air/fuel ratio question...........

[fred cook]

I have been tuning the fuel injection on my 3.3SS engine using an a/f ratio gauge. At the moment, I have it adjusted to run right at stoichiometric (14.7:1) during "normal" driving. At full throttle, it will go to about 13.5:1. While I know that this is close to "ideal", is it too lean for day to day driving? The engine starts easily and once warm holds a nice steady idle at 950 rpms. The fuel injection system that I am using on this engine is a modified CIS system made from a large port air box and later (1980) fuel distributor and throttle body. The miscellaneous controls have been backdated to be similar to a 1973 1/2 type system.

[Vereeken]

At full throttle 13.5 is too lean.

It will not do any harm but you are leaving some horses behind. 12.9 13.1 would be perfect for our engines....



My 2 cents.

Michel

[timmy2]

I set mine to 12.5 at full throttle on my AFR map. Pulls great at WOT.
The 14.7 for cruising should be fine, I keep mine around 14.5.

[fred cook]

Originally Posted by Vereeken

At full throttle 13.5 is too lean.

It will not do any harm but you are leaving some horses behind. 12.9 13.1 would be perfect for our engines....



My 2 cents.

Michel

Not a problem, most likely about 1/8th of a turn on the adjustment screw. Since I am working with the basic CIS system, top end enrichment is related to the cruise a/f ratio. I do have a switch installed that activates the cold start valve at full throttle. It acts as a 7th injector to help keep from going lean. The cold start valve manifold makes certain that each cylinder gets some of the extra fuel. I know that the conventional wisdom would be to use PMO carbs or ITBs, but I wanted to see what I could get out of the CIS, keeping the easy start and reasonable fuel mileage that it provides.

[timmy2]

What are you running at idle when fully warm?
Should be around 13.8 to 14.