Astra H VXR Sprint

On the rolling road over the last few days for final mapping and optimisation, with 99 Octane fuel in the tank. This was to map the ecu to take advantage of the new inlet manifold, steel rods and the K06 turbocharger to make sure fuelling, ignition timing and boost pressure were all correctly optimised. Too lean and Exhaust Gas Temperatures (EGTs) and Cylinder Head Temperatures become too high potentially causing the exhaust manifold to crack, or cause a spark plug tip to fail and burn off or worst case scenario a piston could melt. Too rich will kill power and cause possible bore wash leading to premature internal wear. The ignition timing needs to be optimised to be as advanced as possible for maximum power gains, but without instigating any knock retard due to detonation, which again will cause running issues and eat into the ecu’s safety margin, especially when driven hard on track.

On the Rolling Road

When the car was again mapped back in June 2012, after I had made the first changes to the car the engine was producing good Stage 3 power and torque of 292bhp with 342lb ft torque (290bhp and 336lb ft on another run), with ignition timing, knock retard and fuelling all correct and safe which made the car very useable on track and road. Last time the car was checked on the rolling road during 2013 it achieved 300bhp during an unloaded run, although running a little leaner due to the lack of load.

Now the ecu is being mapped to suit the new spec. With a base map configuration for the new set up the improvement was to 327bhp, however the engine was running far too lean through the mid range, then richening up above 5,000rpm so this fuelling certainly needed addressing.

A quick adjustment to the actuator was made to alter the break off pressure, further rolling road runs were made to check fuelling, boost and ignition and all the relevant changes were made to the software after consulting the data logging output.

This final mapping session with mapping changes has produced a very healthy 336bhp and 355lb ft torque (repeated on two back to back loaded runs) and even after several hot runs (heat being a big issue with turbocharged cars – they hate it and it is kills power) the engine produces around 328-330bhp, so very good for a 90,000 mile engine.

These changes have made a massive difference to the overall car with huge gains in power and torque above 3,500 rpm where it is all useable. The difference in the power and torque is clearly evident and can be seen in the graph below:

Before and After Power and Torque Graphs