JoeMag

On a CIS fuel head, when the plunger in the middle in the fuel head is pushed up by the flapper plate moving down, how does that increase the fuel flow?

thx!
Joe

Win Rice

Joe,

The barrel of the control valve has 6 metering slits in it. As the plunger moves up it uncovers more of the slit allowing more fuel.

I have a PDF of a Bosch technical manual I can send you, if you send me a PM with your e-mail address. It has everything you would ever want to know about CIS.

Win

Olli

also sent a PM

JoeMag

PM sent, thanks. Ok, and I'm sure I'll read about this, but does the control pressure effect the movement of this plunger? ...or does it just make a differential pressure larger causing move flow?

Also, in a typical application of 0.8 bar, is the plunger maxed out in it's movement up? ...how about 1 bar?

Win Rice

The control pressure acts on the plunger, less control pressure, more plunger movement and a richer mixture. Boost enrichment comes from the pem setting (height) in the WUR, which lowers the control pressure under boost. And yes, eventually you can lower the control pressure enough to bottom out (top out?) the plunger and there is no more fuel available.

Played with mine enough to get 11.8 Max AFR at 1.0 bar, 6400 RPM (stock rod bolts!). But just about wore out the WUR bolts doing it.

Win