How accurate is the boost calculation when you use: Crank pulley/blower pulley X blower ratio X max RPM?

I tried to max out my F1 using a 7.25" crank pulley and a 4.10" blower pulley with a 5.4 step ratio spinning to 7300rpms and I am only seeing about 15psi. I can not see any dust anywhere around the blower, so I am ruling out belt slip.

Don't get me wrong, I am happy with the power it is making, but I was expecting to get more boost from the F1.

Does anyone have any suggestions? Does anyone elses boost come out right with this formula?

 

Those calculators can only give you a ball park figure. Your actual boost is going to vary depending on cam specs, efficiency of the motor, etc. Does your boost build steadily all the way to 7300rpm, or does it level off at some point?

 

Exactly We ran a F1R that would only push 18lbs,then switched compression and Cam which put boost at 26lbs..No pulley changes.

 

I keeps going up, all the way to 6800-6900. I can feel it pulling hard from about 5K to 7K, but I could not look at the guage while trying to watch the road at the same time. My cam is in the 250s with a 650s lift. On the dyno, I could only see about 15lbs at 6900 though. I thought it might be slipping some, but after running it for a while and taking it to the track, I still do not see any belt dust. I have a 3.75 pulley, how much of a difference would I see in swapping pulleys?