h2k

I have a R33 skyline with a RB25DET stock turbo. Now what I've gathered from reading forums is that it has a Garret produced T25 turbo with ceramic internals wich don't like very high boost. A buddy of mine is replacing his T28 steel internal turbo on his 200sx s14 engine and I was wondering if it is a good upgrade on my engine, but most of all if it is bolton? Now I've read trough lots of forums but some claim that the T25 on my skyline has a T3 flange to fit on the exaust header? Will A T28 from a 200sx be a direct bolton on mye RB25DET header and is it a good cheap ugrade as the T28 should be slightly bigger then the T25 I have? also it has steel internals and should be safe to run 1.2bar boost on it.

I installed a HKS fuel cut defencer this weekend and took it out on track day, adjusted the cut defender until the "rich and retard" point no longer occured and now I can adjust my boost like I want and the fuel popping in my exaust because it lowers the timing is gone. I have also installed a air/fuel ratio gauge to make sure im not running lean air/fuel mixture and now its a hole world of a new car. Runs like a champion The conclusion is: when you upgrade airfilter, intercooler and 3"exaust the RB25DET ecu riches fuel and retards timing because airflow increases. Wich again makes so much and thick exaust that the standard T25 exaust wastegate cannot get rid of excess exaust and boost spikes above default 0.6 Bar. Funtime

I have 4 separate boostgauges to make sure Im not getting a wrong reading. One is the original VDO gauge. One gauge wich is connected to the same outlet as the VDO gauge with a T-piece. The apexi avc-r digital gauge wich I have connected with a t-piece between the inlet and the boost dump valve. One gauge wich is connected with a t-piece where the actuator gets its reference boost. One the cold side of the intercooler flow, just about in the middle between the IC and the throttle. I'm getting consistant boost levels on all 4. The cooler im using is a large Hybrid intercooler with hardpipe kit and silicon hoses. Core size 600mmx300mmx77mm with 3" inlet and outlet. I'm leaning more and more towards the theory that the fuel enrichment funtion on the ECU is forcing me to produce to much exaust, and with a to large exaust there is no restriction there so the turbo spins up to much. I live in norway and we don't have a dyno within a 10 hour drive away from where I live and it costs blood to use. It's not a boostcut defender, its a fuelcut defender. Though the fuelcut is activated to prevent overboosting. But in my case its producing overboost :\

Another theory is that I understand that the ECU monitors the air beeing sucked trough the filter and when it gets to much air the ECU respons with a fuel cut function by richening the air/fuel ratio to decrease boost. But since I have increased the air supply with filter and larger intercooler, and the exaust with free flow, it just keeps produsing exaust making the wastegate to small. I've ordered a HKS fuel cut defencer as I've talked to a guy having the exact same setup as me and is having no problems adjusting the boost down under 0.8 bar if he wants with a bleed valve. Only things he has that I do not is a HKS fuel cut defencer and a adjustabel fuel pressure regulator.

Today I tried to unhook the actuator rod from the wastegate and I held the wastegate completly open with a steel wire like this: Wich should send as much exaust possible away from the turbo. Low revving the car was very sluggish but when I passed 4500rpm the boost just launched like a rocket all the way up to 0.9 Bar in 3rd gear. Wich means one of 2 things: 1. The wastegate is clogged up by something, burnt oil remaints etc. But the arm moves very lightly and it makes a "dry" sound when I close it. 2. The wastegate on the T25 turbo is to small to dump all the exaust on a RB25DET engine when you have a podfilter, 3" exaust and a large FMIC. Does anybody else have the same mods as me and are still able to run at original boost? I've ordered a fuel pressure regulator so I don't run with to little fuel and to much air since that will kill my engine soon :\

The wastegate and diecast downpipe with the lambda probe is original and I dont think it is sticking, I've tried disconnecting it from the rod comming from the actuator and the wastegate arm moves very lightly from closed to open and it feel right. However if we say that the waste gate arm is a 0 degree angle when it is closes, and fully open at 90 degree angle. The rod comming from the actuator only pushes it open about 45 degrees. I've tried adjusting the lengt of the rod but that only resulted in the wastegate beeing about 15 degrees open with no boost, wich makes the car really sluggish. And 60 degrees open with full boost(0.9 bar). Tomorrow I'll try hooking the wastegate arm of the actuator rod and running the car with the wastegate completely open. If it still boosts then the wastegate is clogged or my engine is producing to much exaust and my wastegate is to small to deal with it.

Im running a R33 gts25t with 3" exaust, filter and a large FMIC. And Im getting a bit to much boost. Im getting boost up to 0.9Bar after 4500rpm. Im getting fuel cut 0.8Bar so I want to run 0.75 in boost untill I can afford a fuel controller and/or fuel pressure regulator. I removed the standard original 2-step boostcontroller and tried to run boost from the compressor side directly to the solenoid regulating the wastegate arm. Wich should give me the lowest possible boost, but still Im boosting 0.9-1.0Bar. I took off the heat shields on the turbo and connected a compressor directly to the solenoid and measured with a gauge when the actuator starts to move the arm and when it is fully opened. It starts to open about 0.5 bar and reaches it's max open wastegate at 0.9Bar. Is this correct? This seems wrong to me since the car ran fine(max 0.6bar) with the original 2-step controller before I installed the intercooler. Before I had only exaust and airfilter. But this problem occured after I installed the FMIC. Now I have tried a manual bleed valve and a Apexi AVC-R to controll boost but they can only INCREASE the boost. Now what I need is to change the actuator so that it starts to open the wastegate at about 0.2Bar and is fully open at about 0.6Bar and if I want to increase the boost I can use a boostcontroller/bleed valve to increase it to whatever I want from there. Is it possible to adjust the standard actuator by opening it and modifing the springs or something like that?

I have a RB25DET with: -3" exaust from stock turbo and back -Apexi air filter -Large front hybrid intercooler -Apexi AVC-R boost controller Before I installed my AVC-R boostcontroller the original 2-stage boost controller used 0.45Bar boost up to 4500Rpm then it jumped to 0.65Bar all the way up from there. In other words: 2000rpm-4500rpm the boost is 0.45 4500rpm-7000rpm the boost is 0.65 Before installing the Apexi AVC-R solenoid controller I removed the original solenoid controller. The problem is when I reach over 0.80Bar boost the engine studders, kind of like when you hit the rev limiter but more random and in shorter bursts. -Is this what is called "flatspots" ? Im running Denso spark plugs but I do not know the model nr or gap. Will regapping them to 0.8 help ? -Does my engine have a fuel cut or a boost cut? Would a fuel cut defencer fix this? Where is the original ECU's pressure sensor, would blinding this hose stop fuel/boost cut? -Or am I getting to little fuel? Will a Apexi digital Fuel controller fix this? -How much boost are you other R33 gts25t owners running on your stock turbos and what have you done with fuel? Why don't you just keep the boost under 0.80Bar then? well if I program the AVC-R to boost 0.75Bar it quickly adjusts boost so I reach 0.75 as fast as possible in the rpm register but as soon as I pass 4500Rpm the boost spikes to 0.95Bar. If I adjust the boost to 0.5Bar with the AVC-R it still jumps to about 0.9 something bar when I pass 4500Rpm. I've tried to adjust boost duty cycle but it still overshoots. I find this very weird since I HAVE removed the original solenoid controller and still it seems like a 2-stage boost controll happens at 4500rpm. -Now where is the best place to connect the AVC-R boost hose that control the solenoid on the turbo, just after the turbo known as the "hot side" or the "cold side" after the intercooler?