external velocity performance

Claire Mendes Real (asker) Feb 10, 2020:

The context was the tests of the additive in the engine, so, I have choosen "par rapport aux tests sur route" opposite to a test bench, as you proposed.
Thank you

Daryo Feb 10, 2020:

Any more context?
There must be some clues elsewhere in the ST as to what exactly is "external" in relation to what.

If the whole text is part of some advertisement or article already published, it would be helpful to have the whole text.

My guess would be that "external" means "external to the diesel engine" i.e. "external velocity performance" would be the performance of the engine when mounted in a vehicle (as opposed to when tested out of the vehicle on a test bench). But it could also be something totally else!