I recently installed the 10.5 hotside on the car, and was pleasantly surprised to see it hold 25 – 26Psi all through my fourth gear pulls (with good race fuel).
Q: Is this everyone else’s experience with the 10.5 hot side?
Nevertheless, this past weekend it started dropping boost from 25-26 to 21Psi. My wife races the car regularly and she complained that the A/F readings were reading too rich ... and this was when the air temps were dropping from 90+ to into the 70’s ... we were doing an afternoon/night event ... so I was expecting the opposite to occur. A quick test on a near by road showed me the boost drop issue (like when the hotside was stock).

I did a quick and dirty boost leak test last night on the car, pressurized the system to only 10Psi in the hopes that it would be an easy find. Only thing I found was a leak at the throttle body, a reasonably noticeable leak that I could not place my finger on (literally). Came from the little black plastic unit on the TB, the one that the throttle cable hooks to. If I moved it a little then the sound of the hissing changed (again noticeably).

So my questions are:
1. Can this little leak (tested at only 10Psi) at the TB actually be a responsible for my drop in boost? And if so, how would I address it?
2. Do I need to run more air into the system to check perhaps the BOV (which is an adjustable APS recirculation+venting unit)?
3. Could the crappy weather be hurting me that much, even though my wife had gone almost 3 tenths quicker in far hotter weather (St. Louis a week back)?
4. I run a ProfecB (black with dials) on the car, could that be the issue? Should I just get a manual BC? I recently changed the houses running to the actuator. I also double and triple checked the dip switches on the back). Maximum boost has always been 25-26 Psi.

Any help in relation to this would be appreciated. Thanks.

 

personally i would do a pressure test again but at higher psi. i usually use my compressor and put it to about 30-40 psi and you will surely find where it is at if there is one. also use some soapy water in a spray bottle. this will come in very handy. is the part you are referring to have the spring on it that goes into the tb for the butterfly valve? good luck.

 

lil off the topic, but where do you tap in for pressure testing? I was thinking to put the air through the intake (removing intake and making a fitting to get in the 3inch opening) and pressureize it that way?

 

I did exactly that, but didn't see any bubbles anywhere.

That's exactly where it apears to be leaking from ... if i jiggle the spring, the tone of the hissing changes.

I tap in at the turbo inlet side ... I wanted to test the entire system. I suspected the APS dual vent BOV, but couldn't pressurize more than 15PSi cause my homemade connector kept blowing off. But thanks, I will definitely leave that option open.