View Single Post
911st 911st is offline
Registered User
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Sorry if I am a bit rusty on my CIS stuff.

The amount of fuel that flows is almost totally dependent on the differential pressures in the head.

The head is amazing as it is self compensating for differances in true fuel pressure so that it always delivers the intended fuel flow. That is, if the supplied fuel presure to the head is low, it delivers the same to the injectors as if it should somehow go high.

When the differantial pressure lowers, more fuel is allowed to flow into the orifices inside the head.

I think all the adjustment screws do is allow balancing of the flows between injectors.

The key to more fuel flow is to allow the metering plate to advance further. This has to be done with lowering the control pressure like Andial dose or change how the metering plate reacts to air flow changes. This would have to be done with changing the cone the metering plate moves in or change the wind-age of the metering some way by adding mass above the stock metering plate so it dose not begin to stall at higher rpms a begin to lean the A/Fs.

If matched correctlly, the metering plate will start to stall a small degree after the motor reaches max hp so the A/F's will fall off the righ amoung along with HP.

People seem to think the head is running out of fuel, it is not.

It is just that Porsche designed the metering plate/cone to fit the profile of a 300hp motor.

The metering plate movement is such that the A/F's almost match a 300hp motor perfectly. Again, it is designed so the A/F's fall off the right amount to keep the A/F's the same after peak HP.

It is when we try to go past this we have difficulty.

There is some compensation available by playing w the WUR control pressure when the boost circuit is triggered. Porsche did this with the 94 3.6 turbo.

Just some thoughts.
Old 06-16-2008, 01:45 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #25 (permalink)