Gerben approached us in 2018 after struggling to get his Big Turbo Mk5 GTI tuned successfully. He was experiencing persistent issues with EPC (Electronic Power Control) lights, limp mode, throttle cut and inappropriate injector mapping for the setup. Specifications as follows:
Model: 2008 VW Mk5 GTI
Engine: 2.0 4-Cylinder TFSI (Turbo charged, direct injection) - BWA
Transmission: 6-Speed Manual
ECU: MED9.1
Location: THANAS CPT
The Shopping List:
- Forged Motor (IE connecting rods, JE pistons, ARP fasteners)
- Mambatek GTX3071R - Internally Gated with External Gate conversion
- Tubular exhaust manifold
- GFB G-Force III Electronic Boost Controller
- Audi R8 Coilpacks
- Audi RS4 direct injectors
- Audi RS4 rail pressure relief valve
- Autotech High Presure Fuel Pump Internals
- DW65v Low Pressure Fuel Pump
- Performance Intake
- Billet valve-cover with catch-can
- Polyurethane/Billet engine mounts
We got to work identifying the ECU software version and defining the ECU, which would enable us to alter all of the necessary parameters. We logged the vehicle in its current state, identifying issues and items to be addressed. With the issues identified, we began building a custom tune for the vehicle. We made the following adjustments:
- RS4 Injector scaling (Flow constants, Injection phasing, Injection-pressure, injection-voltage, warmup tables etc)
- Autotech HPFP geometry scaling (plunger volume adaption)
- Rail valve purge threshold matched to RS4 valve level
- Low pressure fuel pump controller mapping to suit the DW65v element
- Optimised Ignition advance for 95 octane fuel (no additives / WMI)
- Optimised VVTi for spool and higher VE during transient conditions
- Optimised injection timing and phasing for RS4 injection and knock suppression
- Restructured torque-load tables to appropriate values for BT
- Rescaled VE maps for BT flow
- Recalibrated MAF to suit intake and turbo arrangement
- More ECU related items involving the words optimised and calibrated :>
We then relogged the vehicle, and made some adjustments to the Electronic Boost Controller. The vehicle responded well to the map edits, smoothing out the drive, and with higher power and torque across the rev range. The EPC faults and limp modes were also solved. However we struggled to get consistent boost response, and the spool was much more laggy than we expected.
The wastegate setup was not the usual arrangement for an externally gated, big-turbo setup. The turbo was an internally gated turbo, with a divorce-port downpipe:
The wastegate actuator had been welded, and an external wastegate, venting from the tubular manifold was used. At this point the owner opted to take the vehicle back, and investigate the issues. This was not an issue, as it was in good driving order, bar the unusual boost response and an exhaust leak or two that was picked up.
As it was a long-term project, the owner worked on it over the next one and a half years, fixing small issues on the car. It was found that although the actuator arm had been welded, the wastegate flapper was not welded shut. This allowed for a constant exhaust gas pressure bleed. This explained the lack of consistent boost response ,and laggier than normal spool-rate.
With the issues finally resolved, it was placed on the dyno (pure pump fuel, no additives or WMI) and with the exact same tune from 2018, put down a very respectable:
Power: 320 kW / 430 hp
Torque: 543 Nm
As the vehicle has not been re-calibrated since 2018, and with many changes since (wastegate issues, exhaust leaks), it is quite impressive indeed, definitely lots more to come after we get the car back onto the dyno for some fine tuning (and some re-adjustment of the EBC to smooth out the overshoot!) #NoHumpZone.
Thanks for reading, we'll update this blog post with dyno figures after the retune.
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