volumetric efficiency

[Edward Hernandez R]

> 
> "We concluded this when we got an volumetric efficiency of 1.1 !"
> 
> What makes you think having a volumetric efficiency of 1.1 makes your 
> meter incorrect? It is entirely possible to get volumetric efficiencies
> greater than one. What engine? What rpm? What was it designed to do?

The engine is a SAAB 2.3L standard production engine (fuel injection, 
no turbo, no EGR). The volumetric efficiencies close to 1.1 was obtained 
around 4000 rpm. Normally the vol. eff. should be 0.85 (see any engine
book) which makes an error of (1.1-.85)/.85=29%.

How can vol. eff. be greater than 1?


You need to think more about what the engine books are trying to tell
you, which is this: conventional carbuereted production engines have
a typical max vol eff of ~85%. There are always fliers in any set of
data. Today's production engines can easily exceed 90%, especially
with fuel injection and tuned intakes. The project I am working on
will achieve 103% vol eff at peak torque and 97% vol eff at peak
power. This is with full exhaust and inlet sytems in place and will
be a production engine. These are stellar numbers for a production
engine, but are par for course for my target market. Still, 85% is at
the low end of average for the data I've seen on today's engines.

Vol eff values greater than one mean than you have achieved natural
supercharging with a properly designed intake manifold working with
a matched camshaft. This isn't a miracle, just rare. Race engines
regularly achieve 100% or greater. Production engines are not far
behind. Saab make good engines with high specific outputs. 110% might
be high, but they certainly make more than 85%.

In any case, books only give guidelines and averages. They are by no
means absolute nor up to date with the latest technology.