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Thread: Intake and restrictor

  1. #1
    Hi everybody,
    our engin uses a carburetor, and we are searching for some useful info about the optimal volume of the required plenum. Any help to gain access to these info is acknowledged.
    PS: Or any article about intake system and restrictor.
    Hamed

  2. #2
    Hi everybody,
    our engin uses a carburetor, and we are searching for some useful info about the optimal volume of the required plenum. Any help to gain access to these info is acknowledged.
    PS: Or any article about intake system and restrictor.
    Hamed

  3. #3
    The restrictor is just a converging-diverging nozzle, any fluids book ought to cover that pretty well. Not much more voodoo beyond that, just remember that your flow isn't steady state...

    As for making the restrictor work with a carb, I personally have never heard of this working successfully, at least the way our rules are written. The carb needs a clean vacuum signal to work right, and the restrictor fouls that up pretty badly. Not to mention the fact that with a carb, you're giving up quite a bit of airflow considering all your fuel has to flow through the restrictor too. And your manifold needs to accomodate wet flow.

    If you're just starting out, and have more time than you do money, a Megasquirt would be a pretty solid start, although you may have to make some sensors. Performance Elelctronics sells a computer that is a bit pricier, but more user friendly, plus they do a lot of work with FSAE teams and have a decent selection of the sensors you'll need to make it work.
    Dr. Adam Witthauer
    Iowa State University 2002-2013 alum

    Mad Scientist, Gonzo Racewerks Unincorporated, Intl.

  4. #4
    We are using a Kawasaki Dual carburettor engine. How do we use a restrictor in this case? Are there any double pass air filters ( which allow two passages of air) or do we have to diverge the air volume through two plenums into the carburettor? And how exactly does a single pass restrictor fits into all this?

  5. #5
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ani_V:
    We are using a Kawasaki Dual carburettor engine. How do we use a restrictor in this case? Are there any double pass air filters ( which allow two passages of air) or do we have to diverge the air volume through two plenums into the carburettor? And how exactly does a single pass restrictor fits into all this? </div></BLOCKQUOTE>

    All the air entering your engine must enter through a single 20mm (19mm if E85) restrictor. If you are using two carbs, you would still have to design your intake so they both flow through the same restrictor. If you then wanted to split the air into two separate plenums afterwards, there is no rule against this.

    Remember that your carbs have to be upstream of the restrictor as there are no throttling devices allowed downstream. So the only allowable order is: Carb, restrictor, plenum, runners, engine.
    Chris Noll
    UB Motorsports Formula SAE: RIP 1987-2010

    "A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster."- Jeremy Clarkson

  6. #6
    Since ours is a dual carburetted engine, the air flow will have to be split after passing through air filter. Are there air filters that have multiple outlets suited for this purpose or do we need to convert a single outlet air filter to a dual one to deliver air into both air horns??

  7. #7
    Quick search on K&N's website yielded that they have a bunch of them that are dual outlets. You will have to check if any of them will work for you as you will need one specifically with your center to center distance and size.
    Chris Noll
    UB Motorsports Formula SAE: RIP 1987-2010

    "A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster."- Jeremy Clarkson

  8. #8
    What all are the important factors that should be taken into consideration while determining the arrangement and orientation of the cooling system ? Like the angle at which Radiators will give max cooling and less drag? Importance of fan and shroud and the clearance between them? And most importantly what all mathematical calculations go into making cooling system more efficient?

    P.S. : This is my first time with the Project

  9. #9
    Our engin had four carbs, out of which we placed one over the restrictor with the restrictor angle of 14 degrees and runner length of 10 centimeter, the volume of our plenum is 1.2 lit . and the model of engine: zx_6r. After all we failed to start the engine easily and after we started it we couldn't reach the rpm to more than 6000 with this restrictor system. Now, what do you think our problem is? Do you think if we use two carbs we won't have any problems anymore? And about the optimal volume of the plenum, what's gonna be your idea?
    Hamed

  10. #10
    I think both of you guys need to do a good amount of reading. No one on these forums is going to tell you how to design a cooling system from the ground up or tell you how design your induction/fuel system.

    IUST_Persian, I know very little about carbs as we rip them off and throw an EFI system on the engine. I would say though that if the engine required 4 carbs to run correctly when you started, you probably need to deliver as much fuel as those 4 could for your engine to run.
    Chris Noll
    UB Motorsports Formula SAE: RIP 1987-2010

    "A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster."- Jeremy Clarkson

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