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Hi, Alirght, i've been searching on here and around the internet for the past 4 days trying to find a a solution but so far nothing 100% certain. I had a stock RB25 turbo high flowed and worked on to take a billet compressor wheel and stage 3 turbine so turbo should be good for 450hp The specs i got from the shop are this: Compressor housing is stock modified stock modified/bored out for the bigger wheels Turbine housing is the stock modified/bored out for the bigger wheels Comp Wheel 54mm/76mm billet Turbine Wheel Stage 3 Garrett The turbo also had the stock wastegate actuator converted to be adjustable and was set 9psi so from the looks of it i figure the turbo should be somewhere around a gt3071 or gt3076 equivalent. The car has blitz return flow front mount, 550cc injectors, Turbosmart FPR, Apexi Fuel pump, 3 inch turbo back exhaust w/bell mouth 3 inch downpipe, straight pipe (ie. No cat), Apexi super suction intake kit, Nistune for RB25, Z32 MAF For boost controll we had a Hallman MBC controller put in temporarily and then later on AEM Tru Boost would be used permanently. Took the car to the dyno and....we can't controll the boost. It hits 15psi around 3000 and by the time it reaches 6000 it's hovering around 25psi. The boost curve on the dyno graph is a straigh 45degree line with no taper. Shoots up and keeps going up. Took out the boost contoller and ran the Vac line from wastegate to nipple on the compressor hot side pipe and same thing happened. Removed downpipe check for obstructions, nothign there ....just a nice big 3 inch bellmouth Checked all the piping and no leaks, ran air compressor to wastgate and it opens normally at 9psi. Looked at the Internal wastegate port and it's been ported/bored out to max, anymore and you compromise the exhaust housing. Any of you have any suggestions or solutions? Maybe you guys ran into a similar problem? Only thing I can think of at this time is the internal wastegate port is just too small and can't flow enough exhaust gas to control boost. Which means turbo probably needs external wastegate? Or the stock bored out nissan housing is way to small causing restrictions. I don't want to go external wastegate as I am really only looking for 320rwhp to 340rwhp (240rwks - 255rwkw) and its just a street car. Hoping i would be able to pull something close to that with internal WG setup. Next step is just putting back in my old semi upgraded Stock oem turbo and dynoing that to see what i get and calling it a day. any help would be great! thanks! Pic of exhaust side of turbo:
