There is one atmosphere of pressure on the fuel in the float bowl. There is
slightly less than one atmosphere of pressure in the carb throat above the
jet. Thus petrol does "squirt" out of the jet.
Really the same thing as it being siphoned. The height of the gas in the
jet when there is no vacuum in the carb is fluid seeking it's own level, but
when the engine is running, some gas is always being sucked up around the
needle.
Phil
Mk1 Midget
-----Original Message-----
From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On
Behalf Of Ptegler
Sent: Friday, March 09, 2001 12:30 PM
To: Max Heim; MG List
Subject: Re: SU Adjustments - Float Height - Pressure????
BTDT
the single, two, or none washer arrangement
to adjust the float level effects fuel level in the jet
but it's not a one to one relationship.
You need to take into account the 'lever' length
of the float as it relates to its own 'floating' position
vs. at what fuel level the valve is closed/open.
Pressure?
What pressure is in the float bowls? If you had any pressure
it would 'squirt' gas out the jet into the carb
rather than requiring it to be 'siphoned' by the rushing air stream.
The height of the fuel in the jet is nothing more than gravity....
liquid seeking its own level.
Paul Tegler ptegler@gouldfo.com www.teglerizer.com
----- Original Message -----
From: "Max Heim" <mvheim@studiolimage.com>
To: "MG List" <mgs@autox.team.net>
Sent: Friday, March 09, 2001 12:41 PM
Subject: Re: SU Adjustments (LONG!) was: Float Height Issue
OK, I admit this is more complicated than I thought...
I'm still a little dubious that a pressure differential of .0012psi could
make any discernable difference (difference of + or - 1/32nd inch fuel
depth, which is about the difference one washer thickness would make).
> Charley & Peggy Robinson wrote:
>
>> 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.
>>
>>
>> Cheers,
>>
>> CR
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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