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

[Stephen Andersen]

> I've got a Eaton M62 on my BMW 1.9l and get 2psi @1000. Full 
> boost (8psi) is around 3k-3500. Its run a 1.75x engine speed. 
> 
> Shawn 

Shawn,

I looked at the MP62 for my 2.5 engine, as well as the 1600AX
and 2300AX Lysholms (Whipple).  At 5psi, the Eaton was only 30-31% 
efficient (calculated based on delta T, since Eaton does not have
compressor maps), at 10psi, it was just about 50% (AE).  These
efficiency numbers are at max rpm only.  This compares to around 
55% for the 1600AX at 5psi, and 64% for the 1600AX at
10psi.   I also found in my calcs that the Eaton would cost
almost 2x the drive horsepower of the Whipple, which surprised
me.

These numbers are obviously with a whole lot of assumptions piled
up.

Anyway, the roots style blowers are less (volumetrically) efficient 
at low rpm than the screw compressors, and typically will require
a more rpm before they can overcome internal leakage and make
significant boost.  Of course, they are also WAY cheaper...

Steve


 
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org