Technical > Wiring & Sensors
boost control
multiplex:
we can do the same thing a number of ways.
what firmware are you currently running?
I'm using a similar valve as shown above - actually its the GM valve alot of the MS people use.
boost pressure line is t'd and one side goes to the front of the wastegate. the other goes through the valve and to the back of the wastegate.
the valve is then set to always be open so that both sides of the wastegate see the same pressure.
vems has a setting "actuator off below this pressure". this is the setting you are looking for.
anything under that value, the valve is open. once it hits that value, the valve starts to bleed off pressure to the back of the wastegate allowing it to open.
in my situation, i found if my target boost is 210 kpa, i need to set my "actuator off below pressure" to around 160kpa. Otherwise you get a nasty boost spike before it settles out.
I'd like to find a way to move that value up though.
BenFenner:
I'm not running any particular firmware just yet. VEMS will be going in this weekend or next. I was just asking for my own knowledge. It seems the way you describe it, that no "quick spool" is employed as in the link I posted. As far as I know, with the "grainger" valve method, there are no boost spikes.
BenFenner:
Now that I think about it, the methods I'm talking about assume there's a spring holding the wastegate closed. The way you describe it, it seems you're using boost pressure instead of a spring. That could have a lot to do with what's going on.
multiplex:
no, its is in a sense duplicating the 'grainger' valve.
unless i'm misunderstanding, that valve is just a pressure adjustable check valve. it doesn't open up until a certain psi. thats what vems would be doing in a programmable sense.
i'm using a 9 pound spring in my wastegate, so there is a spring in the system.
do you know what psi they typically set the 'grainger' valve to?
BenFenner:
So you do have a spring? I see....
You understand the grainger valve correctly. It prevents any pressure in the line until a certain pressure is met, then it lets that signal through. The dodge guys set this check valve to what ever boost setting they want to achieve. The valve is adjustable. it takes a little practice, but you can set it anywhere from 7-30 psi (or more).
It was designed at first to be applied to stock cars. The stock wastegate spring is for 7 psi, but starts creeping open at 0 psi, as most wastegates do. Instead of slowly creeping open from 0-7 psi, they want the valve to slam open. They want it to stay shut until 7 psi (or what ever setting) is met, and then open quickly to stop boost creep. The idea is that boost comes on much quicker. I've ridden in a car before and after this modification, and the results are tremendous.
From what you're saying, I still don't see how you get the same effect, as you said yourself you need to set VEMS at 160 kpa if you want to see 210 kpa. That just isn't right. =]
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