Correct vacuum line setup with external wastegate and BCS

[Technology]

I've just gotten it to work now with ECU controlled boost, but I hooked it up wrong the first time and boost wouldn't go below 22-25 psi at WOT. This could be very bad for someone who needs lower boost, like a pump gasoline tune or stock engine. My tune is good for 29 psi, so it's not that bad of an issue. This write-up will explain how I did it wrong and how to do it right.

 

http://i36.photobucket.com/albums/e6/vip09/Ebay/STP63351Large.jpg

 

I have this exact item (MAC boost control solenoid available on ebay) and as you can see from the little diagram on the right of the label, in it's open state, air can flow freely from port 2 to port 3 or vice versa. When closed, air can travel from 2 to 1 or 1 to 2 (shown in the unmarked box with the arrow). As I have the vacuum lines now, the turbo boost goes into 2, and the top port of the wastegate is connected to 1. Like I said, it won't make less than 22-25 lbs unless I modulate the pedal. The wastegate spring is 17 psi and will open normally with only the bottom port connected and no boost controller connected. With the top port sealed off the air inside is acting like an extra spring, but not as accurate, and when the BCS does open, boost will be difficult to control.

 

The bottom port (under the diaphragm) on the wastegate is supposed to receive pre-throttle plate turbo pressure (no vacuum), the top is supposed to see whatever the boost controller sends it, but I have it so it's totally blocked off when the BCS is closed. It should be open to the atmosphere so that it doesn't impede the regular wastegate opening pressure. Tomorrow morning I'm going to switch the lines and take it for a test drive. If I am correct, I will edit or reply to this thread with the results.

 

As an aside, the way I have it currently hooked up, the nipple on the turbo compressor goes to the bottom side of the wastegate, the wrong input on the BCS and the underside of the blow off valve (to assist quick response - it's a Greddy Type R with 15 psi spring). You may realize, as I just did a short while ago, that the BCS is bleeding off boost, and not allowing the wastegate or the BOV to get full boost. It's been like that since I replaced the Greddy Profec B spec 2 with the MAC valve. I feel like an idiot for not realizing that. It's soon to be remedied.

[polarisman14]

That looks like the same solenoid that is on my E-boost2 unit. Same setup, at least. Nice work.