Diesel fuel additives.

[rambling robin]

I too remember the fun days of drilling out inlet manifolds on A series engines and fitting a water injector of some sort. During those days of soaring oil/petrol prices, 15% inflation and petrol rationing preparations you'd do just about anything to get better mpg.

 

The reason why engines seem to be more powerful in the cool of the evening / damp days is nothing to do with water and everything to do with air. Cool / damp air is denser than hot dry air. The volumetric efficiency is therefore greater - for any given intake stroke you get more air if it is dense and therefore more energy per ignition cycle, so the engine works better.

 

Most of the diesel additives seem to focus on injector cleaning, no harm in that. 2 stroke oil would act a bit like the old Upper Cylinder Lubricants - Redex etc. which puzzles me given that one of the reasons for the long life of diesel engines is the fact that they are running on oil already. However the reduction in sulphur content would be the equivalent of removal of lead in petrol so it would possibly help with top end lubrication. I do have some concerns with additives on modern turbos and EGR valves and DPF exhausts.

[George Collings]

And the cooler charge is the reason most turbocharged engines have an inter-cooler that looks like second radiator between the turbo and inlet manifold.

 

The turbo extracts some of the heat energy dumped by the exhaust and uses it to compress the incoming air, that heats it making it less dense but the intercooler dumps some of the heat to the atmosphere to regain charge density.

 

There is a net gain in thermal efficiency and therefore fuel economy as long as the temptation to use the ability to use the extra air to burn more fuel is resisted.