03/09/2026
This R32 GTST came through the workshop this week for a tune and some troubleshooting. The car had been previously built by another NSW workshop, and for the most part the combination had been put together well. There were, however, a few areas that needed attention before we could get the most out of it.
We started with steady-state to establish a baseline and assess the drivability of the combination. During transient throttle, we identified an initial flat spot and slight stumble at low RPM. Investigation pointed towards the oversized throttle body, which was creating a very aggressive change in airflow for the amount of throttle movement at low load.
Ideally, we would have addressed this mechanically with a more appropriately sized throttle body, however given the constraints of the existing setup, we worked within what we had and continued with the tune.
Moving into the power runs, we immediately identified a significant fuel delivery problem. Fuel pressure was dropping heavily under load, making it impossible to safely continue tuning.
We went through the fuel system methodically and found multiple issues contributing to the problem. The in-tank fuel pump had failed, the external reusable fuel filter was heavily restricted, and the fuel pump wiring was far from adequate. The existing wiring setup was creating unnecessary voltage drop and was simply not suitable for reliably supporting the pump under sustained load.
We replaced the failed pump with a Walbro 525, fitted a dedicated +12V relay-controlled fuel pump harness, replaced the restricted filter and then verified fuel pressure and voltage supply under load before continuing with the tune.
Once the fuel system was stable, we were able to complete the tune and safely bring the combination up to 20psi, where it produced a solid 350rwkW.
The final power figure is only part of the result on a car like this. Finding and correcting the fuel delivery issues was the priority. There’s no point chasing power if the fuel system can’t consistently support it.
350rwkW @ 20psi.
Fuel system sorted. Tune completed. Another RB back on the road turbing heads!
Hope you enjoy it Rawan!
