Thread: CIS fuel head
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beepbeep beepbeep is offline
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Originally Posted by Alan L View Post
Thanks for the help guys, and Goran, you can relax now.
Seems Bosch and I came to the same source of steel for the pistons - the coeff of expansion was the same, and mine came out 0.7 gm heavier by the time I finished it in the original shape. I intentionally left extra on originally - better too heavy than light - can always take some off.
Jeez. First you split the fuel head, then you made your own plunger piston. That's seriously hard-core! I dissasembled many things but wouldn't touch CIS with a 10-foot pole (except throwing it out and replacing it with EFI)

So you recieved your WBO2? That's excellent! I hope it has functionality to log AFR vs. RPM, it's quite hard just to look at the indicator.

As far as I understand, you first synchronized the individual injector flows by measuring the fuel flow vs. time and adjusting their spring tensions and then fiddled with "collective" CO adjuster screw by turning it 1 turn until you got your idle right?

I suggest doing a WBO2 pull now and checking AFR's during the load. Usual CIS behaviour is fairly rich AFR's (around 12 or so) during the boost, then leaning out above 5500 RPM towards 13's.
CO screw mostly influences AFR's at idle and low loads, it's the shape of CIS flapper-cone that is doing the air-fuel "mapping" after that. About on-throttle hesitation: as far as I know, CIS doesn't have any accelleration-enrichment device except the inertia of plunger itself. When you boot it, plunger is supposed to overswing briefly and squirt extra fuel. You new DIY-plunger maybe isn't "run in" yet so it doesn't move as freely as old one.

If I understood everything correctly, you bought Japanese car with later US-spec engine that has been rebuilt recently, ROW dizzy and fuel head, 964 WUR and Mercedes fuel regulator? Challenging to say the least!
Thank you for your time,
Old 12-05-2007, 02:05 AM
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