Hey guys,
I have a GIAC tune. I used to see 1.1-1.2 bar. Now the car struggles to hit 1.0. I built a leak tester and tested the system at 25psi. There is a very, very slight leak somewhere around the plenum. I soaked the area with soapy water and couldnt see any bubbles. I removed the y-pipe and throttle body to check the o-ring and vacuum line at the plenum. No visible issues.

I highly doubt my subtle leak is causing a .2-.3 bar drop. I am going to replace the o-ring and clamps between the y-pipe and t-body(one broke) Does anyone have any thoughts other than that leak as to why I am dropping boost??

Thanks in advance. Maybe its time for some billets while shes apart

 

Subtle ain't got nothing to do with the leak.

Fix the leak and regain full boost.

 

So you loaded the system up and couldn't find or hear the leak. You said it's around the Plenum. Go buy yourself one of those Dr Stethoscope mechanics use. Youll find it then.

 

Looks to be the Venturi tube leaking around the outside of the valve. Thats the only leak I could find. Would that be enough to cause the drop in boost? It takes a few minutes for the sealed system to drop off from 20 psi.

 

If you 've done a boost pressure test and significant leaks is not showing I suggest you check you wastegates or cats on your exhaust..... pretty common for sticky wastegates. Cats can collapse or melt on tuned cars.

 

if its near the plenum, its probably just one more cracked #16 check valve. its just a piece of plastic. that will just about kill .2 of boost. pressure test and listen, you should hear it "hiss" if its cracked.

 

Turbos and Tubi exhaust are off now. W/Gs seem intact, and the cats have no visible obstructions or melting. I will be ordering a catless system and some hybrids today/tomorrow.

After I found the leaking Venturi valve, Im hoping the is the main cause. Maybe Ill order and replace #16 as a precaution.

 

They're cheap enough ( -50? ) known to fail and you're right in there so yeah, prudent decision that will serve you and you'll know all those parts will be new again. Most of us change the venturi, - #16 and the n75 same time given their interactivity with one another. GL. sounds like you'll have it sorted.

 

Thanks for the help. I appreciate your insight. Hopefully I can get all my parts in the Friday and test her out next weekend. Ill keep the thread updated.

 

you're welcome and np! this place is a great resource and over 2 tt's, have had most all boost issues known to car and mankind still had to learn the check valve on my own though so yes, pls post your results. it helps us all!

 

Any idea of where I can source these parts quickly? Price is great at ECS and Pelican Parts, but wont ship until the end of the week. I may just order them at my local P dealer

 

Ordered at my local dealer. Be here Wednesday

 

If it is taking more than 10-20 seconds to lose pressure then chances are a leak isn't your main issue. Your turbos crank out a ton more air than your compressor and a tiny leak isn't going to cost you .2psi.
My car normally sees 1.5 bar when the weather is cold and now that it's hot outside I rarely see 1.4. It may be a combination of higher ambient temp and a small leak but the air loss you described isn't going to cause a .2 bar loss.

 

as i remember my continual nagging issue that persisted ( until I was able to isolate and pinpoint the source of my assumed "minor" leak at the check valve ) my boost loss was right around .02. perhaps the size of the crack/leak is commensurate with the percentage of lost boost.

 

All leaks have been fixed. Now I'm just waiting for my billet 1668s and ICs from Sam. We'll see what bar I'm hitting after install and retune.