Ha ha, I double checked that the other day. It's connected to the side port.

 

Did you change the air in your tires?

I'm out of thoughts on this one... got me swingin...

 

Well 87944turbo is sending a couple MBC's my way to test out so I can see if the LBE is the problem. Anybody think it could be the cat? Any other ideas?

 

If it is the same cat you used with the APE chips I don't see how that could cause the 'new' issue. It's very unlikely that new chips could make your boost fall off. Do you have a A/F meter? I'm still thinking vacuum line leak, especially with your dual port configuration.

 

I don't have an A/F meter. I'm pretty sure that I've gone over every vacuum line and tee and replaced the ones that looked bad.

So how would the boost fall below 10.3 psi (the Tial spring pressure) if it was a vacuum leak? I definitely think that I could have a leak but wouldn't the Tial spring pressure keep the boost above 6 or 7 psi? Am I not understanding how things should work?

 

Well, with a leak two things are happening. First you won't be pushing with the spring on the Tial as hard as you should under boost, but as you suggest the spring 'should' hold. But secondly you would just be loosing boost. Since boost is not linear your loss could very well be at higher rpms.

 

You may want to take a look at this link. Does a good job of illustrating the relationship between boost pressure and exhaust pressure which combine to open the wastegate.

 

1) Here is an easy way to test the cat. In nuetral, rev up your engine to approx. 2,500 RPM, and hold the RPM steady there for this test. Note the highest vacuum reading, but most importantly, note if holds steady. If it is not steady, if vacuum decreases, then you have some exhaust obstruction, either a collapsed pipe, a bad, cat, or bad muffler, or....

2) Did you check if the BOV is in good condition?

3) Did you check that the wastegate did not burn through a gasket, or if the bolts got loose and is leaking valuable exhaust pressure to the turbo?

4) With a 10 psi spring, you should be able to run without any MBC whatsoever and be able to hold a maximum of 10 psi of boost.

5) Lastly, if you want to run 15 psi of boost, you MUST run the wastegate in dual port, the second port helps keep the wastegate closed until it reaches boost pressures above what spring is rated at.

 

MAKE SURE YOU TOOK THE JET OUT OF THE BANJO BOLT!

 

I got a new spring from LBE once, they said it's rarely the cause and it wasn't. Check your hoses, top and bottom.

 

Thanks for the replies.

- The original banjo bolt is in (no jet)
- I'll try the cat test as Trucho suggested
- Checked BOV, great condition
- Wastegate looks great. My mechanic modified the stock bracket to use with the Tial so it has some support. All bolts are tight. I have the copper gaskets.
- I'll give it a shot with hooking it up in dual port mode

Any more ideas?

 

Just did the test that Trucho suggested. The needle is completely stable. No wavering what so ever.

 

is this an 86 951 and if so did you replace the venturi? I replaced all the vacuum lines also but still have a huge leak under the intake somewhere that I suspect is related to the venturi lines.

 

You do NOT have to run in dual port mode to run 15 PSI! I am running single port on this same WG and have my boost set at 17 PSI. It is rock solid. There is debate as to whether dual port or single port gives quicker response. Once I get a few other issues out of the way, I'm going to do some logging both ways and see what I find. It will be awhile though as we are buying a new house and that, unfortunately; takes priority on time.

 

Check your bigger hoses and lines. They can easily blow a leak under higher boost and then have the vacuum suck them back closed. I've had this happen on my BOV. Came loose, good idle vacuum but would cause similar higher boost let down. When the system went back to vacuum it would suck the hose back on and seal until the next big boost.