Base

The end of 2022 started project made great success during the race season 2023. The big steps in harmonization of the chassis, engine and driver were the key parameters for this success.

Goal

The aim for 2024 was increasing the troque from 4500-9000 rpm by around 10 Nm on average to push the system of chassis-engine-driver further for another 5/10 s laptime reduction on the reference race track.

Process

The variables for the engine itself were: pistons, connecting rods and camshafts for a low pricing but harmonized setup with respect to driver style, chassis weight, budget and no customization, only of the shelf parts are allowed. The variables were reflected with market available parts and their specification into the 1D-simulation to find the best system available for the budget. That was a huge challenge, not only to find the specification of available parts, but also to handle the effort for the decision process on rational levels. The engine parts list, which was the result of that optimization process, was quite unique, but price worth.

Result

The best laptime climbed up the reference track best list from 17th to place 15th before a Corvette Z06 and a Porsche Cayman RSR, which was quite impressive. Customer run the reference track with an 0.6 s shorter laptime, while loosing some time on the brake, compared to last year.

Engine failure - late '24 season

On the way of another PB the 2024 built new engine had a rare engine failure. The piston pin broke on #4. The ordered pistons came with a light weight pin of 71 g and 3.47 mm wall thickness (5115 alloy), the ordered connecting rod with 430 g, rated for 440 whp. The rare observation was, the pin didn't bent visually, but folded itself inside, the rod small eye separated.

We made a deep dive analysis of logs till the incident and the engine damage parts itself. All other bearings came out in very good condition, the other 3 cylinder liners came out in very good condition. All indicators let us to the verdict we suffered a not matching Wöhler curve of these two, the rod and the wrist pin.

One ackward thing to mention, the 2024 chassis allowed up to 1.6 g peak and 1.4 g lateral accelerations continously, which introduced a rolling oscillation, causing engine speed oscillations of +-200 rpm under full load. The more torque was available, the higher the oscillation amplitude was. This put some additional load into the cranktrain and will be addressed for the 2025 season.

Finishing of '24 season

We collected up a stock Honda K20Z3 block, which showed acceptable compression test results, swapped the engines and retuned the engine calibration. During that time the chassis of the car was refined and adjusted again. On the reference track the customer was able to get near to the built engine laptime with +0.4 s (better brake point inclusive).

Plans for 2025

Further improvements to cut down laptimes.