i have a rb25det neo and have had alot of problems with it. idk if it comes with a factory boost cut feature tha needs nistune to turn it off or a boost cut defenser put on it. if anyone has had this issue let me know how you fixed it. it did it with a stock turbo and with the new one which is same as stock just steel wheels instead of the plastic ones.

I'm moving this to the RB forum. Good luck!

Are you hitting higher than 180 kmh? If so, yes, it has a fuel cut. It will scare the crap out of you when you hit it. I would not advise Nistune as I had it on my RB20 and it melted all 6 pistons from a lean spot at 4K rpm that was in the ecu. Just go ahead and buy a good management system ans save yourself the trouble.

idk if im hitting higher than 180 kmh. it happens when i floor it and hits 4000 rpm. it looses all power and falls on its face untill i get out of the gas.

In any gear? If so, may be going into fail safe mode. I had a bad MAF do that once, but it never let me go past 2500 RPM.

its not the maf. it wont do it if the engine is not fully warm. its when it hits full boost at operating temp. first threw fourth gear.

Then it may be fuel delivery issue. Gets hot, fuel pump wont pressure up. Just guessing here.

There is a fuel pressure control module that designates the voltage to the fuel pump. At idle, it drops to 11 volts, and only goes to like 12 volts when driving. There is a way to bypass this giving the fuel pump the full voltage from the alternator, thus allowing the fuel pump to reach higher pressures and maintain them. This may not be the issue, but it is a mod that 90% of the guys I know who own them, myself included, do this right off the bat. I will find the instructions on how... Very easy, especially since your battery is located in the trunk anyways..

http://www.gtr.co.uk/forum/144974-r33-g ... h-mod.html

Try that link. Has a picture of what to do and what not. Easy, quick mod. Also, you may want to tape up your coil packs stems. Another quick fix that 90% of Skyline owners do is run electrical tape from the bottom of the coil pack, down the stem to the spark plug. A lot of missfire is fixed when this happens. You may not have a problem, but you will. It creates miss fires when engine warms up and high rpm is reached. Or just replace the coil packs, but if you are on a budget, try taping them first. It is a quick fix.

*Edit, just saw you had a 240sx, so the control module won't help unless you actually have one...disregard that. If it is not a Skyline, I cannot help. Sorry..

i have an external relay added cause when swap was done the fuel pump wouldnt prime. im glad you put that coil pack mod on though. i have split fire coil packs but if they start acting up ill tape them.

waiting on new alternator to put on then to find out whats going on with this boost cut. i have a feeling its gonna have to be tuned out. but ill be grateful to it back up and running again. if anyone else has a clue why it would cut on me id like to know.

I would check for a boost leak bud. Ive got a neo myself and was having problems with cutting out at higher RPMS, especially after 4-5K rpms and it turned out I had multiple small boost leaks.

theres alot of thread on how to check for them but heres a link for a quick look
http://www.vfaq.com/mods/ICtester.html

take off your turbo air intake pipe and slap this on there with a tire gauge and start pumping it up. Use a spray bottle with soapy water and starting spraying everything that sees charged air.

also I would double check your fuel pump wiring, make sure to have thick gauge wires for both the power and ground. If you look this up, theres multiple threads about people having issues with thin wiring not letting the fuel pump see full pressure and causing a lean condition --> VERY BAD. Again multiple people have posted fixes, so look for them if this is the case with you.

Good luck!

well now i got kinda a bigger issue i got a small hole in one of the coolant line behind the engine. i think its the small hose. does anyone know if i have to pull the motor to get to it.

shouldnt have to but Im not sure what hose your talking about. Some long nose needle pliers will come in handy to get the clamps off.

i believe its the one thats in the back its skinny and goes to a metal hose. i believe it goes to the cooling lines for turbo not sure though.

found the issue. the intake going to the turbo was collapsing on itself under full boost. took a couple years and a buddy of mine to figure it out.