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Re: SU Adjustments - Float Height - Pressure????

To: MG List <mgs@autox.team.net>
Subject: Re: SU Adjustments - Float Height - Pressure????
From: Max Heim <mvheim@studiolimage.com>
Date: Fri, 09 Mar 2001 14:40:53 -0800
on 3/9/01 10:30 AM, Ptegler at ptegler@gouldfo.com wrote:

> 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.
> 
OK, call it 1/16th, then... (.0024psi)

> 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.
> 
That's what CR was talking about (not me) -- greater depth of fuel = higher
pressure due to gravity. I'm not convinced that this (fractional variation
in level = significant variation in fuel flow due to pressure) has any
real-world effect, myself.

> 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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