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Thread: 2.4 with an SSD and a 45DCOE

  1. #101
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    balancing runner lengths

    hope this up loaded ok did it on paint which i don't normally use . Orange is the path to measure volume. don't count volume in grey area and the balance tube is shown "drilled" through the flange under carb in green. Number 1 will still have slightly less volume and 4 slightly more. this could be fixed but its not really worth the effort .
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  3. #102
    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Hmmm....very interesting! I liked this manifold because it eliminated the shared plenum that my Midikit manifold has, but you're suggesting I somewhat re-unify the two carb barrels by putting a balance tube between them. The longer ram tube on the "short side" is an interesting idea and an easy thing to do.

    I don't have any appropriate tubing parts, but here's some plumbing stuff I cobbled together to visualize what you're saying. Is something like this what you're suggesting:

    IMG_4711.jpg IMG_4712.jpg

    Based on your thoughts, I'm wondering if a wall welded inside the plenum of my Midikit manifold to separate the two sides, but with a 3/8" or so hole in it for balancing would make it work better?

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    Is something like this what you're suggesting:

    Yes that would do the job but if the flange under the carb is thick enough I would just drill it from 1 side and bung the access hole,
    But having said that I have even tapped in 2 fittings and used a short length of fuel line in the past.
    And yes, it does make it work better especially at idle which is very important on a street car. over 3000 rpm the balance tube is not needed but I have seen no negative impact having one. You can set up an experiment running a manifold like you have with 1&2 isolated from 3&4 then add the balance tube and see the difference for yourself. If you don't run a balance tube with a single dcoe style carb on a 4cyl often the rough idle will splash fuel around internally causing the idle mixture to be all over the place even if the carb is soft mounted.
    Last edited by tekenaar; 02-18-2017 at 02:20 PM. Reason: taped . . . fittings?
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  6. #104
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    Balance tube

    I just noticed in your pics, the manifold is upside down, the tube would be better on top so fuel can't sit in it I have never fitted one under the manifold.

  7. #105
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    Just looking at how pretty the manifold is and how a balance tube is going to distract from that, although I'm sure the performance added will be worth it, is there another way to accomplish the same thing? The mounting flange is thick, could a channel be milled into that between the two barrels to help balance them?

    Harold

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    The mounting flange is thick, could a channel be milled

    Yes , It could be drilled from one side of the carb mounting flange deep enough to make the balance port but not all the way through and then bung the 1st access hole. The bung would be the only visible sign of the mod.

  9. #107
    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Very interesting idea Harold! I think this is what you're suggesting:

    Steinmetz SSD with balancing channel.jpg

    Man, I really thought you had found a great, simple to do, solution. I could carve a channel out with an angle grinder and be done in a jiffy! But, I thought I'd check to see if there might be something on the carb between the barrels that a channel would screw up. Well, there is a metal access plate there to get at the throttle and springs, but worse yet, I checked my lashed together assembly and I see that the two soft mount gaskets leave a big 1/4"+ gap between the carb and the manifold between the barrels:

    IMG_4723.jpg

    So, what I think Alex is possibly suggesting is to drill sideways through the flange, into and through one barrel/runner, through the flange that separates the barrels/runners, and into the other barrel/runner, then tap and plug the drill hole's entrance.:

    IMG_4724.jpg IMG_4725.jpg

    Okay, doable. The flange is about 5/8" thick, so a 3/8" hole would be the biggest that would be safe to drill.

    My questions at this point are: Would doing this truly have a meaningful effect? Would a little ole 3/8" hole about 2" long, that close to the carb barrels, really have the desired balancing effect? Dual side draft set ups don't worry about balancing, why do I have to with this single side draft set up? Idle quality and low speed, stuck in traffic, drivability IS of utmost importance to me. I spend most of my driving under conditions like that. One could very justifiably say that a side draft is very inappropriate for my driving conditions. But the power and response IS a whole bunch of fun when I eventually get to the fun roads! So, I'm game for any ideas, such as this one, that will address idle and low speed drivability quality. Now, the Midikit has a humongous shared plenum that's even bigger than the runners. There is a tremendous sharing of the vacuum signal coming from all 4 cylinders and affecting both barrels, to one extent or another, simultaneously. This is apparently not how side drafts were meant to be operated. The Steinmetz currently eliminates both barrels being simultaneously affected by the vacuum coming from all 4 cylinders. The way I see it, is that the Steinmetz sets the carb up more the way a side draft was intended to be set up, with each barrel dedicated to the vacuum pulse of one cylinder at a time. Since each barrel is feeding 2 cylinders, but with staggered pulses of vacuum through a single, split runner, the barrel will behave like a dual side draft set up, just with twice as many vacuum pulses coming at it. So each barrel delivers the air/fuel twice as often as a dual side draft's carb barrels. In essence, the carb barrels are working as though the engine was turning at twice the rpm as a dual side draft set up. I would think this would be a good thing, when it comes to idle and low speed driving. At idle, twice the air is going through each barrel as compared to a dual side draft set up. To me, this sounds like very good air flow through the carb at low rpms. Aren't many idling issues caused by the low speed and volume of air at low rpm's?

    Just a bunch of thoughts there at the end.....

    ....YOUR thoughts?

    Last edited by The Scifi Guy; 02-19-2017 at 09:19 AM.

  10. #108
    Member My location guyopel's Avatar
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    Why not make a spacer plate that has the chamber in it and that way you can keep you manifold as-is? Example: Carb then spacer plate then manifold.
    John
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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Yeah, I could do that, too. I'm not worried about drilling the manifold, the plugged off hole on the rearward side won't be noticable. I would do it right now, IF you guys convince me that it will be an effective and worthwhile thing to do. Someone else suggested to me "Why not drill and screw in another brake booster vacuum port in the runner for cylinders 1+2, then tie it together with the one on the runner for cylinders 3+4 with a T-fitting?". Yeah, I could do that too. But if a 3/8" hole and a plug will do the job, that's far simpler and cleaner.

    But, is 3/8" big enough? Is a hole in that location a good effective place for one? Why do I need to have a balancing passageway when dual side draft set ups don't?

  12. #110
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    Two side drafts have all equal length intakes. The concern that is discussed here is unequal length of runners of your intake.
    They bent the intake forward in order to leave more space between carburetor and the heater box. Good idea! Yes, that created unequal runners, so what? Going through the trouble of connecting them might or might not give you little smoother idling. It is highly unlikely that reputable name like Steinmetz would put on the market bad design.

    My suggestion would be, just go ahead and install the thing the way it is and enjoy the ride.

    P.S. I have attached picture of BMW single side draft kit. Equal length of runners? Yeah, right.
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    Last edited by P.J. Romano; 02-19-2017 at 12:59 PM.
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    3/8 is all you need

    Side draft Webers are basically made to feed 1 cyl (evenly spaced strong clean pulses) a large plenum softens the pulses and reduces ram effect and the benefits of having a SDW.
    With the steinmetz manifold pulses are uneven stuffing up the low speed running 3/8" is enough to keep the are moving at all time through both throats other wise cyl 2 and 3 get less fuel when the air speed through the carb drops off. Firing order is 134213421342 so 2 draws then 1 there is then a delay while 3 and 4 draws and the air at low rpm stops moving through the 1st throat so when 2 draws airspeed needs to build before fuel is pulled through and is runs lean then all is good for cyl1 but in the meantime flow has stopped in the other throat and 3 runs lean and 4 is ok. At higher rpm the pulses are close enough together that is is not a problem.
    The manifold above is a crossover design to create even pulses linking 1&4 and 2&3 eliminating the need for a balance tube but the way the runner wrap round almost 2 plane effect robs flow and power. I prefer the steinmetz design.
    Hope this helps. I say drill and plug.
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    So the idea with the balancing passageway is to keep a little bit of air passing through one or the other barrel while they are in between pulses? Okay, I understand the purpose now.

    I can do both PJ and Alex's ideas. I can just put the assemblage on the car....undrilled....and see how it performs. Later, I can remove it and add the passageway and see if things improve. This would then let me see the difference between unified and ununified runners.

    Ha! And if I totally fug things up, I can always put the Midikit back on. Ha!

  15. #113
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    Quote Originally Posted by The Scifi Guy View Post
    So the idea with the balancing passageway is to keep a little bit of air passing through one or the other barrel while they are in between pulses? Okay, I understand the purpose now.

    I can do both PJ and Alex's ideas. I can just put the assemblage on the car....undrilled....and see how it performs. Later, I can remove it and add the passageway and see if things improve. This would then let me see the difference between unified and ununified runners.

    Ha! And if I totally fug things up, I can always put the Midikit back on. Ha!
    Wise,wise
    Was it Konfuzius who say?: Never touch a running system
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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    I drilled a 3/8" hole in my Steinmetz SSD:


    IMG_4770.jpg
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  17. #115
    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Although I trusted the logic of Alex's idea to drill the hole, I still wanted a second opinion from another guru, so I just received this response to my inquiry:


    Quote Originally Posted by RallyBob

    I'm a big fan of balance tubes. I've always done it. If you look at any of the side draft intakes I've prepped, I always tie them in together for a street car. Better vacuum for brakes, better idle quality.

    As far as the drilled hole between runners, I've even done that on a Record Sprint intake. Works well.




    (Gee, I sure am glad he didn't say "NO! Horrible idea! You'll melt your pistons! The manifold will explode!")



  18. #116
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    OK but how do you balance individual throttle bodies if they are all connected? It can be a real problem on multi-carburetors setup. Even on a single DCOE, balancing between throttle bodies is now possible but not when they are connected.
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  19. #117
    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    An example of shared plenum vacuum:


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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    Quote Originally Posted by P.J. Romano View Post
    OK but how do you balance individual throttle bodies if they are all connected? It can be a real problem on multi-carburetors setup. Even on a single DCOE, balancing between throttle bodies is now possible but not when they are connected.
    Typically, even motorcycle carbs have a common tied-in vacuum line. It's not uncommon to plug each port for balancing/tuning, then reconnect for running.
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    balancing between throttle bodies

    Hi Gordon, I think your are over thinking it. A single DCOE does not need balancing, because both throttle are on the same shaft they don't need synchronizing and better still the stay in sync.

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    2000 Post Club Site Supporter My location P.J. Romano's Avatar
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    Quote Originally Posted by gt alex View Post
    A single DCOE does not need balancing, because both throttle are on the same shaft they don't need synchronizing and better still the stay in sync.
    That should be the case if all cylinders have equal compression, which is seldom the case, so the ability to balance two adjacent cylinders is important. It is especially important when each barrel is feeding single cylinder like at DSD setup. Older Weber DCOE carburetors did not have the ability of balancing between barrels on the same carburetors (Solex DHH side drafts always had that feature). The solution with DCOEs was to interconnect the intakes.

    Weber has fixed that issue and later DCOEs can be balanced between two barrels on the same carburetor via compensation screws (Position No. 11 on the attached picture). In Gordon's case we have two unequal length intakes and it was concluded that the balancing is needed in order to secure smooth idling. I would always prefer to balance them on the carburetor via compensation screws but interconnecting intakes will do the job.
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