There are a lot of people saying that a 3.4 would be better than 2 smaller superchargers. The answer is NO. The only way to answer is with this long boring explanation.
Twin superchargers compared to a single all depends on several things. First, you need to correctly match the blower CFM output to the desired power output of the engine. This must be done without over spinning the supercharger, keeping the operating range in the sweet spot of the blower or peak adiabatic efficiency.
To achieve over 1000HP you need a lot of cool air. About 1600 cfm to start. So what S/C has an output of 1600 cfm? A 4-liter single could work but man the rotors would be really heavy and the blower to far forward. A 3.3 only puts out 1236 cfm @ MAX 11,000 rpm and the pair of 3.3 screw rotors and gears weigh 22.65lb, also the blower is so long, the output delta sits over front of the manifold blowing forward and down not in the intercooler.
Rotor mass or weight should also be considered. This is important because getting these rotors to spin up and slow down consumes engine power and affects acceleration rate.
So what about two 1.6 L blowers? Lets compare the two options:
Two 1.6L (3.2L)@15psi vs One 3.3L@ 15psi
Rotor & gear weight: 18.4 lbs (9.2 ea.) vs 22.65 lbs
CFM flow: 1236.2 @ 11.5k vs 1236.2 @ 11k
Max cfm capable: 1624.72 @ 15k vs 1236.2 @ 11k
Max RPM: 15k vs 11k
Power used: 90hp vs 104hp
Temperature: 242.6F vs 250.8F
Adiabatic efficiency: 63% vs 57%
The compressor map for this data can be found on Lysholm’s web site. As you can see, a single 3.3L will not support a cfm level of 1600 cfm and if you over spin it to get there the output numbers get really bad. And then you get to be MY new best friend continually bringing me your trashed out supercharger to replace.
An Additional benefit with the quad rotor manifold is the large open plenum that the air can easily flow through.
Also, you don’t want to oversize the blower for your desired application. Otherwise you will be operating outside of its efficiency range.
When you use 2 superchargers in parallel you cut the engine size in half. So each 1.6 L S/C is working 2.7 L of engine. This makes a perfect match.
Just to cover all concerns of belt drag, the addiction of 1 s/c pulley is less than 1/8 hp.
Both Jim and Art made their own twin supercharger manifold and made very big power. Whipple has about 100 Quad rotors thought the world in boat’s and one on a truck, mine.
This set up is expensive to build, time consuming and big in size and I'll never do this again.
Twin superchargers compared to a single all depends on several things. First, you need to correctly match the blower CFM output to the desired power output of the engine. This must be done without over spinning the supercharger, keeping the operating range in the sweet spot of the blower or peak adiabatic efficiency.
To achieve over 1000HP you need a lot of cool air. About 1600 cfm to start. So what S/C has an output of 1600 cfm? A 4-liter single could work but man the rotors would be really heavy and the blower to far forward. A 3.3 only puts out 1236 cfm @ MAX 11,000 rpm and the pair of 3.3 screw rotors and gears weigh 22.65lb, also the blower is so long, the output delta sits over front of the manifold blowing forward and down not in the intercooler.
Rotor mass or weight should also be considered. This is important because getting these rotors to spin up and slow down consumes engine power and affects acceleration rate.
So what about two 1.6 L blowers? Lets compare the two options:
Two 1.6L (3.2L)@15psi vs One 3.3L@ 15psi
Rotor & gear weight: 18.4 lbs (9.2 ea.) vs 22.65 lbs
CFM flow: 1236.2 @ 11.5k vs 1236.2 @ 11k
Max cfm capable: 1624.72 @ 15k vs 1236.2 @ 11k
Max RPM: 15k vs 11k
Power used: 90hp vs 104hp
Temperature: 242.6F vs 250.8F
Adiabatic efficiency: 63% vs 57%
The compressor map for this data can be found on Lysholm’s web site. As you can see, a single 3.3L will not support a cfm level of 1600 cfm and if you over spin it to get there the output numbers get really bad. And then you get to be MY new best friend continually bringing me your trashed out supercharger to replace.
An Additional benefit with the quad rotor manifold is the large open plenum that the air can easily flow through.
Also, you don’t want to oversize the blower for your desired application. Otherwise you will be operating outside of its efficiency range.
When you use 2 superchargers in parallel you cut the engine size in half. So each 1.6 L S/C is working 2.7 L of engine. This makes a perfect match.
Just to cover all concerns of belt drag, the addiction of 1 s/c pulley is less than 1/8 hp.
Both Jim and Art made their own twin supercharger manifold and made very big power. Whipple has about 100 Quad rotors thought the world in boat’s and one on a truck, mine.
This set up is expensive to build, time consuming and big in size and I'll never do this again.
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