A dyno tells you output. It does not tell you what the combustion event is doing inside the cylinder. That matters when we’re leaning on an engine like the L5P, especially around a nominal 180-bar maximum cylinder pressure. With the KiBox, we can see the full in-cylinder pressure trace in real time: how pressure builds, where the peak occurs, and how it bleeds off after the event. That lets us evaluate not just power, but how that power is being made. When injection starts 7 to 8 degrees before top dead center, the pressure curve tells us exactly how the cylinder responds. That information is what keeps tuning and testing from turning into broken parts.
The test begins during warm-up of an L5P Duramax as the team prepares to study combustion behavior under increasing load. The engine is described as having a nominal maximum cylinder pressure of 180 bar, and the objective is to determine how far it can be pushed without damaging the engine.
To monitor the engine safely, the team uses instrumentation that measures pressure directly inside the cylinder.
Rather than looking only at maximum cylinder pressure, they analyze the entire pressure trace throughout the combustion event, including how pressure builds, where it peaks, and how it falls afterward.
Peak pressure alone does not reveal everything happening inside the cylinder. The rate of pressure rise, location of peak pressure, and pressure decay all provide important information about combustion severity.
Examining the complete curve allows the team to determine whether combustion remains controlled or is becoming excessively aggressive as power increases.
At this stage of testing, injection timing is approximately 7 to 8 degrees before top dead center.
With fuel being introduced before the piston reaches TDC, the resulting combustion event creates a noticeable shape in the cylinder-pressure trace as pressure builds around top dead center.
Injection timing directly affects when cylinder pressure develops relative to piston position.
Advancing combustion can cause pressure to rise earlier and more aggressively, increasing mechanical loading on the engine. For that reason, the team is watching not only maximum pressure but also exactly where that pressure occurs in terms of crank angle.
The in-cylinder pressure instrumentation is considered just as important as the dynamometer itself.
The dyno measures engine output and load, while the cylinder-pressure equipment reveals what is happening inside the combustion chamber, providing information that can identify dangerous conditions before they result in engine damage.
The goal is to push the L5P intelligently rather than simply increase load until something breaks.
By monitoring the complete cylinder-pressure trace against the engine's nominal 180-bar design level, the team can explore the engine's limits while identifying dangerous combustion behavior before it causes a premature failure.
