Direct Injection

[James Ballenger]

Gary Derian wrote:

> I am aware of Orbital's work.  Their system is a great way to make a 2
> stroke meet emission requirements.  The air assisted injection is necessary
> to achieve fuel air mixing in a limited time since injection occurs after
> the exhaust port is closed.

You mean intake port?  It is necessary to obtain acheive the mixing in the short
period of time, a plus is the good atomization.

> The main benefits to direct injection explained here seem to center on the
> ability to create a stratified charge, a combustible mixture near the spark
> with excess air elsewhere.  This improves part throttle economy.  It also
> reduces HC and CO emissions.  NOx are also reduced but not enough to suit
> current emissions standards.

I dunno about that, from their documentation, orbital claims marginally lower hc
and co emissions with a whopping 85-95% reductions in NOx.  They claim the
injected air results in egr dilution which facilitates the lower NOx.

> So now we have stochiometric fuel mix and economy gearing.  So where does
> direct injection help?  I'm not saying we should stop research on this
> matter, but this list, it seems to me, is primarily concerned with improving
> the performance of our cars by modifying the factory injection systems.  For
> these purposes, direct injection has no benefit.

    Orbital seems to be engineering their system for the best emissions/ fuel
economy and have found a slight increase in torque as a side benefit of sorts.
If one of use were to take the same system and fire it a few degrees earlier, we
would end up with a good mixture and superb atomization of the fuel.  If we were
to richen the mixture a little, we could be running a system that produced far
more power than an mpi system run today and still be able to beat the sniffer.

    James Ballenger