I made up this graph to try to show my boost problem. What I did was replaced my s4 turbo with a s5 unit, and changed out my exhaust to full 3 inch. I also had a friend make me a custom manifold. I used to make boost at around 2.5k rpms and now it is about 3 or later. Also my boost peaks then falls off. I doubt it is boost spike because it never used to with the old turbo, and I was using the same boost controller. The two possibilities I can see are the boost controller and the manifold. I will try swapping boost controllers, but I doubt thats the problem, and i cant see how the manifold could cause the boost to drop off. Maybe it could account for the slow spool up though. Tell me what you guys think.

 

do you still have the stock downpipe? how big did you port the WG

 

wg is ported as big as i could without getting larger than the flapper, but i know it still seals. The exhaust is full 3 inch with no mufflers, cats, nothing!

 

damn thats wierd, That boost drop seems pretty regular. Judging from that graph it looks like your droping off right past 5k. The only thing i can think taht would cause that is the WG, maybe you ported it too much? Yeah i wouldent think the boost controller would cause it nor the manifold so id check that WG first. But cant you simply turn up the boost with those controllers?
I have a s5 turbo on the way im going to use the stock s5 mani, and i have no boost controller so i hope i dont run into the same kind of problem. Good luck!

 

I have s5 and the same setup mate my wastegate is not ported and I have more or less the exact same readings as you except my boost does not start dropping off until 5800rpm.
the reason you are not making boost until around 3000rpm or above is the 3" exhaust go back to 2 and a half and you will hit boost sooner I am also under the impression that because of the 3" exhaust it is now creating its own boost.
your graph shows only 4th gear I would think that in 5th at 120mph or above when you floor it with your boost controller turned down it wants to boost to 14-15psi I have this problem and hear the odd pink now and again I hate it!!!!!
as to a cure ......................???????????????????/

 

Well, so far I know its not the boost controller cuz i swapped them out. I cant just turn up the boost, because then although i may get 10 lbs in first and second, i would then be getting like 15 in thrid and forth. So I dont know what to do.

 

get bigger injectors... y ou should have atleast 720s with the 3" exhaust and TID. but yer numbers are still low for some reason.