Wastegate question/issue.....

[Big Bald]

So I am at the dyno yesterday, and the plan was to run 36-38psi. I have a Tial 44mm with a 1.4 Bar spring setup (Big + Small Blue Spring). When I turned the boost controller all the way up, I can only get 31psi. We swapped the one I had (Hallman ES) with another MBC (Hallman Pro) and I could only get 31psi out of that one also.

This is using only the side port on the gate. To get more boost out of the gate, do I need to start using the top port also? I know some people do it, but I was under the impression that I could achieve up to 40psi off of the side port only. I have no problem using the Top port, but I want to make sure I am not masking another issue. The Gate has a brand new diaphragm in it so I know that's not the issue.

So my question is for those running past 31psi, how do you achieve this with a mbc? Or do I need to look beyond using Hallman manual boost controllers?

 

[spinninfwdlaser]

Hallman boost controllers can go well over 31psi. Many people running big time drag cars use mbcs due to lack of complexity, and great response. Your MBC is not the place you are having troubles with at all.

 

[delta448]

Is your turbo big enough to flow the air required to get more than 31psi? If you are able to monitor boost and can get off the throttle quick enough to keep things together, you could always disconnect the vac line to the WG to see your max boost.

 

[turbo addict]

There are a coupe of different ways to do this. First BE VERY CAREFUL and watch the boost gauge and be ready to get off the throttle very fast.

Run a boost line strait to the side of the wastegate and run another one to the top of the wastegate. Now put the BC in the line to the top port of the wastegate and make sure that the BC is turned up as high + as it goes, in this configuration the BC will work the opposite of how it normally does. Now go and check your boost, to increase boost you turn the BC down to feed more pressure to the top of the wastegate keeping it shut, so - is more boost and + is less. If you do this and are still not making any more boost get back on here and tell me and I will tell you the next step.
I have done this many times with a hallman and other BCs.
(BC=boost controler)

 

[ThingyNess]

Generally speaking, you aren't able to raise the amount of boost by as much as you might want using only a boost controller. It's not the boost controller's fault either, usually.

If you want to make sure the boost controller's not the issue -- take it out of the loop. Just yank the vacuum/boost line to the wastegate and leave it off. Take it out for a spin, and watch your boost gauge carefully. If the boost goes higher than it was with the MBC cranked, then you know it's the issue. If not, the problem lies with the wastegate, which is likely having its piston blown open by the manifold back pressure.

Once the pressure in the manifold times the surface area of the piston (or flapper) exceeds the spring preload in the wastegate, it will open. If this is your issue, the fix is to use a stronger spring in the wastegate, in your example, say, something like 25-28 psi, to keep the piston from being blown open. Or, alternatively, get a more efficient hotside, either with a bigger A/R or bigger turbine wheel, to lower your exhaust manifold backpressure.

Edit: I just realized you were already using a pretty bloody big spring setup. If you want, add some shim stock inside the wastegate cap itself to add to the preload of the spring if you don't want to have to buy a replacement.

 

[turbo addict]

Generally speaking, you aren't able to raise the amount of boost by as much as you might want using only a boost controller. It's not the boost controller's fault either, usually.

If you want to make sure the boost controller's not the issue -- take it out of the loop. Just yank the vacuum/boost line to the wastegate and leave it off. Take it out for a spin, and watch your boost gauge carefully. If the boost goes higher than it was with the MBC cranked, then you know it's the issue. If not, the problem lies with the wastegate, which is likely having its piston blown open by the manifold back pressure.

Once the pressure in the manifold times the surface area of the piston (or flapper) exceeds the spring preload in the wastegate, it will open. If this is your issue, the fix is to use a stronger spring in the wastegate, in your example, say, something like 25-28 psi, to keep the piston from being blown open. Or, alternatively, get a more efficient hotside, either with a bigger A/R or bigger turbine wheel, to lower your exhaust manifold backpressure.


Edit: I just realized you were already using a pretty bloody big spring setup. If you want, add some shim stock inside the wastegate cap itself to add to the preload of the spring if you don't want to have to buy a replacement.

That is what the top port is for to increase the pressure on the other side of the diaphram you don't need a bigger spring the boost will hold it shut.

Again you don't have a rig the wastegate, it is designed to take boost on the top of the diaphram to hold it shut. don't shim it. If you do what I said and you still don't get any more boost then come back on here and I can tell you how to reroute the lines a different way that will make as much boost as the turbo will make.

 

[Big Bald]

I can finally get back on the board.

I can boost past 31psi with the WG disconnected and taking the MBC completely off the car. This means that somehting is going on with the MBC. I called Hallman and they are going to mail me a heavier spring to use and try. If that does not work then I will try hooking up the MBC according to the instructions tial proviced with their WG. It is not blowing open under high boost like I originally thought.

I honestly hope the heavier spring fixes the issue. However, I know a couple other who I have spoken too that uses the mbc with a top port and are able to run above 31psi. I do not want to do that if that is only a band aid....but i will if that is the only option I have.

 

[ThingyNess]

Well if you can boost past 31psi with the wg disconnected, then as you say, the MBC is the issue. The heavier spring should fix the problem nicely.

 

[oldman]

Damn, talk about post whoring, how many sites did you post your problem on.

 

[Big Bald]

I see you get around. Spring should be here any day now....i still find it funny that Tial and Hallman gave complete opposite answers from each other.

 

[oldman]

I see you get around. Spring should be here any day now....i still find it funny that Tial and Hallman gave complete opposite answers from each other.

Honestly this was an easy problem to diagnose, I don't know exactly what each of them said to you but anyone with fair amount of knowledge on turbo systems would have immediately suggested test run with both fittings open. The guy on Talk got you running in circles for an extra week, I'm glad everyone on this thread was pretty much right on as far as troubleshooting is concern.

 

[Big Bald]

I prefer to gather ideas from others with far more knowledge then I may have. I was genuinely wondering if I was trying to run high boost incorrectly with the way the mbc was connected.

The guy on Talk is not the only one who suggested running the mbc that way as Tial said the exact same thing. I however learned somehting new about MBC's that I did not know.

 

[oldman]

My point is, if you would have taken mine advice on talk and Jeff's advice on Link and immediately report back the result of the test run, you would have been talking to Hallman the next rather than a week later. With no boost reference to the wastegate, if you can boost over 31psi it's the MBC spring, if you can't is the wastegate spring, it's that simple. If the result pointed to the wastegate spring instead then we can talk about how to utilze the top port to help you hold more boost.