More on injection.
The list has taken a turn and started talking of air flow, which is correct.
However, not all cylinders suck at the same time, therefore, it is not
nearly a 6:2 ration of size. The suck goes alternately from front to rear
carb - look at the firing order. The firing is 120 degres apart and so
is the suck. You can figure out that there will be SOME overlap but really
what you get is "pulses of suck" through the carb - even if they happen at
very high speed.
I would think this is much less condisive to economy and emissions compared
with a the PI. Remember also the air intake in a PI is really only that,
an air intake. As in porting and polishing, anything you can do to improve
airflow into the motor will help. Taking out the bends and curves of a
carb manifold is beneficial - one of the reasons the late manifold is
inherently a better design. Long runners also increase low end torque,
wheras short ones are great for maximum flow at high revs. The SHO twin
runner system in the Yamaha-Ford is a perfect example of this principle.
The Bosch K Jetronic mechanical FI system used an airflow system to
determine fuel metering instead of vacuum. In modified form this was
successful at emissions testing until the 85 VW GTI (got one). All the air
passes the metering plate which is shaped as a cone is. The air flow opens
tha plate against the cone in a perscribed ratio and this feeds a signal to
the distributor block for fuel. Thus, even if vacuum is low, as in full
throttle, fuel is delivered according to AIR flow.
I've always wondered about fitting the FI system from an early Porsche 911
to a 6 cyl TR.
Dave T
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