boost prblems cant figure out

[zrk666]

my profile is up to date! i was getting on my car so i could run 15psi becuase i had it set for 10. i was using a different boost controller before runing 10 but when i switched it would go to 15 the drop off to 11-12 psi. the drop would occur when the car hit 15 and then a second or less it would then drop. my question is that the wastegate is to big, or can it be the MBC?

i havedone booost leak test- nothing massive to where it wuoldnt drop that much.

i didnt blow any hooses or short anything out it just wouldnt hol 15psi.

 

[RossY]

I would say either the boost controller or the wastegate. Check your boost controller first since the problem started when you switched the boost controllers.

 

[oldman]

1. Which brand/type mbc,both old and new, and were they hooked up the same way? Include any changes before and after the mbc install.

2. Are you sure you're not set at 12psi while spiking to 15 instead of setting at 15 and dropping to 12? If you're tapping off the BOV line, try switching back to the J-pipe nipple and see if it holds at 12psi.

3.

i havedone booost leak test- nothing massive to where it wuoldnt drop that much.

Either you have leaks or you don't, if you know you have leaks, fix them. How much pressure and for how long was the system holding during the pressure test?

 

[ddavisaf]

Exactly, a leak is a leak. First order of business is going to be fixing those leaks. With a good boost leak test to go off of (holding 20 psi for a minimum of 30 seconds) we'll be able to troubleshoot the problem more accurately.

 

[zrk666]

1. Which brand/type mbc,both old and new, and were they hooked up the same way? Include any changes before and after the mbc install.

2. Are you sure you're not set at 12psi while spiking to 15 instead of setting at 15 and dropping to 12? If you're tapping off the BOV line, try switching back to the J-pipe nipple and see if it holds at 12psi.

3.
Either you have leaks or you don't, if you know you have leaks, fix them. How much pressure and for how long was the system holding during the pressure test?

1) the brand and type of the MBC of the one i am using is unknown it came with the car. the one my buddy has is the joe p. they were both hooked up the same way i would post pics but my digital camera is no where to be found. they were both hooled up like the gt50's from the nipple of the compressor housing spliced into befor going to the wastegate.

2)i am sure it is set for 15 because fully spools at the same rate to 15 then holds for a second or so then dies to 12. it will hit 15 then hold for a little while then slowly drops to 12. hard to put in words.

3) i know my biss screw leaks a little but havent done a recent boost leak test. will try the problem today or twomorrow.

 

[oldman]

Let's do a simple test run with nothing connected to the wastegate actuator, this will result in all out boost so be sure to feather the throttle and keep boost at about 16psi. If you're able to hold 16psi+ without falling off, the problem is related to the mbc. If the problem persists, which I suspect, you're most likely looking at boost leaks or a dying turbo.