Evaluating Charge Robbing
Turbo Mini Forums

I've been having a play with the simulation outputs for the new 998 turbo.

As I've been able to simulate the siamese ports, I thought it would be interesting to see how much is actually lost in perfomance terms due to the siamese inlets.

So I've plotted the flow for the inner and outer cylinders:


This is after I've optimised the manifold runner lengths.

The green line represents the total flow through the inlet valve overlap period. As you can see, the outer cylinders actually pull air out of the inner cylinders. Not surprising when you think that as the inner cylinder piston is rising after BDC, the outer cylinder piston is falling and the outer cylinder exhaust valve is open and pulling air through.

So then I've plotted the VE for the inner and outer cylinders and the average. Overall, the effect on performace is only about 3-4%.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

how about as a test on the dyno cuting the spark to each cyl in turn and obseving the change in power.

Joe, not one of your best ideas :)

Let's first see if we get the predicted power output on the Dyno.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."