Sterling

So I wanna mate my M-62 Eaton blower to my stock 12A, and force feed it an additional 10psi of fuel air mixture.
(Blower thru an IC thru a modded Nikki).
I have asked alot of questions here, and recieved tons of info, but the 'jury was still out' as to whether I need a blow-off valve in my application. Some said adamantly, "Yes - definitely - you'll blow up without one..."; and some said it'll just make shifting easier.

Unfortunately, I think alot of people were putting in their "turbo-experience" two cents, and things started not making sense (to me, I mean).

Please help me out on this, Keeping in mind that this is for a blower application where boost should basically be constant (is'nt that right?).

And one more question...
When guys like me supercharge something (or even when a kit is sold) why don't they just gear it really high, and install an adjustable valve to bleed off excess pressure?
Example:
The blow thru sytem I wish to install could push out 20 psi (it can't really, but let's just pretend, yeah?).
20psi is too much for me. I could put a bigger pulley on and gear it down, but if I upgrade my ignition and add water injection, I'll have to make a new (slighly smaller) pulley again.
In fact, any time I want to change the boost level, I gotta make another damn pulley!

Why is it not a matter of practice to go ahead and put that 20psi geared pulley on there, and install a valve that you turn a **** and bleed off a bunch of boost continously?
So it's constantly being bled so you only get 8 psi, maybe even routed to something clever like the front brakes or an exhaust shroud. Then you get an MSD retarding box. So you turn the valve a bit tighter so as to put you up to 12 psi.

Does this work?

I will have to use a pressure sensitive fuel regulator anyway. I wish to do this, and run a simple fex shaft to the valve so that I can mount the **** on my console.

mperformance

Sterling I'm no expert I'm learning just like you on this...but won't the supercharger rob power all the time, if you bleed off the boost that much with a valve won't you be actually loosing the efficiency of the all-time-boost from the supercharger?

Just my opinion...

etherhuffer

Sterling, The ability to pump air changes with rpm, the supers are not a constant output unit. So you are correct. You set the boost with a pulley. sort of. If your output exceeds what you can handle, then a blow off seems smart. The centrifugal blowers with a variable pulley(See CVT transmissions) are the best. Centrifugal or variable pulleys can broaden where you get boost. I only know old style Paxton/Roots stuff. I would ask Atkins, as they sell the nice blowers. Sounds fun. I think blowers are more fun than turbos, even if they are less efficient. Get a 50's haircut. It will help you think about blowers and you will fit in at the next hot rod show. Ha!

MarkPerez

No blow off valve needed,,on superchargers,,any kind
that are belt driven,,(all) the pulley's are everything,,
the terms,, overdriven,,and underdriven,,,these are
what 'boost' would be,,turbo's are controlable for big
dollors,,,but blowers,,beltdriven are not like that,,
so you need to know what % overdriven,or underdriven
will work the best for the 12a,,,ask atkins for pulley info

V8kilr

then you have to remember that even though the bleed is regulating 8 psi it will also have a much higher psi at idle,
it would have the same as if you were running a 20 psi super at idle,
see what i mean?

so yes your max boost would be regulated to 8 psi but your idle boost would probably be to high for comfort


if it could be done

personally if your going to go through the trouble i would ditc the nikki
"i wouldnt trust any nikki with an additional 8 psi force feed into the engine" and get a holley 650 tuned down

but then you still have the probl that the 12a is just not ment to be force fed stock with the compression ratio it has,
but maybe 8 psi would be nice.

Sterling

mperformance wrote:
"Sterling ... won't the supercharger rob power all the time, if you bleed off the boost that much with a valve won't you be actually loosing the efficiency of the all-time-boost from the supercharger?"

--The blower is robbing because of the work it's made to do (compressing air); Not because of the RPMs. The GM cars use a valve that opens the input and output chambers of the blower in the plenum so that it basically free wheels while the engine is at cruising speed. (Obviously, air is bypassed into the throttle somehow.)

etherhuffer wrote:
"Sterling, The ability to pump air changes with rpm, the supers are not a constant output unit. So you are correct. You set the boost with a pulley. sort of. If your output exceeds what you can handle, then a blow off seems smart. The centrifugal blowers with a variable pulley(See CVT transmissions) are the best. Centrifugal or variable pulleys can broaden where you get boost. I only know old style Paxton/Roots stuff. I would ask Atkins, as they sell the nice blowers. Sounds fun. I think blowers are more fun than turbos, even if they are less efficient. Get a 50's haircut. It will help you think about blowers and you will fit in at the next hot rod show. Ha!"

--Smart *** w/ a dovetail!
I don't understand...My positive displacement Roots Eaton M-62 blower puts out 1.02 liters of air in one revolution (mathmatically). If it's tethered to the engine in a direct
drive ratio of two to one, then one engine revolution will make the blower revolve twice, putting out two liters, beit at 750 RPMs engine speed, or 7K RPM engine speed.
Should not the pressure remain constant?
What is causing the change...more heat with higher revs due to more compression?
THAT does'nt make sense to me either because the engine is eating it up as fast as the blower is dishing it...The blower is still trying to cram two liters into a one liter space no matter WHAT the RPMs are.

I feel like I'm missing a big piece of the puzzel.

mark perez wrote:
"No blow off valve needed,,on superchargers,,any kind
that are belt driven,,(all) the pulley's are everything,,
the terms,, overdriven,,and underdriven,,,these are
what 'boost' would be,,turbo's are controlable for big
dollors,,,but blowers,,beltdriven are not like that,,
so you need to know what % overdriven,or underdriven
will work the best for the 12a,,,ask atkins for pulley info"

--I've already talked to Dave Atkins a long time ago. It was regarding his Camden blower, which I almost bought. But then I started doing research on blowers in general, and found out some things about the Camden blowers that are'nt all that great.
They are a two lobed straight rotor, 0* pitched gear tooth, suck through design that requires an oil line to be tapped. They require (according to someone I trust) approximately 70 HP to drive at peak power.

The Eaton firstly is an OEM part on some GM cars, with rebuilds being guaranteed for 100,000 miles. (No, that was not a type error!).
They are a helical three lobbed rotor design with extensive development in entry and exit porting, which drops their parisitic power needs to 45 HP.
They are also self contained (no oil lines), and can be mounted in any direction needed.

The pulley diameters are blower specific. The Camden 7 Inch blower has a 112 cfm displacement. (So they said...Mine is huge, and only has a 70 inch displacement. Perhaps it's the other lobe.)

V8kilr wrote:
"then you have to remember that even though the bleed is regulating 8 psi it will also have a much higher psi at idle,
it would have the same as if you were running a 20 psi super at idle,
see what i mean?

so yes your max boost would be regulated to 8 psi but your idle boost would probably be to high for comfort


if it could be done

personally if your going to go through the trouble i would ditc the nikki
"i wouldnt trust any nikki with an additional 8 psi force feed into the engine" and get a holley 650 tuned down

but then you still have the probl that the 12a is just not ment to be force fed stock with the compression ratio it has,
but maybe 8 psi would be nice. "

--I don't see how it will be misbehaving at idle when there's a bleed. Like I stated before, the pressure shoulb be the same in the box whether it's at idle or at 7K.

I will not ditch the Nikki. I am in the process of reconfiguring one for this application, and I'll be willing to put it up against any Holley once this is done.

I'm shooting for well over ten psi...if the blower can deliver.
I can drivwe it two to one at the most. this tops it at it's redline at 8K engine speed. I won't be shifting up there anymore, anyways.
But before I go nutz turning up the boost, I'll be doing water injection and ignition retarding.

...One thing at a time!

mar3

iTrader: (8)

It's an extreme example, I know, but this is how Einstein approached subjects to people who had a hard time grasping principles you can't readily see with your own eyes. And before the flames begin, I am not claiming to be Einstein...think of it this way. You turn the engine by hand, one full revolution which means your blower has done two. What is the pressure obtained in the chamber now? That's why SC boost is not constant. Boost builds with RPM as it exceeds leakdown percentages until you reach the point where the air is being beaten up before it can even enter the the intake tracts and so heats up, reducing efficiencies. You might see more boost on a gauge but you're not making more power at that point. Use the formula I provided to figure out the boost, but keep it at 7 psi or so unless you beef the engine. 10 psi is too high....forget bypass valves, they're used on today's engines because there is no carb. The ECU and injectors take care of the fuel requirements irrespective of where the air is coming from. You don't have that luxury with a carb'd car...if you want real power go with a tur...oh, sorry, sterling, I don't know what came over me!! Don't make me post the GMHTP article again!! Despite what some think, the centrifugal is not a better SC, it's just cheaper to adapt to different engines...

Sterling

...Don't **** me off, Man!
Cough...Ahem...I sorta lost the equasion you gave me. In fact I can't remember if it was something you posted, PMed me, or Emailed me.

Hell..I can't even remember what day it is half th...OH CRAP! IT'S MOTHERS DAY!
Gotta go!

If this pig is gonna increase pressure with RPMs, then what kind of increase are we talking about?

Cooling is top priority for me. I'm gonna run a big-*** IC and water injection for this thing.
Is there a magic point where raising the boost any further
suddenly makes the temp skyrocket?

Also, the Camden 5 inch blower starts off with a 6lb pulley for sissys. You can get a 15 lb pulley for the larger Camden for a 13B.

So how is it there's no way I can gain anything power wise by stuffing 15 psi into my 12A when there are guys that turbo and frequently hit that number or better?

MarkPerez

Sterling,,superchargers pump the same psi,at 750 rpm
or 9000 rpm's there's no lag..it's a constant,,,
as far as a inner cooler, i don't think that is a way to go.
turbo's run a presurized system, sorta like an a/c unit.
i don't think thats going to work with a supercharger
blowing through a carburator,,or a carburator on top
of the huffer,,it don't work like that,,now if you had EFI,
maybe !! also what kind of 'hood' or top piece is going
on top of the carburator ?? is it already made by a co. ??
(paxton) or someone else. or are you going to make it yourself ? the eaton sounds better at 45 hp , then the
camdem at 70 hp, to drive them....i'm all for the supercharger thing,,trust me,,

theNeanderthol

iTrader: (1)

Actually eaton superchargers (roots type) are different. The boost is a function of rpm. I have an article on it somewhere. If you look at a graph of boost vs. rpm, it would look like the right half of a smiley face ( without the eyes and nose) The only superchargers that put out constant boost throughout the rpm range are lysholm compessor superchargers. They are the twin screw type. They are 80% efficient too. As opposed to 50% for roots type. They came on the mazda millenia S. Here is a good site showing boost vs rpm for roots type and for lyshlom type. http://www.whipplesuperchargers.com/concept_twin.html

Felix Wankel

As you know, the reason for a BOV is to prevent compressor surge (compressor wheel spinning backwards) when the throttle plates are closed.

I don't believe a supercharger suffers from compressor surge being that it is constantly driven by a belt. It has no way to turn backwards.

This is an assumption I make from seeing so many 5 speed Mustangs and 6 speed Z28s with Vortechs and Paxtons under the hood, and no BOV's.

REVHED

No no no! Blow-off valves are very important especially on supercharged engines... assuming that it's a blow-through setup.

Can you imagine what happens when the throttle plates snap shut at 7000rpm and the supercharger which is belt driven is still trying to spin away and push air through the engine? This can result in bent throttle butterflies, broken drive-belts or possibly damage to the blower.

On a draw-though system there is no such problem as when the throttle closes the blower or turbo will happily continue to spin away in vacuum.

Sterling, I think you're confusing blow-off valves(which is what I just explained and which you definately need) and over-boost relief valves.

Obviously, blow-off valves are placed in between the blower and the throttle butterflies. A vacuum signal is sourced from the intake manifold and fed into the top of the blow-off valve. That way when throttle closes and the manifold is under vacuum it will pull the valve open and vent the boost into atmoshphere. A blow-off valve should never open under boost alone. The general rule is to use one that is rated for twice the boost you'll be using.

An over-boost relief valve on the other hand is a simple device that opens once a set boost pressure is reached. I really don't see why you'd need one in a supercharged application.

REVHED

*sigh* A supercharged engine will benifit from an intercooler just like a turbo engine.

In fact it's a great idea as rootes style blowers are generally pretty inefficient meaning they produce more heat for a given boost pressure.

And what difference does it make if it's EFI or carburetted? None.

etherhuffer

Sterling, I agree with Mar3 in that you show a certain psi, but the efficiency changes with rpm due to heat. I also would note that each super is very different in efficiency across the range of designs. (which is to say I don't know the differences exactly) Part of setting up a super is asking where you want the best boost efficiency. Most guys want it in gears one-two-three. gears four and five are better served with a turbo. Also with a nod of the hat to Mar3 remember that PV=nRT, your gas constant equation says your volume, pressure and temp are all dependent on each other. Another point on the blow off: If you pull off the throttle, the response of the super is different based on the the mass of the lobes, whether you are direct pulley or clutched, etc. On a direct drive pulley your crank speed is your blower speed adjusted by pulley size. On a centrifugal clutch drive there is a variable relationship between max and min pulley drive and the crank speed. So there is a small lag there. I think for a practical answer, you need to know who has set up each type of blower and see if they have a good track record.

jeremy

iTrader: (1)

i'm sorry to interrupt but i keep seeing this and thinking "we don't have valves". so with that, if you're going to get a valve job, make sure and get some titanium springs.

jeremy

iTrader: (1)

oh yeah, and sterling you're thinking of a wastegate. like revhead said, blow-off valves go psssssssst.

Sterling

Did you all PM each other to get together and **** with me? Cause you're all saying different things!!!

mark perez
Sterling,,superchargers pump the same psi,at 750 rpm
or 9000 rpm's there's no lag..it's a constant,,,
****This is what I thought, and have read, but not what etherhuffer and mar3 are saying. I think they are saying that it increases due to heat generated by tumbling the air.

as far as a inner cooler, i don't think that is a way to go.
****Definitly going to have an intercooler.

...what kind of 'hood' or top piece is going
on top of the carburator ?
****Fabbing the box myself.

theNeanderthol
Actually eaton superchargers (roots type) are different. The boost is a function of rpm. I have an article on it somewhere.
If you look at a graph of boost vs. rpm, it would look like the right half of a smiley face ( without the eyes and nose)
****Untrue. Roots are positive displacement blowers. Centrafugal blowers are RPM dependant. Positive displacement blowers give a set amount of volume per revolution, beit at 1000 rpms or 10,000 RPMs.
Centrifugal blowers (basically a belt driven turbo) will increase output multiplicatively as RPMs are increased. IE, @ 2000 RPMs, the centrifugal blower puts out "X" cfm. But @ 4000 RPMs, the centrifugal blower puts out "X squared" cfm.
@ 2000 RPMs, the PD blower puts out "Z" cfm. But
@ 4000 RPMs, it will still put out " two times Z" cfm

The only superchargers that put out constant boost throughout the rpm range are lysholm compessor superchargers. They are the twin screw type. They are 80% efficient too. As opposed to 50% for roots type.
****This statement is basically untrue, unless of course you are a sales rep for Whipple, or some other company that uses helical lobed rotors in their blowers. The screw-type rotors have a much smoother action than the old straight line design. The air is'nt beaten to death, temperature is kept down, and efficiency goes up. Bearing load is also lessened a great deal. (I've done my homework.) The Eatons are helical lobed (screw type), rear entry, yadda yadda.
But all positive displacement blowers (Vane and Roots) will theoretically put out constant boost.

http://www.whipplesuperchargers.com/
****Looked, did'nt see anything different than the Eaton design, ect the Eatons are rear entry (don't know if Whipple uses rear entry. The Whipples certainly are cleaner more presentable.

Felix Wankel
As you know, the reason for a BOV is to prevent compressor surge (compressor wheel spinning backwards) when the throttle plates are closed.
****No, I did not.

I don't believe a supercharger suffers from compressor surge being that it is constantly driven by a belt. It has no way to turn backwards.
****This is the first I've ever heard of that. (Never thought a turbo could spin backwards. I guess that would'nt be too good.

This is an assumption I make from seeing so many 5 speed Mustangs and 6 speed Z28s with Vortechs and Paxtons under the hood, and no BOV's.
****I find that comforting, but are they all blow thru design? I'm sure they are all EFI, too. What happens when there's no computer to read the fuel needs?

REVHED
quote:
--------------------------------------------------------------------------------
Originally posted by mark perez
No blow off valve needed,,on superchargers,,any kind
that are belt driven,,(all) the pulley's are everything,,
the terms,, overdriven,,and underdriven,,,these are
what 'boost' would be,,turbo's are controlable for big
dollors,,,but blowers,,beltdriven are not like that,,
so you need to know what % overdriven,or underdriven
will work the best for the 12a,,,ask atkins for pulley info
--------------------------------------------------------------------------------
No no no! Blow-off valves are very important especially on supercharged engines... assuming that it's a blow-through setup.

Can you imagine what happens when the throttle plates snap shut at 7000rpm and the supercharger which is belt driven is still trying to spin away and push air through the engine? This can result in bent throttle butterflies, broken drive-belts or possibly damage to the blower.

On a draw-though system there is no such problem as when the throttle closes the blower or turbo will happily continue to spin away in vacuum.
****All of this seems to make perfect sense to me.

Sterling, I think you're confusing blow-off valves(which is what I just explained and which you definately need) and over-boost relief valves.

Obviously, blow-off valves are placed in between the blower and the throttle butterflies. A vacuum signal is sourced from the intake manifold and fed into the top of the blow-off valve. That way when throttle closes and the manifold is under vacuum it will pull the valve open and vent the boost into atmoshphere. A blow-off valve should never open under boost alone. The general rule is to use one that is rated for twice the boost you'll be using.

An over-boost relief valve on the other hand is a simple device that opens once a set boost pressure is reached. I really don't see why you'd need one in a supercharged application.

-----------REVHEDs responce to Marks quote:---------------
*sigh* A supercharged engine will benifit from an intercooler just like a turbo engine.

In fact it's a great idea as rootes style blowers are generally pretty inefficient meaning they produce more heat for a given boost pressure.

And what difference does it make if it's EFI or carburetted? None.
****I'm inclined to agree with everything that REVHED has said thus far.

etherhuffer
Sterling, I agree with Mar3 in that you show a certain psi, but the efficiency changes with rpm due to heat. I also would note that each super is very different in efficiency across the range of designs. (which is to say I don't know the differences exactly) Part of setting up a super is asking where you want the best boost efficiency. Most guys want it in gears one-two-three. gears four and five are better served with a turbo. Also with a nod of the hat to Mar3 remember that PV=nRT, your gas constant equation says your volume, pressure and temp are all dependent on each other. Another point on the blow off: If you pull off the throttle, the response of the super is different based on the the mass of the lobes, whether you are direct pulley or clutched, etc. On a direct drive pulley your crank speed is your blower speed adjusted by pulley size. On a centrifugal clutch drive there is a variable relationship between max and min pulley drive and the crank speed. So there is a small lag there. I think for a practical answer, you need to know who has set up each type of blower and see if they have a good track record.
****I'm all set in the way I wish to pulley it. I will not be futzing about with a centrifugal clutch. I understand that what you are proposing is a way to achieve what I was originally asking asking about. However, I still fail to see why I can not expect to regulate the psi of the blower, be it a constant flatline pressure, or an increasing pressure relative to RPM due to heat from compression, buy installing a valve...Perhaps in the body of the blower itself, as the original bypass valve was done. (I've since milled that part off as it was integral with the original throttle body hook up.)

I also still have difficulty grasping the efficiency indexing of the blower with respect to RPMs. The difficulty is the paradox of the rotary engine; as it becomes more efficient as RPMs increase!
PV=nRT...Pressure X Volume = (What?) x Temp.
This means P=nRT/V with V being a constant one liter (I LOVE an easy equasion!!!

Missing "nRT"; However assuming "T" is Temp.

Thanks, guys.
Feed me more info!!!

etherhuffer

Sterling, this if fun. Hope we are not chapping your hide. Volume=gas constantxsecond constantxTemp/Pressure. So as the temp increases, the volume goes down. Thus the intercooler to keep your efficiency up. IF you can compensate for temp, you can keep the volume up. The other efficiency loss is via turbulence of the flow and mechanical designs ability to pump air, which are related somewhat. So, find the maximum of your unit in psi. Get the pulley to set your peak boost where you want it. Then, given the limits of your motor, decide if you need a wastegate. The engine does not care how the air and fuel got there. It just cares about how much kablaam goes on and how much knock that creates. I think everyone who owns a modded turbo II should be able to give you a number. If you are carbed, there is a fixed number for you, cause you ain't got a knock sensor and EFI.

MarkPerez

I've never heard of an inner cooled supercharger,,
i thought the inner coolers are used with turbos,
because you know,,turbos operate off the exhuast=
heat..the best is a cold dense fresh air,,right,,and the IC's cool down the air some,,but thats a lot of plumbing,,
maybe i'm thinking of only one type of supercharger
food for thought ,..

mar3

iTrader: (8)

This is simply wrong. If it were true, you would generate 10 psi at idle and you don't...reread my earlier thought experiment and think about it! Boost rises with rpm in a fairly linear fashion until you hit the heated air barrier...I'm getting very tempted to post the GMHTP article again...

MarkPerez

What i'm saying is,,i've never heard of an inner cooled
paxton supercharger,,i'm not saying that it couldn't
happen,,i've just never heard of an IC,,SC,,turbos,,yes
i'm taking all this in,,trust me,,because i've got the $$$
and just as soon as something is found to give the 12a
with the nikki at least 30-40 more ponies i'll be second
in line to buy one,,or two,,,as long as the engine will
live for a while,,to make it worth it,,i already have to
keep on top of my 82 to keep it on the road,,you know ?

Felix Wankel

Mark, the heat is generated from the compression of the air, not whether or not it is a turbo or supercharger.

A turbo spins much faster than a SC, therefore the air is heated much more. Thats why you almost always see intercoolers used with a turbo.

Sterling, have you checked around to find a CFM number for the supercharger? I'm also curious as to how you are going to design the intake, aren't all the Eatons on those Bonnevilles blow through? That should call for a big boxy intake manifold...

Sterling

etherhuffer-
You're not "chapping my hide." These are the type of threads I come on these sites for!
Please tell what the representatives are in the equasion "PV=nRT".
You've confused me with the following statement:

"So as the temp increases, the volume goes down."
You mistyped, or I'm not understanding.

"Then, given the limits of your motor, decide if you need a wastegate. The engine does not care how the air and fuel got there. It just cares about how much kablaam goes on..."

Remember, this all started because I wanted to easily manually set boost so that I could increase it as I added things like water injection, timing failsafes, and possibly even a knock sensor.

mark perez
"I've never heard of an inner cooled supercharger,,
i thought the inner coolers are used with turbos,"

Production SCed cars don't usually have an "intercooler"; and here's my guess as to why...
They run at very low boost, first of all. Second, they have an internal bypass valve that opens up when the engine is at cruise speed. This way, the blower is basically freewheeling in vacuum like REVHEAD was saying (in reference to draw thru design). There simply is not enough heat generated, and so the cost of using ICs outwieghs the benifits in production application.
Most blown hotrods in the past have used draw thru set-ups. This does'nt allow you to use an intercooler. (Want gas in your IC?!)
However, the production set-up does use blow-thru which lends itself to the use of ICs, but like I say...They have little to gain.
Of course, I feel that ANY set-up can gain SOMETHING by the installation of an IC.

mar3
quote:
--------------------------------------------------------------------------------
Originally posted by Sterling
mark perez
Sterling,,superchargers pump the same psi,at 750 rpm
or 9000 rpm's there's no lag..it's a constant,,,
****This is what I thought, and have read, but not what etherhuffer and mar3 are saying. I think they are saying that it increases due to heat generated by tumbling the air.

--------------------------------------------------------------------------------
This is simply wrong. If it were true, you would generate 10 psi at idle and you don't...reread my earlier thought experiment and think about it! Boost rises with rpm in a fairly linear fashion until you hit the heated air barrier...I'm getting very tempted to post the GMHTP article again...


Ahh keep yer knickers on!
I'm understanding by your example that until you get any compressor runnin at a certain speed, you've got little or no pressure.
(This is why I don't bother doing compression test on rotaries unless I'm looking for a bum seal. Afterall, at such a low RPM, you're really only measuring the strength of your battery because your starter rpm will change with battery output.)

I'm certain that's true for a roots blower, but there must be a threshold where suddenly, it does TAKE IN the Volume Per Revolution it is designed for, and continues TAKING IN that same volume Per Revolution until the RPMs begin to exceed the intake ports flow efficiency, and the machine begins to TAKE IN slightly less air, tumbling it as it shoves it thru - (just like any other port design, I suppose, beit manifold, exhaust or home plumbing!- efficiency will optimise, than max out, then regress towards inefficiency.)
As the tumbling temp gets really high...Even though the INTAKE VOLUME is getting a bit smaller, the OUTPUT VOLUME is actually increasing beyond it's "Peak Performance Output Volume" coefficient due to temperature increase.
The blower has by now become an inefficient and detrimental parasite to my engine.
The OUTPUT MASS has changed from a healthy helping of oxygen laiden air at peak operation to a heat soaked, spacely oxygenated breath that lends itself well to detonation.
It now takes in a bit less volume, overheats it, and spits out something that tries to occupy more volume. The air has heated up so much upon exit that the pressure, which registered as somewhat steady throughout most of the "useable range" of the blower has suddely skyrocketed by comparison, though the Volume Per Revolution on the INTAKE side might acctually be lower due to tumbling.

Do I have that right?

Now; Something you said in your previous post makes me wonder...

"Despite what some think, the centrifugal is not a better SC, it's just cheaper to adapt to different engines..."

We were never discussing cenrifugal SCs. Only PDs. (So mind yer Qs!) J/K
I was just wondering where you were headed with this, because noone disputes that they put out multiplicatively more mass with increased rpm.


Felix Wankel

"Sterling, have you checked around to find a CFM number for the supercharger? I'm also curious as to how you are going to design the intake, aren't all the Eatons on those Bonnevilles blow through? That should call for a big boxy intake manifold... "

est. 500 cfm @ 16K.
The graph shows it @ 460 @14K RPM, but the Magnasun site, which mods the Eaton housings under liscence, says you can run them to 16K...Just not all damn day!
Anyway, I could gear it 2:1 if I want...I'll never want to expose the engine to shifting @ 8K with a blower on it.
The Eaton is very linear in it's climb with respect to RPM vs cfm, right up to 16K. Course I realize all that changes when you slap it on an engine.

The plenum and box; everything, will be fabbed by me.

Despite what I believe mar3 is trying to illustrate, these blowers are EXCEPTIONALLY efficient. Unfortunately, as I've read, and seen thru my own questions, many people have not paid attention to the significant advances in flow efficiency made by the leading Roots style blower manufacturers.

It has been said by PD blower users and advocates, that the PD Roots blower will take the way of the turbo in production autos.
Certainly I don't want to get into any debate as to which is better for performance or the like. It's simply to illustrate that auto manufacturers are looking at them!
Look at it from their perspective...Blowers run cooler, no IC needed, easily bypassed for economy, and less hassel....IN AN APPLICATION WHERE THE INDUSRYS DEFINITION OF "PERFORMANCE" IS 'JUST GOOD ENOUGH' TO SELL CARS!
For the top-o-da-line performance cars, turbos will surely be used.

Mar3 -
"EEEK-EEEK...The BLOWERS are coming! The BLOWERS are coming!"

jeremy

iTrader: (1)

"So as the temp increases, the volume goes down."
You mistyped, or I'm not understanding.

more on the line of as temp increases, DENSITY decreases, therefore less oxygen

turbos also have the problem of being driven by the exhaust. so the heat absorbed in the exhaust turbine is transferred into the intake turbine via the shaft and there close proximity. imagine the underhood heat generated by a turbo and now think of being inches from the source. supercharges can benefit from intercoolers but not near as much as a turbo can.

mar3

iTrader: (8)

Yes, but the reason you don't hit a peak psi and hold it as revs climbs goes back to the efficiencies...even at 80%, you're letting 20% air escape compression at max psi when sealing is optimal because of sheer rotor speed...at lower rotor speeds your losing more...


I was dissin' the earlier post by etherhuffer...don't you memorize every line in a thread you initiate??

Damn your eyes!! Now I'll have to get 150 HP jets of NNNAAAAAAWWWSSSSSSSS for my streetport!! Course, it might help if I just got it running again....