2026 Q3 Review - Hatchback

With the summer's heatwaves seeming to get hotter and hotter, it was important to ensure that the hatchback's mapping was accurate and that the engine could deal with the additional heat when the car was driven enthusiastically.

Whilst mapping, it became apparent that an oil cooler would ideally be required for trackday use, as during consecutive ramp runs the oil temperature would quickly heat up to around 120 degrees Celsius (although an engine protection limiter was mapped in to reduce engine revs if the oil temperature exceeded this temperature). The downside of using a rotated intake manifold was also discovered, as the aircon compressor was sorely needed to combat the heat! To provide an additional safeguard against excessive heat, the smallest external wastegate spring was used, which kept boost levels to a very modest 0.8 bar until the conservative 6.5k rpm redline.

At Oulton Park, the ambient temperature was around 34 degrees all day, and the hatch was not equipped to be driven at full throttle all day long around the challenging and undulating circuit.

With the engine protection limiters keeping things in check, the only thing which required changing during the day were the tyre pressures and the engine fan settings, which were altered to ensure that the fans would spool up when the engine temperature exceeded 95 degrees regardless of how fast the car was going. After this change, the coolant temperature never exceeded its normal operating range.

With only a couple of days' rest for the hatch before competing in a two day sprint event at Curborough sprint course, time only allowed for some basic check over to make sure that the engine was still healthy, and to check that the tyres had survived the journey back to Cardiff following the heat at Oulton Park! With only a small crack in the coolant tank bracket to be monitored, it was time to set off to Curborough.

With temperatures still hovering around 30 degrees Celsius on the Saturday, it was important to see how the hatch dealt with the temperatures before driving at 100%. However, with a class of only two cars (the other being a BMW M4 Competition edition), second place was a certainty if the hatch could make it through the weekend. With the shorter track meaning that runs took just over a minute each, this was much easier on the car compared to Oulton Park. Having completed practice without the engine protection limiters cutting in, it was possible to push on during the timed runs, with corresponding improvement in the times.

The course was different for the Sunday, but the hatch still performed well, with temperatures dropping slightly to 28 degrees. With second places for both days, and the car driving nicely back to Cardiff, it seemed that the 2.1 had survived the heat. The things which needed to be worked on included resolving an intermittent misfire, dialling in the launch control boost building strategy (the smaller capacity engine and the large turbo made this tricky during the event), and installing a larger radiator for future trackdays in the heat.

Some cheaper cooling system mods were trialled before committing to changing the front radiator. The first being a 1.3 bar STI coolant reservoir cap, which holds the coolant system at a higher pressure (compared to the standard 1.08 bar cap) before passing coolant to the overflow tank.

This seemed to work as expected during some road testing, although there was a very small coolant leak from the reservoir return pipe, which was attributed to the pipe moving slightly with the higher pressure (and was remedied by fitting a jubilee clip instead of the standard clip). The next mod trialled was an RCM Modine delete kit.

As the name suggests, this removes the oil/coolant heat exchanger, blanks off a coolant outlet from the (three port) water pump, and provides a smaller extension for the oil filter to attach directly to the block. Installing the delete kit meant that the oil is not directly heated by coolant, which would (in theory) allow for a longer oil warmup time (as the coolant tended to warm up before the oil), and would hopefully result in a slightly higher engine oil pressure, due to the reduced restriction in the oil system. The kit was fairly straightforward to install, and once checked for leaks and the engine oil level topped up, it was time to head out for a datalogging session.

There didn't seem to be a huge amount of difference in the oil temperature once the coolant was up to temperature, although there seemed to be a small increase (about 0.2 bar) of oil pressure during a hot idle, and the oil took a few more minutes more to warm up. Overall, it was deemed a worthwhile modification for track/sprint cars, but the improvement was fairly minimal, with a dedicated oil cooler likely being the most effective option (perhaps no big surprise) for sustained track use. The coolant bracket was repaired using the TIG, and a bigger spring trialled in the Turbosmart external wastegate (which turned out to be way too stiff), leaving the occasional misfire left on the list to sort out.

It was originally the plan to enter the August sprint at Castle Combe in the hillclimb car, however, when taking it out for a quick datalogging session the day before to check that all was ok, it developed a fairly sustained misfire when hot. With time running out following swapping spark plugs and coils, the decision was made to compete using the hatchback.

It was once again a hot day, and with two drivers, the hatch had a lot to contend with. The day progressed with no mishaps, although the hatch was rather uncompetitive in the class as the boost was still at a modest 0.8 bar (wastegate spring pressure), the misfire occasionally tended to occur under full throttle, and a protection limiter tended to creep in by the hammerdown straight, which required short shifting to avoid it.

Despite these issues, the hatchback made it through the day and the (gentle) drive back to Pleiades HQ, and next on the list was to investigate the misfire.

The car was firstly taken out for a mapping session to see if changing any settings would help, and if fuelling too much under boost was the cause of the issue. A slightly stiffer wastegate spring was used for this mapping session, with boost increased slightly to just below 1 bar.

After two full throttle ramp runs, the misfire seemed to consistently occur, and tended to creep in during a hot idle too. A set of used ICP coil packs were purchased, and the spark plugs were cleaned with a wire brush and gapped from 0.7mm to 0.6mm. After a road test all seemed well, with the hatch performing as expected. With the temptation to turn up the boost still lingering, we are planning on having another mapping session once the cooler weather returns.