Wastegate Actuator Issue

[Aphix]

I just hooked up my ported 14b with a 16g WG, car runs fine turbo spools good so I give it a little gas and whoa. I hit 20 psi w/ the MBC loostened all the way out. So I pulled the wastegate actuator line and hooked up an air compressor to check out if its working. The arm connected to the flapper only has about half an inch of travel, which is a whole lot less than my T25 actuator. Is there any fix for this?

 

[cruisintalonawd]

it is a real 16g actuator or an ebay one?

 

[Aphix]

I couldnt tell ya, this is how I bought it. My guess is its an MHI 16g actuator.

 

[cruisintalonawd]

Does it have a peice that you can "make" that arm longer or shorter

 

[JusMX141]

ALL MHI actuators open the flapper about 1/4"-3/8". This is what's so hilarious about guys that port the crap out of their housings so the flapper can open 90*.....it never gets close to opening that far.

There are two fixes:

1) The Peepers Mod. http://www.dsmtuners.com/forums/art...boost-creep-modified-wga-peepers-mod-how.html This is pretty involved, and it should be noted that Peepers wrote a blog recently confirming he was still experiencing boost creep even with a modded actuator.

2) Replace your MHI actuator head with a Garrett actuator.

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This type of actuator head has roughly the same spring tension of an OEM Mitsu actuator, but allows roughly three times the travel.

 

[jrohner]

Try it without the MBC, just the line straight to the WGA and see how it boosts.

 

[Aphix]

Just checked the WG. Heres the problem, I'm running a 7cm exhaust housing on a tubular O2 housing with a 16g actuator. So I dont think this is a flow issue. The actuator doesnt have enough travel to open the flapper up enough to properly vent. I took the WG arm off the flapper arm and zip tied the flapper open and there is next to zero boost. So I need to do the WG mod that justmx141 is talking about i think

 

[JusMX141]

Heres the problem.....the actuator doesnt have enough travel to open the flapper up enough to properly vent.

Right and wrong.

The flapper doesn't open far, but then again it doesn't really have to. This is the same actuator used on every 13G, 14B, and 16G DSM bolt-on turbo sold; yet boost creep seems to only be an issue on cars that are lightly modded and trying to run 15psi or so.

The problem isn't the wastegate- it's your exhaust. Your exhaust doesn't have enough restriction, so when the wastegate opens (no matter how far it opens) the exhaust flow will continue to pass through the turbine housing as there is not enough restriction to add pre-turbine backpressure. This is especially a problem on turbos using the Evo III 16G turbine housing as it steps up to 2.5" almost immediately after the turbine wheel, taking away additional restriction.

If you look at the profiles of most boost creep victims you'll see their mod lists all share one thing- a 3" downpipe. I honestly believe this is the root of all the evil. A 3" downpipe is just too big for the wastegate system to properly function on a 14B / 16G running 12-18psi. Once you step up to a larger turbo that is flowing more lb/min or even up the boost on your current turbo, obviously the additional airflow will create it's own restriction at the turbine housing so boost creep will be a thing of the past.


There are other things that can be done, but they will just mask the problem. Porting the wastegate hole and adding a 34mm flapper will often cure the problem, but if you ever want to run more than 20psi the actuator can't hold the flapper shut so you basically shot yourself in the foot. You can attempt to mod the actuator, but don't look for it to solve the problem until you add restriction to the exhaust system or run more boost.

 

[Aphix]

Damn I just set myself up for the worst boost creep ever it sounds like. The 7cm housing on mine is even evoIII 16g. I was wondering why the guy that sold it to me never mentioned a boost creep issue but I makes sense since he was running 23 psi. Thanks for all the good info jusmx141. I think until I start pushing 20 psi what I will do is make an adapter to make the flapper arm half as long, which should make it open twice as wide.

 

[JusMX141]

You'll lose leverage by doing so, but at lower boost levels the leverage required to hold the flapper shut isn't as crucial.


I think if you do something like that you'll be fine for now. You've already experimented running the wastegate actuator disconnected and it didn't creep....in extreme cases guys will build 10-15psi with the actuator disconnected and the flapper blowing in the breeze.

 

[Mr Peepers]

First I guess I'll describe my setup since it's what I'm basing everything off from. 14b with 7cm evo3 turbine and of course, 3" TBE with no cat. Instead of making the actuator open farther(MWGA), I put an adapter (http://i223.photobucket.com/albums/dd107/mrpeepers422/CIMG1217.jpg) that basically did the same thing by moving the pin to half its throw and doubling the flapper movement.

I haven't noticed much difference in ability to hold boost by essentially making the flapper arm twice as short. Creep on the other hand went from 25psi (at 5k, the worst) down to around 18-19 with the shorter flapper lever. I couldn't run more than about 16-17psi by 7k likely because of cams and the 14b running out of breath. Airflow was flat from 4.5k to redline, 24psi to 16 respectively; basically maxing out the 14b compressor. With the adapter taken off the boost taper was identical. I should also note that severity of creep was nearly identical whether the flapper was unhooked or the adapter on.

With the evo3 16g it was the same way. Thought I could keep boost from tapering off as much but it still went down to 20-21 psi by redline, with or without the adapter on.


Basically, moving the pin closer to the pivot helped creep noticeably but didn't seem to affect how likely the flapper was to blow open. My setup is ridiculously creep prone for some reason in the first place so it may be different for other people. I still creep to 18-19ish psi even with the flapper dangling open and about all the porting I can do to stop it...

EDIT: I guess my setup is just weird. If running with the flapper completely open yields almost the same psi near redline as with it hooked up, the tension holding the flapper doesn't really matter much in the first place. Either way, I think moving the pin on the flapper is a good solution, and not too hard to reverse if you need to. Another local has had success as well.

 

[Aphix]

Thanks for all the good info. Mr. Peepers your adapter looks nearly identical to what I had in mind. Hopefully I will have as good of results as you, I'll post up the results after I fab up an adapter.

What I did to hold off boost creep until then is adjust the wastegate actuator arm way out, so to give the flapper more clearance, consequently now I'm running with my wastegate leaking which makes it tough to build boost and still regulate. Hopefully the adapter will fix this.

 

[Scientist]

what about switching to an external gate mounted on the 02?

 

[Aphix]

I dont know how you would do it. The 14b is internally gated and the O2 housing is cast iron.

 

[DSMunknown]

what about switching to an external gate mounted on the 02?

The only way that would happen is if you got something like this or this and uninstalled the cast iron OEM O2 housing.

 

[Aphix]

Heres the finished product. Not too pretty but it gets the job done. I found a piece of scrap metal on my bench and went at it for about an hour. Basically this adapter mounts on the existing pin on the WG flapper arm and replaces it with a closer pin for shorter throw, so now I should be getting twice as much extension of the WG flapper. I cant test it yet with the car running because I sealed an exhaust leak and it needs to dry. But I hooked the WG up to the air compressor and it has nearly full extension of the wg flapper now.

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Sorry for the crappy picture I had to use my phone I cant find my camera or I would have made a video too

 

[Mr Peepers]

Nice. Looks like we think alike

Just make sure the new pin doesn't make the wga arm stick out too far, it wants to bind up a little and won't close the flapper right away. Make it so it just clears the old pin. Or, grind the wga arm down so it can't hit the old pin anyway.

 

[Aphix]

No problems with the adapter, but the creep isnt solved yet. I think I might end up doing some port work to the wastegate outlet. Otherwise I might end up putting a kind of restrictor in the downpipe to bring it down to 2.5" if that doesnt help.

 

[Aphix]

A little update, this car went through some shizz and I ended up slipping the timing belt twice in a row due to some auto tensioner failures. I fixed the engine, blew the transmission right outta the box so I threw in the towel since it was A/T anyways. I kept this adapter on the WG and it never caused me any troubles. Never saw boost creep from a weak actuator spring etc. And I did in fact get the boost situation under control (which I believe was caused from a custom exhaust setup that was full 3" turboback and just didnt quite build enough backpressure).

After some time off I'm back in the DSM game after missing the old girl so much. Just wanted to testify in saying that this option is tried and true in that it wont cause boost creep issues and does indeed magnify the WG actuators throw without adverse side effects.

In response to my above post, porting the hot side of the turbo completely solved my boost spike issues. I said "but the creep isnt solved yet" but should have said the boost spike isnt solved yet.