DI Two Strokes - How do they work

[whichway]

Hi

I more or less understand how my mower works. I think that a two stroke outboard is about the same (chops water rather than grass).

Can anybody explain. or provide a link explaining how the various DI two strokes work - I find the manufacturer's stuff a bit glossy. I am really interested in understanding what pressures are generated, torque curves, the more technical the better.

What is the difference between HPDI, Etec, Optimax etc.

Does anyone know of any comparisons between the DI motors and 4 strokes in the 150hp range.

Does anyone have any facts regarding the reliability of these motors (advice that the father in law's, bosses, next door neighbour's motor failed isn't really what I need, I want to know any inherent problems)

Don't want much do I. :)

Thanks

Whichway

[Mad_Barry]

Regular 2 strokes are inefficient as they spit heaps of unburnt fuel out through the exhaust. To remedy this they basically all compress the fuel & before sending it thru an injector. The higher pressure leads to better atomisation, & therefore burns it more efficiently & less fuel is needed to get the job done.

Some also compress the air to add along with the compressed fuel.

The manufacturers sites aren't that bad at explaining the basics, but you're going to be pushing it up hill to get torque figures & graphs. Even though they are more meaningful than a straight hp rating, none just seem to give them up. The only one I've seen was a graph on an evinrude sales poster showing the 90 etech had more torque than a 100 yammy 4 stroke. No figures, just a couple of pretty lines to be taken with a grain of salt.

If you do find some real figures, please post them up.