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Thread: 3G Go Kart Project , Intake

  1. #26
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    Yeah Im thinking round pretty much like the 2nd diagram I made... that should be good wouldnt it?

    Some of those are gonna be putting that intake manifold pretty close to your head, I bet this is probably the best way of doing it, but what about half lengths and using the pressure waves to stack up on each other? Itll help either high or low I dont remember.
    On bottom 3) What is the purpose of the reduced spot near the head?
    Can you give an example of how/where you would merge secondaries?

    You can do that without flaring the 2 ends too with just using straight pipe, but its a little harder.
    In your diagrams though, where were you thinking of putting the merges, and what size diameters?

    Yeah you know what I realized that after I typed it and thought I deleted it. Your right, the intake is at the back
    what about the lengths of the tubes? equal? What about the 2 barrel flow?



  2. #27

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    A 90 degree tube will be a nice smooth transition from the carb to the head ports.

    Actually it's a 90 degree tube - 15 degrees. so it's a 75 degree tube. for cylinder #2 and #3... #1 and #4 will have to take off 15 degrees at whatever angle you point them. Could get complicated.

    the second version of #3 shows you the taper before the intake port.
    There are nice examples of this also in the intake manifold design thread.
    https://www.3geez.com/forum/showthread.php?t=42065


    notice though it doesn't have a direct line of sight. on #3. for either a 30 or 0 degree angle in relation to the engine tilt.

    You can fix that though.



    Quote Originally Posted by old post
    Runner Length Tuning

    Second Pulse Lenght = 2nPL
    Third Pulse Lenght = 3rdPL
    Fourth Pulse Lenght = 4thPL
    Fith Pulse Lenght = 5thPL

    Pulse with stronger returning wave / narrower power band
    2nd PL (INCHES) = 108,000 / RPM
    3rd PL (INCHES) = 97,000 / RPM
    4th PL (INCHES) = 74,000 / RPM
    5th PL (INCHES) = 54,000 / RPM
    Pulse with weaker returning wave / broader power band

    Effects of Runner Taper

    As taper angle increases, speed of returning wave increases.
    13" runners with a 4 degree taper is equal to 10" runners with no taper.

    Straight runner for low rpm power
    2-4 degree taper good for high rpm power
    this is nice for a 4-1 but it also only has 2 per side.
    http://www.bpeheads.com/specialprojects.htm
    here are example how.
    http://www.burnsstainless.com/MergeC...into1base.html
    http://www.koracing.net/photogallery/DME_YpipeWeld.jpg
    nope, I was going to say make it 4-1. I'll draw you a diagram.
    How is it going to hit your head? I thought that this is going to sit at the rear of the cart. the intake comes off the back of the motor, and so will the muffler.
    Probably the easiest style to fab
    The 15* Tilt is built into base of carb mount...


    it's good for cylinder 2&3, they will tend to run a little richer.
    1&4 will be a little leaner.
    You can add a tiny wall and block maybe 5% - 10% of port 2&3 that will help even out the mixture some.
    Only if it gets really bad... otherwise leave out the wall.
    - llia


  3. #28
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    Re: Custom Intake mani for weber carb

    what about if you have a wall inbetween the two paris leading up to the front edge of the carb? that might help better than wall in front of it?

  4. #29

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    you mean just a divider?

    Maybe, but it still might favor the center cylinders, though it would cut back on turbulence perhaps... at least between each pair (1,2) (3,4).

    - llia


  5. #30
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    Re: 3G Go Kart Project , Intake

    I think that would be better yes it might not be as ideal but it will cut back turbulance and increase air flow so will probably gain more than the other two being ever so slightly richer, what about maybe having three divider between all of them although i think just the one would do. shame we can't have a DCNF carb that we can sit the other way with butterflys that open up onto each pair. that would be better but this is still tons better than stock, although i think using mandrel bent tubing would still be better and the pipes at the inlet port end should taper out as they reach the ports finishing in the same size as the inlet ports.
    What can you do as far as headwork is concerned? anything or are there restrictions also any pics of what a Kart looks like?? P.S. is it worth making up a hood around the carb to get a bit of ram air induction going on?

  6. #31
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    Re: 3G Go Kart Project , Intake

    Cool, that makes sense, would separating 1/2 and 3/4 by putting a divider all the way up and between like http://i23.photobucket.com/albums/b3...l/ramefdwf.gif and rotate the carb 90* make it a 1-2-4? If its a sync carb wouldnt that make sense?

    As for ram air intake, there will be some sort of scoop that faces the front of the car, so its directly forcing air into the carb.

    What I can do and what I can get done by spending lots of money are different. I can do some mild head work, like smoothing and such, not good with removing alot of material though because I havent really done it, I can clean things up and smooth em out basically. I can assemble and dissassemble a head no problem.
    Last edited by FyreDaug; 07-20-2006 at 06:34 AM.

  7. #32

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    Re: 3G Go Kart Project , Intake

    Problem is the throttle plate open to one side... hmm maybe not. Anyways it depends if the throttle plates both rotate clockwise or not... if they both rotate the same direction then that means one half of the motor will be exposed to the back side of the throttle plates while the other the front side. Hard to explain... also they don't always recommend feeding from the side when the carb is like that.

    the 38 could be a bit different though. If you look and the gears it looks like the right side would rotate counter-clockwise and the left side would rotate clockwise.

    This means both sides of the motor will see a front and a back of a throttle plate. Also turning the carb 90* will push the barrels further to the back which will give the air fuel mix more time/room to move from one runner to the next.

    I cant say that having the barrels further apart and opening to the side is any better then having them in the center and opening to the front.

    I would say stick with what it up there now... it helps each side of the manifold gain access to both the barrels.
    - llia


  8. #33
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    Re: 3G Go Kart Project , Intake

    yep i agree only thing i woudl change would be having the smoohest turns in the bends and joins if possible.
    As far as head work goes depends what you can get done and if you know anyone who has the equipment to turn really tough forged steel, if so you could do a big valve conversion using exhaust valves for inlet valves, this will help massively even with the setup you have, also the other biggest mod is to modify the exhaust port so that the ramp around the guide is mostly removed and whats left is turned into an aerodynamic shape to help flow the fuel around the valve stem, this alone will give you a few bhp, also making sure that you have a really nice profiled valve head on all 12 valves, and that the seats are precisely cut and the angles radiused. The other mods are the smoothing and flowing of the combustion chambers to remove any machine marks around the valve seats that will hinder mixture flowing in and out the valves, and the removal of metal around the valves more space the better, it's limited in A20 chambers but even a couple of mm of extra breathing room makes a difference, decking the block and skimming the head will help keep the CR ratio high and using A20A3/4 pistons will help in keeping CR ratio high, obviously bigger the pistons the better so get the biggest oversize you can get in or at least 83mm ones. With some clever headwork and a raise in CR ratio with the inlet and exhaust system you have and the 38/38 carb, stage 2 camshaft i reckon we could be looking at around 155-165bhp maybe more and powerband of around 3.5-7.5k.
    Oh also any improvements to the carb will really help as it will be the bottleneck to the whole engine, so if it has round head screws in the butterfly spindles get them out and use countersunks and grind them flush with spindle shaft, knife edge the butterfly's maybe, removes any casting flash from the internal components etc. etc. maybe even see if theres any possibility of improving the entry in and exit out the carb by radisuing any edges, not seen an inside of a DGV 38/38 if you can send me any pics with one open and shut might be able to suggest some ideas.
    This is really cool when do you think you'll be completing the engine? any pics of what the chassis looks like yet?

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