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HP Gain from Small Opening in Roots Blower Case

Roots blowers are popular in motorsports for making more power. They are made up of a simple blower case with two rotors inside. The rotors spin from an engine driven blower drive. This pumps extra air into the engine. With extra air and the appropriate extra fuel, extra power!

The blower case design was changed in later years to improve performance. One of these areas is the size of the blower case discharge opening.

Original Roots blowers ran on industrial engines. They were simple mass flow devices running at atmospheric pressure. In the mid 19th century, motorsports racers put them on racing engines. They pumped a lot more air into the engine causing boost. This became an easy way to make more power.

However, because they were originally designed to operate at atmospheric pressure, they were inefficient with boost. While they made more power, it was not that much more for the amount of increased air into the engine.

One of the design areas affecting efficiency is the blower case discharge opening. That is discussed in several of our publications. Here are two examples: Continue reading

Converting from Gas To Methanol

Considerations for converting from gas to methanol for motorsports:

Methanol is corrosive.  Fuel systems need to be upgraded to corrosion inhibitive components not necessary in fuel systems for gas.

Methanol requires approximately twice the amount of fuel for the same power level as gas.  Fuel pumps and jetting need to be upgraded for the higher volume.

Methanol has a higher heat of vaporization.  That together with the increased volume can condense the inlet air, increasing the weight of air into the engine.  That together with the proper air/fuel ratio will usually increase engine power.  A power increase as high as 10% is reported by several racers who converted to methanol.

Methanol cooling throughout the intake system of a drag racing engine may eliminate the need for a cooling system that would otherwise be needed for gas.

Methanol is widely available throughout regions where racing is common.

Methanol absorbs moister.  For long term storage, it should be kept in sealed metal containers.  Methanol in plastic containers may get contaminated from humidity from long term storage.  Plastic at the microscopic level is porous and will let moisture in.

Methanol is poisonous in all forms.  It should be handled with protective clothing and eye protection.

More info in our book: 5000 Horsepower on Methanol.