Grainger question, larger hose to WG = less boost spike??

[Guest bastaad525]

I'm trying to track down this problem... ever since installing my I/C, I've been getting wierd boost spiking problems. Originally I had left the hoses routed stock, that is, the two hoses from the compressor body, thru the boost controller (Grainger valve DIY boost controller) to the wastegate actuator. But the boost was acting very weird like that, it would raise up to one boost level, say 12psi, at first, and slowly start dropping off boost as RPM went up, about 2-4psi by 5500rpm. However, it didn't spike much when it would first hit full boost. Well anyways, I didn't like the tapering off, so I decided to instead run a hose from the intake manifold, thru the boost controller to the actuator. I get a much more consistent boost level this way... no more high plateau and then fall off, but it does spike quite a bit.

 

I still have my boost set to settle at around 12psi, but it will spike up to 14 or sometimes even 15psi (if I punch it from high rpm, say 4500+) before rapidly settling down to 12. This is very annoying, I can feel this big surge of power come and go in that instant... but on top of that, it's a little frightening that I might be hurting something, like overspinning the turbo (15psi at manifold = ~17 psi from turbo). I tried shortening the hoses as much as possible but obviously there is still much more length between manifold and WG actuator than from the compressor housing. I then realized that I could get away with a slightly larger vacuum hose... I was using 5/32" hose, which was really tight on the WG actuator nipple... REALLY tight, so I stepped up to the next larger hose, 1/4" I believe? I was just loose enough to slip on and off w/o much of a tug so I used clamps on everything.

 

Now, I would have thought with less restriction there, the boost would hit the controller and WG actuator faster, giving me less spike. I have to get it up on the freeway to fully test it out, but in a trip around the block, it didn't seem to help.

 

So... is it still spiking because the larger I/D hose = more space for the boost to fill = still some spike before the boost fills the increased space to full pressure? Or is it just a limitation of the Grainger valve that it will spike at this level no matter what? Is this something I can fix with a stiffer/softer spring in the grainger valve? Anything else I can do?