Hallman Boost Controller How-To

by Matt (Shik), pictures and editing by Dave (DLC, dackampf)

Installing the Hallman Boost Controller (HBC) on the Subaru Legacy Turbo.

The Hallman boost controller is probably the best manual boost controller you can buy. The performance of it rivals that of many electronic boost controllers at a fraction of the cost. True, an electronic boost controller does offer some advantages, but when comparing performance for dollar, the Hallman can't be beat.


Disclaimer: When you begin to add boost to any car with all other things being the same, your margin of safety starts to fade. It is VERY easy to detonate a motor to death when you start fiddling with boost so be extremely cautious. Personally, if you do not have an intercooler on your Legacy Turbo yet but you want more boost, invest in an intercooler ASAP. If you do not plan on getting an intercooler, I wouldn't go over 10psi and even that may be pushing it. It is true that a few other Legacy Turbo enthusiasts have been running a bit more, but an intercooler can only help things and provide you some protection against detonation. The factory boost cut comes in around 13psi and according to some air/fuel ratios by a fellow enthusiast, the factory system still provides plenty of fuel up to that point. Still, an intercooler should be used.

Disclaimer 2: If you are installing a Hallman Boost Controller, we are assuming you already have a few things. One is a free flow exhaust. Backpressure causes heat in the turbo and as small as the stock IHI turbo is already, you do not need anymore. At the least, you should have a 2.5" or 3" cat-back system with a very free-flow muffler. It would be ideal to have the downpipe since that is probably the biggest restriction in the system, but it is hard and somewhat expensive to get someone to fabricate a downpipe for you since no one offers them at this time. Secondly, you should have a performance air filter or intake system. A K&N drop-in filter will do the job just fine. And lastly, don't even think about raising the boost unless you have a good quality boost gauge such as a VDO or the like. Raising the boost until you hit boost cut, then turning it back slightly is just dumb. Don't ever rely on the factory boost cut to limit your boost, if it is electronic there is always a chance of failure. Get a boost gauge.

Final Disclaimer(thankfully): I am just describing how I installed the Hallman on my Legacy. I have had it on for almost two years and have never had a problem with anything. That's not to say this is the only way or best way to do it, but it works like a charm for me. Always proceed with caution. If your blow-up your motor, it is YOUR fault, not anyone else's. BTW, if you use anything but premium fuel(92 octane or higher) in your Legacy Turbo, disregard this entire web page, you shouldn't be adding ANY boost at all to your car.

1. After you checked you Hallman out, the first thing to do is find the factory boost solenoid. You may find it easier if you remove the intake which only takes a few extra minutes. If you look on the front of the right front shock tower you will see two electrical parts. The brown sensor with two vacuum lines going into it is the map sensor. Leave this alone, you will not need to mess with it at all. Right under that is the boost solenoid. It is a cylinder shaped solenoid with three vacuum lines( two on the side, one on the bottom) and an electrical connection with a pink wire and a black wire.
2. Once you have found the solenoid, follow the two side vacuum lines to their sources, you will not have to bother with the vacuum line that enters from the bottom of the solenoid. OK, one of the side vacuum lines goes to the actual wastegate on the turbo, the other line connects to a little nipple right on the turbo housing. Remove the lines from these two places and remove them from the boost control solenoid as well. You will not be needing these lines anymore. Also, install a vacuum cap on the nipple on the turbo housing.
3. At this point, your boost control solenoid's two side vacuum ports should have nothing connected to them. The wastegate on the turbo should also have an open vacuum port.
4. Now find a place you want to mount the HBC. The shorter the length the vacuum hoses are the better, so locate it somewhere close to the turbo, but easily accessible. I mounted mine to the brake bias located on the side of the right front shock tower. My HBC came with a mounting bracket but I did not use it. I simply zip-tied it to the brake bias and never had a problem with it but if you have a better place, go to it.
5. Your HBC will probably come with ALOT of extra vacuum line. The Legacy Turbo should only need a short bit, but actual length may vary depending on where you mount it. After you mounted the HBC, you can go ahead and install the wastegate vacuum line. This line is the one that branches off the side of the HBC. Simply connect this line to the open vacuum nipple on the wastegate and make sure you zip-tie it at the wastegate as well.
6. Now, locate the vacuum line on the right front intake manifold runner. Simply cut that line and install a vacuum line "T" in it. Now you should have two open vacuum ports, one on the "T" you just installed and one on the other remaining port on the HBC( it should be the one that points strait down and is in a vertical line with the adjusting screw). Now connect the HBC vacuum line port to the "T". Again, the actual length of vacuum hose will vary depending on where you install the HBC so some trimming is most likely. Personally I've found that the intake manifold runner offers a much better boost source for the HBC then the nipple on the turbo housing where the factory had it. My boost was much more consistent with it connected to the intake runner so I've opted to keep it there. Always zip-tie any connections.

7. Your Hallman Boost Controller is now installed! As for the factory boost control solenoid, leave the electrical connection plugged in. You can cap the open ends of the boost control solenoid if you'd like. It's probably not necessary, but it wouldn't hurt.

Refer to the Hallman instructions for adjusting the boost controller. One tip though, make VERY VERY small adjustments! A quarter turn on the adjusting screw can mean major boost increases so do things very slowly. I started out with the screw adjusted all the way open( about 6-7psi), took it for a ride, and began making micro turns to raise the boost to where I wanted it. It may take a few test drives but it's worth it. Also, chances are you will get more boost in 2nd, 3rd, etc. gear then you will in 1st so keep that in mind when finding the boost psi you want. And gently "roll" into the boost when doing your test drives. This way, if the boost is way to high, you can catch it before it goes ballistic. Once you've found the boost psi you want, it would be a good idea to reset the computer to let things adjust more quickly to the added air flow.

Even at the stock boost level(8-9psi), I felt that the Hallman worked much better then the factory boost solenoid did. The turbo seemed to spool-up faster and hit harder. Of course "your mileage may vary", but to me, the Hallman was( and still is) well worth every penny. Some of the fastest Mitsubishis in the country use the Hallman so that alone says alot. For more information on the Hallman Boost Controller, click here.

Extra Tip: When trimming the wastegate hose to the desired length needed, Make sure the small brass connector with the tiny hole in it remains somewhere in that line. The instructions also state this but I thought I would add this info.
According to Marc Hallman: "The hole is a pressure relief that allows the wastegate to close between shifts. If it was not there the valve would close between shifts and trap the pressure between the wastegate and the valve thus holding the wastegate open. This would make the car very laggy between shifts without it."

Depending on where you mount the HBC on your Legacy, it is possible that you will only need the amount of vacumn hose before the pressure relief brass fitting. If this is the case, simply decide how much hose you will need for the wastegate, and then put the fitting somewhere along the piece of hose you will be using.

Good luck!