400Hp Rb26 - Where To From Here?

[scotty nm35]

10mm preload? The actuators will have about 12mm movement total. Sounds like the springs are simply too weak.

[djr81]

Well either that or there isnt enough air pressure/flow to work with them.

Can you get different springs for the HKS actuators?

[zebra]

Not sure if its been covered...

What is your exhaust like?

[djr81]

Not sure if its been covered...

What is your exhaust like?

Um dumps are shiney Tomei items (Well they were shiney once). Rest of system is 3.5 inch. Cant remember what was downstream of the dump pipes but they were round & stainless.

Point is car will run to 22lb just not on the boost controller.

[ichi-go]

Does the blitz bc has like a different port on the solenoid? For example the profec b2 has diff port for internal or external gate (so 3 ports in total)

[Badgaz]

http://www.perth-wrx.com/vb/mechanicals/48287-restrictor-pill-what-why-you-need.html here is a link to what i think you need....

[djr81]

http://www.perth-wrx.com/vb/mechanicals/48287-restrictor-pill-what-why-you-need.html here is a link to what i think you need....

Just for other random people reading this: See the image above. The spring (preloaded by the variable length actuator rod) is there to hold the wastegate shut. By shortening the actuator rod you increase the load on the spring and therefore the wastegate stays shut for longer/under more pressure, all else being equal.

Air under pressure to the diaphragm on the actuator works to open the wastegate. If you are running a bleed valve reducing the air to the actuator will give you more boost as there isn’t as much air flow/pressure to oppose the spring and open the wastegate. If you are running an electronic boost controller surely the last thing you want to do is reduce the amount of air supplied to the controller – simply because controlling airflow is the controllers job. The Blitz is a dual solenoid type which should easilly allow a sufficient range of airflow to work over a 22lb setup. Maybe it isnt the case for a single solenoid type and people put a restictor down stream of it but to my addled brain that is a dodgy way of fixing the problem and would surely reduce the boost controllers responsiveness?

What I am guessing is happening in this case is that there isn’t enough air going through the solenoids to oppose a larger spring force - either because it has shit the biscuit or blocked with something. Hence insufficient preload can be applied to the actuators/spring to hold it shut at 22lb or insufficient air flow provided to open them up. (Choose your preferred failure mode). Hence I can only get a rather indifferent 16lb.

Anyway fingers crossed a new solenoid will fix the problem.

[scotty nm35]

The boost going into the actuator works against the spring to open the wastegate puck. It doesn't hold it shut unless you have a dual port actuator, similar to an external gate, which is very rare in internal applications.

You either need boost pushing from the other side of the diaphragm, or a stronger spring. Putting a restrictor inline acts like a capacitor, smoothing the boost out, it won't help you, nor will winding so much preload into it that the puck can't travel anymore. Preload doesn't make the spring stronger, it just limits the wastegate travel.

[Badgaz]

i thought with a restrictor its the same air pressure but at a higher velocity...which gives a greater range for the boost controller to bleed....i have no idea to the science lol.

[scotty nm35]

It just slows the wastegate down, restricting the speed it can open or close. Not ideal.

Nissan only use restrictors to adjust the amount of air the stock solenoid bleeds off, it adjusts the boost level using the restrictor hole size.

[GTSBoy]

Yes. Important point to remember.....air does not "flow" in a wastegate control line. At least not at the wastegate actuator end of it. It is a simple pressure system. Apply pressure at one end of a (closed) pipe and it turns up at the other end.

The only flow involved is once you start bleeding. By allowing some air to flow through a restrictor you get a pressure drop caused by the flow itself (basically internal gas and wall friction). Not rocket science. Well, maybe primary school rocket science.

[djr81]

See photo for gory details of inside of new boost control solenoid. Pretty basic stuff. Solenoid measures 38 ohms resistance. Guessing the little vents (on the left hand side with the green paint on the end and then behind that) allow the controller to dump the air out of the waste gate lines when necessary.

Oddly (or not?) you can push air through it with no voltage on. Flows from inlet to outlet. Not sure why this is possible.

[scotty nm35]

It should fail in the off position, meaning actuator pressure, so yes, it should be normally open.

[djr81]

Yeah ok fail open makes sense otherwise a stuffed boost controller means then engine will get whatever a shut wastegate will given.

[endless]

I spent a lot of time trying to solve a similar problem. Was sure everything was right, then when i ran out of parts to blame in process of elimination, i pulled the vac line off the stock bov connection to find it was not under vacuum at all.

The re-circulation of air was causing restriction in amount of boost i could run. Workshop missed it during tune also.

Worth a check!

[djr81]

Long story short. Replaced the solenoids. Now have more boost.