New challenges encountered when designing highly downsized gasoline engines (through new PSA Peugeot Citroën powertrain examples)

As a mean to reduce fuel consumption and CO2 emissions, downsizing engines is an essential lever.
Nowadays, achieving regularly 80 kW/l and 170 Nm/l is possible thanks to turbocharger. Last developments from PSA Peugeot Citroën exceed these limits:

- EB turbo PureTech engine : 1,2 liter engine, 3 cylinders, 80 kW/l, 192 N.m/l
- EP6CDTR: 1,6 liter engine, 4 cylinders, 124 kW/l, 205 N.m/l

Downsizing at these levels leads to:
- very high cylinder pressures and thermal flow
- But also an increased probability of abnormal combustions: knock, megaknock with cylinder pressures up to 200 bars.
In this context, the dimensioning of the base engine has to take in account these constraints to fulfill the reliability targets.

On the other hand, limited increase of masses and friction losses is a challenge: new material and/or concept have to be chosen and the last numerical methods have to be used.
We will illustrate this challenge through examples from the last developments of PSA Peugeot Citroën gasoline engines.
The last part of the paper will show the results obtained in terms of performances and CO2 emissions.