850 tdi POWER!!!!!!

[thetroublemaker]

Ok,

I have been out tonight and plumbed it with the top IC hose directly feeding the end of the actuator. I assume this means i have effectively dewastegated my car?

OOPS!

I took the hose off the BCS that fed the actuator and blocked it and the waste gate was full open i think - couldn't even get 0.5 bar boost..... So i simply blank the pipe going to the BCS from the IC hose and all should be well?

[martin_r_smith]

Taking the pipe from the ic to the actuator will stop the wastegate from opening completely, bad news!

if you blocked the pipe from the ic, or just have your boost gauge going in to it, then you have affectively bypassed the bcs. The 0.5 bar you are getting is the standard opening pressure for the wastegate, which means you haven't screwed in the mbc far enough.

[thetroublemaker]

Alas it seems that my car must have a fault somewhere then.

Or i am still doing it wrong.

I have done a diagram showing how i have plumbed it in. If i remove (by removing the pipe and blocking both ends) the IC to BCS hose no matter what i set the BCS to i will get no more than 0.5 bar. Even with the MBC fully home. Therefore in my car whatever happens compressor to actuator without boost applied to the BCS/Actuator my car will not generate sufficient boost.

Does this suggest a faulty waste gate actuator on the K14 - i know they have issues but am unsure what they are.

Please have a look at my diagram attached see if you can go "oh you fool you have got this the wrong way round" or something - pretty sure its correct however!

[thetroublemaker]

Just thought - mine is a MSA 15.8 car - is that relevant to this at all?

[martin_r_smith]

Hmm msa 15.8 shouldn't make a difference. You uave it plumbed exactly as I have mine. If you go back to how you had it when you actually had 13psi and then try more adjustment on the mbc.

If you have the bcs bypassed then the only thing controlling boost is the mbc. If you are still only getting 0.5 bar then your mbc must be the issue. Even if the wastegate was a little leaky it shouldn't be an issue as it won't see boost until the mbc has reached its opening pressure. I would take the mbc apart and see if the ball is stuck! It does happen.

[thetroublemaker]

Hi Martin.

I have done a little more investigation / playing this afternoon.

I have removed the MBC and used a short length of hose to join the metal pipe back together, so back to effectively stock.

1 - With the BCS disconnected by removing its boost source i get 0.5 bar boost max.

2 - With the BCS to actuator hose connected to the boost source i get 1.3 bar all the way pretty much tailing off over 3500rpm as expected. however boost builds slowly as there is no MBC to eliminate creep from the gate.

Therefore in my car, for whatever reason, the hose on the end of the actuator needs to see boost otherwise the waste gate is opened. Very odd how your behaves differently to mine.

I have asked over on TDI club in case someone else can offer assistance, we will see.

[martin_r_smith]

If I connect a pipe from the ic hose to the top of the actuator my wastegate will not open at all, the only thing the stops it boosting to oblivion then is limp mode! Or dead mode!

As I said with no bcs at all and no mbc the wastegate spring will only hold the wastegate shut until 7psi or there abouts, the reason for having the bcs is to apply positive pressure against the wastegate to keep it shut until the required boost level is reached (1 bar as standard). At this point the ecu triggers the bcs so the wastegate can open and diverts the positive pressure into the inlet. The only thing that opens the wastegate is the pressure coming from the compressor housing to wastegate pipe (steel pipe), so if you interrupt this line with an mbc then you will increase boost.

The only problem you can have is the mbc itself or the wastegate is jammed open by carbon build up, the latter is hard to rectify without removing the turbo. Then just remove the 3 6mm Allen head bolts and yank (literally) the wastegate off, clean the wastegate valve and seat and put it all back together, Simple lol.

[thetroublemaker]

I am a bit confused now martin.

So what you are saying is the BCS forces the gate shut when its not bleeding off boost, but that when it is bleeding off the boost the waste gate will open. But that the only control is the metal pipe. Isn't this a contradiction - i.e. the BCS not pressuring the pipe to the actuator will cause the waste gate to open as would 12psi from the metal pipe?

Surely the BCS before being activated puts boost pressure against turbo. when the BCS is activated the boost pressure is removed and irrelevant of what happens on the compressor side the wastegate opens.

[martin_r_smith]

The metal pipe is the boost trying to open the wastegate, it is constantly trying to open it. If there is no boost the wastegate is kept shut by a spring, as I've said this spring opens about 7psi. The bcs is used to regulate boost by applying positive pressure against a diaphragm, on the other side of the diaphragm is the spring. So, when you boot it boost rises and tries to open the wastegate, at this point boost has also built up I'm the bcs lines and is pressurising it's side of the diaphragm thus adding pressure to the spring effectively and keeping the wastegate shut. All the while the map sensor is monitoring the boost levels and communicating with the ecu. When the ecu is happy enough boost has been achieved it triggers the bcs and diverts the air away from the diaphragm into the inlet pipe. This relieves the pressure on the spring allowing it to open the wastegate. So by adding a mbc to the steel pipe you can control the pressure needed to open the wastegate regardless of what the bcs is doing.

[martin_r_smith]

Also the bcs doesn't bleed off boost it merely controls it by applying pressure as needed.