ENGINE PARTS
From season 42 engine will not just a simple development of one part but 4 different parts to be developed and after that put together into one engine - Combustion Engine, MGU-H, MGU-K, Turbocharger.
In addition to that there will be possibility to tune engine performance using 3 tuning parameters. This setting will be evaluated once per day and the result will be available next day. Bad parameters will result to loss of quality by 3-4% while perfect setting will give 0.3% bonus.
Tuning also enables to adjust engine performance so some attributes will be better while others will be worse. So for example on tracks where maximum speed is much more important than other attributes, tuning engine to boost maximum speed and decrease acceleration might give little improved lap times.

ENGINE DEVELOPMENT
Obviously developing high quality part for engine with new rules will be much easier and faster than developing full engine in current rules.

SUPPLIER ENGINES
There will be also supplier engines available. At the beginning they will be stronger than best engines developed by the teams but will not allow engine tuning. There will not be done much improvement on supplier engines so after few seasons they will become weaker than developed.
There will be no cheap engines available and team who purchases engine must stay with the selected supplier for 5 seasons at least.

ENERGY STORE
With new engine KERS will become obsolete as MGU-K is similar and now part of engine. In place of that we introduce new part called Energy Store. From season 42 KERS will NOT be used on cars but Engine Store will.
Energy Store will be also available to be purchased from suppliers. There will be 2 suppliers with quality of 50% and 70%.

MORE DETAILS
More details can be found in our blog:
New Formula 1 Engines Idea
New Formula 1 Engines Details