Can't Get the Boost Lowered to 15 psi ?

[Tim Cucci]

I have a fairly new TA/49 with V4 I/C and THDP. I also have a non heavy duty wastegate actuator. I also have just done a rebuild (400 miles). I have ported heads also. I was bypassing the W/G solenoid and spool was very slow but I could controll boost around 15 psi but it was slow spool. I now have hooked up thru the solenoid and spool is very fast but I can't get it down below 17-18 psi. This is a brand new solenoid. I want to utilize the solenoid but can't adjust the boost lower with the actuator rod.
I am running a Thrasher 92 chip which is great by the way.
Anybody got any suggestions or seen this problem?
Thanks
Tim

Oh yea I can hear a spitting type noise when boosted high like the solenoid is relieving . I never heard this with the sock turbo.

 

[Richard Inglett]

I guess I'll Start Some Ideas

Tim,

A couple of months ago you offered to let me borrow your valve spring removal tool. Since we haven't met, it was quite a gracious offer. Thanks again and by the way, I really like the PTE 210/210 billet roller cam. Upper end pull is back and I don't have to worry about wiped-out cam lobes anymore.

Regarding your boost control problem, first question is does your turbo have the waste gate hole enlarged. Should have a diameter around 1-1/4". Second, are you getting crazy knock retard numbers when you hear the popping. By crazy, I mean in the 20 and 30 degree range.

This is just my theory based on observations of what false knock did in my case. On-line experts may or may not agree but like I said, it is a theory. Therefore, hope following gives you some ideas. Seems that enough knock retard causes the exhaust gas temperature to rise which in turn increases the boost. Increased boost then causes more knock retard so the upset condition keeps feeding itself. Result... popping spittting noise you reference. Please keep in mind that I have a Racegate to control boost so I do not have a solenoid or actuator. However, you may have problems with your actuator, have a leaking vacuum hose or have something that is causing boost control problems.

Hope this helps.

 

[UNGN]

I would have to go with the orifice in the "Y" being too small. Have you recently changed this? You may want to try a "Y" from the autoparts store without an orifice in it to see if this lowers your boost. A small orifice can raise the boost by almost 5 psi vs. no orifice. If that lowers the boost, ream your "Y" orifice out to .050"

A Thrasher 92 will always spike in first gear to a couple pounds over the set boost level, that's just the way they are. With ported heads, you need to start thinking about an injector upgrade, anyway as even bluetops won't keep up with the flow potential.

 

[tc86gn]

I had the same problem and thanks to UNGN's advice I fixed it. Thanks UNGN!!