A snapshot of Lysholm Autorotor Superchargers
The Lysholm / Autorotor Supercharger is a unique and very practical chager. The unit is a great compromize between a positive displacement supercharger (that creates boost pressure by over pumping and over feeding the engine with air) and a compressor (similar to a turbocharger) that compresses the air inside the supercharger housing before sending it out to the charger piping.
The unique three-five design of the twin screw chargers relies on a 3 lobe and a 5 lobe rotor intermeshed to capture the air flowing into the supercharger for inter-screw compression. The combination of an intermeshed 3 lobe and 5 lobe rotor means that the rotors inside the housing are operating at different rpms with a ratio of 5:3 to keep the rotation of the lobes (3 lobes to 5) in synchronsim. This complex design allows the rotors to capture air (in its natural volume) from the back of the blower housing, and push it foward as the screws rotate. As the air is moved forward it is captured and compressed between the intermeshed rotors as well as being pumped (in positive displacement) from the inlet port at the back of the charger housing to the outlet port near the front.
Because of this unique design, screw style chargers are able to outperform simpler rotor based chargers in two aspects:
1- The blower is able to acheive a higher pressure ratios because the compression is combined between positive displacement (overfeeding) and between direct compression of the air (inter-screw compression).
2- Since the air is compressed inside the housing, the housing is able to ingest and move more air (higher CFM ratings) for a similarly sized roots style blower.
These kinds of superchargers boast great adiabatic efficiency of up to 68% while at the same time being able to deliver that high efficiency at high boost levels of up to 18 psi. With such a high potential peak boost level, these chargers are capable of matching the top end delivered by a typical turbo system, without the lag and throttle delay disadvantages of spooling a turbo. Because of the positive displacement nature of this charger, the charger will always be able to make boost at any rpm so long as they bypass valve is closed.
Some applications for this unit include the OEM install of 1.1Liter Lysholm / IHI hybrid in the Mazda Millenia motor.
Other kits include the BBM upgrade kit for the Volkswagen Corrado. The kit replaces the G20 centrifugal supercharger with the lysholm twin screw system. As you can see in the dyno below, the twin-screw outshines the smaller centrifugal unit both in the lower rpms and in the top end and this exactly the result of the inter-rotor compression keeping flow and efficiency up to par at higher rpms while positive displacement fills out the low rpm torque.
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Here is an overview of Lysholms available chargers:
| Lyshom | pressure ratio | Boost | CFM | HP | effeciency | displacement (liters) |
| 1200 AX | 2.2 | 18 | 636 | 424 | 64 | 1.2 |
| 1600 AX | 2.2 | 18 | 848 | 565 | 66 | 1.6 |
| 2300 AX | 2.1 | 16 | 1059 | 706 | 65 | 2.3 |
| 2300 R | 2.2 | 18 | 989 | 659 | 68 | 2.3 |
| 3300 AX | 2.2 | 18 | 1236 | 824 | 66 | 3.3 |
| 3300 R | 2.2 | 18 | 1236 | 824 | 66 | 3.3 |
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