to drop off all boost...I'd say just swap in the HF mani and see if that fixes it

 

thanks for the info, i will switch manifolds and i am running 4 bleed valves, should i add another or will 4 be fine?

 

found the problem, small hole in manifold i overlooked, manifold to turbo flange blew apart, switched to metal now boosting 7psi, gotta turn it down a little.
gonna switch to hf manifold and a t3 turbo.