turbo and WOT injector

[Buchholz, Steven]

The one thing that I have not seen discussed here is the relative
distribution of air and fuel to the individual cylinders.  While Audi has
tried to even out the flow to each with the large air reservoir in the
intake manifold, it remains true that at high flow rates on the WX and MC
engines (which have the TB mounted at one end of the reservoir and aimed
rearward) there will be more air flowing to the rear cylinders than the
front ones.  Given that you have a system that provides the same amount of
fuel to each cylinder you will naturally find that the mixture in the
rearmost cylinders is on the lean side, while the mixture in the front
cylinders will be rich.  Adding pulsed injectors into each intake runner
could be used to address this variation, but it would require either
individual measurement and control of the mixture at each cylinder or a
compensating algorithm that would apportion more fuel to the rear and less
to the front.  The thing I've always kinda liked about the sixth injector in
the flow is that it actually would tend to distribute the fuel in a similar
manner to the distribution of the air.  In this case we are not talking
about an injector mounted in the CSI location, but something in the airflow.
I forget the manufacturer, but I've seen this sort of setup installed in an
urquattro that had bumped up boost.  

Steve Buchholz
San Jose, CA (USA)