My concern was in the volume of air that passed from the intake through
 the chamber and out the exhaust, and the amount of fuel in that flow. It
 appeared to me that if the injector timing could be manipulated so that
 at cruise power the air passing through to the exhaust carried the least
 possible amount of fuel, better efficiency would result.
 It may be that the volume lost is inconsequential, or that the timing
 cannot improve the loss - but since lean cruise fuel flow is less than
 half max power flow and therefore injectors are on less than half the
 time, it seems reasonable that some injection timings will be better
 than others.
 One reason direct injection engines can get better fuel mileage is that
 they lose no fuel out the exhaust during valve overlap.  It is also one
 reason that port injection engines can get better mileage than those
 with throttle -body injection.
 I ask the group's forgiveness for my intrusions - I know I have a gift
 for causing unintentional irritation.

 Victor Roberts


 You have a valid point there Victor. When the fuel is injected
 relative to
 top dead center could be important.

 So far we have no control over that as Tracy does not publish the source
 code of his system. We think he injects fuel once a rev. I'll find out
 as soon as I get my engine instrumented with a data aq system.

 Paul Lamar


 Paul it is probably a good idea to inject into the chamber after the port
 closes to prevent charge dilution. I talked to Orbital about direct
 injection, and their system was banned by some racing organizations as
 being a mild form of supercharging. It wouldn't matter to us of
 course. You
 have used the oil injection hole for a good vacuum source, and it seems a
 good one. Someone in the group suggested it as an injection port and it
 would probably be good for that as well.
 Bill Jepson


It would appear that injecting fuel into the oil injection hole after
the intake closed would likely result in the fuel being concentrated
just ahead of the trailing apex seal and a relatively lean mixture at
the leading plug.

Victor Roberts


The positive is that the air flow might assist in moving the charge along.
The reason I was thinking of it is that you could inject before there was
positive pressure in the chamber. Any later and you would need the high
pressure pump used in proper direct injection. The location of the
injectors on the 16b is no surprise. They could use a low pressure
injection. The orbital system was not true DI. The maximum pressure was 4
bar. The 16b could use a lower pressure injection pump and save on pump
power.
Bill Jepson