how is stock boost level controled what stop it going over 9psi ?

The wastegate and actuators control that.

Well essentially a thing called a waste gate. It's a little flap in the exhaust housing of the turbo, once x amount of pressure has been achieved the waste gate opens venting off the air that isn't needed to spool the turbo any faster as its hit the desired level.

That preset value is controlled by the actuator, its like a pressure valve. The Actuator activates and deactivates the waste gate. So the flap stays shut allowing you to build boost by passing the maximum amount of exhaust gasses to pass, the subsequently venting off the excess.

Going back to that preset value, the stock actuators on the z32 are loaded for 7 psi. By a process of restrictions know as boost jets(yes from factory) and the boost solenoids the actuator is tricked into only seeing 7psi when in reality it is seeing 9psi. This is why safety boost is 7psi. So to increase from the stock 9psi, we do the same trick. Either by process of a manual boost control, electronic boost controller or boost jets. All those pieces of kit essentially do the same thing, fool the actuator into thinking its seeing 7spi at whatever your chosen value is.

That is a very simple version of what's occurring. If you disconnected that vaccum line that went to the actuator the turbo would produce boost until it flat lined out, and if the wastegate was fully open your car would be laggy as hell, struggling to spin the turbo. So you need that control.

 

Now for the important bit, YOU MUST MATCH THE AIR IN WITH THE APPPRIATE AMOUNT OF FUEL. By that I mean the car must have a fuel map to match the amount of boost your running, more boost is more air passing through the engine. IF YOU DONT YOUR ENGINE WILL BLOW UP. Either because its way to rich and is drowning the cylinders with fuel, contaminating the oil, lots of black smoke. Or most likely run lean, ie too little fuel for too much air, this will melt the pistons very quickly

 

If you want more power, and your upping the boost you must hap the appropriate map. I would also suggest you had the right supporting mods and service items ticked. Trying to put 400 odd horses through a 15 year old cambelt, Pushing the engine beyond its cooling capabilities or expecting that old clutch to hold onto all this new found power are bad ideas.

i have a MBC am going to fit and new chip for fueling i am told the stock solinoid is kept in but on pics i have seen its removed an the pipe from the mbc goes rite to the actuator on the turbo so am confused

i have a MBC am going to fit and new chip for fueling i am told the stock solinoid is kept in but on pics i have seen its removed an the pipe from the mbc goes rite to the actuator on the turbo so am confused

 

 

Leave the original boost solenoids connected, keeps a level of safety boost protection if detonation occurs and also the boost controller duty / gain can be set at lower levels whilst still attaining good high boost figures gives a quieter operation of the boost controller solenoid.

 

Jeff TT

so can u just use the oem pipes that comes from solenoids and just plug them into a t piece and then into the mbc

so can u just use the oem pipes that comes from solenoids and just plug them into a t piece and then into the mbc

 

Correct.

 

Jeff TT

am still having brake isses fitted the braided hoses and the pedal is still shoft then the engine has to be the brake booster issue i have changed everyting else