Fuel Curves

[Chris Morriss]

In message <s5eec1c7.082 at MAIL.TAIT.CO.NZ>, Bruce Robertson <bruce_robert
son at MAIL.TAIT.CO.NZ> writes
>Hello,
>
>What would an ideal plot of manifold vacuum versus injected fuel
>quantity look like? I am still on the job of tuning my Lucas mechanical
>injection - last night I measured the fuel curve and it seems a bit dodgy to
>me (although my opinion is not very qualified). At low vac the fuel
>delivery is high, and it drops very rapidly (and linearly) until it reaches
>about one third of its original quantity, and then it changes slope and
>linearly decreases until it gets to max vac. This means that about the first
>10% of the total vac increase reduces the fuel quantity by about 66%
>and the last 90% of vac reduces it by 33% (the two parts of the graph
>are both linear of course because it relies on springs to derive the
>curve). Does this seem good/bad/otherwise to anybody who knows?
>
>Any comments gratefully recieved.
>
>Regards
>
>Bruce Robertson
>Lucas injected Bond Equipe Sufferer - New Zealand
>
I had a look at various published fuel curves for MAP systems when I did
my original analogue unit.  Most show a fairly linear increase in fuel
delivered per revolution up to about a MAP of 0.8 bar (or thereabouts)
as the MAP rises at WOT towards 1 bar, then the fuel delivery rate
increases a bit to get max power out of the engine.  Your measured break
point seems to be in the wrong place!

Does the Lucas mechanical system give a squirt every crank rev?  I used
to have a Mk2 Bond Equipe with the standard 2 litre engine.  It's now a
Moss kit-car.


-- 
Chris Morriss