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 at 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
> > (aptfast.com) and then get the jetting sorted.
> >
> >
> > Daniel1312
> >
> > PS. Most books on the DCOE aren't that good but you might find it helpful
> to
> > buy some anyway.
> >
> > In a message dated 01/04/00 18:01:26 GMT Daylight Time, branch@valinet.com
> > writes:
> >
> >
> > << And on another note: My 1275 had been suffering from a
> hesitation/misfire
> > at
> > low rpm and high load situations. Then it went away. Runs Great! So I
> went
> > a-looking for a reason and found the mickey-mouse hat on the Weber was
> > missing!!!!! For anyone with Weber side draft experience then:
> > 1. Why would this improve the performance of this carb?? And what does
> it
> > indicate is wrong with it with the hat on?
> > 2. Should I just leave the damn thing off?
> > >>
> >
>
>
> -------------- >>
>
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