Ken ... When l worked for LUCAS in Birmingham the test
track we used was M.I.R.A .. this was also used by
S.U to find the correct needles for
British cars fitted with the S.U carb.
.
lf you go on line and check it out M.I.R.A ( it's
near Birmingham my home town )
M.I.R.A, Motor Industry Research Association
test track Nuneaton
also '' "" ""
'' "" "" "" Birmingham
Norman Nock
--- Alan Seigrist <healey.nut@gmail.com> wrote:
> Ken -
>
> The SU carb needles work to very fixed mixtures at
> different throttle
> settings & loads... what this means is when you tune
> your SU carb at
> idle, it will likely not be in tune as you drive the
> car at different
> speeds.
>
> If you want to tune an SU carb's mixture at all
> different loads and
> RPMs, the only way to do it is to have a test track,
> a stack of
> different needles that run lean, and then drive the
> car around at
> successively different loads and speeds with a
> mobile gas analyser and
> then sand paper the needles down until you get
> correct mixture at all
> speeds and loads. Some people have done this with
> spectacular results
> in terms of mileage and power, but an exceptionally
> time consuming
> process.
>
> Long story short is your mechanic doesn't understand
> how SU carbs
> work. A gas analyser at idle is no more useful then
> just tuning by
> ear and using the dashpot piston lifters.
>
> Alan
>
> '52 A90
> '53 BN1
> '64 BJ8
>
>
> On Tue, Jun 10, 2008 at 10:21 PM, Freese, Ken
> <Kendall.Freese@aerojet.com> wrote:
> > I have recently been conversing with a long time
> British sports car
> > mechanic, but I think he is mistaken in his
> approach to adjusting SU
> > mixtures.
> > He is using a gas analyser without a rolling road,
> adjusting the mixture
> > at idle and then complaining when it changes
> dramatically at off idle to
> > 2800 rpm or so. He can't understand it.
> >
> > I say adjust at idle and don't bother with any
> other rpm since the
> > needles take care of that and if the engine is
> stock, they are ok. Just
> > check the plugs after a drive. If the mechanic had
> a rolling road then
> > he could be concerned with non idle conditions and
> needle profiles.
> >
> > Who is right?
> > Ken Freese
> > 65 BJ8
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