Dan Balassi

Just an FYI for all interested parties.

After testing the wastegaste operation on my 2nd gen anniv turbo, it seems the wastegate is designed to close under vacuum (idle and low RPM's), but as soon as the intake pressure comes up to atmosphere or 0 psig, the wastegate goes full open and stays that way regardless of boost levels.
So in order for a boost controller to have any effect, it must be designed to hold a vacuum on the wastegaste as the intake pressure is rising.

This may not be news to some, but I've been trying to setup a manual boost controller on this car and it will not work!

Wankel7

So if the wastegate doesn't move from wide open how does it control boost?

How much pressure did you feed it?


James

M's

maybe your actuator is broken

The Unsent

i'd say its the actuator.

Rob500

You don't need to hold a vacuum - just something less than the wastegate spring requires to open. The wastegate actuator is sprung at about 5 psi. But remember you're not going to be able to reduce boost.

Rob

Aaron Cake

iTrader: (1)

Your wastegate actuator is broken. It should not be open full at 0 PSI. It should start to open around 4 PSI or so.

Rob500

Aaron,

In a previous post he said he had 14psi boost in 4th gear. Either he has tremendous boost creep or that actuator is not opening. Maybe he doesn't have the wastegate plumbing connected properly.

Rob

Aaron Cake

iTrader: (1)

Regardless of what he is boosting, the actuator should not be opening the wastegate at 0 PSI. If he is experiencing 14PSI with a wide open wastegate, he has too much exhaust/intake and needs to port his wastegate at the very least and VERIFY that the actuator is working properly.

Dan Balassi

Yes, I am getting 14psi in 4th gear. I actually disconnected the wastegate actuator rod, and can feel the spring force still there. I can push the rod back in against the spring with my hand. At idle, the vacuum on the wastegate pulls the actuator rod back in all the way. This certainly must be "closed" position. While idling, I pull off the vacuum hose, and the wastegate actuator rod goes all the way out via the spring force in the actuator. Its only my opinion, but I think the full open wastegate is limiting the max boost, and that this number varies depending on exhaust system backpressure, turbo etc.. which may differ from car to car. I can't find any info on the factory "pop off" valve or if there is even one there. One other thing, I drove the car with the wastegate "closed" or what I think is closed, and got a lot of boost(14psi) very quickly without full throttle as you would expect if the gate was closed. The car seems to be running well. I have 105Kmiles on this motor, with Racing Beat Exhaust, Fuel Cut controller, Bonex intake with custom cold air intake, and Walbro GS341 fuel pump.

Has anyone else actually checked the wastegate actuator? and does what I'm saying make any sense?

Rob500

Aaron,

Absolutely! I agree that wastegate should not be opening at 0 psi.

Rob

Rob500

Dan,

The normal position is closed. It should require pressure to open it.

"but I think the full open wastegate is limiting the max boost, "

Your wastegate is certainly not limiting max boost.

Dan Balassi

If the wastegate being open is not limiting boost, then what is?
Can anyone confirm or deny my testing on the wastegate actuator?
At idle - actuator rod pulled all the way in.
Pull off vacuum line at idle - actuator rod all the way out.

Manual also says to check that its pulled in at idle to verify proper operation.

Rob500

Your understanding of how the wastegate works is incorrect.

With the vacuum line off, at atmospheric pressure, the actuator spring holds the wastegate closed. Pressure is required to open the wastegate.

My understanding of what you are seeing is:

You have pressure trapped between your MBC and the actuator. When you remove the pressure signal line you are actually releasing that pressure and the valve is closing. Not opening. Believe me I've seen this happen.

To your comment about the wastegate limiting your max boost:

If the wastegate is open (and I think it probably is) your boost is being limited by your intake, exhaust and the turbo itself. 14 psi is an indication that you are beyond the capabilities of your wastegate to control boost.

Rob

Aaron Cake

iTrader: (1)

That makes no sense. The wategate actuator is pressure operated, not vacuum operated.

If you can easily pull the arm out with your hand, then it has the wrong spring or a broken spring. The spring is actually quite strong, and takes EFFORT to pull with your hand (especially with your arms crunched in the engine bay).

If you are PUSHING something, then you are pushing the twin-scroll actuator.

Dan Balassi

Is it possible to get this connection between the wastegate and the actuator backwards? I did have the car worked on a few years ago to remove a broken exhaust stud, and they took all this stuff apart and put it back together.
I hear what you guys are saying, but what my car is doing makes no sense. When I disconnected what I think is the wastegate actuator rod from the gate, I wired the gate "closed"(at least what I think is closed, which is the position with the rod pulled all the way in) then I drove the car, and as soon as I gave it some throttle(not even hard throttle) the boost instantly jumps to 14psi and I quickly let off the gas to stop it. This response sure does act like a closed wastegate, but if that is true, then the wastegate actuator is either connected wrong, or broken. From underneath the car, the wastegate is on the bottom/engine side of the turbo, and has a metal tubing line going back and up to rear of the engine compt, with a short piece of factory vacuum hose connecting it to a metal tube on the intake? If anyone has a picture, it will in be worth a 1000 words forsure.....

NZConvertible

You had me a bit stumped on this one, because I can’t see how even a broken wastegate actuator could do this. Sitting at my desk this morning it clicked (no idea why). You’re not watching the wastegate actuator, you’re watching the twin-scroll actuator! And it’s doing exactly what it’s supposed to do. Looks like Aaron spotted it too.

The wastegate actuator is the smaller of the two actuators and is connected to the wastegate flap in the turbine housing, whereas the twin-scroll actuator is connected to a flap in the exhaust manifold.
Not connected to the twin-scroll actuator it won't...
It sounds like you have the same problem that afflicts all modified FC’s with stock turbos: boost creep due to a very small wastegate port. Running that much boost is not a clever idea, because neither the stock intercooler or the turbo itself can do it safely or for long. At least you've got a decent fuel pump, which has probably saved your engine. Get the turbo off and port the hell out of the wastegate port. The bigger the port the better the wastegate can control boost. You can port past the edges of the stock flap, but this will slow the response of the turbo. It’s a much better idea to fit a much larger wastegate flap and enlarge the port to suit the new flap.

Modifying the turbine housing and downpipe so the wastegate dumps into its own separate pipe is another way to increase wastegate flow and reduce boost creep.

Dan Balassi

Thanks, I'll take another look this weekend. What boost level do you think is a safe max?

NZConvertible

Personally I wouldn't go past 10-11psi with the stock turbo and intercooler.

Dan Balassi

You were right. I had the damn thing hooked to the switching solenoid, not the wastegate. Since my boost is already plenty high, Do you think there is any advantage to keeping/using the boost controller?
On another note:
Do you know where I might find a short piece of 3inch flex hose for my custom intake tube?