Ok so all i've done to the car in the last few weeks is sand fiberglass and body fill the bonnet vent and one front wing. Haven't been able to do much else as the weather has been bad and i now have a new born baby boy who is now 2 weeks old.
What i have done is some Supercharger mathematics in order to prepare myself and get some rough figures. I have taken these calculations from various websites and hope that anyone looking to supercharge in the future could benefit from this. Also this is a great place to store my workings out just incase i lose my paper work
.
These calculations will be able to help me determine what s/c pulley size i will need, and to see that it will give me the correct drive ratio to run the s/c at the optimum rpm speed to avoid generating to much heat rather than HP. It's not a case of changing the s/c pulley to make more psi because as i said above it could potentially take the charger over the optimum rpm and raise outlet temperatures. So if you did want to make more psi than what i have worked out below then you will have to upgrade the charger to possibly the M62 (not possible for me unless I upgrade engine internals and i don't think i have the space for it in the engine bay
).
S/C - Supercharger
NA - Natural Airflow
Del Sol Specs- Engine size - 1493 cc
- Engine Cubic Inches - 91.1
- Red line RPM - 7000
With the information we already have about the car we can work out how much it is essentially 'breathing'.
NA CFM = RPM x Engine CI / 3456
7000 x 91.1 / 3456 = 184 cfm
OR the calculation below can be usedNA CFM = (1/2 Engine Displacement x RPM) x LPM
1493 / 2 = 746 cc
746 x 7000 x 0.3531 = 184 cfm
Eaton M45 Specs- Displaces 45 cubic inches a minute or 750 cc or 0.75 ltrs
- Optimum max rpm range (my theory based on MAPS) 10,000 to 11,000
Normally at this point you would already know the
crank pulley size and the
s/c pulley size in order to work out the
Drive Ratio. The calculation would be :
Drive Ratio = Crank Pulley Size / S/C Pulley Size
Once I have removed my Air Con system I will be able to measure my crank pulley size and find out what s/c pulley i will need by using this calculation:
S/C Pulley Size = Crank Pulley Size x Drive Ratio
These calculations tell us how much the charger is blowing into the engine. I have guessed the Drive Ratio to calculate the max s/c rpm for 10,000 and 11,000 rpm.
Max S/C RPM = Red Line RPM x Drive Ratio
S/C @ 11k : 7000 x 1.57 = 10990 rpm
S/C @ 10k : 7000 x 1.43 = 10010 rpm
S/C Max LPM = S/C Displacement ltrs x Max rpm
S/C @ 11k : 0.75 x 10990 = 8242.5 lpm
S/C @ 10k : 0.75 x 10010 = 7507.5 lpm
Convert LPM to CFM = LPM x 0.3531
S/C @ 11k : 8242.5 x 0.3531 = 291 cfm
S/C @ 10k : 7507.5 x 0.3531 = 265 cfm
The charger must supply the engine with its NA as well as the 'boosted' air supply.
"Boosted" Excess CFM = S/C CFM - NA CFM
S/C @ 11k : 291 - 184 = 107 cfm
S/C @ 10k : 265 - 184 = 81 cfm
Boost PSI = Excess CFM / NA CFM x Atmospheric Pressure (14.7)
S/C @ 11k : 107 / 184 x 14.7 = 8.5 psi
S/C @ 10k : 81 / 184 x 14.7 = 6.5 psi
(These answers do not take into account for loss of psi through intercooler, length of system, etc)