[Diy_efi] New project

Mike erazmus at iinet.net.au
Fri Nov 22 02:23:14 GMT 2002


BMW claims they can achieve greater than 100% VE on their M3 class
engines for a sizable upper part of their rev range - amazing what
intake tuning can achieve !

3L at around 250-300bph  NA is quite nice, a friend bought on and took
me for a spin - keeps pulling well ! beyond 200K/mh,

rgds

mike



At 12:57 PM 18/11/2002 -0800, you wrote:
>Dennis Noordsij wrote:
>
>> One thing you mentioned, a VE table for SD. If you take the MAP, compare
it to
>> the ambient pressure, isn't there a nifty formula that takes the size of
the
>> throttle opening and angle of the butterfly to calculate exactly how
much air
>> would have moved in due to pressure differences? Which would give you the
>> exact amount of air almost as accurately as a MAF could? Every time you
>
>No, it's much more subtle than that.  Volumetric efficiency captures the
>entire path of the air from the atmosphere through the air filter,
>intake ducting, throttle body, plenum, runners, intake manifold, ports,
>valves, cam timing/overlap, etc.  If air was incompressible and
>inviscid, then you would be correct that simply knowing the displacement
>of the cylinder and air's temperature and pressure would be sufficient
>to determine exactly how many air molecules entered the cylinder.  In
>fact this is the definition of 1.0 or 100% VE, the amount of air that
>would enter the cylinder if the air was some ideal fluid that has no
>compressibilty or resistance to flow or other dynamic effects.  But
>that's not the case, and it's not something that you can calculate
>analytically.  You could get a rough initial map by assuming a constant
>VE (of around .7 or so) for all spots but it will certainly need some
>refinement.
>
>Brian
>
>_______________________________________________
>Diy_efi mailing list
>Diy_efi at diy-efi.org
>http://www.diy-efi.org/mailman/listinfo/diy_efi
>
>

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi



More information about the Diy_efi mailing list