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Author
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Topic: Supercharger CFM rating???
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VNMKING
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Member # 480
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What's the typical CFM output on a blower?? Please post CFM with PSI. I know someone out there knows.
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"VNMKING"
Posts: 1000 | From: Roseville, CA | Registered: Oct 2001
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Jeff S
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Member # 371
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Typically anywhere between 800-2000 CFM. A S-trim is 1000cfm, a T-trim is 1200cfm, a YS-trim is 1500cfm and a Novi 2000cfm is 1700 as examples. CFM has virtually no relationship with the PSI the supercharger outputs. Boost is simply the amount of backpressure.
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Posts: 2121 | From: San Jose, CA | Registered: Aug 2001
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VNMKING
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Member # 480
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Are the ratings you gave when these blowers are at max impeller speed? How I figure it you must aquire a certain amount of air flow to create back pressure. That's why i'm curious about CFM.
Thanks for the reply
Posts: 1000 | From: Roseville, CA | Registered: Oct 2001
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Stimson
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Member # 51
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Yes its at max impeller speed. CFM and pressure are two very different things... CFM is Cubic Feet per minute... how many cube shaped "boxes" of air the super charger can spit out in a minute. Pressure is the ratio of force to area. Blow air out of your mouth at a constant force... now tighten your lips to make the area that you're applying force through smaller... congradulations, you've increased pressure (or boost in supercharger terms).
Posts: 2373 | Registered: Jun 2000
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VNMKING
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Member # 480
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posted
Thanks for the reply.
I still think that they have some correlation. Reason: As rpm increases so do both CFM and BOOST. Know hear me out. I understand that the two alone mean completly different things, but if I were able to replicate the same CFM into the motor it too would create backpressure and cause a psi reading on the gauge, correct? I mean the air exiting your mouth in your example has the same CFM rating wether or not you mouth is more open than before there is just a higher psi rating IN your mouth when it's more closed, right?
[ September 05, 2002, 02:28 AM: Message edited by: T-TopTerror ]
Posts: 1000 | From: Roseville, CA | Registered: Oct 2001
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VNMKING
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Member # 480
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posted
Am I making since to anyone???
Posts: 1000 | From: Roseville, CA | Registered: Oct 2001
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Stimson
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Member # 51
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Yes, I see your point, the more air you try to force through the area, the more resistance that area will produce... resistance results in HEAT and now we're getting into adiabatic (sp) efficiency and other topics I'm not well verse in ![[Smile]](smile.gif)
With out getting too complicated, here is how I look at things.... first I always have to know what the over all goal is. For example, if its road racing, do a 351W swap, don't waste time with a blower for a track car. If its a street car or a weekend track/street warrior then everything in the combo has to match... for your typical off the shelf aluminum heads/intake/cam 5.O running around 10 lbs of boost, you can get a small blower and pulley it up (A trim or Novi 1000, ect) or you can get a "medium" size blower like the S trim which will make more power or you can get a big blower like a Novi2000 or T trim which when pullied down to 10psi will make less power than the better matched S trim.... now you get better heads/intake/cam and want to run more boost.... in the 16ish psi range the S trim will start fading off and the T trim or Novi2000 will start standing out....just a very general way at looking at things. With that said.... people here are making 700+ HP with an S trim.... what's your goal? ![[Big Grin]](biggrin.gif)
Posts: 2373 | Registered: Jun 2000
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93PONY
Mr. Valve Events
Member # 60
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posted
Blowers are rated at CFM & boost simply because slapping a T-trim on a 1.8 liter Honda will create so much pressure (boost) that the thrust bearings in the blower would melt & cause the blower to fail.
The CFM rating is how much air the blower can move & how much power it is capable of. Efficiency of the compressor comes in to play, hence why a T-trim pullied to 5psi on a stock motor will make less power than an A-trim at 5psi on a stock motor. The T-trim isn't designed to work efficiently at such low rpms. You've got to know how to read compressor maps....
Anyway, boost is simply back-pressure. If your motor can gulp 200cfm & the blower is pumping 400cfm, you get boost. But, if motor is gulping 400cfm, the same blower will not make any boost.
Now, belt driven blowers are run off a gear drive. So, 6000 engine RPM's may end up spinning the blower 50,000rpms, but when the engine is spinning 1000rpms, the blower (impeller) is only spinning at ~8333rpms. If the blower is rated at 1000CFM at say 50,000rpms & pullied to make max RPM's at 6000 engine rpm, then at 1000rpm, that blower is pushing ~166cfm....so you'd think, but at that compressor speed the blower isn't efficient & not blowing much air at all. & so the compressor map isn't linear... Anyway, basically, a centrifugal supercharger creates boost exponentially, but an engine doesn't use air exponetially as RPM's increase, so the more RPMs you pull, the more CFM the blower is pushing...the more boost (pressure) you get.
This is one of the reasons why Turbos make so much more power. They aren't gear driven & therefore not engine RPM dependant.
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Posts: 4265 | From: Fair Oaks, CA | Registered: Nov 2000
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VNMKING
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Member # 480
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quote:
Originally posted by 93PONY:
This is one of the reasons why Turbos make so much more power. They aren't gear driven & therefore not engine RPM dependant.
What about a kenne bell vs. a turbo???
Thanks guys for all your information. I was actually working on an invention that may now need a feww more things to actually make work. Where did you get all your tech info. I'm a walking book worm when it comes to these things and am striving to know the most. Hook a brotha up.
Swanson- my goal is 400rwhp 11.80 120mph street tires. I know it's nothing major but this is my daily driver.
Posts: 1000 | From: Roseville, CA | Registered: Oct 2001
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93PONY
Mr. Valve Events
Member # 60
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posted
Try this book: Maximum Boost by Corky Bell
The roots blower is one of most in-efficient designs out there. It has a large housing...in most cases (like the wipplecharges...a modified roots) 1.5-2.2 liters! These blowers pack massive amounts of air with very little RPM compared to a centrifugal....but unlike a centrifugal they do not make boost exponetially as RPM's increase & are therefore limited by RPM.
To make things easy... A turbo makes the torque of a Roots & the HP of a Centrifugal. There are more benifits to a turbo aside from max boost at low RPM's. The powerstroke of a turbocharged engine is longer.. 60 degrees of crank rotation vs 45 degrees on an NA or supercharged car. This is due to the pressure in the exhaust manifold...usually 1.5-2 times what the turbo is producing for the intake.
A turbo charger is simply a cetrifugal supercharger driven by HEAT & exhaust flow....yes HEAT! This is due to the expanding gasses of the exhaust...it spins the impeller faster.
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www.advancedenginedevelopment.com
SCT dealer
Dynotuning
(916)715-7569
Posts: 4265 | From: Fair Oaks, CA | Registered: Nov 2000
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Stimson
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Member # 51
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posted
One thing to note, that book was written in 1984. 20 years ago, tubros are roots blowers were your only options really. Paxton had that inefficient ball drive centrifical and thats about it as far as I know.
A book I really like is the 5th edition of the Bosch Automotive handbook. ![[worship]](graemlins/worship.gif)
Posts: 2373 | Registered: Jun 2000
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jayl
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Member # 185
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haha he called you swanson!! lol, i believe its "Sawson"
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Posts: 3821 | From: Hayward | Registered: Mar 2001
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Stimson
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Member # 51
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posted
quote:
Originally posted by jayl:
haha he called you swanson!! lol, i believe its "Sawson"
Yeah, my name is like on the top of every forum, wtf more can you do eh? ![[burnout]](graemlins/burnout.gif)
Posts: 2373 | Registered: Jun 2000
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93PONY
Mr. Valve Events
Member # 60
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posted
quote:
Originally posted by st5150:
One thing to note, that book was written in 1984. 20 years ago, tubros are roots blowers were your only options really. Paxton had that inefficient ball drive centrifical and thats about it as far as I know.
A book I really like is the 5th edition of the Bosch Automotive handbook.
Haha! Realy 20 years ago! Actually, I haven't read it....just always heard it was a good place to start.
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www.advancedenginedevelopment.com
SCT dealer
Dynotuning
(916)715-7569
Posts: 4265 | From: Fair Oaks, CA | Registered: Nov 2000
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WIKD 281
CaliforniaFords.com
Owner
Member # 40
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posted
quote:
Originally posted by st5150:
quote:
Originally posted by jayl:
haha he called you swanson!! lol, i believe its "Sawson"
Yeah, my name is like on the top of every forum, wtf more can you do eh?
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Faster than most, slower than less.
Posts: 1941 | Registered: Jun 2000
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