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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Originally Posted by 911st View Post
The IA head gets is its increased fuel flow from having the builder adjust it to out of specs. This is done by playing w the tension of the springs around the internal orifices and the orifice height.

(Doing so was my idea and was a result of my conversation w the builder on behalf of the first guy that did this.)

This screws up everything in the design of the CIS system. If you set the idle A/F correctly, your cruse A/F will be to rich. You know with it dose to the A/F's on boost. It also adds to lag in that people start playing w increasing WUR's control pressure settings or delaying enrichment on boost.

It can only really be tamed w a mappable system that can take control of control pressure and all rpm points and load conditions.

Other wise one would have to change the cone shape the metering plate moves in so it moves slower than it is supposed to. One may get away w trimming the stock plate to balance things back out.

I believe the only real physical mod they make is when converting a US head that has the frequency valve/ lambda loop set up to make it into a euro head.
I've heard that the IA fuel head mod is:
CNC enlargement of the metering slits in the control plunger cylinder and enlargement of the orifices the fuel flows through to get to the fuel line banjo fittings.

A plug is installed where the lambda pulse valve hooked up next to the fuel inlet on post '86 aluminum colored USA heads.

The individual allen head fuel flow fine adjustments next to the banjo bolts are then painted green.

Once they are modified there is no resetting it back to stock because the metering slits have been enlarged to flow more fuel.
Old 06-16-2008, 05:09 PM
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