just get yourself a boost controller. I have one made by blox and it kicks ass. you can turn up the psi too 55 if you want to

tanx 4 reedin teh thred.

As for your problem, I think at this point, we need some pics of the specific parts. Something that you think is fine and normal may actually be a problem, however unlikely it is.

One thing I havent seen mentioned is the boost controller spring. Home depot MBCs are definitely the best thing short of an EBC, which I personally dont care for much anyways...but they still have to work to begin with.

Outside of that, I have no idea. Wouldnt hurt to post pics though :P

stfu dumbfuck queer.

Hmm, today I experimented with the MBC I got from Egay. I run a 14psi actuator. Withouth MBC I spool around 3300rpm and have a nice 14 psi boost, no overshoot. I run the MBC on minimal and I spool by 3100-3200rpm but it will overshoot if I apply throttle quickly from an off-throttle situation. My basis conclusion is that the MBC cannot bleed quickly enough... so I will probably revert to the simple 14 psi wastegate actuator run of the compressor housing and be done with it for this year.

Can I tune a helper spring to get me 13psi without an MBC? I'll take it right out if I can and suffer the 100rpm hit on spool.

I believe this is the cheap way SRT4 guys and such raise boost in their cars. There's an assortment of info floating on the internet about "wastegate shimming." It works, but its cheap and really not the way to go.

I have been trying different things for the past couple weeks and have some conclusions and I'd like some advice on what to do to fix the problem.

1. When my boost signal is sourced just before the throttle body and run through my home-depot MBC, the boost spike is very severe.
2. When boost signal is sourced just before the throttle body and run directly to the the wastegate actuator, there is boost spike but it is not as severe as with the MBC.
3. When boost signal is sourced from the compressor outlet and run through the MBC, there is about the same amount of boost spike as with scenario 2, but I get boost drop as the RPMs rise.
4. When boost signal is sourced from the compressor outlet and run directly to the wastegate actuator, there is no boost spike, but there is boost drop with RPM rise.

My conclusion is that as the turbo spools, it pressurizes the charge piping and by the time the pressure wave makes it to the throttle-plate, the first part of the pipes are overcharged. The overshoot is much worse at higher RPM, and nearly non-existent at lower rpm.

I have pretty much concluded that I need to purchase a real MBC from ebay or something, and that should fix the MBC-related spike, but how do I fix the drop with RPM without introducing overshoot based on the pressure wave?

I hope this makes sense outside of my head...

Good findings, and somewhat to be expected. I havent dont preTB yet, only comp. housing. You didnt log your 4 tests now did you?

I have some logs of 4th and 5th gear runs and i THINK my boost drop off is minimal... how much do you see? I run 14psi/195kpa.

I don't have any logs of any of these runs, so I don't even know how much boost drop off I have. I know there is some, and it's not negligible, but it is probably only a pound or two.

Do you have a fair amount of length in your MBC to WG signal lines? If you do, try to shorten up the signal lines so there's less delay for that air to reach the WG. I reduced my boost spikes by about 1 psi by cutting about 2 ft of excess tubing.

The signal line runs straight across from the TB nipple it's sourced from (in the charge pipe), to the MBC, to the wastegate. The first line is maybe 2.5 feet long, and the second is maybe 8 inches.

Just read through your thread again and don't see any mention of adjusting the actuator arm itself for preload. Is it adjustable? Every actuator I've had responds dramatically to the adjustments - not that it provides stable boost, but always shows improvement over a first try fitting.

I don't think it's adjustable. How would I find out for sure?

Most if not all "new" internal wastegates come with a threaded actuator arm nowadays. Theres a retaining nut on it, usually closer to the wastegate diaphragm.