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Old 02-23-2009, 12:58 AM   #1
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Thumbs up Not sure where to post...power adder...

ok, so I thought id introduce some Supercharger info for the general public that might not know this information, just like a fun fact...a really long fun fact....

So....let me start off by saying that there are three types of superchargers out there.

Screw
Centrifugal
Roots

And Example of a roots type, like the one in the Bonneville or in the '03-'04 Cobra. It was Patented by the Roots brothers in in the mid 1800'*. It is a positive dispalcement supercharger. It has an external compression system, so... it acts like an air pump that takes the inlet air charge and compresses it in the cylinder and manifold. It it maintains constant boost across all rpm ranges. It only creates boost when the throttle is opened substantially or most likely under a load. And, intake air volume is in direct proportion to engine/blower speed.

The rotors inside typically have three lobes positioned approximatly 120 degrees apart centered on each rotor shaft in a helical pattern. This increases the number of pumping cycles, reduces air flow surges, in turn increasing its efficiency.

The rear end plate of the casing houses bearings that support the rotors. the fron houses another set of support bearing, houses rotor gear train drive that maintains precise rotor timing also known as rotor phase. these gears are similar to a transmissions as they are helical gears in order to make the gears have a greater contact surface. the gears are operated in an oil bath.

There is actually a safety device in these things, its called a backfire valve. This spring loaded pop off valve is located on the blower housing or in the intake manifold. It opens at a specified pressure to prevent damage to the unit during engine backfire.

As opposed to the roots type supercharger, the screw type is an internal compression blower. It compresses air inside the case as it passes along the rotors. So, the faster the unit spins, the more boost the unit creates. this makes the unit more efficient than the roots type since it creates less heat.

Now, the centrifugal supercharger is also an internal compression supercharger, but... its design is very very similar to a turbocharger except, that it is driven by a belt, not your exhaust. it uses a centrally mounted impeller to compress the air. the faster the impeller spins, the more boost the unit creates...henceforth, it will make maxumum boost at maximum engine rpm and minimal boost at minimum engine rpm.. for this reason, this design is popular in traction limited or stock applications where large amounts of low end torque are not needed or desired. This style supercharger has an internal drive unit to provide approximately a 4.5 to 1 ratio to accomplish high impeller speeds.


Now, blower drive ratio and boost...

the blower may be an under drive, 1:1, or an overdirve ratio Most drive systems incorporate pulley sizes that allow the drive ratio to be altered in steps of about 3%. Typically, overdrive ratios will, increase boost, decrease belt life and draw more power. Under drive ratios typically have the complete opposite effect.

Drive ratio is only one thing that determines boost. the other factors are; engine displacement, clearance inside the unit, valve timing, compression ratio, belt slippage and exhaust design. the best intake system starts with a better exhaust system. The amount of boost that can be safely ran is determined by compression ratio of the engine and gasoline type that will be used. example; to control detonation, an effective compression ratio of 12.5:1 or lower must be obtained when used with 91 octane pump gas.
Effective compression ratio= combines static(mechanical) compression ratio with the amount of supercharger boost. The formula to find this number is as follows....

(boost divided by 14.7)+1)xStatic compression.


For example...a 9:1 compression engine with 10 pounds of boost has an effective compression ratio of 16.0

Other contributing factors to detonation are as follows;
ignition timing
coolant temp.
cooling efficiency of cylinder heads.
Air fuel ratio
intake air temp.
Spark plug heat range
Cumbustion chanber design
and exhaust backpressure.



The reason why some superchargers are more efficient than others is bacuse of a thing called Adiabatic Efficiency. This means how well a compressor uses the energy put into its driveshaft without heating the air or the unit excessively.

Roots style are about 50% efficient.
Screw style 65%
Centrifugal style 75%
And turbos are as high as 85%



So, I hope i kept you entertained and helped you understand superchargers a little better.


Thank you for reading,
Eric.
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Old 02-23-2009, 02:25 AM   #2
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You didnt mention Bonneville in the post...... so, LOL, off to the Lounge it goes,
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Old 02-23-2009, 02:32 AM   #3
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You didnt mention Bonneville in the post...... so, LOL, off to the Lounge it goes,
Are you serious? Lol! I did! Look at the description of the roots type supercharger. I give the Bonneville and the cobra as the example. So... Ha! Good one though. Lol!
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Old 02-23-2009, 12:40 PM   #4
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Mentioning Bonnevile,....1 point. Mentioning Ford -2 points. Total....... Moved to Lounge. ROFLMAO!!! Actually, I'm kinda busy today and just a brief driveby login, later I may put this in a writeup/essay section not yet added to tech info. So if you want to fix the hem, or ruffle up the pleats, it will be a couple days if I use it. I like the article but need it purged of other models and would like the year/model blower/and refinements as they pertain to the Bonneville. Nice writeup.
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Old 02-23-2009, 12:48 PM   #5
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Quote:
Originally Posted by GXP Venom View Post
Mentioning Bonnevile,....1 point. Mentioning Ford -2 points. Total....... Moved to Lounge. ROFLMAO!!! Actually, I'm kinda busy today and just a brief driveby login, later I may put this in a writeup/essay section not yet added to tech info. So if you want to fix the hem, or ruffle up the pleats, it will be a couple days if I use it. I like the article but need it purged of other models and would like the year/model blower/and refinements as they pertain to the Bonneville. Nice writeup.
^Meaning^ "Your a horrible journalist, I dont know why I hired you, now get off your *** and re-write it and make me happy about your employment or your FIRED!" lol j/k made me think of a newspaper editor critisizing a journalist about the article
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Old 02-23-2009, 07:48 PM   #6
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Thanks guys! Ill work on it. I'll fill in what eaton did with the bonnie. Wow... I was really bored last night. not to mention that i was not so sober... i did pretty good tor drunk posting...
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Old 02-25-2009, 11:29 PM   #7
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Ok... So... What i found is that GM decided to use the M62 on the Bonneville Because the Supercharger was designed for engines from a 2.5 to a 4.0. This is actually the 5th gen. of this supercharger. Then for the siries two of the bonnie, GM decided to use the the new M90, which was designed to be used in engines from a 3.0 to a 5.0. The difference in these two is that the M90 has a a bigger air flow capicity than the M62.

Now, I also found out that Eaton superchargers are roots type, but special roots type. the rotors are actually twisted in a 60 degree helical pattern and a special geometry inlet and outlet ports to assist in reducing pressure variations that allows a smooth transition for the air to exit the blower reducing operation noise. This improves its efficiency. And with the helical pattern of the rotors and an axial inlet, the supercharger can be spun up to 14,000 RPM while reducing package size.


Is that good enough? I couldnt find the edit button....
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Old 02-25-2009, 11:44 PM   #8
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Looking good. I'll have the gearheads look it over and kick the tires. I'm V8/Nitrous informed, */C'er challenged
Back to the basement, I'm tinkering with the ControlPanel.
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Old 02-25-2009, 11:49 PM   #9
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Thank you. Im actually trying to get a good deal on a ABS actuator assembly for my Dads 93 K1500 Blazer... i didnt know that they were so expensive... sheesh! the dealer i used to work at wants to charge him 1300... after my discount.... oh my god! they say i will get the cost price that is $700.... im gonna talk to my boss at midas see what i can do... just another day in paradise livin the dream!

BTW... have fun with the control panel!
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Old 02-26-2009, 12:04 AM   #10
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It'* a crazy world in the parts universe. I just bought a Bosch fuel injector pump assembly for my 3500. List $2700, Rockauto $2100. Truck Plaza got it for me from Cummins for $1800 + labor and other repairs. The parts service at Rockauto said, "Well, the value of the vehicle keeps going doooooown, and the cost of parts keeps going uuuuuuup, so you have to decide when it'* time to replace iiiiiiiit. At $44,000+ for new, it'* going to be a long time before I replace it!......like when the frame falls in half.
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