[Diy_efi] New project

[Geddes, Brian J]

On a turbo car, is VE effected by pre-turbo intake path characteristics? =
 It seems to me that since the turbos are "pushing" the air at the =
throttle body, pre-turbo intake wouldn't matter to VE.  But it would =
affect maximum boost level...compressor efficiency as opposed to engine =
efficiency, I guess.  Is this the way it actually works?

- Brian

>=20
> No, it's much more subtle than that.  Volumetric efficiency=20
> captures the
> entire path of the air from the atmosphere through the air filter,
> intake ducting, throttle body, plenum, runners, intake=20
> manifold, ports,
> valves, cam timing/overlap, etc.  If air was incompressible and
> inviscid, then you would be correct that simply knowing the=20
> 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=20
> a constant
> VE (of around .7 or so) for all spots but it will certainly need some
> refinement.
>=20
> Brian
>=20
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>=20

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