Out of control boost spike!
 

just redid my whole setup. use to have a 60-1 with an ebay 50mm wastegate. I could not get the car to spike anything less than 17psi.

Now i have a gt4088 and got a precision 46mm wastegate set at 7psi ..

Went for a drive and got into boost . ( a big BANG came and i saw 24psi.)


The wastegate is hooked up to the side port to compressor housing as per instructions.


why am i having these issues??

i cant keep the car on low boost. im about to lose a motor over this ..

I have my boost controller turned off and the line is not hooked up to the wastegate.. so the boost controller is completely isolated from the situation.

any ideas?

If you heard a "Big Bang" then something broke... I would take it out the wastegate and inspect it (maybe the diaphragm tore). Also check the vacuum hose going to the gate and verify that it is connected to the correct port(s).

THis is hopw my simple mind sees your prob.

You ALREADY had boost creep problems.
BIgger TURBO. SMALLER Wastegate. = more boost creep..

7psi spring on a GT40. you better have twin 46mm wastegates for that...

how about a 60mm wastegate with a 13psi spring

found the problem ...

but lost my motor last night on that spike...

That sucks... what was the problem?

the wastegate had a third fitting that i didnt realize needed to be capped.

It has two side ports and the top port..

Im use to having the one on top vented if not using a boost controller and i thought the side one would be the same way.

but found out they were connected and instead of the gate actually seeing the boost so it could open it bled out the other side of the gate.. I installed the provided cap and bench tested the wastegaste and it opened .

So it was my fault for not realizing it prior to running .. SO time for a rebuild and now i know what needs to be done.


compression results were 95psi on 3 faces in the front rotor and rear rotor had i 75 psi spike and the other 2 faces were in limbo..

Gotta research everything before you do that haha I'd refuse to drive my car if I had a spike that large until I found the problem.

Sorry to hear about the motor though man.

its all good .. the car was tuned on the 17psi spike .. held like that for 3 years.

but the reason it wouldnt go lower was the shitbomb ebay wastegate.

i bench tested it with my compressor and even with a 7lb spring it would open at 16psi..

Now the precision will open at about 6 psi. Too bad i did all this after the motor is toast.

Saving for my new shortblock now.

Wastegate PLACEMENT is a whole lot more important than the size of the wastegate! I run a pair of TIAL 44's with my GT45 , boost remains at the gate pressure of12psi whenever it is asked to. Once the signal line to the rear gate came loose , so that gate stayed closed all the time , and I could not tell since my boost was still at 12 psi up to the rev limit!

Hmm my buddy is running a egay WG and it's holding his boost to around 15 psi pretty well on his BP w/ T70 setup.