What is a Blower?

Question

I've heard of this component being used on Hot Rods.

• What is a blower?
• What does it do?
• Are there specific requirements for utilizing one?
• Are there any disadvantages of using a blower?

Answer 1

A 'Blower' is another name for a supercharger, particularly 'Roots' type superchargers that use long figure-of-8 shaped vanes to force or 'blow' air into the engine.

The only 'specific requirements' are that the engine internals are strong enough to cope with the extra power and the fuel system can provide enough fuel to match the extra air from the blower.

In terms of performance, the only 'disadvantages' to using a blower is that it is belt driven from the crank. It uses some power from the crank to turn the blower, which is power that could otherwise be driving the wheels. This is, of course, offset by the fact the blower enables the engine to make much more power.

Roots blowers are briefly described in this SE question.

Answer 2

Turbo just for completeness. A turbo uses the exhaust gasses being pumped out of a car to spin an impeller which in turn spins a propeller. This creates pressure simply due to volume of air being moved rather than keeping the air from escaping.

• is always delayed due to needing increased exhaust pressure to spin up
• recycles wasted power through the use of exhaust gasses
• heats up intake air
• typically requires a blowoff valve to relieve pressure due to the delay in spinning down
• requires high rpm to work correctly
• more fuel efficient due to using the last bit of expansion of the burnt fuel charge
• better high rpm power

Centrifugal is a belt run turbo more or less. You have just the propeller half of a turbo connected to the crank via a belt similar to a how a supercharger is run. Like the turbo this requires high RPM to generate the PSI

• does not heat up the intake charge much (intake charge is heated due to pressure and mechanical movement of course)
• requires high rpm to work correctly
• no lag due to running directly off the crank
• no blowoff valve (I think) due to fast spin down time
• less parasitic drag but I do not know if this is offset by the higher RPMs required to make it work
• better high rpm power

Roots type is an air pump with tight tolerances forcing air through giving high pressure with relatively low RPM.

• does not use a fan
• low RPM
• Pressurizes air much like an air compressor
• more moving parts
• has has more parasitic drag due to the gear mesh it needs. This might be offset by the lower RPM's it needs to run
• better low end power

which one is best? anything but a turbo? But that is my opinion.