Skydive@AI

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This is a log we pulled from RS-S4's '00 A Box/X Chipped S4. I know it's got DV problems because I can hear them dumping boost during shifts. These graphs look suspicious though. Has he dropped a turbo, or might a DV be stuck open? He reports that the car "pulled hard" when he first chipped, and shortly thereafter, the fun was gone... As one can see, he almost never makes requested boost, with the exception of a couple of minor spikes.

He's off to the dealer for a couple of 710Ns, but I think he might need more than that.

Thoughts?

zapco98

depending on how large the tear is, it is more than likely leaking lots of boost through the tear - it may reach X amount of PSI before it actually leaks bad - thats what it looks like, I would imagine that if he had a blown turbo, he would see smoke, and or have a check engine light, and wouldn't be making more than 5psi(limp mode).

wishbone

pretty much your basic leak... f-hose, tbb, diverters, all could be the problem..

Levish

get on a wide open stretch of road

get in 3rd gear at about 1000 rpm then go WOT all the way to redline, then let off the gas

it will give a more detailed view of what is going on.

but it looks like you are never making the boost requested so start by looking for leaks everywhere, tighten clamps that look loose. You may also be looking at a failing turbo.

you should be getting a bit more boost than requested in some places so don't stop looking until you get to that point. Also check injector seals for leakage.

Kent L

So WOT from 2nd gear through say 4th. How the graph looks during the shifts can often indicate the state of the BPVs.

pattersom

Limp mode too...

Skydive@AI

It makes power... and then doesn't.

pattersom

The car computer will put itself in limp mode if it received a DTC that may potentially put the engine at risk if full power is applied.

An "event" will trigger limp, after which time the actual boost will hit a "boost limiter" of sorts. This is apparent in the graph since the actual boost flat lines at a certain point (looks similiar to the point I have seen). It strange that the requested boost is not effected by the limp mode.

Limp mode will reset after restart until another event is witnessed. This should make the engine pretty safe against leaks since this is one of the DTC's that triggers limp mode.

Skydive@AI

He replaced the errant DVs with 710Ns this morning. Upon cursory inspection of the stock units, he states that one looks fine, but the other is internally covered in oil.

This sounds like a dead turbo to me...

He's just out of factory warranty, but has what he says is a good aftermarket policy. He's looking to go K04 if his K03s need replacing.

zapco98

if you had oil in your throttle body boot, then you might be suspicious of a blown turbo - but in the BPV thats totally normal.