Question: What is the meaning of the metering rod codes, such as Q11, Q09, R09, and V11?
Answer: Most metering rods are the same overall length@ 2.583 inches. The letter designation refers to the grind length on the metering rod. A Q=2.030 inches in grind length. A V=2.010 inches in grind length. Shorter grind lengths are leaner rods overall, while longer grind lengths are richer rods overall.The number designation describes the starting metering rodthicknessfrom the upper mid-range to wide open throttle. The numbers vary in increments of two thousandths of an inch. An 11=.080 inches. A 13=.082 inches (leaner than an 11). A 09=.078 inches (richer than an 11).
Quelle: Unofficial Tuning Guide