Automotive manufacturers go to huge lengths to achieve the perfect/maximum thermal efficiency in engine design striking the perfect balance from a induction temperature and the heating point of the fuel vs permissible exhaust temperature (EGT) whist targeting the idea push/pumping(expansion) cycle or adiabatic process. Extracting more performance from a diesel engine for a manufacture is purely down to controlling EGT relative to particle and Nox (nitrogen oxide) emissions the very reason implementing the use of DPF systems.
So how is the damage done? – By modifying the lambda (fuel relative to air) the first issue is the over loading of the DPF management cycle as the filter is designed to handle a certain amount of matter vs measured flow vs a oil quality / engine ageing strategy, think of it like this – tuning a engine it is a given performance air filters provide more airflow by using better more expensive materials. Currently there is no material solution for DPF to achieve performance increase other than (at best) an increase regeneration cycles to keep flow optimized resulting in increased fuel use for such a regeneration leading to the inevitable shorted life cycle. So adding fuel = Dead DPF.
Turbochargers suffer greatly from tuning ignorance, and are a fundamental component in managing the efficiency of a engine. The compressor map of a turbo dictates the dynamics of the air heating process with the cylinder temperatures vs EGT calibrated precisely known as the ‘flame wall’ as diesel fuel ignition timing is dictated by the mass vs relative fuel temperature respecting thermodynamic variables / eg – the fuel pressure (endothermic reaction), fuel mass (duration), start of injection (timing). We see issues with calibrations where the mass (duration) is modified the SOI (timing) is modified along with increased rail pressure resulting in the movement in flame wall causing a cascade rise in EGT thus damaging the turbocharger due to the pardox of increased boost pressure only compounding the issue. Another issue born out of over fueling and flame de-tuning is the sooting of the exhaust wheel of the turbo causing a imbalance of the turbine and jamming of a variable geometry where applicable thus greatly reducing the life of the turbocharger.
Drive line and chassis harmonics – Manufacturers again go to huge length to control engine running frequency and this ‘noise’ causes long term damage to components a simple example is the presence of a dual mass flywheel which is tasked in part to countering this issue in conjunction with tuned engine mounts and phased injection strategies. By not respecting these components in a calibration all will lead to early failure.
The work is already done in the ECU to increase the performance to a sensible point without compromising the powertrain the key is understanding the physics on which the calibration was designed, so the next time you see a youtube video of a vehicle pumping a dyno cell full of black smoke think about what you have read here and the ignorance of some tuners.