can anyone help me?? no boost before transition!

[philsmith1a]

Since replacing my turbos I am only seeing about 1psi of boost before 4000rpm, after 4000rpm I am seeing 1.1bar. Also when I put my foot down I am seeing negative boost instead of 0 that it used to.

 

I have tried and tested everything I can think of and all the suggestions from other people’s posts.

 

I have checked:-

 

All vsv switch as they should

Put pressure through EBV actuator to check its arm moves

Checked EBV actuator arm has not fallen off

Checked EBV hoses are the correct way round

Checked IVAC actuates as it should

Also tried the TTC mod and it boosted exactly the same apart from there was obviously no boost at all before 4000rpm

 

Like I say I am getting the correct boost pressure once both turbos are engaged so I really don’t think they are cooked.

 

Any thoughts what to do next guys or what is wrong????

[philsmith1a]

Anyone?

 

All i can think is its the actual valve that the EBV actuator opens.

[Ian C]

If the power delivery above 4000rpm feels correct then you must be running both turbos at that point. This isn't a wastegate or EGCV or EGBV issue, as they don't affect boost production on number one turbo (well, the EBV does but even if it was wide open all it'd do is slow boost production, not stop it).

 

To have zero boost from a working turbo #1 means you're venting the boost out through the #2 intake. This is the job of the ICV to prevent, so focus your investigations there. It should be permanently shut below 4000rpm, so that should be easy enough to test - especially as it's on the top of the engine

 

However, the ICV has a secondary function - when #2 starts prespooling, the pressurised air has to go somewhere. There is a one way reed valve flap in the ICV housing that allows air to pass from #2 into the shared intake stream, but not the other way. If this flap has stuck or failed, then it would allow boosted air to vent backwards into turbo 2 and dump to atmo.

 

-Ian

[Swampy442]

I was about to say the reed valve as well

[philsmith1a]

Cheers guys! I will check it out ASAP.

[philsmith1a]

Right, the IACV is definitely working as it should (i.e. when revved to 4000rpm its hammed lifts off its stop). I have also cleaned the reed valve out in the IACV housing.

 

Now the boost starts to rise at 2500 very slowly to about .35bar then it shoots up at about 4000 to 1.1bar.

 

From how Ian C described it, wouldn’t this behaviour suggest the EBV is the issue here?!

 

Also it’s worth noting that the issue was not present before the turbo assembly swap therefore it points to a fault with a component which is new to the car (EBV).

[Ian C]

That could well be a wide open EGBV. I've not had any direct experience with that problem, or read much about it on here before, but theoretically it fits. Slow boost production due to the 'wastegate' being wide open.

 

The EGBV button is spring loaded shut though, so for it to be permanently open it's either damaged or stuck. It needs inspection and testing. Bit of a bastard because it's the most inaccessible thing on that side of the engine