|The V9 has two trims, and F and a G. The F is a left cut of G map. The step ratios differ between these blowers, and this results in different boost ranges. Our V9 has a 1.72 step up ratio @ 48,000rpm. Working with what we had in our kit, the F trim, we set out to optimize the track. Frustrating for us was that this blower made little boost in the original stage 2 configuration. |
Next has been the debate about pulley diameter and RPM. All V9 blowers use a gen 3 gear set from Vortech which has a gear ratio of 3.61. This is a key fact when optimizing impeller speed for durability and efficiency.
48,000 is the target RPM for efficiency and 50,000 is the RPM target for durability with our f trim V9. With the stage 2’s 2.62 diameter pulley, we see that at around 6800RP +/-.
Crank P dia. X 3.61(step up ratio) x shift point / all divided by blower pulley diameter = impeller speed.
Downsizing the pulley will be detrimental for two reasons.
1) The R32 has a 5.41” crank pulley and if the blower pulley is reduced in size, the tension required to hold the belt will overload the main axle of the blower causing premature one sided wear on the oil seal.
2) If the pulley is reduced, the RPM would have to be limited anywhere in the range of 6200-6500 RPM to avoid over spinning the impeller, any RPM past 6200 will be on the down side of the flow rate for the V9
Theoretic boost from the Vortech V9 F trim is a simple calculation.
(14.6est BP x1.72)-14.6BP = 10.5psi @ 48,000 impeller speed.
For those at altitude, you would use the est Barometric Pressure for your location less 14.6. HPA is nearly right at Sea level so 14.6 is what we use for our calculations.
Please note; this is the estimated output measured in the boost track just past the compressor and not in the intake manifold.
Instead of focusing on the pulley, we have taken some additional steps to optimize the Blower’s intake track which has resulted in over a 1.2 PSI gain in our boost track at the compressor outlet.
The G trim is worth 1.3-1.5 psi more with the same dimensions that we are setting the F trim up for. it has a step up ratio of 1.8 @ 48,000RPM
IF, you opt for what Vortech labels as an HD unit, this uses the straight cut gears and has a lower ratio 3.45. The G trim with a 3.45 will behave similar to the F trim running the 3.61 as the impeller RPM's shift downward with the 3.45 ratio.
The formulas are in my post above, so you can run the exact numbers and see what you should except for boost out of the blower at 6800rpm based on your altitude from sea level. 48,000 impeller speed efficiency point is the target.
G trim in HD app, 3.45
(5.41x3.45 x 6800)/2.62 = 48,400rpm
@ 48,000 the G yields a 1.8 step up ratio
(14.6x1.8)-14.6 =11.68psi @ 6800RPM – theoretical Boost at blower.
The same G trim with the Gen 3 gears would look like this
The max boost with the G trim and Gen 3 gears would be reached earlier in the power band (6500RPM)and the durability threshold would be then just past redline allowing a slightly more usable powerband.
We will have the G trim retro fit in our V9 blower but will retain the Gen 3 Helical gear set to retain the 3.61 ratio, but as you can see, we are speaking about a 500RPM swing, not to bad!
Hope this makes sense.
The Vin plate on your blower will define your trim and gear set and the service staff at Vortech seem very quick at getting that info.