Hey everyone. On my S5 TII, I have a turbo back exhaust now and I'll be adding the old cats back onto it because I'm sick of my daily driver smelling like poop... and not being able to floor it because I don't have my WG ported.

When I added the DP and PS, I bypassed the stock EBC to set the boost down at 5.5psi to keep the creeping under 9psi. Tomorrow I'm putting everything back together the way it was. I reattached the stock EBC today. Even with it reattached properly, it wasn't working. It was still set at 5.5psi and not rising at all.

Under what conditions would the boost be limited? Is my EBC broken? Should I just put together a home depot MBC to set my boost back at 9psi?

 

Buuuuuump It Up

 

Why not just put the main cat back on?

 

today, I reattached both cats. It was boosting 9psi right after I did it. Then I drove it 10 minutes ago and all it could hit was the damn 5.5 again. It's like 50 deg F outside... not heatsoaked at all. The car is back to stock... 100%. What's wrong?

 

PS... new fuel filter like 5k ago. plugs like 8k... coolant is almost ready for a change, but fine. oil level is fine.

PS I was reading 14:1 A/F under boost from my narrowband when it was hitting 5.5psi... this morning it was reading 10-11.

 

ps... it was hitting 10-11 A/F... and 9psi. just wanted to clarify

 

5.5 is stock, it shouldn't go higher then that if it's running like stock.

It's possible that the wastegate was sticking until it warmed up, but i kind of doubt it.

 

it's an S5. 5.5psi is not stock.

 

Ok, just took it out again. Motor was cold. Waited for it to warm up. I hit the thottle and there was my 9psi again. After driving for like 10 minutes... it wouldn't boost more the 5.5psi. Maybe it's a temperature problem?

 

bump....

 

Ok, just did a couple checks.

1. Stock EBC
I checked the resistance as per the FSM, and it's a solid 32 ohms... perfect

2. Pressure Sensor
5V to terminal w/ pressure sensor removed

2V read with no vacuum applied. on terminal D
0V with vacuum applied on terminal D

FSM says it should be reading 2V at 2psi vacuum. It read that w/o vacuum and read 0 with vacuum applied. Could this be the cause of my 5.5psi problem?

 

Do you have an aftermarket boost gauge to verify?

 

Yes. I assume you mean verify the fact that I'm getting 5.5psi...

 

Is the restrictor pill still in the line between the compressor housing and the tee?

 

compressor housing and what tee? the one that the pressure sensor plugs into?

 

The steel line that links the compressor housing and the wastegate actuator has a tee in it, which leads to the soost control solenoid. The steel line is connected to the compressor housing and wastegate actuator by short lengths of rubber hose. The hose on the compressor side has a restrictor in it that it necessary for the EBC to work. You said you bypassed the EBC before so I though you might have removed the stock rubber hoses and not realised there was a restrictor in one of them.

 

So, I found the pill at the T to the pressure sensor. I didn't find any pill in either of the short hoses from the metal lines to the stock boost controller.



Which line is it supposed to be in (left or right) as I can't tell at all where each metal hose leads to? Can someone also get me the specs as to how big the actual air flow space on the pill is so I can fab something up?

 

Ttt

 

Maybe the problem is not EBC related. Maybe it's the secondary throttle plates not opening everytime, resulting in lower boost. They hang on the black cam/damper outfit.

 

What kind of voltages should be coming from the N370 pressure sensor under boost?

 

You're on the wrong side of the engine...

The compressor housing and the wastegate actuator are on the turbo.

 

Ok, well I've never touched those vacuum lines. There's no reason for a restrictor to not be in that line. Does anyone know the voltages under boost the pressure sensor should be sending?

Again, I checked my pressure sensor as per the FSM... and it read 0V with any vacuum applied off terminal D.

 

About 3.65 vdc at about eight psi boost.

You should read around one volt give or take a point at idle with the vac hose connected to the sensor.

 

just to double check, it should be receiving 5v... right?

edit: Thanks so much HAILERS

 

Five volts on one wire, would be a brown/white wire on a series four, and an output of about 2.3 vdc on a brown/red wire if it were a series four with the key to on but engine off. I don't have the series five wire colors but I think they are the same color.