Both the blue and ultimate series emanage offers subinjector control for the purpose of adding an additional fuel injector. Majority of us do not use this feature, and in this article I'll use it for a different purpose. If you already have the greddy boost pressure sensor then you can use the greddy subinjector map as an electronic boost controller map. Blue emanage owners may have to purchase additional wiring.

Parts Needed:

- GM Boost Solenoid (part # 1997152) $10.32 at www.gmpartsdirect.com
- Solenoid Connector (part # 15305891 $18.79 at www.gmpartsdirect.com

I picked up a couple GM solenoid connectors at a local pick and pull junk yard for free. Take your boost solenoid with you to the junk yard and visit some GM cars. Some GM cars use this connector as their intake temperature sensor connector or coolant temperature sensor connector. I don't understand how they could charge so much for a simple connector. And no, I didn't make note as to which vehicles I got them off of.

Electrical Installation:

Since the GM Boost solenoid is non-polarized, it doesn't matter which end of the wire gets ground and which wire gets 12 volts. My wire had one red lead and one blue lead, so I used the red lead for 12 volts, and the blue lead for the emanage ground. If you actually purchased the GM solenoid connector, you'll have two white wires as leads. Wire up the GM boost solenoid as indicated in my diagram.

Vacuum hose installation:

The GM Boost solenoid has three vacuum nipples with one nipple attached to a foam filter. Leave that filter on. The adjacent nipple to the foam should be connected to your wastegates. The remaining nipple should be connected to your Y-pipe, as illustrated in my diagram. Don't reverse the solenoid.

Location:

My GM Boost solenoid fit well near the factory boost solenoid location.

Usage:

100% duty cycle means maximum boost. 0% duty cycle means lowest boost possible (wastegate pressure). The GM Boost solenoid with no power, by default is normally open. This is a good thing, in the event of a failure you will run only wastegate pressure (low boost). You could also use other high speed solenoids in place of the GM Boost solenoid. Be sure to select one that is normally open for safety reasons.

Simulated MBC:

If you're still using a MBC, you can simulate it pretty well with this setup. Just enter the same duty cycle number everywhere on the map. And now you've got a simulated MBC. You'll have no idea how much boost you'll make just like a real MBC. You have to drive your car and check out the results. If you didn't make enough boost, you would turn your MBC **** to make the air passage smaller. Similarly on the GM Boost solenoid, you need to increase the duty cycle to reduce the air passage. This process involves a lot of trial and error until you've reached your goal. What sucks about a MBC is you gotta pop your hood open, undo your seat belt, climb out of the car, adjust the MBC ****, close the hood, climb into the car, put your seatbelt back on and make another run each time. With this simulated MBC, you just reach over to your notebook and change the duty cycle. Enjoy your new simulated MBC.

Spoolup:

The previous example sacrifices spoolup a little bit. Suppose you want a target boost of 17psi. Ideally, you would want the solenoid to be fully closed (100% duty cycle) anything below 17psi for maximum spoolup. But in reality, this control system cannot react that quickly and would overshoot easily. What you should do is keep the wastegate 100% closed a few psi before reaching your target. In my example, I chose 11 psi, but you can experiment to see what works best for you.



Noise:

The GM Boost solenoid is rather noisy especially when you're at idle or crusing around and at WOT you probably won't even hear it over the engine noise. There's no point in over working your solenoid when you're below wastegate pressure. Since the TD04 wastegates open around 6 psi, you could theoritically keep the solenoid turned off during this time. But wastegates don't swing open exactly at 6 psi either, they slowly creep open as they approach closer to their target psi. Anything below 4psi and under I keep the solenoid turn off (0% duty cycle). Having 0% duty cycle here won't hurt spoolup. As you can see in my map, at 5 psi I fully close the solenoid before reaching the wastegate critical pressure of 6psi. I don't want the wastegates to prematurely open as we approach it.



Duty cycle:

As you can see in my map, after 5000 rpms I had to tweak the duty cycle. If your boost falls off, increase the duty cycle. If your boost overshoots, decrease the duty cycle.



Safety:

In my map, anything above 18 psi has 0% duty cycle (wastegate pressure). So if you accidently overshoot, you'll go back to wastegate pressure. This is something your everyday MBC can't do. Protect your engine from overboost.



Adjust your boost:

Now suppose you want to increase your boost, ie. from 17 to 18 psi. Just copy all the cells from 12psi through 17psi and copy them into the new location of 13psi through 18 psi. And copy 100% duty cycle on the 12 psi row to keep the wastagate closed for maximum spoolup. Eventually when you increase the psi a lot more, you'll have to retweak the duty cycle again.

Other solenoids:
For fun, I tried the stock boost solenoid. I could only get about 12 psi, and the boost fell off. Not worth persuing.

Conclusion:

Well, there you have it, an affordable electronic boost controller that can be made roughly for the same price as a MBC. My old AEM EMS uses this same strategy to control the GM Boost solenoid, but also offered the option of using two feedback circuits. But one thing I do like better on the ultimate is the ability to change the PSI scale and RPM scale independantly from the fuel map scale. I couldn't get this fine PSI increments on the AEM EMS without screwing up my fuel map scale.