Microsquirt boost control help

I'm having trouble getting any kind of boost control at all. I'm on Microsquirt V3 and am trying to get open loop working. I have a boost control valve from a Saab 9-5. When I activate it with battery current it operates and switches flow from the top to middle port. Middle port and bottom port are connected when de-energized and the top port is blocked. I have boost signal from turbo hooked to the top port and the waste gate hooked up to the middle port and the bottom port to atmosphere. I've tried various settings, low, middle, high frequencies and normal and inverted polarity. I have switched 12v going to the valve and the ground going to ALED, this is also the pin selected in TS. Fortunately I enabled over boost protection since I'm getting no response from the boost control valve and it's pegging out at 21psi. What I don't understand is why the controller has to work on an oscillating frequency thing instead of just on and off action once it gets to the target pressure. I do have a Mac valve as well that I can use, any help would be appreciated.

VB242 said:

...What I don't understand is why the controller has to work on an oscillating frequency thing instead of just on and off action once it gets to the target pressure...

Click to expand...

Well, from what I can see, it appears that the valve bleeds off pressure to the wastegate actuator. That air is apparently supposed to be returned to the intake. Doing so allows the wastegate to be tricked into overboosting on purpose.

source

When you are pegging the duty cycle at 100% (on / off, without PWM), there is no way for the air to the wastegate to be bled off.

I'm pretty sure you're going to have do dig further and find out how this valve really works. Might even have to build a PWM controller and set up gauges (unless someone else has documented all of this for you?)

The valve I have is different than the one you've referenced but operates in a similar fashion. I'm pretty sure I've got the hoses hooked up to the correct ports but will try them reversed. I'm about to hook the MBC back up and set it to 21psi and screw it.

You want to plumb it so:
wastegate goes to common port
turbo compressor goes to port that flows to common port when not energized
3rd port open (not blocked)

When no power is applied, it should act just like a hose between compressor and wastegate. Boost is set by the wastegate preload.

The oscillating frequency, aka PWM pulse width modulation, is suppose to hold the valve part way open, or average out to part way open. The more open the valve is, the more pressure is bled off. Say the valve is dumping 50% of the pressure. This would result in twice the boost pressure before the wastegate opens.

bobxyz said:

You want to plumb it so:
wastegate goes to common port
turbo compressor goes to port that flows to common port when not energized
3rd port open (not blocked)

When no power is applied, it should act just like a hose between compressor and wastegate. Boost is set by the wastegate preload.

The oscillating frequency, aka PWM pulse width modulation, is suppose to hold the valve part way open, or average out to part way open. The more open the valve is, the more pressure is bled off. Say the valve is dumping 50% of the pressure. This would result in twice the boost pressure before the wastegate opens.

Click to expand...

I was thinking about how to connect the hoses the wrong way. I will change them and see if I can get this thing working. Thanke once again Bobby

Update: my gorilla like hands ripped the valve apart whilst removing the hoses, reinstalled MBC for now. I'll try and find a place for the Mac valve since it's considerably larger