After installing a IX turbo + ported exhaust manifold + titek O2, I'm getting a lot of boost fluctuations at WOT. Tried changing recirc valve and tried bypassing MBC (going back to stock boost control), but it still does the same thing.

With factory boost control, at WOT, the boost spikes up to ~25 psi quickly, then drops sharply down to ~15psi. Sometimes it will spike a 2nd time and drop again, other times it'll slowly climb up to 17-18 psi after the first spike.

With an MBC, it'll pretty much do the same thing, spike up to 25 psi, then drop down. I can actually feel a SOTP loss in power when the boost drop occurs. On the drastrip today it almost felt like a bog.

Here's some video clips showing this. I'm at WOT the whole time that the boost is fluctuating:

stock boost control:
http://s132.photobucket.com/albums/q...t=a_stock3.flv

http://s132.photobucket.com/albums/q...t=a_Stock1.flv

MBC:
http://s132.photobucket.com/albums/q...ent=a_MBC2.flv

I suspect the wastegate is somehow screwed up. It seems like the wastegate initially stays shut (intial boost spike), then swings wide open (sharp drop in boost). This is causing wavy features in my dyno, and its killing my times at the dragstrip.

The turb was sent through the mail, so I suppose its possible that the WG was damaged.

I don't know much about wastegates, and I don't want to blindly replace parts. Any suggestions on how to troubleshoot this problem?

Thanx

 

Have you checked the preload on the wastegate actuator arm?

 

Check to see if the WGA is moving smoothly, you can pump air into it with a bicycle pump.

 

Dv?

 

Do you still have the factory lines in? Do you have an upgraded pill? Also is this the stock WGA? Sounds like you messed with that. That or you have a massive leak somewhere.

 

I couldn't tell you about the stock BCS system, but, since you first experienced the fluctuations, the creep, as well as the taper with the MBC still installed, then I would say that you need to increase wastegate preload in the order of an additional 4-6 PSI at least.

 

Looks like too much preload on the actuator. Does it do the spike even if you try to run wastegate pressure?

 

So I pump air into the nipple of the WGA? Then what do I look for specifically?

 

Be VERY careful with pumping with a bike pump. Too much pressure and you can kill the actuator fast.

I take it the actuator came with the Evo 9 turbo? Can you take a photo of how much preload you have on the arm? You can do this by taking the arm off the flapper and show how far the pin is from going in the hole.

 

Its the actuator that came with the stock ix turbo. I verified this w/ the prev owner of the turbo. I never really worked with wastegate actuators before....so I pull out the cotter pin where the arm of the WGA meets the flapper, and look for the offset? I can try tomorrow and get a photo.

Is the preload something that is adjustable?

Also, how hard is it to replace a WGA? Can it be done w/o pulling out the turbo?

 

The preload is adjustable you just turn the WG arm like you would a screw to make it tighter or looser.

 

If you have a tubular 02 housing or no heat shield on the stock 02 housing, it's pretty easy. If you remove the radiator fan, it's cake to get to.

 

Beware of messing up your radiator. A piece of cardboard does wonders to ensure that you don't inadvertently hurt something.

 

Since he states that his boost drops down to 15 PSI, then his WG must be preloaded to 15 PSI or less. This isn't too much preload when using an MBC. In fact, the WG's on the Evo VIII's often came from the factory preloaded to 14-15 PSI.

 

i agree with most. check the preload on the actuator. shortening the rod increases the pressure and lengthening decreases pressure.