Super charger pressure formula?

jsbike, Jun 12, 6:05am
I want to work out approx pully sizes I will need to produce 10psi, anyone know how I would work this out! I know the super charger shifts 1.4L of air per rev (its a toyota sc14 charger), and I know my engine is 2500cc, I know i need to measure the pully size on the charger too, though I have yet to do this. Cheers in advance for any help anyone can give.

johnf_456, Jun 12, 6:52am
Google it there is probably a calculator out their.

jsbike, Jun 12, 7:00am
not for the sc14 it seems

johnf_456, Jun 12, 7:00am
Bummer, good luck I don't know too much about those super chargers.

zooki007, Jun 12, 7:04am

guider1, Jun 12, 11:07am
Arent they around 8-10psi on the mighty Levin!

gsimpson, Jun 12, 11:21am
Engine is 2500 4 stroke so induction is 2500/2=1250cc/rev
Supercharger 1400cc/rev
Atmospheric pressure is 14.7psi, you want 10 more so maths are
Volume per rev required 1250+1250*10/14.7=2100cc/rev
So supercharger has to turn 2100/1400=1.5 rev per engine rev
Therefore the crank pulley has to be 1.5 times larger than supercharger pulley.
I am sure someone will point out any errors. It is late.

for_an_angel, Jun 12, 11:36am
I have never done the math or noticed a difference but this bit of info could be helpfull.maybe .The SC14 produces 8psi on the 2TZ-FZE 2.4l in the Estima and 7-8psi on the 4A-GZE. There is a 10psi pulley for the 4A engine so if you took the difference in size between the standard and 10psi pulley of the 4A engine and applied the same increase to the 2TZ pulley you should be pushing enough air for the 2.5l. in theory lol

jsbike, Jun 12, 9:25pm
good thinking agent 99! I know 10 psi on a 2500cc is starting to push the s14 a bit, though it will only be working to 3000rpm

jsbike, Jun 12, 9:29pm
anyone able 2nd this! Makes sense to me and my poxy math skills

skin1235, Jun 12, 9:39pm
1 1/2 times larger will slow the charger down, it needs to be a smaller pulley on the charger to gain speed over the crank
top of my head says 1/3rd smaller ( one crank rev = 1 1/2 charger rev)

_peas, Jun 12, 9:44pm
4A-GZE uses a SC12 from factory.

That maths seems to work just remember that when talking size you are talking about the circumference not the diameter of the pulley.Otherwise disaster may ensue!

jsbike, Jun 12, 10:02pm
the bigger the crank pully, the higher the boost. Reducing the sc pully isnt really an option as its a clutch system, like an air con pump. I want to keep this if poss

skin1235, Jun 12, 10:34pm
so you'll need to be looking at increasing the crank pulley size, or clipping in a larger pulley as a drive for it ( some crank pulley's are multi run different sizes - not sure if such is manufactured for you engine though)

jsbike, Jun 13, 4:46am
found a similar calculation on the net, going from the one on the net, to produce 10psi I need to spin the sc @ 7500rmp when the engine is @ 5000rpm. In theory I could run 10psi right up to engines redline of 8000 rpm at which time the sc would be doing 12000rpm, which I have since found out is the sc14's maximum recomended rpm. Hopefully I only need to have the sc run to around 3500-4000rmp max

gsimpson, Jun 18, 2:05pm
That's what I said wasn't it! Crank pulley larger.