Results 1 to 10 of 10

Thread: Dcoe????

Discuss the Austin Healey Sprite and the MG Midget. Two different but similar cars sometimes referred to collectively as the Spridget.

  1. #1
    Yoda
    Join Date
    Dec 2008
    Location
    South Dakota
    Posts
    3,930
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    4
    Thanked in
    4 Posts

    Dcoe????

    I'm hoping there are still some Weber DCOE GuRu's on here.

    Anyway, I want to lean my idle jet slightly. Currently a 50-F8. Should I drop the orifice size [50] or the air correction [F8]? Does it matter?

    Trying to get better cruise mileage.

    Kurt
    65,66 Midget
    57 Berkeley, MGA
    Working on quality rather than quantity

  2. #2
    Yoda TOC's Avatar
    Join Date
    Jun 2008
    Location
    Floe Ice, Antarctica
    Posts
    6,338
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    23
    Thanked in
    23 Posts

    Re: Dcoe????

    Not a guru.....used to work with Webers.....but then we were only interested in how much we could get through them and what it did for acceleration an top end.
    http://www.redlineweber.com/html/Tec..._typical_i.htm

    I haven't seen a need in days gone by to re-jet idle circuit from factory, as we could adjust idle mixture for each bore AND air bypass.
    The amount of mileage change at highway speeds from a slightly rich idle circuit would seemingly be negligible.


    How does the pipe smell running warm at idle? Plugs getting black with extended idle?

    Just interested.

  3. #3
    Yoda
    Join Date
    Dec 2008
    Location
    South Dakota
    Posts
    3,930
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    4
    Thanked in
    4 Posts

    Re: Dcoe????

    TOC, I haven't done an extended test at idle. Color Tune indicates that it is maybe just a tad rich. I't is my understanding that the idle adjustment screws and the idle jet are what you are mostly using at cruise. I dropped the main from 140 to 135 and it was obviously too lean so my next move would be to tr. y and lean the idle jet a bit. Only getting 25+ MPG while my other Spridget with virtually the same engine but a single HS6 gets low to mid 30's at freeway speed's. With a 7 gallon tank I don't get far between fills. As a friend like's to say about his DCOE carbed Jensen Healey, it will pass everything but a gas station!

    Kurt
    65,66 Midget
    57 Berkeley, MGA
    Working on quality rather than quantity

  4. #4
    Yoda TOC's Avatar
    Join Date
    Jun 2008
    Location
    Floe Ice, Antarctica
    Posts
    6,338
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    23
    Thanked in
    23 Posts

    Re: Dcoe????

    Weird. Yes, I know excessively rich idle mixture works into cruise. But I am trying to remember...too many carbs, mostly downdraught...principles are similar.
    Off idle, transition circuit, power circuit, cruise circuit.

    Slightly rich, can't recall that affecting cruise mileage, but who knows.

    RAM is full.

    Need to reboot.

  5. #5
    Yoda TOC's Avatar
    Join Date
    Jun 2008
    Location
    Floe Ice, Antarctica
    Posts
    6,338
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    23
    Thanked in
    23 Posts

    Re: Dcoe????

    "The correct interworking of all circuits together is the ultimate goal of a properly tuned DCOE. However, one must be careful as the circuits overlap one another; it is possible to sometimes fix an over-fuel situation in one circuit by under-fuelling in another. "

    Weber calls "transition circuit" "progression"

    "The Idle Jet is inappropriately named as it primarily controls the cruise mixture more so than the idle mixture. In fact, the Idle Enrichment Screw directly controls the idle mixture. The Idle Jet simply feeds it.

    When cruising along a street or highway in a Datsun, the Progression Circuit is the main contributor to the mixture entering the engine. Only the fuel level and Idle Jet are at play. It is very important to select the correct Idle Jet and set the correct fuel level in a DCOE carb so that a suitable air/fuel ratio at cruise is obtained. In the tuning section below, selecting the correct Idle Jet at cruise will be the first and most crucial step. The mixture at cruise can not be tuned by the main circuit nor can it be significantly tuned by the Idle Enrichment Screw. The cruise mixture must be set by selecting the correct Idle Jet AND by setting the correct fuel level. "

    So, it does. Now you need data, so you know how rich it is, try another set of jets, and check again.
    You are not in the "main circuit" at cruise, rather the "progression" or "transition" circuit.

    All the settings are done from know good and correct fuel level settings.

  6. #6
    Yoda TOC's Avatar
    Join Date
    Jun 2008
    Location
    Floe Ice, Antarctica
    Posts
    6,338
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    23
    Thanked in
    23 Posts

  7. #7
    Yoda
    Join Date
    Dec 2008
    Location
    South Dakota
    Posts
    3,930
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    4
    Thanked in
    4 Posts

    Re: Dcoe????

    TOC, I thank you for that. Since fitting a DCOE I have had to take a crash course in how these things work and I have seen that site. Neverless I appreciate that.

    I'm thinking maybe a call to Redline or Pegasus might be in order or just taking a chance on my next move. Folks with DCOE's DO end up with extra jets and other bits. Like a fool I let a coffee can full of Weber bits go with a car a while back.
    65,66 Midget
    57 Berkeley, MGA
    Working on quality rather than quantity

  8. #8
    Yoda TOC's Avatar
    Join Date
    Jun 2008
    Location
    Floe Ice, Antarctica
    Posts
    6,338
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    23
    Thanked in
    23 Posts

    Re: Dcoe????

    All those years of messing with Webers...and Mikunis...and Quadraflushes, Thermotoilets...
    Zenith, Stromberg, SU's.....even Ford Variable Venturis...and guess who got to work on THOSE in shops?
    Like a downdraught Stromberg...crossed with an SU.....and here I am, running 2bbl downdraughts on my Fatheads, and twi single bbl downdraught Solexes on the jag.

    Good thing I avoided Hilborn Injection.

  9. #9
    Yoda
    Join Date
    Dec 2008
    Location
    South Dakota
    Posts
    3,930
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    4
    Thanked in
    4 Posts

    Re: Dcoe????

    Pegasus site makes it look as if dropping the F number by 2 might be worth a try. The warnings were right....I'm wracking up a expensive collection of jet's.
    65,66 Midget
    57 Berkeley, MGA
    Working on quality rather than quantity

  10. #10
    Jedi Warrior SD Bugeye's Avatar
    Join Date
    Jan 2015
    Location
    South Dakota
    Posts
    615
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    3
    Thanked in
    3 Posts

    Re: Dcoe????

    Get on eBay some times you can pickup a used collection there on the cheap
    Door handles,Bootlid,Glovebox all fads
    59 sprite

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •