How can I test my wastegate?

[exile]

I am in the proccess of troubleshooting my uncontrolable boost. I am running a evo3 16g with the actuator that came with it. I tried using two MBCs.. one was an eBay controller that at lowest setting would start opening at about 10psi (I can tell because of the o2 dump) but wouldn't open all of the way until 20+psi. I ordered a Joe-P MBC from a trader and it's unscrewed ALL of the way and I'm not seeing ANY sign of it controlling my boost.

I was curious, before I try it.. I don't see why it wouldn't work but couldn't I techically connect my air compressor to the pressure source for my MBC and set the pounds to 10psi and see the wastegate start to open? Couldn't we adjust our boost that way as well? If it won't work please explain to me why because I thought it was a 'dumb' system it worked as long as it 'seen' pressure.

I just want to rule out my wastegate, it's the "stock" MHI wastegate and I think the spring inside maybe set higher? I should be able to take the actuator off of my t-25 and use that correct? I KNOW that one works great.

If I can't test it that way, what other way could I test it?

I've been driving this beast for 4 weeks without a MBC and I'm going to blow my engine if I don't get this fixed.

 

[djseclipse]

Just port the flapper area of the turbo, not just the inlet and outlet. My evo 3 is ported with the 34mm flapper and I dont see any creep. I have it set now at 15psi and it holds steady all the way to redline. If nothing else if you have the money go ahead and buy your fuel mods, cause these babies love 20 + psi.

 

[donmagicjuan]

I am in the proccess of troubleshooting my uncontrolable boost. I am running a evo3 16g with the actuator that came with it. I tried using two MBCs.. one was an eBay controller that at lowest setting would start opening at about 10psi (I can tell because of the o2 dump) but wouldn't open all of the way until 20+psi. I ordered a Joe-P MBC from a trader and it's unscrewed ALL of the way and I'm not seeing ANY sign of it controlling my boost.

I was curious, before I try it.. I don't see why it wouldn't work but couldn't I techically connect my air compressor to the pressure source for my MBC and set the pounds to 10psi and see the wastegate start to open? Couldn't we adjust our boost that way as well? If it won't work please explain to me why because I thought it was a 'dumb' system it worked as long as it 'seen' pressure.

I just want to rule out my wastegate, it's the "stock" MHI wastegate and I think the spring inside maybe set higher? I should be able to take the actuator off of my t-25 and use that correct? I KNOW that one works great.

If I can't test it that way, what other way could I test it?

I've been driving this beast for 4 weeks without a MBC and I'm going to blow my engine if I don't get this fixed.

It sounds like you're experiencing boost creep, not a faulty boost controller. EvoIII's are known to creep, especially with a free-flowing exhaust. Your best bet is to do as djseclipse suggested and port your turbine housing.

If you have a ball-and-spring MBC, you should be able to hear it start to leak by when you pressurize the intake system. These valves work by opening at a set differential pressure with respect to the stock wastegate actuator setting, not with respect to atmosphere. The stock actuator pressure for an EvoIII 16G is ~8 psi. So, if you have your MBC turned all the way down, it will open at a 0 psi differential, and control boost at 8 psi. It follows then that for a desired boost level of 20 psi, the MBC will open when the differential pressure across the valve is 12 psi. You should be able to see the actuator move when you press up the system high enough, but I wouldn't necessarily trust that method as the most accurate means to set your MBC.

If you want to confirm either the MBC or the wastegate as the problem, simply disconnect your MBC and run a vacuum line from the controller's boost source directly to the wastegate actuator. If you're not creeping you should see roughly 8-10 psi like this. A better alternative to test for creep, however, is to physically disconnect the actuator arm from the wastegate flapper. With nothing holding the flapper closed, you should see no more than a couple psi. If you see more than this, you have some porting in your future.

Finally, I'm pretty sure the stock actuator from your T25 will not be compatible with your 16G.

Best of luck!

 

[exile]

I'm sorry I didn't specify my turbo specs (because I didn't suspect the turbo) but I have an evo3 16g.. ported *everything* with the 34mm flapper and o2 dump to combat boost creep. I SHOULD NOT see boost creep from my desired 10psi to 20psi+ when WOT. If it's going to creep that bad then I need to decide on a new turbo setup.

Oh.. and fuel mods are coming *TODAY* =) That's mainly the reason I need this boost steady so I can tune and go to the shootout.

 

[daren_p]

You can't really set your MBC accurately by hooking it up to a compressor but yes you can veryify its operation by doing this. Hook the compressor directly to the WG actuator and slowly increase the pressure. The actuator should be fully extended ~ 13 psi or so. You can rule out the MBC being the issue but removing it from the system & hook the pressure source line directly to the WG actuator. With it hooked up this way you should see ~8-10 psi.

 

[steve]

I don't see why it wouldn't work but couldn't I techically connect my air compressor to the pressure source for my MBC and set the pounds to 10psi and see the wastegate start to open? Couldn't we adjust our boost that way as well? If it won't work please explain to me why because I thought it was a 'dumb' system it worked as long as it 'seen' pressure.

The factory procedure to test the wastegate actuator is to connect to the WGA nipple and apply pressure. Putting the MBC inline tests both but since you want to know if the WGA is working start there.

Steve

 

[kenamond]

I'm sorry I didn't specify my turbo specs (because I didn't suspect the turbo) but I have an evo3 16g.. ported *everything* with the 34mm flapper and o2 dump to combat boost creep. I SHOULD NOT see boost creep from my desired 10psi to 20psi+ when WOT. If it's going to creep that bad then I need to decide on a new turbo setup.

First off, do as donmagicjuan suggested and disconnect the WGA arm from the lever on the turbine housing, verify you can open the flapper freely with your fingers. Then do a test run at full boost and monitor your boost gauge. If you get more than a few psi, it's creep *period*. If it doesn't boost more than a few psi, it might still be creep (I'll explain below).

Depending how they ported your evo3, they probably didn't port the wastegate entrance much, and that's what you need to do if you're going to run moderately low boost on an evo3. The exhaust gasses simply can't make the bend and squeeze out the WG fast enough to control boost (i.e. bypass sufficient exhaust flow around the turbine wheel). Another problem with the evo3 is that the WGA doesn't open the flapper very far; the actuator arm throw is only enough to open the flapper about half way if that. So even if you do the test above and get a few psi boost max, with the WGA arm connected, it's holding the flapper half closed, which makes it much harder for the exhaust gasses to pass through the WG. In the test, the door could open all the way (no arm limiting how far it opens). If you do a search on EVOIII and Creep, you'll see MANYMANYMANY threads even with factory port jobs.

Oh.. and fuel mods are coming *TODAY* =) That's mainly the reason I need this boost steady so I can tune and go to the shootout.

If you get supporting mods to run 20psi, you may be able to dodge creep with your fuel mods. The evo3 WG seems to be able to keep up when you're flowing much more air (~20psi). You may be able to get around the creep issue if you just accept it, more or less, and the fuel upgrades are one necessary step making this possible.

 

[exile]

Yeah, I understand about the boost creep and trust me I've read a lot of the posts. I read that even porting most of this stuff doesn't do much. I figured the o2 dump would give me a huge advantage. I'm planning on running 18psi on the 16g and if I get creep at that point then the turbo goes right out the door. I have the box right here with the fpr, and pump. Along with Link I should be ready to go by Saturday afternoon. I'll keep you all posted for an update.

*Also: I removed the pin from the arm when the turbo was sitting on my desk for 6 weeks before I installed it (what else can I do with it ). So I know the flapper opens freely*

Thanks for all the suggestions and quick responses.