Ok I am at a loss.
I have been having this odd boost issue. I will let the car completly warm up, go for a drive, and only can hit 5psi MAX. It runs smooth 5psi all the way to 6k where it hits a brick wall. Im told this is fuel cut, so I never go above 5.5k.

Now recently, on odd days I could hit 8psi+ no problem. I was chalking this all upto a dying turbo, bad sticking wastegate, So I bought a low miliage, great conidition stock S4 turbo. I cleaned it, ported the wastegate, and replaced the WG actuator lines. Its supposidly has 30k off a JSPEC, so the next to non shaft play kinda got my hopes up.

Fast forward to this weekend, I swap turbos. I get the new one on, and get rid of the cracked exhaust manifold and missing downpipe to straightpipe gasket. I took the time to port the wastegate, well withing reason. I Hop in the car, warm it up and I hear a kinda odd sound, a tat-tat-tat _____ tat-tat-tat____ you get the idea. I figure its my loose twin scroll tube hitting the downpipe/motor- and take it for a test drive. BAM 5psi. Nothing more, other then a great spool time and quiter and smoother ride.

My idle is still random as hell. When I first started it, 950, shut it off, started it, 700, shut it off- 1200, then to 1500. Then it pulsed a little, then it settles at 1500.
Sometimes when in gear, it will drop to 1200, im assuming this is due to a bad neutral saftey switch.

I have a Rtek 1.5, walbro, and new fuel filter on the way. Im thinking mines clogged because it seems even at 5psi I am running lean.
Any input welcome .

 

Normal response - Have you checked and adjusted the TPS and make sure it's operating properly. Check BAC for internal seal leak, and check for any vacuum leaks. It's a start.

 

No vacume leaks. TPS is sitting perfect at 1ohm, has a flawless swoop.

My bac dosent work :-\. Im pretty damn sure the ecu circuit is fried, a used ecu is on the way.

 

do you have emissions??? Mine would only hit 5 psi until I took out emissions and for some reason after that everything worked great. Infact I got a fmic and ported the wastegate because it was boosting to high

 

I have the EGR valve and rats nest, but cats and air pump and ACV are gone.

 

with a bigger wastegate of course your only gonna get 5.5 psi. sicne stock actuator has a 5.5psi spring meaning the wastegate opens at 5.5psi adn lets all extra gases out. you need a boost controller to raise boost.

 

I just realized that, 5.5 for s4, 8.5 for S5.

So I need a manual boost controller, any plans for one out there?

 

7.5 psi for a S5 =)

just goto a local parts shop and get a small air check valve, and the vaccum fittings for the end, chances are the guys in the parts store will be able to direct you to what you need. If I had a digi-cam I would show you a pic of mine. Just remember the teflon tape on the threads

 

Actually the S5 has the same problem (the 5 psi limit) if you connect the WG right to the turbo outlet with no boost controller. The S5 had a EBC built in.

Go with a MBC or EBC and you should have no trouble boosting higher--and with the Rtek you won't need a FCD.

 

please post the how to make my own ghetto boost controller...i been looking for a while with no luck

 

It probably only hit 5psi until you removed emissions becuase of an intake/vac leak! It has to be, I mean if the pressure only holds till 5psi, its blowing out somewhere..

 

Main reason for getting one .

Thanks guys, I read up on how to build a MBC and will try it AFTER I get the new parts installed.

 

http://www.geocities.com/chmwatson/FAQs/mbc.html

And no, my car ran fine with no emissions for months.