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309 Posts
Discussion Starter #1 (Edited)
Amazingly effective/cheap BCS mod

I just finished installing a GM boost control solenoid in my car and all I can say is that it is AWESOME. It gave me full boost about 750k earlier, a much more steady boost responce, and more direct control over how much boost I want to run. This was all done for under 50 dollars and about 45 minutes of time.

This mod was started by TheMadScientist over on NASIOC

so all thanks to him. I'm posting this because I dont think this mod is getting enough attention for how much benefit it gives.

Anyone who has any sort of engine management that is user tunable can do this mod. DO NOT DO THIS IF YOU HAVE A REFLASH OR COBB. It will NOT WORK because you need to adjust the wastegate duty cycle. A car that can use deltadash will work fine.

You will need these parts:

Order here

GM Part#

1997152 boost control solenoid
12102747 Pigtail connector

In addition to that, you need to buy a 1W 10 Ohm resistor (I used 2W 10 Ohm). These can be had for under a dollar at an electronic store.

I used new vacuum tubing from my local Pep Boys. 5/32" which is a little big, but I havent had any problems. Stock our cars use 350mm and 5/32" is 400mm.

You will also need a soldering gun.


The stock BCS is located under a metal guard plate on the passenger side of the engine. If you follow the vacuum hose from the intake and from the wastegate, it will end up at the BCS. The stock BCS only uses two nipples while the GM has three. First thing to do is to take off the metal plate to gain access to the BCS. There should be three bolts that hold the metal piece in place. Take those off and undo the BCS. You are going to need the power connector that's attached to the stocker for power to the new BCS, so just make a note of which wires are which. The fatter wire is the +. Remove all of the stock vacuum hosing. If you have a UTEC you are not going to need the ABC. You also are not going to need the resistor in the stock hosing. When you remove the intake hosing, there is a connector that connects the nipple off the intake to the smaller 350mm hosing. Keep this because you will still need it.

Once all of the stock hosing is out of the car you should be left with just the intake connector. (and the plastic elbow piece that connects the different size hosing)

Now in order to power the new BCS, you are going to need to either cut or splice the old power connector to the new pigtail that you ordered. In addition to that, you will need to run the resistor in line as well. What I did was cut the pigtail line in half and do the soldering outside the car. I took the resistor and attached it to the pigtail like so:

O------x resistor x --------- +

I put it on the power wire.

So now you should have the new pigtail with the resistor soldered in. Now you just need to connect the wires up to the stock wires. Once this is done, you will have power to the new BCS.

Next you need to run the vacuum lines. This is going to look a little different than how it was running before, because now you will have direct control instead of using a bleeder system to control boost.

The single side of the BCS connects directly to the turbo nipple.

The intake connects to the lower side of the two nipples while the wastegate connects to the upper one.

An easy way to tell which goes where is to blow through the single side of the BCS. The hole that is naturally open goes to the wastegate.

Check the picture.

Hope this helps,


898 Posts
Looks like a great mod.:thumbup: Do you think any autopart stores would carry this part? Probably too specialized I guess.

I've been waiting for someone to be the guinea pig with this idea.

656 Posts
just order it from the link. shipping was lightening fast, and they gave me a t shirt too. ;)

couple of hints:

you DO NOT need the resistor. i have been running without the resistor for over a week with no problems. the extra current drawn by the lower DCR coil does not affect anything.

you DO NOT need the harness if you're adept at electrical stuff. for example, i used some extra crimp connectors for the utec harness which i picked up a while ago. they fit nicely on the solenoid pins. if they didn't i was going to solder wires directly... it's tight, but if you know what you're doing it can be done cleanly. i didn't get the harness and it worked out to ~20 bucks shipped.

the solenoid works very well. there's a long history of doing this mod over on scoobynet (uk site). they call it the "3 port boost control solenoid" mod. obviously a different solenoid, but essentially it is the same mod--changing the bleed-based boost control into an interruption-based system.

now i've just got to work on boost spikes while flat foot shifting... :confused1

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