Thread: td5...overboost, no guts and i'm at a loss

Hmm boost modulator, melted cat, both of these we had and caused symptoms similar but the boost modulator seems to match best
a quick simple test is
"a very simple test to see if it is the MODULATOR and it was to join 2 of the hoses attatched to it, the one from the wastegate and the one from the metal hose under neath then take it for a run"

The recordings look much better but the comparing the MAF (red) and MAP/IAT (blue) air charge values the MAF looks on the high side.



There is also some evidence of limiting in the boost readings which is visible in the above at 47 seconds.



You can see the dip in manifold pressure at the green line. This occurs immediately prior to the wastegate activating and while the accelerator way 1 voltage is increasing (c4*10 to make it visible on the graph).

This suggests you are leaking boost, which means the turbo is sucking more air than normal for a given boost reading. My guess is you probably have a split/failed hose between the turbo-intercooler pipe and the wastegate modulator. This will leak boost and allow overboost to occur simultaneously.

cheers
Paul

Thanks for that Paul,

I replaced all of the hoses from the wastegate modulator last week, the wastegate modulator is also brand new and original.

i will check and recheck all hoses this afternoon.

just wondering if a fault in the wiring from wastegate to ecu could cause the same prob?

Would the leaking boost also be causing the high maf or is it a separate problem?

thanks for the help mate!
Pete

Originally Posted by Pepi

Thanks for that Paul,

I replaced all of the hoses from the wastegate modulator last week, the wastegate modulator is also brand new and original.

i will check and recheck all hoses this afternoon.

just wondering if a fault in the wiring from wastegate to ecu could cause the same prob?

Would the leaking boost also be causing the high maf or is it a separate problem?

thanks for the help mate!
Pete

I suspect it's two sides of the same problem. It's a bit difficult to be 100% on the problem from the readings alone - all you can do is look at the information and try to think through what can potentially cause the kind of behaviour you are seeing. TBH I've only recently put two and two together on the air charge calculations, so while I know they should be pretty close to each other on a std setup, it's a bit of a leap to use the information to ID the exact cause of a discrepancy.

I don't think a wiring fault to the modulator will cause this. If a fault causes the wastegate modulator to stick open it will behave the same as if you bypass the modulator - the wastegate will open earlier than it would normally (in other words it behaves like a defender ) and you'll see less boost in the midrange. If the modulator fails shut the wastegate doesn't open at all and the boost will increase to the point the ECU limits at 2.42 bar absolute pressure. As I understand it neither scenario will cause higher levels of mass air flow combined with normal levels of boost.

The wastegate operates on the exhaust side of the turbo so wastegate opening should be seen as a reduction in amount of air flowing through the MAF as the turbo slows.

This is why I'm fairly sure the culprit is somewhere between the turbo and the inlet manifold.

cheers
Paul

I will have a good look over the next few days and
will post findings.

Thanks again Paul for your help.

This may sound simplistic, but after driving 700 km's last week, on my weekly check of the D2, during which I grab the silicone intercooler hoses & push/ pull, the hose on the inlet manifold was loose. Trying to tighten both clamps I have there, it became obvious one was cactus. Replaced same , tightened all others, & the lift in performance was obvious. I dare say a lot of the turbo air was not getting to the combustion chamber. Just a thought, Bob

thanks Bob,

i will be checking all hoses, clamps over next couple of days...hopefully find something simple!

cheers
Pete