I had to use a pulley that runs my fuel injection pump that is 16 cogs, old one is 14. My pump has 28 cog pulley. Main bypass was .076 my question is how much should i increase my bypass pill size? 8 nozzles at .038.
Percent bypass was 33.3 with the .038 nozzles and .076 bypass.

You are slowing the pump down by 13% when you switch to the larger 16 tooth pulley. If the pump is slowed down then wouldn't the bypass jet need to be smaller to keep the same pressure in the line? You're asking how much to increase the bypass jet but I think you need to decrease t. I'm not sure if you decrease it by 13% since the pump slowed 13% but that seems like a place to start. If you are going to reduce the bypass jet by 13% you'll end up going from a 0.076 to a 0.071.

By changing the crank pulley to 16 teeth, you have increased the volume by 14.3%. Your pump changes from a 4.2 GPM to a 4.8 GPM. To have the same pressure at the nozzles, you will need a .0888 bypass pill. So a .088 is a little rich and .089 is a tiny bit leaner.

Joe

thanks Joe, i came up with these numbers based off my pumps output of 4.68 gal/ min
Old flow amount to nozzles = 3.12156 g/mn

Old bypass 33.3%
Pump now overdrivin by 14.285%
New bypass percent = 41.64%
New pill for bypass .092
I appreciate the help, as a mistake hear could be costly! Do you see anything wrong with my calcs?

With a .092, I show a 3 psi lower at the nozzles than the baseline with the .076. If it were me, I would stick the .088 in it and make a run.

Joe

Thanks Joe. I will try the .088.