carburetor position

Discussion in '2-Stroke Engines' started by oldguy387, Mar 18, 2011.

  1. oldguy387

    oldguy387 Member

    I have installed a Raw motor on a mountain bike. My carb will not fit under the frame. Can I install a small angle adapter to place the carb at an angle outside the frame? Will the gas get to the motor? Thanks Dale
     

  2. ibdennyak

    ibdennyak Guest

    Yup. Several people have done that, often using copper plumbing fittings. One thing to keep in mind is that on a 2 stroke, intake length can have an effect on the power band. Theoretically a longer intake run will give more low end torque, and less high revs.
     
  3. oldguy387

    oldguy387 Member

    Thanks for the quick reply. Heading to Lowe's plumbing section this after noon. Thanks Dale
     
  4. Dave C

    Dave C Member

    There is zero room for a carb on my Mongoose Paver. I have an adapter to a larger size for my CNS carb then a clear plastic tube that's fuel proof then into a massivly ported CNS carb intake from Pirate Cycles. The tube acts as a shock absorber for the carb. It can take a hard slam from potholes without transfering the shock to the carb....in theory:thinking:

    Longer intake passages, up to a point, can add torque. There's a small block Chevy intake for racing called a "Torque Link". It has much longer than stock(or other raceing manifolds for that matter)port runner designed to help stock-based motor to develope more torque to help them out of the corners.

    A longer intake port is a tuners way to make max power.:helmet:
     
  5. motorpsycho

    motorpsycho Active Member

    wrong on the long intake runners making more torque on a small block chevy. Go look closely at some of the street and race manifolds. Notice that the manifolds made for idle - 5500 rpms have short, curved intake runners and a dual plane plenum design. These intakes make low end torque.
    Intakes made for 5000 rpms - 8500 rpm's (or more) have straight, long runners with an open plenum design. These intakes make more power at high rpms and are pretty much useless until you get into the suggested rpm range where the intake flows best.
    If you run an intake manifold on a small block chevy that has long, straight runners on the street, the car will be a pain in the neck to drive in traffic because the low end torque needed to drive normally won't be there. On a street engine you want to make most of your power on the low-mid range where the engine will actually be in that rpm range. it's doubtful that most street engines will see 6000 - 8500 rpms constantly.
    On a drag race motor you want to make most of your power midrange-top end. you want to kill off some of the low end torque so you don't burn the tires off the line. You can help the engine get into the rpm range faster with a stall speed torque converter.

    Idle-5500 rpm Chevy Small Block, For Idle to 5500 RPM Street-Driven Performance
    [​IMG]



    5000-8500rpm Chevy Small Block, For 5000 to 8500 RPM High-Performance Engines
    [​IMG]

    a 2 stroke engine is a different animal and it may work opposite for them...i'm not sure on that.
     
    Last edited: Mar 22, 2011
  6. Dave C

    Dave C Member

    :rolleyes7:
     
  7. motorpsycho

    motorpsycho Active Member

    Whatever...I'm sorry for being so intelligent.
     
  8. Dave C

    Dave C Member

    ...have you ever even seen a McFarland Torque Link Manifold? Completely different design, made for making more torque to help large small block race cars pull out of the corners harder.

    Don't quote to me on what the various forums have to say about the Torque Link, the vast majority are drag racers and have a different need that an oval track car. That's why there's more than one manifold made and even then many times the selection of the manifold is made by the scientific method of brand loyalty and not what is the actual best performer.
     
  9. motorpsycho

    motorpsycho Active Member

    yes i have seen a Mcfarland torque link and guess what...they are for MIDRANGE torque, not low end torque.
    If you google that intake you will find that there are a lot of statements saying that these intakes are made for high rpm oval track engines.
    the intake is essentially like a single 4 barrel tunnel ram intake, which has long, straight runners....good for 3500- 8500 rpms.
    They are not good for low end torque...I'm telling you, if you want low end torque, short, curved intake runners is the answer (on a small block chevy anyway).
    I'm not saying that this is a bad intake manifold and they actually do make a lot of power...but it's midrange power.
     
  10. sunsetboy

    sunsetboy Member

    I currently run a CNS intake to a stock carb and notice an improvement in performance not much but just enough. I used the intake for the same reason because the stock carb would not fit directly under the frame of my Felt.
     

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  11. professor

    professor Active Member

    Motor- I don't want to get into a peeing match, but it is a long standing principle that long runners promote low end.
    The chevy manifolds you picture say the same thing:
    The dual plane actually has longer runners than the single. (Both are designed to fit under the hood).
    This would also hold true for any engine, 2or 4 stroke.
    Because it is based on a reflected wave principle which helps to pack the cylinder at certain rpms.
     
  12. motorpsycho

    motorpsycho Active Member

    ok, lets not turn this into a peeing match like you say.
    but if what you say is true, then why do pro stock drag engines that operate between 5000 - 9000 rpms ONLY use long runner tunnel ram intakes?
    Why do all high rpm engines use long runner intakes. open plenum designs, large port intake and exhaust ports, very large valves, high lift /high duration cams, large tube headers, high stall speed torque converters, or twin disk clutches that allow slip off the line, and lock up after the car is moving?? everything in this case is designed to flow at a very high rpm.

    Why do all low end, high torque street engines use short runner intakes, small port intake and exhaust ports, very low stall speed torque converters, or regular clutches, small diameter headers, and high lift / low duration cams? everything in this case is designed to make maximum torque at a low rpm where the engine will actually be operated in.

    here's the deal....on a street engine you want maximum punch at low rpm (from stop light to stop light) so you would build a low end torque engine that will not need to rev to the moon to make power. On a drag engine you want to kill off the bottom end torque to help with traction off the line. so you build a motor that makes max power at high rpms. this combo will get the car off the line with plenty of power but not so much tyhat it will burn the tires off, and once the car is in motion and the slicks are hooked up, tthe cam, long runner intake, big port heads, large diameter headers all start to flow and make tons of power.
    I'm not saying that I know everything, I'm just saying that i have built both kinds of engines and I know what i'm doing.
    I'm not saying that you can't run a high rpm engine on the street because i've done it...but the driveability stinks unless you get it up into the rpm range where everything starts to work and flow. circle track engines are designed in a similar way but they want as much mid range and top end power as possible.

    I can already tell that no matter what i say, someone will say that i'm wrong.
    Do yourself a favor and look it up, then maybe you will see what i'm talking about.
     
    Last edited: Mar 25, 2011
  13. geebt48cc

    geebt48cc Member

    Awesome, True!!!~ I agree with all said. ;)
     
  14. Drylakerunner85

    Drylakerunner85 New Member

    ^^ very true! i drive a 10,000rpm redline machine daily on the street and it honestly sucks. gotta rev the **** out of it at the same time hold it down for it to get going out of the crosswalk pass the intersection while trying not to chirp of first gear (which naturally happens every time) build the engine around for what you entend on using it for, dont build it just because he or she said its better this or that way, its your engine, its your bike, and your riding it, not them :rolleyes7:
     
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