Flow Bench Users

**katana** · 24-09-2018, 12:30

Hi all,
Is there a direct conversion for CFM flow @ 10" to CFM flow at 28" Water. Just came across some figures for my bike head that seem low - (all at 0.400" lift) - IN 102.5 & EX 93. Its a reworked 4V - large valves 30 / 26mm dia's for a turbo application (hence the low total lift).
Just wondering - its on and working but the figures concern me?

**Graham** · 24-09-2018, 12:45

yes, in a book at home i have a chart which gives you a multiplication factor to go from any of the common depressions to another. although i usually do it the other way round, so the only one i know off the top of my head us to turn 28" into 10" you multiply by 0.6

ive never flow tested a bike head, but those figures do look low to me even given the relatively low lift, you head is only flowing about the same as a decent pinto or vw abf, that said what is the head? if its an old air/oil cooled gsxr motor then they are probably about right, if its something newer perhaps not

**katana** · 24-09-2018, 15:25

if its an old oil cooled gsxr motor

- got it in one! - Aircooled were the GSX range. re. conversion if 28-10 is x 0.6 then logic says 10-28 is / 0.6 ? So..... IN 102.5 & EX 93 become IN 170 and EX 155 cfm's - they sound about right.
Graham Wilcox did the flow testing - anyone know of him?

**Graham** · 24-09-2018, 18:14

i ran gsxr 750's and 1100s, and for a long while had a 7/11, what i always wanted to try was get a 750 head onto an 1100 motor, because i figured with the 750 head being much more downdraft it should be able to flow more and make more power, the frame rails wouldnt allow it with carbs, but throttle bodies (which were not around back then) could be another matter, certainly in terms of bhp/litre the 750 made more backing up my train of thought