The purpose of a test is to accept or reject a hypothesis.

In order to test my project's  hypothesis, there are a number of approaches I can undertake which may aid in accepting or rejecting the proposed hypothesis.

First, let's consider engine braking in general. The most notable use of engine braking is large commercial [diesel] trucks with heavy payloads (typically towing. In this application, in order to preserve brake life, the engine is placed into a lower gear which, in turn, increases engine speed (without much, if any additional fuel), resulting in the engine converting the vehicle's kinetic energy into 'air' compression within the engine's cylinders.

I suspect that instead of converting kinetic energy to compression - it (the vehicle's kinetic energy) can be recovered by an auxiliary load on the engine. In industry, these loads are either auxiliary (intentional as a value-add to the engine's primary power output function) or parasitic (unwanted, typically wasted and dissipated as heat).

The first task is to identify how much auxiliary load I can place on the engine under controlled conditions, and what the fuel rate response looks like.

To do this, I need to:

1. Measure engine speed

2. Measure fuel consumption rate

3. Apply an auxiliary load(s).