Hi Fellows
A friend of mine asked me for help with his boost creep issue. We discussed already bit and checked some things already. I try to describe:
- 3.3l Turbo 82
- Precision Turbo 5862 CHRA Ceramic bearings / Trim 0.82
- 964Turbo IC
- K-Jetronic, enrichement by cold start injector (boost steered)
- GHL headers
- Powerhouse dual outlet muffler
- Tial F46P Wastegate (0.7bar spring -> 1.0bar in reality)
- 964 BOV (plastic one)
- electronic boost control (via wastegate ventilation)
Some small other upgrades, but not relevant here I guess, because motor was running fine.
After winter time he went out for a ride, but boost was increasing, at 1.1bar he stopped. For some unknown reason, max boost increased.
Different measurements:
0.4bar spring with wastegate muffler:
He checked and tried a couple of things:
- Tial F46P Wastegate with 0.4bar spring: No change, stock seems even bader
- Boost hose from IC to Tial checked and replaced
- Boost control removed, wastegate ventilation into the open
- Wastegate muffler replaced
- BOV removed and IC port closed
- checked for general leaks (only hearing and watching, no pressure tests)
- Wastegate spring removed and valve block full open: Still about 0.4bar
- SDS ignition
I was not on site yet, but maybe someone has an idea or even better has similar issue. For me it's sound quite strange. What else could have such an effect without changing some components?
All inputs are welcome
BTW Boost pressure reading by stock clock and Zeitronix ZT-2
Seems to lean from 0.7bar up
Seemst to be fine (plateau at 0.4bar) and then loose control and increase, visible on all 3 pics