Alright, so about 4 days ago my car was running fine (15 psi on S20G). I took the car out last night, and did a few pulls 1st-4th and i was only hitting 10 psi 1st and 2nd and just barely was getting 12psi in 3rd and 4th. My wastegate is set at 10psi.

My MBC is pretty old, and could this possibly be my problem? I also did a boost leak test, but for some reason the boost gauge in my car wont show any pressure being built (normal?). I did find a small leak-using some soapy water-at the BOV, where it connects to the IC piping, its not HUGE though. To ease you, yes, I have searched. Could the leak at my BOV have been there the whole time but I just never noticed it, or is it possibly new and causing my problem? Is it possible though that I just need a new MBC? What seems more plausible?

Any other suggestions?

it'd say you have a big boost leak and just haven't found it yet.

you might wanna check where you tapped into for your boost gauge... you should be getting a reading while doing a boost leak test.

Found 2 boost leaks today. One at the BOV where it screws into the IC piping, and another at a coupler on the IC piping down below. Fixed them both, still have to give it a good test run though!



edit: Alright so i just went out and drove, i was hitting the same boost levels though. I dont know what else to do, except for try a new MBC...?

you should verify that your boost gauge is opperating correctly. borrow one from someone and hook it up in place of yours. I would also recommend trying to hook it up somewhere else just to make sure that anything else isn't interfearing with your readings and also check the connections and lines for any kinks or cracks. if you end up with the same results then I would also recomend looking at the connections of your turbo manifold. it's possible for the gaskets to leak only when in boost and release enough energy to act as another wastgate. also look at the valve in your wastegate, look carefully at the seating surfaces and make sure that they havent burned away. wich could lead to finding other underlying issues.

Alright, the past few hours I have done a couple more things. First off, I did another boost leak test, and it came back the same with nothing bad.

So after doing a bunch of different tests with the MBC and boost leak testing, my friend and I decided to unhook the vac hose from the wastegate and go out and go VERY easy on the car to see if i could get over ~10psi. I went out for a drive, and the same thing happened, only 10psi. Did I unhook the wastegate hose correctly (just simply took it off and left it hanging off and plugged the other end of the hose where it connected to my MBC.)? Is my wastegate stuck open and causing me all this? If so, how do I check to see whats exactly wrong with the WG, and how will i (most likely inevitably) fix it?

P.S. It is an internally gated S20G

Well, I found the problem.

I was completely stumped. I got a new wastegate actuator and it still did not fix my problem. I ruled out boost leaks. So I decided to check my catalytic converter to see what condition it was in, and it is just dead. I was running to rich for to long, bad idea. So, after going out and test driving it to see how it drove without the cat, i gave it some gas in third and got to 20 psi pretty quickly! I forgot that through all my MBC tests of tightening it to see if my MBC was my problem that I had left it all the way tightened.

So, now I need a new 3" cat (staying legal ;)) I am glad that I found my problem though :)

Anyone know of a quality hi flow cat 3" In, 2.5" out?

the only one I have seen so far is this one:
http://www.modernperformance.com/product_info.php?cPath=230_234&products_id=1254&osCsid=f37d6cba8172d3ce35880c0361184324


hope it helps.