Throttle enrichment - why, how much?

[David Chambers]

> 
> It was *drivable*, but it had some nasty gotchas.  I had a settable, fixed
> boost
> and a settable, fixed decay...  One of my main problems has been attempting to
> tune
> this guy.  How different is static (ie, engine in neutral) vs dynamic (drivin')
> for
> this?
Engine in neutral and engine driving under load are TOTALLY different
fuelings. For free revving in neutral you might have idle fuel at 2ms
and fuel at 5000rpm no load at 2.5ms ie very similiar to idle fuel all
the way up the rev range under no load. For full throttle ie full load
you might use 7ms. The numbers quoted are just to show the ratio they
depend on lots of things related to each engine so please dont just use
them on your motor.


> 
> > This function is needed to allow for the engines requirement of a static
> > richer mixture during transient acceleration and also to allow for the
> > lag between the air flow and the fuel flow due to their differing
> > densities in the manifold. Ie with something like throttle body
> > injection with injectors a long way from the valve you will need more
> > percent and slower decay. With race type inlet runners one per cylinder
> > and injectors close to the valve you almost don't need any boost.
> 
> Hmm. a compromise.  This is a FSAE class car, so it has a single tuned inlet
> (splits into 4),
> but the injectors are mounted about 2 inches away from the intake.
> 
> > With regard to the sensors it depends which ones you are trying to read.
> > I read load every revolution, calc RPM every rev and everything else
> > about 10 times a second.
> 
> "Load"?  what sensor does that?
> 
> -Thor Johnson
> thormj at iname.com
Load to me means the throttle position or you could use MAP on a road
car.
David Chambers