Good advice CR. On the SUs that DON'T have adjustable jets,
like those used on the Series I e-types, the float setting is much more
critical. There is no 'nut' to tweak. (Dang! Hurts to even type that!)
Charley & Peggy Robinson wrote:
> Yes Max, you are missing something. The flow rate for any given
> combination of needle/jet position is dependent on the difference
> between atmospheric pressure pressing down on the surface of the fuel in
> the float bowl and the pressure in the venturi. The pressure in the
> venturi is lower than the pressure in the bowl.
...caused by the venturi effect of the raised bridge. When air moves
faster, as in squeezing through the space above the bridge, it's pressure
drops. Bernoulli or someone came up with that. :-P
> The atmospheric
> pressure in the bowl pushes the fuel thru the jet into the lower
> pressure environment in the venturi. Now, we know that as you go deeper
> in a body of water, the pressure increases.
...at a rate of 0.465psi per foot. A twelve foot deep pool produces a
pressure of 5.6psi or about 1.4 bar absolute. But I digress...
> The same thing happens in
> the microcosm of the float bowl, albeit the pressure change is very
> small. That's why the float height affects the mixture. When you tweak
> the needle adjusting nut, you compensate for that, among other things.
>
> As I stated in another post, I've experimented with different float
> heights. I found it to be a waste of time if the jets are going to be
> readjusted, because the jet adjustment cancels out any reasonable change
> in the fuel level. Once it's determined that the float valve is
> functioning correctly, the thing to do is experiment with different
> needle and/or jet combinations, IMHO.
>
> Cheers,
>
> CR
--
Rick Lindsay
Diamond Geoscience Research
5727 S. Lewis Ave., Tulsa, OK
Voice: +1 918-747-3456
Fax: +1 918-747-8599
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