possible supercharger?

Discussion in 'Performance Mods' started by datz510, Jul 13, 2008.

  1. datz510

    datz510 Member

    I was up all night brainstorming. I was trying to think of a way to to apply forced air induction on one of these little bike engines.

    The idea came along to use an air motor.. You know, the kind typically used to run an air tool in your garage. What if one was to run the air motor backwards, say by chain driving (or gear driving) what would normally be the output shaft and using the air input/output as the inlet and outlet for the forced air induction. The effect would basically be like a miniature roots type supercharger.


    The inlet, you'd attach the carb to, which coincidentally would also serve to lube the air motor blades using the 2 stroke oil. The outlet would then be plumbed to the intake of the engine. The shaft, which would normally be driven by the compressed air would actually be driven from the crank of the engine. Mabye need a 2:1 ratio to get the compression at the outlet. All it would take is 3-4 psi boost to get a noticeable gain in power output.

    Another link on the operation of an air-motor:

    I may take apart one of my junk air tools to see if it might be useable in such a manner.

    With 2 stroke engines, the only big problem I could think of is that if both the intake and exhaust ports are exposed by the piston, any pressure built would just blow the intake charge right out the exhaust port. This might require a higher intake pressure. I'd imagine that the effects of the pressurized crankcase would become more apparent at higher rpms, as the exposure times of the ports would be much smaller duration...

    Any ideas? Opinions?
    Last edited: Jul 13, 2008

  2. Hey its worth a shot. You might look into modifing an air tool. though i would avoud impacts and air ratchets, they both ipicaly ese postion motors. I have rebuilt a few, you might be able to modifey a die grinder or small buffer sander
  3. datz510

    datz510 Member

  4. datz510

    datz510 Member

    A unit similar to this one looks like the best bet so far: Now if I can just find one surplus or dirt cheap to try it out.



    Gray Metallic

    Height (In.)


    Air Motor

    Length (In.)

    Max. RPM


    Port Size (In.)
    NPT 1/4


    Running Torque @ Max. Pressure & RPM (In. Lbs.)

    Shaft Dia. (In.)


    Rotary Vane

    Width (In.)

  5. datz510

    datz510 Member

    Ok.. found a lot of 10 of some similar units on ebay for $80 total, including shipping. might make an offer on them so I can do some experimenting.
    Last edited: Jul 14, 2008
  6. datz510

    datz510 Member

    Sweeet.. found that these little units i found can generate 15 psi at 0.6 cfm at their rated 3600rpm. Any idea what a 50cc HT engine runs, cfm wise? Im willing to bet that they will operate beyond rated rpm with oiled vanes.. And since we'd only need 4-5psi boost at most, these should fit the bill. These are considered oil-less vaccum pumps/compressors.

    Might be getting a deal on 10 of them for a song.
    Last edited: Jul 14, 2008
  7. datz510

    datz510 Member

    Ok.. I did some research and found the pressure curve for these rotary vane comressors that I have a possibility of getting. They are small enough to use on a bike, BUT maximum output is around 1 cfm.

    On a 50cc 2 stroke engine, you're gonna bring in approx 50cc of air/fuel mixture every single revolution of the engine. At cruising speed, my tach reads around 5900rpm. 5900 rpm x 50 cc = 295,000cc of air/fuel mixture being used every minute. This converts to 10.4 cubic feet per min of air/fuel mixture being used. Way way above what these little compressor units will do

    So, im gonna have to pass on this deal... see if I can find a unit that will provide around 10cfm at 4-5psi.