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I HATE to make another post like this, but I am pretty frustrated. My car is only boosting 7 psi (spring pressure). Here are the details:
Set up: simplified sequential
PowerFC
AEM Truboost electronic boost controller set up like version 2
On a coldish Saturday morning, I do the first pull out of my neighborhood and the car rockets off to 22 psi I stop it before any damage occurs. I pull onto the highway and again runaway boost, this time 17 psi. Kinda scared me except for the fact that my knock sensor on my PFC showed only a value of 17, which is low/good for my car. I shut off the boost controller and drove it slowly the rest of the way to work, being careful to not go into boost.
12 hours later I get off work, it is dark, I am exhausted. I pop the hood on the car, thinking maybe the hoses to the wastegate actuator popped off and that is why I was over boosting. Everything looks fine. I drive the car home with the boost controller off, not wanting to deal with it. The car drives fine at 7 psi on spring pressure.
The next weekend I decide to take the car out with the boost controller turned on. Even with it on, it is still boosting to 7 psi. At this point I assume it is the mac solenoid. I installed a new mac valve and nothing changed. I tested to make sure the controller is proving power to the solenoid and it reads 12v. I adjust the opening pressure on the boost controller (some controllers call it gain) and I can notice a difference in my spool speed. I am then thinking maybe my actuators are stuck open or some weirdness is going on with them. I hooked them up to my air compressor and I could hear them open and close. Last thing, I visually check for boost leaks. I cannot find any.
Any suggestions? Tomorrow I am going to pull the uim and look for vacuum leaks or any weirdness.
You may be too conservative with your start point on the boost controller after your over boost. I don't know how your particular boost controller is but many have a 0-100 settings of duty cycle and you really get absolutely nothing until you get to like 30 or 40. It's typically worth going up in steps of 5 until you start making progress.
Could also be with the overboost you popped a boost leak somewhere.
You may be too conservative with your start point on the boost controller after your over boost. I don't know how your particular boost controller is but many have a 0-100 settings of duty cycle and you really get absolutely nothing until you get to like 30 or 40. It's typically worth going up in steps of 5 until you start making progress.
Could also be with the overboost you popped a boost leak somewhere.
Dale
So I set it back to its original settings before the overboost and got nothing. I talked to Jimmy today and did a boost leak test on the car with an air compressor. I could not find a leak. Maybe uninstalling and reinstalling the intercooler piping fixed it? Waiting on a new pulley kit to come in before I put the car completely together and test drive it. Hopefully will be ready by Sunday and I can play around with the boost controller some more.
So I did a few more boost test on the car using an air compressor and a pvc end cap. I could not find any leaks. Also tried the old trick of spraying brake clean around areas where there could be a leak to see if the idle would raise.
I did kinda what Dale said and raised the duty cycle of my boost controller to see if I could get any response. With it turned up pretty high ~75% I am able to get the seconary turbo to boost up to 8.5 psi above 5k rpm heading to redline, but the primary turbo stays at 7 psi. It is like the car is falling on its face and then once the 2nd turbo kicks in, it takes off.
My hunch is that something with the actuators is out of wack. I can visually see the that waste gate actuator rod is connected. I thought maybe the nipples around actuators are leaking or sticking open, so I hooked a might vac up to them and they were able to hold vacuum.
At this point I am 100% stumped. I admit that I don't know enough about this car's turbo system, to even know where to look next.
I've never run that method of boost control with stock twins, but I did a little poking around datalogging the stock ECU outputs before switching to a standalone. The Wastegate solenoid is held around 90% duty cycle at low RPM in primary-only mode, and the Precontrol solenoid duty cycle controls boost. It's set around 30-40%, from what I remember. If you do 30% to both solenoids at low RPM, I suspect the wastegate will bypass too much exhaust gas for the system to feel responsive at low RPM.
I'm not familiar with the PowerFC, can't you configure it to control boost using the stock solenoids?
Make sure you didn't do something stupid like I did and have the wg controller plugged into the pre control solenoid or vise versa. I was boosting off the spring and getting a normal transition and the car would take off with the secondary. A couple times it boosted higher, but it was basically a bit erratic. I have no damn idea when I even did this.
I solved the issue! Wow I feel like an IDIOT (learning is occurring). My AEM Truboost is broken. Driving the car around today I thought, "Is there even a difference when the controller is on or off?" Nope. So I went out and got the cheapest manual boost controller I could find and rigged it up. Sure enough, I got boost at 11psi.
Even with a new MAC solenoid and my Truboost registering that it is connected and powering the solenoid, there is something in it that is not causing it to actuated the solenoid. I will be calling AEM tomorrow morning.
11-24-21, 10:44 PM
