Thread: Pants-less 930
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DDDD DDDD is offline
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Join Date: Jan 2007
Posts: 1,077
Originally Posted by rhjames View Post
excuse me for venturing into the unknown (I'm from that "other" Porsche realm know as the 928 side of things), but I still didn't quite get the deal about two other injectors on the CIS setup you guys were discussing......?

I am in the middle of building a blown/stroked/Euro 928 engine, using the CIS setup that my Euro 928 came with.

Where are the two other injectors plumbed in at? Are they down stream of the turbo, or just prior to the intake ports on the heads, or are they plumbed into the intake manifold?

While I'm not going to be using turbos, I will be using a roots type supercharger and was curious about extra injection to coincide with the blower's increased air compression (volume)to prevent detonation.

Any thoughts or guidance from any of you?


P.S. NIce job on the Carrera......funny looking exhaust though----maybe you'd like my header sidepipes on my 928 better? Loud as heck (no muffs inside), but absolutely zero backpressure......
I am not knowledgble enough to explain this well, but I have had another friend look at the set up recently and essentially the two extra lines don't deliver fuel, they change the pressure so that the WUR flows more fuel. The lines are using pressure to trick the WUR or manifold or something into thinking that the car needs more fuel flow.

The CIS system runs on vacuum, so if you can change the pressure when boost comes on, you are essentially making the car richer, almost like when you start a lawn tractor and at first you pull out the choke to get extra gas into the tractor to help it start. Only in this situation, the 'choke' application is permanent, in other words the change in pressure to the CIS system constantly causes more fuel to flow, especially under boost.

Greddy sell these set ups...
Old 10-01-2007, 06:14 AM
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