Newb question - ebc pwm to close or open?

[BigD]

Hi guys,

Sorry I'm still learning EBC so please bare with me if these are painfully basic questions. When you install the solenoid, do you install it so with no power, the WG sees full pressure, or none? Seems like a safer idea to leave it open and control the flow by closing. But then the "valve off until X boost" seems to be backwards vs the intent. I assume the purpose of the feature is to build boost as quickly as possible. But for that to work as intended, don't you have to have the valve dump boost when closed? So in effect, to have max boost build until certain pressure, don't you need the valve to be ON the other way (valve off = full boost to WG)?

Also, say I have a 14 psi spring, and I want to have 25-30psi in top gear, and lower boost in the earlier gears. I see most people leave the bottom port alone and boost-control the top port. Is there any benefit to providing the reference boost to the top port, and then boost-controlling the bottom one (negative signal)? With that arrangement, I can see how "valve off until X pressure" working as intended if valve off = full boost signal, since with the valve off, the WG will have 0 net pressure.

[BigD]

Since my boost valve is a MAC, I looked up the AEM instructions to see how they recommend hooking it up and it just confuses me further. It seems to only suggest the way I'm thinking for an internal WG. But for external, they seem to suggest a method similar to what I mentioned last, that I haven't heard recommended elsewhere:

For those who don't know the MAC valve, to make the references below clearer, it has ports 1,2,3. 1 and 2 are side ports, 3 is the front (the way the valve is drawn, port 2 is on the left, 1 on the right). With the valve off, 1 is closed, 2 and 3 are connected. With the valve on, 1 and 2 are connected.

[Joof]

Did you ever figure this out?  Using the same valve and am getting ready to hook it up.

[BigD]

Yeah, you open it. It became clear when someone explained the roles of the 2 ports for me. The boost control acts as a negative for the reference. In that, the bottom port (not the top like I thought before) provides reference pressure on the diaphragm, so the valve opens when the pressure matches the spring pressure. But if you provide a counter signal to the top port, you can "cancel" out the reference signal, up to 100% (in theory, but in practice you should expect to run boost up to 2x spring pressure). So the valve, when not powered, should be venting the top port of the WG to atmosphere. And when energized, connect it to the boost reference.

[Joof]

That's what I thought, just looked here quick for some clarification.

Thanks!

Now to wrap my head around how to tune it properly.

[BigD]

It's so sad that you're going to be up and running before me

[Joof]

...but you're build makes mine look soo boring it isn't even funny 

Maybe not though, I'm shooting for driving in 3 weeks - which may be way optimistic as engine parts are still getting powder coated.  That means the engine is still out of the car and on the stand. Lol. 

On the plus side the only fabbing left is cold side + exhaust.

What's the word on yours?  Still charge piping fab?

[BigD]

oooh then I have a chance! Yeah still welding. It was supposed to be done this week but looking at the pics he sent me, I realized that he made me a 3" downpipe when I requested 4. He said it's 4 from the WG back, saying it's better this way for heat, less lag, more linear WG signal... the last 2 don't even make sense. He agreed to make a new one in 4" turbo back so... now f if I know when it'll be done.

[fphil]

Now to wrap my head around how to tune it properly.

I have just been through part of it, you may have look to
MembersPage/FPhil/BoostControlUnderstanding . .  .