Boost

[lee-bob]

Hi all,after boost problems I checked solenoid only to find the red pipe had snapped off so I fitted mbc.car only boosts to about halfway on the gauge and on another gauge straight from the inlet it's about 4psi.i wound the mbc all the way out and still the same,any ideas? Or do I need a certain boost controller? Many thanks

[jifflemon]

Whats sort of MBC are you using?

I'm fairly certain the Turbo doesn't respond well to MBC's, as they use a similar system to the Saab APC.

Essentially, boost is controlled by the ECU, which opens a solenoid to bleed off boost.

[Irolllowvo]

Jeff is right, the ignition ecu (small black unit in the centre console) also controls boost.

I stole this segment which may be of use;

"The b18ft has a wastegate, which is connected to the turbo housing by a little silicone line. On it, you will also find a little electromagnetic valve. This valve is used by ECU to control the boost.
One of the major problems with the b18ft is that the ignition controler also has an overboost switch you can not tamper with. The result is that with this ECU it is not possible to go above 0.9-1 bar"

My vehicle is fitted with a bleed valve, there is no vacuum pipe to the ecu the port on tgevecu is blanked. I have to say I'm not overly excited about this as it carries it's risks.
However it may be helpful to you in the interim.

Previous car I had was fitted with a cheap mbc, I uprated the recirculating dump valves to vw/Audi parts as found on the tt Turbo

I used 2, one was fitted after the icv and the other into the pipe that fed the turbo. The car was idling erratically before hand as the diagphram had failed in the standard recirc valve. I believe the use of the mbc had killed it.

Hopefully this information is helpful

Ed

[WhiteWolf]

If I remember correctly the failsafe level of boost is 4psi, say for example the solenoid was unplugged it would register only 4psi...
There are resistance parameters to be met for the boost solenoid but I can't remember them, maybe 30ohms??
I would get rid of the boost controller and try and get a modified ecu done by board member Robou...
Good luck...

[fireblade]

Regarding the boost valve, I would like to know how it works.
The valve has three hoses connected, one goes to the wastegate actuator, but I don't know where the other two hoses goes to. The valve also has an electrical plug that I think it connects to the ECU.