turbo boost falls from 5k-redline.

[Vilhelm]

Well when I first got my car back from the tuner (he mapped it), the car pulled hard as hell. It pulled harder and harder all the way up the the rev-limiter. Then a couple of months ago it started loosing boost pressure from 5000 to redline. Back when it worked 100% it spiked at 1.7 bar, fell to a stable 1.5 all the way to redline.

Then it started getting these strange boost problems a little while ago where the boost pressure would build up before 4000 RPM to 1.2 bar but nothing would really happen before 4000 RPM, then it kicked away, but then the boost pressure started falling to 1.0 bar @ redline.

Anyways, I sent my car to KRBtrading.no, to get a new manifold and some other things to it. They did an amazing job. Then engine bay (where the manifold, turbo, WG) is a work of art! All the pressure hoses were changed out so there are no leaks.

So I got the car back and I still have the same issues. But now because of the new WG the pressure does not spike @ 1.7, but it spikes at 1.5, goes to 1.4 and then it drops near 1.3 at redline. This makes the car pull "equal" throughout the RPM range once the turbo kicks in. I want full boost @ redline!!!

I have a turbo XS MBC so I don't get why I loose pressure? The ECU doesn't controls the boost anymore when I have a MBC?

Mods are in signature.

TIA,
Vilhelm

[1975DCS]

Maybe a stupid question, but why didn't you try to find the problem before sending it to KRB (which are pretty good I guess!)? Or did you hope the new parts (like hoses) would solve the problem?

[S2central.net]

What is this turbo, engine and intercooler arrangement that can go to full boost at the red line ?

All except the most exotic turbos will not perform well at max boost to the rev limit - any turbos that are setup for that will be large and laggy for poor mid-range / part load performance.

Can you post a compressor map for this T3/T4 turbo ?
I can advise a good boost profile - I very much doubt it will be efficient at redline on max boost. It may be damaged already. Bet you have some scarey air temperature. Maybe I'm wrong - is it some very large compressor on a T3/T4 hybrid ?

Paul

[Vilhelm]

What is this turbo, engine and intercooler arrangement that can go to full boost at the red line ?

All except the most exotic turbos will not perform well at max boost to the rev limit - any turbos that are setup for that will be large and laggy for poor mid-range / part load performance.

Can you post a compressor map for this T3/T4 turbo ?
I can advise a good boost profile - I very much doubt it will be efficient at redline on max boost. It may be damaged already. Bet you have some scarey air temperature. Maybe I'm wrong - is it some very large compressor on a T3/T4 hybrid ?

Paul

It's a 450 HP capable turbo. I don't know the exact name of it. It's a turbonetics turbo. The IC is custom made at FLS (tuning company). It's a 3B engine with the mods listed in my signature.

Before it started this BS it pulled HARD all the way to redline. Doesn't have that same pull in it anymore. Can the "chip" "stop" working?

[Jamo]

To me the problem is this:

After 1st mapping car overboosted to 1.7 and dropped to 1.5 and held it to redline.
Now car is boosting to 1.5 and dropping to 1.3 to redline.

Have you check the pipe to the ecu, fuel pressure regulator?

One thing that hasn't been mentioned which I would change before the hoses is the WGFV.

Check the altitude sensor and knock sensors.

Bit of a list of things to check

Has the system been pressure tested for leaks?