Running stock twins with a hallman MBC on the wastegate line.

Here are my symptoms:

-MBC adjusted all the way out (spring loose inside) still boosts to 12 psi in low gears
-in 5th on the highway it only boosts to 10psi WOT IIRC
-turbo control actuator does not move when I do KOKO like the troubleshooting guide says
-no secondary transition
-do not get 4 psi when i WOT in neutral, it's more like 0

Here's what I just did to the car: traded out rebuilt twins for low mile stockers. The rebuild ones had a perfect 10-8-10 but were noisy. When I first put on the new ones I had a rattle and they didn't make enough boost. The rattle was the precontrol actuator rod out of adjustment and not holding the flapper closed. I fixed that and then they started to overboost.

What I've checked and has passed inspection:

-correct routing of lines to MBC
-BOV
-charge control actuator works during KOKO
-made sure the wastegate line went to the correct (USDM driver's side) actuator and correct nipple on actuator by disconnecting lines and blowing through them
-pressure and vac tanks hold

I'm running out of ideas, time, and patience and could use some help. Thanks everyone.

 

Are you running with the extra pc / wg actuator nipples capped?

(I would)

 

Nope. They run to the PC and WG solenoids just like stock.

 

Long term, either take out the MBC and control boost with a PFC and stock solenoids (no pills), or cap the nipple to the solenoids and control it only with an aftermarket boost controller of some sort.

but what you should do first as a diagnostic procedure is cap the nipple on the actuators that go to the wastegate/precontrol solenoids. Then remove the MBC's and run straight uninterrupted pressure sources to one nipple on each actuator. That should put you right at spring pressure assuming nothing else is wrong.

 

I found that with my manual boost controllers they did not work well unless I put a cap on the actuators. Too much air passing through the actuators unless your boost controller spring was very sensitive.

IIRC Damian eventually did the same thing but it's listed at one of the later posts in his thread.

 

Well, I only have one MBC and it's on the WG pressure line. I think I'm going to cap off the aux nipples on the actuators, but leave the MBC there. Maybe eventually put in another MBC on the PC.

ARGHX, why are you against MBCs and say I should use a boost controller? I thought these hallman MBC's were supposed to work pretty well.

 

I am not against MBC's. I said "aftermarket boost controller of some sort." in my mind that includes MBC's. they get the job done. I prefer tuning the stock solenoids through a PFC actually, but there is a cost and a learning curve that many would understandably like to avoid.

 

OK, I understand. Unfortunately a PFC is not in my budget right now.

I just got done capping the extra actuator nipples and I've gotta drive to the UPS depot down I95, so we'll see what happens. So far boost looks lower on the short ride home from work.

 

Ok, I'm officially confused. Couldn't get the boost over 7 psi regardless of MBC adjustment. No transition. Boost gradually fell off to ~3psi after 5k rpm or so.

 

If you only have a boost controller on the wastegate, then that's the only one I'd cap off. I hadn't directly asked whether you have a controller installed on just one or both.

I would reconnect the precontrol to it's solenoid or else you might not generate enough boost on the primary to activate the secondary.

Dave

 

the whole point of this exercise was to start with an underboosting car and then set the boost to where it needs to be, rather than starting with an overboosting car and risking the motor as you tried to drop the boost down

 

Ok, I'll try that this weekend.

well at least we've accomplished that, right? hehe. i'll post back after reconnecting the precontrol to the solenoid.

 

reconnecting the precontrol to the solenoid fixed it. turbos are working great and the wastegate keeps it at 10psi.

 

I lied. My boost pattern is still off. I'm getting 10-5-8 in third gear. Seems to be proper timing, just not the right pressures.

My turbo control actuator still does not move when I KOKO after building good vac and pressure in the tanks.

The turbo control solenoid under the UIM and next to the ACV (not the rats nest turbo control solenoid) does not click with KOKO. I took off the connector and it's not getting +12v between the terminals with the key on.

With the key off, both terminals are 0v. Key on they both go to 12v.

 

There you go - replace that solenoid. It's a very common bad actor.

I can't guarantee it will fix the 5psi transition but it will help a lot.

 

Ok, but I'm kind of confused about the voltage at the connector. Why would both wires have 12v?

 

Oh, both terminals on the same connector? That's not right. I think you're onto something with that.

Does it make 12v on both sides with the solenoid connected or disconnected? Hopefully it's just a shorted solenoid.

David

 

that's just the connector, no solenoid. starting to feel like i'm losing it... i swear this car worked before i switched turbos. haha

Here's what I'm gonna do. I know the hot wire (black/white, just like all the other solenoids) is good and has 12v key on. The ground wire, which the ecu controls is pin 4R on the ecu harness. I'm going to make sure the two ends have continuity. Then i'll ground pin 4R with the ignition on and see if i can make the solenoid work that way.

Hopefully that will tell me if it's wiring or in the ecu. Sounds relatively sane, right?

 

Sounds reasonable. Good luck(?!)

 

Well, that was def a bad solenoid, got open open circuit when i put the multimeter on it, new solenoid was about 34 ohms. It's def better, but not 100 percent. I need to do some country road pulls this week and 2x check the pattern.

I actually managed to R&R it without pulling the UIM believe it or not. Not sure i'd recommend it though....

It's def pulling better after 4500, but i'm pretty sure it still dropped to 6 psi and only maxed out at 9 psi.

Starting to see why you guys told me to throw these things away, but I'm too damn hard headed.

 

Have you checked to make sure your pre spool line a pill in it? If it doesn't, that could be your problem.

 

Nearly 100% i checked that when i capped the WG to solenoid line. I can always double check it when i tear into it again.

I think i'm going to one by one ground the turbo related solenoids at the ECU harness with the key on and check for clicking, taking the more accessible ones off. Then double check the line to solenoid routing.

I'm leaning towards something precontrol related since i get good primary and my transition happens at the right time. Maybe CRV or charge control?

 

Wait, if you have MBCs you should not have a pill in that line.

 

It's just in the precontrol line, since there's no MBC on it and i just let the solenoid/ecu control precontrol. The WG line is straight hose to the MBC.

 

I just got a chance to mess with the car this evening.

RECAP:

- i get good primary boost
- 4 psi WOT in neutral
- MBC on wastegate ONLY
- precontrol is still controlled by stock ECU
- my boost pattern is 10-5-8, so i get a large pressure drop at transition and it will not build full boost afterwards... would this indicate that the secondary is not producing any boost and the pressure is being fed back thru the secondary when the charge control actuator opens?
- i also sometimes have a hard time generating any boost pressure at all and the car feels sluggish

I switched the lines to the turbo control actuator and it caused no transition at all. I just switched it back after verifying that the lines were hooked up right to begin with:

I checked:

- pressure and vac resevoirs (good)
- put a mity vac on the turbo control and actuated it. (good)
- put vac guage on turbo control vac supply nipple under pressure tank. key on i got vac for a second then it switched it off.
- put pressure guage on turbo control pressure supply nipple under pressure tank. key on i got pressure for a second and it switched off.

each time i did key on key off i got pressure or vacuum reading for a second, then relay clicked and back to zero.

any suggestions? I'm considering going poor man's non-sequential for the time being.