Right, not trying to go a lot past 23psi. But if I go from my current 21.5 / 21psi at 7k, up to about 23psi, some gains will be seen. I'm definitely not trying to hold 28psi at red line, but may 2psi more.


No boost leaks. I tune my own car, so not sure what else to tune for to hold boost. Timing is about 10 at 7k and afr is about 11.4. I messed with different MIVEC maps at that RPM range, still can't get more boost at red line.


I actually have those springs sitting in my garage :lol: I will give those a shot.


Would upgrading the actuator do the trick?

OP do you still have the nut on the wastegate arm? Take that Batch off, cut two threads off the arm, tighten the turnbuckle down as far as it will go and re-install. I will bet you some cold hard money that you will hold more than 21-21psi at 7000. :D

Mikey

It is possible that your setup is out flowing the turbo. If you had a turbo speed sensor you could get a better feel for what is happening based on shaft speed. My setup has the same issue with holding boost to red line as seen in the graph below. Boost hits 24psi, but then drops to 19 by redline.

I pressure tested the car well past 30psi with no leaks. I may try removing the stock BOV to see if there is some dynamic that cannot be simulated with the pressure tester. My car has bolt-ons with no tune(except modded MIVEC map) using Greddy Profec B boost controller.

http://www.eng.fsu.edu/~jthagard/EVO/EVOSCAN/240z2.jpg

Upgrading the wga would help... if the crack pressure of the wga is raised the waste gate wont open and lower the psi... the helper spring is basically the same thing... after you swap or add the spring you'll have to readjust duty cycle as im sure you know...

It smells like you're on to something.

If the backpressure in the turbine housing is higher than the wastegate can handle it will be forced open regardless of where the boost controler is set. This is why larger exhaust wheels are necessary sometimes to achieve more power and boost with the sacrifice of a slightly slower spool.

Omg is your afrs correct 15.0 to 14.1??

To the other person crush your bov that helped me just remembered but dont over due it use a vise grip or take it off the car and press it even both sides not just the middle that would cause it to leak.

Achilles, thats boost not afr. You might not be able to hold anymore, your setup might flow exceptionally well like someone else already said. If more heat comes, its not worth it. Torque might go up but power up top will fall off faster.

this guy is right... when i had my stock turbo running like that i was pumping large amounts of water and meth to compensate for stock injectors... i did make insane power but without something to compensate your just screwing yourself...

I have some interesting logs displaying this level of backpressure and the results where I hooked up a pressure sensor on the turbine in addition to the manifold. I compared backpressure and charge pressure, as well as other channels on logworks for both stock VIII turbo as control, and BBKFULL as experimental. The stocker backpressure would increase with RPM so long as the gated load was constant, Like 45psi backpressure for 23 psi boost near redline. The FULL turbine however would give a flat turbine psi which makes sense since the full turbine is at least 30% larger. I am söao convinced 60psi would be easily achieved with strong enough spring on stocker.

My conclusion was backpressures were consistant with boost for both turbos, the only difference was the stocker backpressure became proportional to rpm, furthermore proportional to wastegate load. And the full backpressure remained less than boost

I think some might be posted on the cbrd forum

That for the most part is correct. However, there are ways around that. If you shorten the wastegate arm you are shortening the travel of the wastgate arm, limiting how far the wastegates opens and at what psi it cracks. It is common to do this to induce a bit of creep in higher rpms. The only time it becomes a problem is if you start to overspin the turbo. 420-440whp seems to be the safe limit and under a 32psi spike holding no more than 25psi out the top. That is my rule of thumb {thumbup} Or you can weld the flapper shut and make over 500whp like ER did on there stock turbo {OMG}

Mikey

I used the HKS EVC VI on my IX. It lets you set the boost by RPM.

when did this problem start? im not sure if this just started or you noticed it when you were tuning. i would def recommend upgrading the wga. i have a red with the fp wga and its holding 26-27psi all the way through redline

That is a nice EBC. You are essentially forcing 100% WDC from 6k rpm and up. Those help a lot more than a std MBC however, I would still mod the wastegate. ;)

Mikey