Blowers
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I'll be investigating and reporting on these and any others I can find...... | I'll be investigating and reporting on these and any others I can find...... | ||
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First of all, why a blower? What good is it? | First of all, why a blower? What good is it? | ||
| − | By increasing the pressure of the intake charge, you push more air into the cylinder. More air, when mixed with more fuel, makes for a stronger combustion burn. The stronger burn pushes harder on the piston, which pushes harder on the crankshaft, which creates more torque/hp. This article will only address mechanically-driven blowers or superchargers. Turbochargers will be covered later in another article, probably by someone else, because although I know they work very well, I just can't get wrapped around the maps used to size them. Maybe later..... | + | |
| + | Engines, for all intensive purposes are air pumps. The more air you can put through them, the more power you can get out of them. Consequently, a blower can and will push air through an engine at a moments notice.By increasing the pressure of the intake charge, you push more air into the cylinder. More air, when mixed with more fuel, makes for a stronger combustion burn. The stronger burn pushes harder on the piston, which pushes harder on the crankshaft, which creates more torque/hp. This article will only address mechanically-driven blowers or superchargers. Turbochargers will be covered later in another article, probably by someone else, because although I know they work very well, I just can't get wrapped around the maps used to size them. Maybe later..... | ||
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| + | [[PARTS OF A BLOWER]] | ||
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| + | Blowers are very simple in nature and have very few parts. They are made up of an intake (scoop), case (to contain the vanes and hold the drive pulleys), vanes, drive (pulleys), and a exhaust manifold mount (usually, incorporated into the case. | ||
This will get us off to a good start................................................................ | This will get us off to a good start................................................................ | ||
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ROOTS TYPE.... | ROOTS TYPE.... | ||
These blowers were never designed to compress air, just to move air from one place to another, sort of like your house fan. You'll find several explanations of why the Roots brothers originally designed this blower, but the one I like the best is that it was designed to blow air down into mine shafts so the miners could breathe. No internal compression takes place in the blower, but the restriction of the closed intake valves in your motor allow the buildup of pressure in the intake manifold and head ports. The centrifugal and screw type blowers make pressure inside the blower. | These blowers were never designed to compress air, just to move air from one place to another, sort of like your house fan. You'll find several explanations of why the Roots brothers originally designed this blower, but the one I like the best is that it was designed to blow air down into mine shafts so the miners could breathe. No internal compression takes place in the blower, but the restriction of the closed intake valves in your motor allow the buildup of pressure in the intake manifold and head ports. The centrifugal and screw type blowers make pressure inside the blower. | ||
| − | There are Roots designs which have 2 lobes on each rotor and others with 3 lobes on each rotor. There are also variations where the rotors are "twisted" into a helix along their axis to help prevent the "backwash" of air between the rotors and reduce "buffeting". Here's the | + | There are Roots designs which have 2 lobes on each rotor and others with 3 lobes on each rotor. There are also variations where the rotors are "twisted" into a helix along their axis to help prevent the "backwash" of air between the rotors and reduce "buffeting". Here's the aerospace engineering definition of buffeting afforded by answers.com: "The beating of an aerodynamic structure or surfaces by unsteady flow, gusts, and so forth. The irregular shaking or oscillation of a vehicle component owing to turbulent air or separated flow."...................................... |
http://en.wikipedia.org/wiki/Roots_blower........................................................... | http://en.wikipedia.org/wiki/Roots_blower........................................................... | ||
Here's a neat animation showing a straight-on view of the rotors in a 3-lobe Roots. Air entering is in blue and air exiting is in red................................................................... | Here's a neat animation showing a straight-on view of the rotors in a 3-lobe Roots. Air entering is in blue and air exiting is in red................................................................... | ||
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The Roots types we are most familiar with came as original equipment on GMC two-stroke diesel engines. The number of cylinders and the cubic inches per cylinder is the way the engines were designated, so the blowers just naturally were called by the same designation. For instance, a 4-71 blower would have come off a 4 cylinder inline motor with 71 cubic inches per cylinder for a total displacement of 284. This blower would be a good choice for a motor of around 300 cubic inches and could be overdriven (by juggling drive and driven pullies) to feed a larger motor or underdriven to feed a smaller motor. Here are some of the GMC motors I could find..... | The Roots types we are most familiar with came as original equipment on GMC two-stroke diesel engines. The number of cylinders and the cubic inches per cylinder is the way the engines were designated, so the blowers just naturally were called by the same designation. For instance, a 4-71 blower would have come off a 4 cylinder inline motor with 71 cubic inches per cylinder for a total displacement of 284. This blower would be a good choice for a motor of around 300 cubic inches and could be overdriven (by juggling drive and driven pullies) to feed a larger motor or underdriven to feed a smaller motor. Here are some of the GMC motors I could find..... | ||
| − | 2-53, 3-53, 4-53, 6V-53(V-configuration rather than inline), 8V-53, 12V-53, 2-71, 3-71, 4-71, 4Twin-71, 6-71, 6Twin-71, 6Quad-71, 8V-71, 12V-71, 12VTwin-71, 16V-71, 16VTwin-71, 6V-92, 8V-92, 12V-92, 16V-92, 6-110, 6Twin-110, 12V-149, 16V-149. Add to those....Turbo.....Turbo Intercooled.....Turbo | + | 2-53, 3-53, 4-53, 6V-53(V-configuration rather than inline), 8V-53, 12V-53, 2-71, 3-71, 4-71, 4Twin-71, 6-71, 6Twin-71, 6Quad-71, 8V-71, 12V-71, 12VTwin-71, 16V-71, 16VTwin-71, 6V-92, 8V-92, 12V-92, 16V-92, 6-110, 6Twin-110, 12V-149, 16V-149. Add to those....Turbo.....Turbo Intercooled.....Turbo Aftercooled.....those are documented but may be a few others. Not certain if there was a 171, and there were some V71 Twins and Quads.. inline had High and Low blocks. There were also V-53 and 6-71 alloy block versions. |
The most popular for hot rod use today would be the 4-71, 6-71 and 8V-71 (just called 8-71) units. There is some work to be done on a stock (fresh off the diesel) "Jimmy" blower that you maybe find at a swap meet or on ebay. The rear case cover bearing bosses need to be strengthened with steel collars and the rotors must be clearanced to the case interior. These and other oiling mods or sealed bearings will be addressed in Pat Ganahl's book. If you're considering a blower, it is well worth the investment to buy and read this book.....http://www.themotorbookstore.com/supercharging.html | The most popular for hot rod use today would be the 4-71, 6-71 and 8V-71 (just called 8-71) units. There is some work to be done on a stock (fresh off the diesel) "Jimmy" blower that you maybe find at a swap meet or on ebay. The rear case cover bearing bosses need to be strengthened with steel collars and the rotors must be clearanced to the case interior. These and other oiling mods or sealed bearings will be addressed in Pat Ganahl's book. If you're considering a blower, it is well worth the investment to buy and read this book.....http://www.themotorbookstore.com/supercharging.html | ||
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