With a small increase from 6% to 9% nitro, in preparation we dropped the AFR to from 3.7 to 3.4. As a result, we picked up a tenth of a second and about 4 MPH over 6% nitro. Part of that increase was that we were hitting on all 8 cylinders better than with 6%. We are running the engine rich with a low amperage magneto. And performance was reduced for the 6% mixture as a result.
We are using www.airdensityonline.com/pro-calcs/ to determine our nozzle, main bypass, & high speed jetting changes. With this caclulator, we are able to set up an air to fuel ratio target from our spare jetting inventory, maintain a peak fuel pressure, and set up our high speed jet opening point. That is determined from the pressure at the RPM for the opening. More about that adjustment in Fuel Injection Racing Secrets.
The the calculator is easy to use and fast.