Aerochargers are better than a twin screw!! hahaha ;-)

[Stephen Andersen]

Greg,

I "respectfully" have copies of the Lysholm compressor maps
in my briefcase, and have done the requisite efficiency
calculations.  While I agree that the lysholm AE is not that
of a centrifugal compressor, they are still pretty darn
good (range of 58-64% for my car), compared to 30-50% for 
a new style (Eaton) Roots.

My point was not really one of efficiency (although I did mention
it), but that rotational speed of the compressor does not have to
be very high to get high pressure output.  

In my application, shooting for 7.5-8 psi, I am quite confident that
the Lysholm will give me at least 6+ psi at 1500 rpm. and climb
from there.

Since you are accusing me of just "regurgitating" magazine info,
I would like to know on what you base your comment that aerocharger's
little plots are "fact"?

Care to share?

And I'll keep the PE in my sig thanks, I don't think I have 
crossed any ethical boundaries here...

Steve

Stephen M. Andersen, P.E.                              (302) 326-6405
Technical Director                                    FAX  (302) 326-6401
AdvanTek International, LLC                     Cell   (302) 547-9842
56 Read's Way                               andersen at Advan-Tek.com
New Castle, DE 19720


> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Greg Hermann
> Sent: Sunday, October 14, 2001 10:13 PM
> To: diy_efi at diy-efi.org
> Subject: RE: Aerochargers are better than a twin screw!! hahaha ;-)
> 
> 
> At 8:31 PM 10/14/01, Stephen Andersen wrote:
> >The boost curve for the Positive Displacement SC
> >on aerocharger's web site is about as far from a
> >"fact" as you can get.  When sized and "geared"
> >properly for a give displacement engine, a PD
> >supercharger will provide within about 10-15% of
> >peak boost given WOT at somewhere just off idle.
> >
> >The twin screw compressors have extremely high
> >volumetric efficiencies and don't need to be spinning
> >very fast to generate boost.
> >
> >Aerocharger's site indicates that the boost curve
> >is linear and starts at or near zero.  Way off base...
> >
> >Steve
> >
> >Stephen M. Andersen, P.E.                              (302) 326-6405
> >Technical Director                                    FAX  
> (302) 326-6401
> >AdvanTek International, LLC                     Cell   (302) 547-9842
> >56 Read's Way                               andersen at Advan-Tek.com
> >New Castle, DE 19720
> 
> Steve--
> 
> I respectfully suggest you get a copy of the VE and AE curves 
> FROM WHIPPLE
> for the various Lysholm compressors which they sell, and run 
> some numbers
> on what level of boost you will get on a given engine at a given
> engine/compressor rpm --without exceeding the compressor 
> mfgr's suggested
> maximum compressor rpm at the motor's redline rpm. (If you 
> know how to do
> this.)
> 
> (I am assuming that you are NOT talking about running a variable speed
> compressor drive.)
> 
> I went through this VERY exercise in an effort to find a way 
> to put forced
> induction onto a 60 cid, 1800 rpm tractor engine. It was all VERY
> enlightening, believe me !!
> 
> The fact is that the Lysholm type screw compressors need to have some
> rotational speed before their VE rises to anything 
> approaching a reasonable
> level. Further, their VE does NOT go that impressively high, 
> even at its
> peak.  (It is ONLY impressively high if one is comparing it to a Roots
> blower !!)  And, furthermore, while the Lysholms have a 
> decent AE, it is
> NOT the equal of what can be achieved with a well designed 
> and selected
> centrifugal compressor wheel and housing.
> 
> AND, furthermore, with all due respect, I  suggest that  you 
> might want to
> consider omitting the part of your signature which is in 
> excess of just
> "Steve" when making technical comments that appear to be 
> doing little more
> than regurgitating the content of a magazine article ! After 
> all, there
> _ARE_ certain "professional responsibilities" that go along 
> with stating
> your professional title ! :-)
> 
> Greg (also a P.E.)
> 
> 
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