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Old 10-22-2005, 08:54 PM   #1
Scooby Specialist
Member#: 88322
Join Date: Jun 2005
Chapter/Region: MWSOC
Location: Indianapolis, IN
2009 BMW 135i

Default Full DIY: GM solenoid install (56k warning)

First, thanks to all those who participated in the discussion of this mod, those who posted part #'s, tried it out first, etc. To help out, I'm going to cover the whole setup, top to bottom in a nice single post to help those out who are going to do this in the future. It would have helped me to have all this info in one post. I take no credit for figuring any of this stuff out or pioneering any part of this mod.

Parts: GM boost solenoid for Typhoon, GM Part # 1997152
Pigtails, GM Part # 12102747
Extra vacuum hose (I used about 3 feet, purchased 4 feet from Autozone for $3.35)
I did not use any restrictors. I don't believe they are necessary at all with a blocking-type setup, which is what I went for. You could potentially use one or two, but I won't be covering that.

The solenoid:
Port 1: Silver plug, by itself on one end.
Port 2: Opposite port, next to port 3
Port 3: Comes with a small filter on it.

I don't believe the solenoid is polarity sensitive, but there is a small + on the case of the solenoid. I didn't go out of my way to test this. I hooked up the + to the yellow line.

At rest: Port 1 and 2 allow air to pass. No air can travel from Port 1 to 3, or 2 to 3.

Energized: Port 2 and 3 allow air to pass. No air can pass from 1 to 2 or 1 to 3.

Port 1: To turbocharger, or optionally another line on the charge air side.
Port 2: To wastegate
Port 3: Back into intake, after the MAF.

Port 3 (optional): Just vent to atmosphere, but you should put a filter on it in case of reversal of flow. The GM solenoid comes with a small filter on this port out of the box, so just leave it on if you wish to port to atmosphere. You will need to block off the line that goes to your intake, though, as it exists in the stock system. Personally, since the line is already on the car, I say go ahead and use it. It is "technically" the right thing to do in a MAF, metered air system.

So a little background on how this works...

At rest, the solenoid allows the wastegate to see all boost pressure.

When energized, the solenoid blocks pressure from the charge air from reaching the WG, so the WG sees the pressure from the intake or atmosphere. The moment after the solenoid is energized, any air pressure on the wastegate blows back out to the intake/atmosphere, releaving any air pressure on the wastegate.

Downsides: If the solenoid fails in the energized position, your wastegate will NOT open. However, the same general risk is present with the stock solenoid in a bleed setup. If it somehow fails in the energized position, it will bleed as much air as the stock restrictor will allow, but never absolutely stop pressure from getting to the WG. Failure in the energized state of either setup will cause massive overboost problems. Overall I'm going to say the risk is similar.

Stock setup, bracket pulled back (three bolts):

Stock BCS removed from car. Take one of the rubber grommets for when you mount the new GM solenoid. If you don't, you'll hear the clicking sound of the solenoid inside the car.

Pictures of the "test" setup. I just mounted it on top. It is easier to see here and was easier to work on, but still secure. With it mounted here, I could hear the BCS click loudly from inside the car. I think this is actually preferrable for testing. Roll up your windows, turn your stereo off.

After confirming it works and doing a quick detune on the boost map, I mounted it in the final location. As above, I used one of the rubber grommets from the stock BCS and mounted it in the stock location on the top of the two stock BCS mounting bolts.
I soldered the pigtails to the factory harness just above the factory plug. I decided to leave the factory plug in place and covered it with electrical tape to protect it. This will allow the replacement of the factory BCS later if needed.

Quick word on tuning:
This will make your current boost map OBSOLETE. You must retune boost. If you have no way to tune your boost map, you should NOT do this mod. UTEC users, go for it. I suggest raising the Boost Gain by at least 5 right off the bat, and reduce the boost map by 25% to start, then work from there. I went from 400 @ 3000, 350 @ 6500 to about 330 @ 3000 and 280 @ 6500 for reference. I moved boost gain from 50 to 55. I still have a lot of tuning to do, but that will give you a general idea where to start. I also had to taper down faster at low TPS.

I'm not a Cobb AP expert, but I would think you will need ST to retune your boost. Do not just do this mod with a simple Stage 1 or 2 reflash! You will overboost like crazy, maybe popping your motor.

Either way, you absolutely MUST have some way of retuning boost for this mod.

Results? I'm still tuning the map, but I think I'm seeing an easy 200-300rpm gain in spool on my stock VF39. I will hopefully be going to the track this coming Tuesday and will have some very comparable dragstrip UTEC logs. I expect a big gain in lower gears. We'll see!

Other note: Some people have suggested putting a 10ohm resistor in line with the new GM boost solenoid, since its resistance is about 10ohms less than the stock solenoid. This resistor will ensure the current draw of the new solenoid is not higher than the stock solenoid. You can do this at your disgression. UTEC users should probably not worry about it too much, because the UTEC's solenoid output has plenty of current capability.

Another FAQ/DIY online:

May 26, 2007: Added 4 port with EWG FAQ/DIY in post #202
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Last edited by Freon; 12-31-2014 at 05:03 AM. Reason: fixed image links
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