Back in March of this year, I did a partial rebuild of the engine in the '88 Spider that included 10:1 (nominal) Motronic pistons and liners generously donated by Ed Prytherch (alfaparticle) and a set of better cams from Richard Jemison. With the higher compression pistons and the bigger cams, I have been curious about the AFR curve in this engine given the often discussed fuel limitations of stock L-Jet. This weekend, Ken Vaughn and I hooked up the Zeitronix to log some data. A representative curve from one of the test runs is shown below. I am encouraged to find that L-Jet does a very good job of keeping the AFR close to 13:1 throughout the rev range at wide open throttle. Richard told me L-Jet could handle the 776/195 cam pairing without issues but I did not expect the AFR to be this close to the ideal, low 13s at the top of the rev range. Perhaps this information can be useful to someone considering engine improvements to an L-Jet Spider.
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