I replaced my secondary injectors today with brand new RC 750's and I'm still not boosting over 6 psi.

Before I replaced them I had the wrong injectors as secondary and the car would not want to rev past 3500. And would only produce about 5 maybe 6 psi.

Now that I have the new ones in the car revs freely no problem but the boost never goes over 6 psi? I have no cats and ported intake and exhaust. Completely stock S4 turbo.

Any ideas?

 

Do you still have the stock exhaust?

 

I do have the stock exhaust but I have a bonez down and mid pipe installed. So there's really no back pressure at all I would think.

 

you still got a stock Ecu too?

 

**** I'm NA with a 2.5" header, to 2.5" piping, and still have a considerable amount of back-pressure. I'm confident that you have more back-pressure than you may be aware of.

 

I have a stock ecu with a FCD. I'm sure there's back pressure but much less then having 3 cats still on and still only pushing 6 psi? Somethings not right.

 

Must be the exhaust. Racing Beat claims and 80 hp boost just switching the their full turbo-back exhaust. Boost would exceed the fuel cut level of 8.? which is why the fuel cut defencer was included.

 

Ok isn't stock boost for a 88 like 7.5? I'm not even boosting that. I'm producing less boost the stock with more fuel and less exhaust restrictions.

I'm sure that racing beat exhaust would be even better but still the numbers don't add up. I feel like im taking crazy pills.

 

are you reading from the stock gauge?
the FCD may be a cheapy and has everything out of whack

...use an independent mechanical gauge.. check for preturbo exhaust leaks
check the twin scroll valve operates and that the wastegate door is held shut without movement on the gate arm

 

pressure test the intake system. all you need is a plumbing coupler, rubber hose, clamps, tire valve stem, soapy water and a compressor.

ok that may be a bit much for most people, a can of carb cleaner works in a pinch.

 

Could be the lever to the waste gate fell off, mine would always come off , untill I got the right size c clips

 

is your wastegate ported?

 

5.5psi is stock s4 level, 7.5 is s5 stock turbo level w/ a electric boost valve controlled by the ecu on top of the wastegate

 

I heard of people bending the wastgate arm to prevent over boost. A local guy from my area did it to my buddys car after rebuilding the engine. He was afraid my buddy wouldnt keep the boost down. He was stuck at 5.5lbs.

 

sounds like that would make the turbo really laggy seeing that the waste gate will never fully close and the turbine will never see full exhaust energy.

 

It does.

I did that to keep my boost down during break in.

 

ewwwww, turbo lag is gross

 

I would not recommend it at all.

 

The waste gate is not ported so I would figure with my set up that it would be over powered quickly and I would have boost creep if anything.

I'm wondering if the FCD I bought is working or legit. Is there an easy way to test it? Its kind of a coincidence that i can't boost anymore then what the stock level is..

What does it feel like when you hit fuel cut?

 

like if you turned the key on and off rapidly in succession. basically the engine loses all power for a moment and then comes back on.

 

^This and a stock S5 turbo without the ecu solenoid also boosts to 5.5 psi.
Sounds like your car is acting perfectly normal with a ported wastegate.

Since it hasn't been explicitly stated, you are trying to use a boost controller to raise boost right?

A stock S4 turbo should creep without cats. But the stock catback isn't much of a restriction unless the mufflers are falling apart inside.

Have you actually inspected the turbo to see if the wastegate has been ported or are you saying that you personally haven't done it?

 

Waste gates not ported, the guy that owned it before me had the car completely stock, I bought it and rebuilt the engine (Ported the intake and exhaust to a med street port (fd housings)).

It defiently doesn't feel like fuel cut then. It just stops creating anymore boost then 6 psi but feels like it just bottle necks. I figured with a FCD that I bought recently that the boost would keep on rising..

 

.

 

So just spray carb cleaner while its running from the turbo to LIM and if the engine revs higher I got a leak? Or did I get the logic wrong? I'm going to do this today.

 

That's not how FCD's work. They just intercept the pressure signal to the ECU. It doesn't do anything to change the boost pressure. To raise your boost pressure, you're going to need a boost controller or fix a boost leak.

If you spray carb cleaner on a leak, the engine will bog slightly, then return to normal after about a second. All the couplers, plastic pieces, under the manifold are good places to try. Give the intake a little spritz to see how it's going to react.