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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
In my opinion there are several things going on that impact additional injectors.

Many think it is because the manifold is not conducive to fuel running through it. That may be but I do not really accept this.

I am more inclined to believe it is the timing of the EFI injector events.

If it fires once per rpm or even twice per rpm the burst of fuel it going to go to the cylinder or couple of cylinders that are on the intake cycle at that instant. The other cylinders will not get as much of the extra fuel and run lean.

I suspect one can overcome this by using saturation injectors that are only run at 100% when on. One could stage two different injectors.

Using an 8 cylinder CIS head with two extra injectors would fit that. The injectors could even have valves on them that are trigger when needed. However, on such a CIS system they would not have to be staged. They can be adjusted around by increasing control pressure so the metering system advances slower.

A secondary opportunity is where they are located. The further from the throttle body probably the better as long as the fuel dose not run down to the hot turbo should it pool

The last factor I suspect that may effect some cylinders going lean and burning through is the exhaust. With an unequal length exhaust tubes to some cylinders at certain times may end up with different levels of residual exhaust pressure when the exhaust valve closes. This could effect how much air is packed into each cylinder on the intake stroke thought the amount of fuel remains the same. That might create a variation in temperature and effective AFR per cylinder.

At least that is what I believe so far.

Last edited by 911st; 01-27-2010 at 08:09 AM..
Old 01-27-2010, 07:57 AM
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