What should vacuum pressure be?

[TeeM403]

Hey im just wondering what the normal vacuum pressure is when hooked up to stock boost controller? Mine says about 16psi is that normal
Seems a
Lil high

 

[EGLTAWLN]

what should vacuum pressure be?

i skipped this post for a long time.
then i couldn't resist what others had to say.
how would a computer answer this question?

i was going to say zero or no air movement, but then thinking about it "vacuum pressure" although an oxymoron, contains one piece of logic. i think it shows a direction of air movement. since vacuum is on the left side and pressure is on the right, the air would move <---- that way.

.

 

[ef_junky]

Can you explain a bit better not only on this but what problem you are having.

Well is the O2housing dump for the wastegate(to the atmosphere) not suppose to only open when under full boost? When the wastegate opens to release the excess pressure to keep the turbo from building 20psi. But as soon as I start the car it's dumping right out the dump like straight from the manifold and under full boost it'll build 10lbs then fall to 4ish around 5k or so

 

[NHerron]

I don't have personal experience with atmospheric dump o2 housings, but from what you say about ability to hold boost at x RPM, sounds like somethings up with it.

What I mean by that is, I don't know 100% how much 'allowable' the wastegate (WG) can leak when closed. However, it should not be open at all at idle and low loads because the WG has a bit of spring preload to it (maybe a couple lbs) to keep it shut. If using anything besides a ball and spring type boost controller or electronic boost control solenoid, the wastegate will begin to crack open before target boost is achieved. This is because the WG diaphragm is always seeing some kind of pressure signal.

Does your turbo have one of those 'adjustable' wastegate actuator rods? (eBay feature hehe)

Have you done a boost leak test (BLT), just to get that out of the way.

 

[vingasoline]

BC272s and Crower 272s are different.

Notice I didn't call mine crowers? Just pointing out that degreeing makes a huge difference.

 

[ef_junky]

No it doesn't it's the factory 2g turbo and I haven't had a chance to do a teat yet goof to fix timing then check

 

[TeeM403]

ahahaha why does everyone gotta get so technical for a simple question

 

[boost97gst]

Notice I didn't call mine crowers? Just pointing out that degreeing makes a huge difference.

U are absolutely correct sir. Im wishing i had bought some adjustable cam gears with the cams.

 

[STI EATER]

My boost gauge is ready around 14-10 (fluctuating) inhg vacuum and building boost is 10psi max around almost 5k then falls to about 4psi I just cecke the timing and exaust cam is out bout tooth or so I think that's my problem. Would like second opinion and I have O2 housing atm. Dump for wastegate and it's open all the time not just under full boost

Are you using any other boost controller than stock? Try running your air line from the turbo outlet strait to the wastegate.