This was originally posted by enginerdI have been doing some FSI research. We have a GDI development group here at work. We will be running hitachi pumps on a test bench. I can't give away any proprietary goods, but i can share some details.
Basically the fuel pump is the limit to the power potential of the motors. They are positive displacement single piston pumps. Driven by the exhaust camshaft with a 3 lobe cam, the pump will deliver 3 pumping strokes for every 2 engine revolutions. The delivered fuel limits the engines torque in the midrange, however it has a large peak power potential.
here is a plot based on the pumps geometric output using an audi 3 lobe 5mm lift cam profile.
The green is a GIAC dyno on an FSI powered car. They were hitting the limit for the stock pump and losing fuel pressure at the torque peak.
more details here
http://forums.vwvortex.com/zerothread?id=2339563unfortunately the usual mud slingers trashed the very good and informational thread.
Whoops - I had to edit the graph. Peak Hp was 230 according to GIAC, not 260 that i Had originally. torque was 260.
Here is the dyno
