PatrickT

Hi

I just did a touge battle with my brother,
so I floored and reved the engine harder than ever before.
At the second pull after about 15 sec the boost droped at high rpms ( about 6k ),
and the exhaust sound became quieter.
I shifted up and it boosted again pulling well.
But the boost droped again when reaching about 5.5k.

In the second run it happened even earlier, at the end the boost started to drop
at 5k.

I saw on my aftermarket boost gauge that the boost always droped to exactly zero.

I think it may have to do with the twin scroll system, because of the quieter exhaust sound when occurring.

Once it happened before, on the Autobahn when reaching 140mph

Is this a engine protection feature or a malfunction of the twin scroll system?

Btw.
I was boosting max to about 12 psi
And I have everything on tape, maybe I will upload it soon.


-Patrick

PatrickT

No one ever had this before ?

-Patrick

Wankel7

WTF is a "touge battle"?

Anyways...how does it run now? Maybe you blew off a hose.

James

PatrickT

Its a duel, driving a mountain pass, but no overtaking
2 runs , in the 2nd run the order of drivers/cars is changed.
The one that pulls away in one run and keeps close in the other one wins.
We finished with a draw, because of my boost problem.
It looked like I was faster on the straight, but a bit slower in corners,
but with no boost there was no real comparison.

examples:
http://www.youtube.com/results?searc...y=touge+battle

The car runs same like before, if there is a hose off, it was off before
but I didnt find anything.
perhaps the linkage of the twin scroll is too loose,
so it closes by itself at high exhaust flows,
but why only after a few pulls ? hot exhaust ?

It also sounds unlikely to my, any other ideas..?

-Patrick

RotaryEvolution

iTrader: (30)

your cat died.

Syonyk

An exhaust restriction would definitely explain the behavior, and a lot of high boost (read, rich mixture) hard running could push an old catalytic converter over the edge.

-=Russ=-

PatrickT

My Cat lies behind the garage, Im running currently an open free 3 " turbo back exhaust, but with noise killer in the tips, maybe they are the problem ?

-Patrick

Syonyk

It'd be worth taking them out. What you're describing is most easily explained by exhaust restriction.

Depending on your mufflers, you may have melted down the packing material if they had a fiberglass type substance in them. You could try removing the mufflers completely and see if it still does it.

-=Russ=-

PatrickT

the mufflers are ,see through, only the noise killers may restrict

but what makes me wonder is that the boost droped to exactly zero
and that it happened at one point, when lifted up and floored down again
it boosted again but only for a short time
I dont know if you can see or hear it in the video when you dont know when it occurs.
I´ll upload it the next days , I hope

-Patrick

PatrickT

Here you can hear it, when it occurs there is almost no exhaust sound left,
sounds like lifting off , but the first second I still floored it,
Than I lifted off and floored it again and it only boosted for a very short time

begins at 0:55

http://www.youtube.com/watch?v=fHruYwrMYuU

I could have got much closer if it wont happen, damn...

-Patrick

Syonyk

And if the exhaust system can't flow, the pressure behind the turbo will be (more or less) the same as the exhaust pressure before the turbo, it won't have a pressure differential to spin with, and won't provide boost, giving you... how much boost? Zero. Just running at atmospheric pressure.

And, if you lift off, the exhaust system will have time to de-pressurize. Which means you'll have boost when you hammer on it, but only for a short period, until pressure builds up and... guess what? No boost!

It really, really sounds like something in the exhaust system is clogged up, badly.

I may be completely wrong, but with what you've given us to work with, that's the far and beyond most likely possibility.

-=Russ=-

PatrickT

Yeah , this might make sense.

But the reason why I still prefer the twin scroll theory is that
the boost drops very rapidly from about boosting 12 psi to 0 psi.
I would expect something smoother if it were a restriction problem.

And it remembered me of the twin scroll plate closing under 2800 rpm

Hm its hard to check this, i should look into the engine bay while pulling

But it still only happens after a few pulls, than the rpm where it occurs decreases more and more ( first 6.5k than 6k , 5.5k , 5k )
If I let everything cool down it begins again at 6.5k ....

-Patrick

Wankel7

Do you still have the double throttle plates?

With that thermowax ?

Or did you do the TB mod?

PatrickT

Oh you are right, I thought about that before.

Once I tried unplugging the hose controlling the plates,
but I think I had the same prob.
And additionally got hesitation when flooring to fast,
what the plates should avoid, so they were deactivated..!!??
and so they are not the origin of my prob..!!??
thats what I thought
but perhaps they get closed by the air flow ( when hot at high rpm )...??

-Patrick

Wankel7

I think the normal problem the secondary throttle plates (ones controled by teh thermowax) have is when they don't open because of the thermowax failing. So, it would not even build much boost to begin with. But who knows......i would look that system over and see if you can wire them open.

Other than that I am out of ideas

James

HAILERS

To check the twin scroll, all you have to do is rev the engine in the driveway. Over 2700 the rod will move open. Let off and the rod will move closed below 2700 or there abouts. Takes about ten minutes to check out if you sitting in your house right now.

Not that and your not thinking it's the exaust???? Then pull the TID off and see if there's excess play in the turbo shaft. Another halfhour job on the outside.

Sounds like a stuffed exaust but if you say no, then check the other stuff out.

PatrickT

I like the idea with the double plates,
it was the first thing I thought too, but I forgot again.
What I like about this theory is that the thermo wax is temperature related
What I dont like is that the boost drops to exactly zero,
but wait, the boost is measured behind the primary throttle right ?

I dont have the check if the twin scroll is switching at about 2800,
I hear it everytime I drive.

Also the turbocharger has been replaced in the meantime...

-Patrick

PatrickT

Just uploaded an edited version of the clip.

http://www.youtube.com/watch?v=n2M-2XNoWuw

showing when the "boost leak" occurs
and added the second run + intro