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From: Nial Stewart on 22 Jul 2010 14:54
I am afflicted with the love and ownership of a classic Mini...

http://pimz.com/site/data/portfoliopix/classic_mini.jpg

These were fuelled with SU carbs (until the last few years when Rover
developed a reasonable solution to fuel injecting siamesed input ports).

The SU uses a tapered needle to regulate fuelling, the needle has to have
the correct profile along its length. The needle in my car almost certainly
isn't correct, it always drives better with the choke out.

I have been thinking of making a rig so I can properly measure & log the A/F ratio
against the carb piston lift (the needle protrudes from the bottom of the
piston into the jet). This should allow an optimum profile to be deduced
and the correct needle produced.


I can use one of these to measure the A/F ratio....

http://www.innovatemotorsports.com/products/lc1.php

...but need a method of measuring the piston lift _fairly_ accurately and
without loading the piston too much (the lift is regulated by a spring
and too much extra weight on the piston would affect this).

I can mount things so that a vertical probe sits on top of the piston and
be moved as the piston moves. (I'll try to get a picture tonight).

I can used an LVDT but this is expensive and overly accurate for what I'm
doing.

Can anyone suggest any simpler/cheaper method of measuring this?

Thanks for any thoughts.


Nial.


From: Tim Wescott on 22 Jul 2010 15:06
On 07/22/2010 11:54 AM, Nial Stewart wrote:
> I am afflicted with the love and ownership of a classic Mini...
>
> http://pimz.com/site/data/portfoliopix/classic_mini.jpg
>
> These were fuelled with SU carbs (until the last few years when Rover
> developed a reasonable solution to fuel injecting siamesed input ports).
>
> The SU uses a tapered needle to regulate fuelling, the needle has to have
> the correct profile along its length. The needle in my car almost certainly
> isn't correct, it always drives better with the choke out.
>
> I have been thinking of making a rig so I can properly measure& log the A/F ratio
> against the carb piston lift (the needle protrudes from the bottom of the
> piston into the jet). This should allow an optimum profile to be deduced
> and the correct needle produced.
>
>
> I can use one of these to measure the A/F ratio....
>
> http://www.innovatemotorsports.com/products/lc1.php
>
> ..but need a method of measuring the piston lift _fairly_ accurately and
> without loading the piston too much (the lift is regulated by a spring
> and too much extra weight on the piston would affect this).
>
> I can mount things so that a vertical probe sits on top of the piston and
> be moved as the piston moves. (I'll try to get a picture tonight).
>
> I can used an LVDT but this is expensive and overly accurate for what I'm
> doing.
>
> Can anyone suggest any simpler/cheaper method of measuring this?
>
> Thanks for any thoughts.

A linear encoder.

Or hand-wind an LVDT. It'll still be complex, but it'll be cheaper
(assuming you can read it).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
From: TTman on 22 Jul 2010 16:04

"Nial Stewart" <nial*REMOVE_THIS*@nialstewartdevelopments.co.uk> wrote in
message news:8arifiF2onU1(a)mid.individual.net...
>I am afflicted with the love and ownership of a classic Mini...
>
> http://pimz.com/site/data/portfoliopix/classic_mini.jpg
>
> These were fuelled with SU carbs (until the last few years when Rover
> developed a reasonable solution to fuel injecting siamesed input ports).
>
> The SU uses a tapered needle to regulate fuelling, the needle has to have
> the correct profile along its length. The needle in my car almost
> certainly
> isn't correct, it always drives better with the choke out.
>
> I have been thinking of making a rig so I can properly measure & log the
> A/F ratio
> against the carb piston lift (the needle protrudes from the bottom of the
> piston into the jet). This should allow an optimum profile to be deduced
> and the correct needle produced.
>
>
> I can use one of these to measure the A/F ratio....
>
> http://www.innovatemotorsports.com/products/lc1.php
>
> ..but need a method of measuring the piston lift _fairly_ accurately and
> without loading the piston too much (the lift is regulated by a spring
> and too much extra weight on the piston would affect this).
>
> I can mount things so that a vertical probe sits on top of the piston and
> be moved as the piston moves. (I'll try to get a picture tonight).
>
> I can used an LVDT but this is expensive and overly accurate for what I'm
> doing.
>
> Can anyone suggest any simpler/cheaper method of measuring this?
>
> Thanks for any thoughts.
>
>
> Nial.
>

Buy the right needle..... plenty of places in the UK selling MINI stuff...
is the air filter nice and clean ?


From: Nial on 22 Jul 2010 16:10
> Buy the right needle..... plenty of places in the UK selling MINI stuff...
> is the air filter nice and clean ?

You tell me which of the several hundred that are available is the
right one and I'll go and
buy it!

(The car's modifed a bit and I'm planning a fair bit more).


Nial.

From: TTman on 22 Jul 2010 17:04

"Nial" <nial(a)nialstewartdevelopments.co.uk> wrote in message
news:e06f18c8-c877-4669-9c25-34d8afdb11f2(a)t10g2000yqg.googlegroups.com...
>> Buy the right needle..... plenty of places in the UK selling MINI
>> stuff...
>> is the air filter nice and clean ?
>
> You tell me which of the several hundred that are available is the
> right one and I'll go and
> buy it!
>
> (The car's modifed a bit and I'm planning a fair bit more).
>
>
> Nial.
>
It's a complex subject and a dying art....change anything and you need to
re-needle. start here :- http://www.sucarb.co.uk/


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