20v keep blowing turbo, help please

[newsh]

What MAF hose are you running, is it the original one and is it old and soft? It's possible for the turbo to collapse the MAF hose at high RPMs and boost, that will stall the turbo.

Otherwise you need to make sure the DV is opening when the throttle closes and the N75 is connected correctly and there are no boost leaks anywhere in any of the small pipes.

If the DV doesn't open you get a lot of fluttering sound through the airbox..

[Greg_S]

On the MAF house later pipes hand a metal coil to stop them collapsing

[george21]

I welded 3" maf hose from stainless steel, so collapsing it is not possible. Dump valve checked and rechecked, boost from turbo goes to the side of it, bottom to the maf pipe.

[george21]

Its quite a minefield!

http://www.s2forum.com/forum/showthread.php?t=18357&highlight=oil

Shame the Turbo guy can't be more definitive as that would help. If was from being stalled then that suggests the BPV. Not impossible to install the BPV backwards or even a new component to be be faulty. If it was through surge then thats a function of the turbo characteristics which may or maybe not be solvable through careful mapping or worst case a better choice of turbo.
If its not on the car, i.e the oiling system, then its might be something to do with the incompatability of the turbo with your goals. The K7400 has a relatively small turbine which makes it a poor choice for elavated power levels. A K27 hybrid can be a pick n mix of many components which might not be compatable. Do you know the exact spec in terms of comp wheel and turbine housing etc?
Is the software compatable with the turbo?
I am guessing that the car did not have the same characteristic before so basically its a matter of backtracking to see what has been changed and how that might effect things!

What turbo rebuilder says is that shaft is twisted on the cold side, compressor wheel damaged and he can see some bronze on the shaft from the bearing,
oil seals on the cold side and hot side are good.
So bronze on the shaft means that it touched it at some point because of the oil starvation or when shaft was twisted from stalling then it was rubbing on the bearing. Turbo was bought new from forum member "hoffer"
K27 hybrid. I don't remember spec from top of my head as turbo is at the rebuild shop.
All i remember that hot side is k26/6

[twoqu]

Cold side shaft bending could be due to overspeeding. It would be bent from the thrust shoulder up.
Of course its often difficult to tell what failed first! As you have said effectively the centralisation of the shaft is basically down to the oil, so any disruption in the supply would cause issues.

[caterpillar]

2 things: the oil RETURN side, are this ok, collapsed rubber...or is it metal pipe??.... next... the cranccase ventilation... the blowby in crancase... how are this solved.. the pressure from blowby, MAY give this problem...the pressure are so high, the oil cant go in the turbo, because the backpressure from the returnpipin, will not aloww the oil goin in the turbo... and the last what oilpressure are you have in the enhgine

[newsh]

Good point, are you still using the one-way-valve in the PCV system? The one under the inlet manifold near the throttle body?

[george21]

first of all thank you very much guys from trying to help me!
oil return pipe was checked and cleaned and fitted back in, original aby pipe.
regarding sump breather system i raised this question myself, if it is to much blowby through piston rings and bad ventilation you will get a counter presure in the sump, stoping oil draining from the turbo. but how do i test that?
at the moment i have installed new one way valve and conected to maf hose as per original, just n80 valve not connected enywhere, just electrical conection pluged in, but no wacuum pipes pluged in as nowhere to plug it them as engine fitted to the
ur quattro, no carbon canister. shall i chuck everything out and leave just an open pipe without any valves etc, breath to atmosphere?

[K Simmonds]

This problem must be very, very frustraiting!

On the breather system I wouldn't vent it to atmospheare, you really want the vacuum from the engine to keep air pressure in the crank case negative. A well thought out catch tank set up is the solution here, I don't think it's your problem though.

What software having you been using with the K26/7?

[george21]

This problem must be very, very frustraiting!

On the breather system I wouldn't vent it to atmospheare, you really want the vacuum from the engine to keep air pressure in the crank case negative. A well thought out catch tank set up is the solution here, I don't think it's your problem though.

What software having you been using with the K26/7?

I sent ecu to prj and told him specs.
I don't think it is a breather as well, but everything have to thought as simply i CAN NOT afford blowing any more turbos!

[K Simmonds]

In that case I also doubt the software is causing this to happen, anyway if I read right it did the same thing with another turbo and different software. Which means it must be something to do with hardware, but what

Just a thought, have you tried another wastegate? In theroy it could be sticking and causing the turbo to overspin.

[martinws]

You must be going mad.
What would happen if oil thermostat was jammed open/closed?

Can you fit an oil pressure send before and after turbo to monitor whats going on across the turbo?

[george21]

Good point, are you still using the one-way-valve in the PCV system? The one under the inlet manifold near the throttle body?

I thought about what you asked and NO i am not using one way valve, just an oil breather one end is in the block other end into the maf hose. I thought i don't need one way valve as i am not using carbon canister and n80. Am i wrong there?

[george21]

You must be going mad.
What would happen if oil thermostat was jammed open/closed?

Can you fit an oil pressure send before and after turbo to monitor whats going on across the turbo?

Why you think i'm going mad
I don't think there is a point fitting a pressure gauge after turbo as there will be no pressure, it is a free flow to the sump.

[newsh]

I thought about what you asked and NO i am not using one way valve, just an oil breather one end is in the block other end into the maf hose. I thought i don't need one way valve as i am not using carbon canister and n80. Am i wrong there?

That should be fine but it would be better to have a catch can in between. The good thing is that there should be no way for boost pressure to get into the crank case as the maf hose is always under vacuum.