Boost Only At High Rpm, Rb25 W Mods Gt3076r

[AlexanderK]

Hi, I am a newcomer to this forum, It's my first skyline and a first turbocharged car as-well,

Couple weeks ago I purchased 1994 R33 GT-s with some mods, but It has trouble getting to boost.

mods as go:

Forged pistons,

Greddy style Intake,

Top Mount mani

Z32 - Ecu&Maf

FMIC

Blitz Dual SBC - Boost Controller.

HKS External Wastegate?? (Hidden deep under manifold, have to remove some stuff to see what it is) looks like early version of HKS wastegate.

LS Coil Pack

GT3076 Ball Bearing with .60A/R

HKS SSQV valve.

The thing is Boost comes on only after 4-4.5K RPM and it has no transition, after 4k it's instant full boost. I tried playing around with Gain & Set on boost controller, I can adjust the boost to my needs but cannot get boost point to come lower.

As I see, this setup should produce boost much easier, I suspect it could be the wastegate, as I see boost coming on at ~3K gets up to .3-.5 Bar of positive boost than back at 0 and I can hear dumping air sound

Is there any way I could check operation of the wastegate? or If you think there could be any different reason for this behavior

[scotty nm35]

You could remove the gate and use a compressor to test it?

I doubt you will get it on that much earlier with a highmount manifold, but make sure the VCT is operating, that will improve the response a fair bit. z32 needs some mods to control VCT I seem to remember, is it Nistuned?

[AlexanderK]

Yes The ECU is nistuned and at least I was told that VCT is operating correctly. I have not gotten around to see whats what on this car just preparing homework for now.

I might think of installing stockish manifold if it help's with the response but I will probably try to stay with top mount and work on other flaw's like horrible fmic piping and a downpipe with dual 90 degree bends hoping to get at least some more respone and check if everything is wired / hosed correctly, as it feels something is just missed.