I think emmissions dynos are not full fledged dynos. I
believe they simply put drag on the drive train ti
simulate road driving conditions.
John Holliday
67 Fprod street sprite
--- Geoff Branch <branch@valinet.com> wrote:
> I think we don't use dynos around here because I for
> one don't even know where
> there IS one. We just started a new inspection
> system in Massachusetts that
> requires the stations to use dynos, but when I asked
> the guy if I could rent
> some time he said he didn't think the Meejit would
> fit (didn't have to go on for
> emmisions because of advanced age) and even if it
> did, he wouldn't know what to
> do with the dyno. I quess it's just programmed for
> the emissions tests.
> Anyway.......
>
> Here are the specs on my 45 DCOE. Car is '74
> 1275cc. Don't know about any cam
> work. Mallory dual point dizzy. No vacuum advance.
> Timing set at approx. 22
> deg. BTDC.
>
> Air Corrector: 175
> Emulsion tube: F2
> Main Jet: 125
>
> Idle Jet: 45 F 9 (have also used a 50F9; made
> little difference)
>
> Accelerator pump jet: 50
>
> Float needle valve: 225
>
> Main venturi: 34
> Aux. venturi: 35
>
> 16MM air horns with a K&N filter
>
> Richening device blocked with grub screw (took me a
> while to figure what that
> term meant!)
>
> Let me know what you think. Should we be doing this
> off the list? Anyone mind?
>
> Geoff Branch '74 Meejit
> ----- Original Message -----
> From: <Daniel1312@aol.com>
> To: <branch@valinet.com>; <spridgets@autox.team.net>
> Sent: Saturday, April 01, 2000 4:51 PM
> Subject: Re: Weber DCOE 45
>
>
> > Geoff,
> >
> > I have the Hammill book who incidentally has an SU
> book out as well
> > (veloce.co.uk) - is it any good, has anyone bought
> a copy?
> >
> > The David Vizard book is a real good source of
> info on calibrating the DCOE
> > and it was written specifically for the A-Series
> engine. It takes out the
> > trial and error but as far as cost goes it is
> worth spending the money on
> > calibration otherwise it was a waste of money
> spend on the carb in the first
> > place.
> >
> > Can't understand why no-one in the USA ever uses a
> chassis dyno. Sure it
> > costs but I bet you would get your money back in
> gas mileage savings within a
> > year (make that a month in the UK).
> >
> > Daniel1312
> >
> >
> > In a message dated 01/04/00 21:33:26 GMT Daylight
> Time, branch@valinet.com
> > writes:
> >
> > << Daniel: Thanks for the beginings. I have a
> Weber book by Pat Braden and
> > one by
> > Des Hammill. Both are interesting, but actually
> not that helpful because:
> > 1. I
> > don't have a dyno and 2. It seems that jetting
> is mostly a trial and error
> > affair that involves 15-20 bucks a pop (8-12
> British Pounds Sterling, I
> > think).
> > I had all the venturi/jet info written down
> somewhere...now will have to take
> > carb apart again to regain that info. I'll send
> it to you when I do that.
> > Meejit's down while I wait for a water pump and
> alternator anyway. Thanks
> > again.
> >
> > Geoff Branch '74 Meejit
> > ----- Original Message -----
> > From: <Daniel1312@aol.com>
> > To: <branch@valinet.com>;
> <spridgets@autox.team.net>
> > Sent: Saturday, April 01, 2000 3:13 PM
> > Subject: Re: Weber DCOE 45
> >
> >
> > > Geoff,
> > >
> > > I assume you mean the jet inspection cover was
> missing when you refer to
> > the
> > > Micky Mouse hat.
> > >
> > > You need a short lesson in how the DCOE works.
> > >
> > > The engine via the DCOE draws air into the
> inlet manifold and induction
> > tract
> > > in two distinct places. The first is round
> hole about the size of a dime
> > > that is on side of the carb (left hand as you
> look at the carb) above the
> > l/h
> > > barrel (a good book or photo might help). This
> hole is used to draw are
> > into
> > > the carb body, more of which later.
> > >
> > > The engine gets the rest of its air through the
> carb barrels.
> > >
> > > If the carb is correctly calibrated (like on a
> chassis dyno) and the jet
> > > inspection cover comes loose or is missing
> (lost) the engine will run
> > rough,
> > > particularly so in mid range rpm (long time
> since that happened to me but I
> > > think it is the 2,500 to 3,800 rpm range). At
> higher rpm there does not
> > seem
> > > to be a problem.
> > >
> > > Back to the dime size hole. If you remove the
> carb top cover complete you
> > > will see that the hole leads up to the top
> cover resticted by the top cover
> > > gasket such that it gets to the area underneath
> the jet inspection cover.
> > > This air is drawn into the gallaries that feed
> the emulsion tubes with air.
> > > It is this air that is mixed with fuel drawn up
> in the jet (idle or main
> > > depending on rpm) that is subsequently drawn
> into the air flow from the
> > > barrels that is subsequently further
> emulsified.
> > >
> > > If the jet inspection cover is missing then air
> is either drawn into the
> > > emulsion tubes/holes in greater quantity than
> would be the case when air is
> > > drawn in only by the dime sized holes OR... air
> is drawn in a lesser
> > quantity
> > > by virtue of a weaker vacuum. To be honest I
> don't know which it is.
> > >
> > > BUT
> > >
> > > Either the mixture leaving the jets (via the
> progression holes or aux
> > venturi
> > > is richer or it is weaker.
> > >
> > > SO
> > >
> > > Obviously your car is not correctly calibrated
> at some point in the rpm
> > range
> > > but I cannot say whether it is too rich, weak
> or just poorly emulsified.
> > >
> > > However, if you provided a spec of the engine
> along with FULL details of
> > the
> > > calibration of the carb I ought to be able to
> guess and along the way add
> > to
> > > my knowledge of how the carb works (eg missing
> jet inspection cover leans/
> > or
> > > richens mixture to detriment).
> > >
> > > Finally, the jet inspection cover is there for
> a purpose (eg unfiltered air
> > > enters directly into the jet system without it)
> so buy a new one
>
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