Discussion in 'Performance Mods' started by JemmaUK, Oct 19, 2008.

  1. JemmaUK

    JemmaUK Guest

    Having looked at the Victa based machine on another forum I had a thought...

    My personal opinion is that machine is more akin to a supercharged engine than a turbo. The general drawback from a supercharger is that it takes a percentage of the power from the engine in order to give back more. However in this case it seems to be exhaust powered.

    Now given that alot of these machines are used in areas where they are borderline legal at best - something that sounds like a squadron of Mustangs warming up on the dispatch apron - isnt going to be exactly sotto-voce

    So how do you get the power without all the tuning and twiddling and general complicatednesses?

    Simple. Use a turbo electric combination drive. In a standard turbo installation the exhaust pressure drives a turbine in the exhaust that pressurizes the intake - which makes for fueling problems and mixture finnickyness - not to mention that the general size of the engines makes it borderline at best.

    How about taking the intake compression stage away and running an electric generator off the shaft. Electrical power from this is taken away from the genset into a controller and hence to hub motors/lights etc.

    Basically you are getting electrical power using a side effect of combustion in the IC engine which means better performance from the bike - lowered petroil consumption, less engine wear and better performance since electrical motive power will be available from the second the engine fires. If a battery is also fitted it could be possible to 'trail in' the IC engine using the electric to get up speed..

    Just a thought..

    Jemma xx

  2. fastboy9

    fastboy9 Member

    There are kits available for cars that use an electric "supercharger", the idea sounds too good to be true, but for cars the boost just isnt substantial enough to give you any real performance gains.
    But... it isnt a worthy addition to a car engine say 1800cc, but on an engine around 60cc, I'm sure this would definetely be worth it!
    A direct power source from the magneto is a great idea. Would it spin a turbine fast enough? Only one way to find out, and I'm sure it wouldnt be that difficult.
  3. mechcd

    mechcd Member

    I don't want to burst everybody's bubble, but those electric turbo/supercharger things simply don't work. They might barely flow enough CFMs for a small engine, but they don't provide nearly enough pressure.

    An idea might be to use a car smog pump hooked onto the engine's output shaft. Those boogers might not have enough flow or pressure. I know for a car application there is a one-way valve to keep the exhaust from teh catalytic converter from going backwards into the pump. Some newer (but not really new :) ) cars have electric ones. Junkyards have tons of these things because people yank them off when getting a new replacement cat.

    Here is a link for a bigger go-kart engine

  4. JemmaUK

    JemmaUK Guest

    Im not talking about an electric turbo.

    I am talking about a turbo electric system where the intake rotor is removed and the shaft connected to a 12/24v generator.

    This would provide free electrical power which when put through the relevant controller would/may be able to run a hub motor.

    Its like the hybrid systems on cars except for the fact that where the hybrids generally use some sort of hydromatic fluid linkage from the IC engine to provide power - this would use the exhaust pressure to provide electrical power.

    Jemma xx
  5. duivendyk

    duivendyk Guest

    In a standard turbo setup the extra power extracted from the exhaust flow is used to get more combustion air into the engine,so that more fuel can be burned thus providing more power.The extra power available in the exhaust is at most 10/20 % of the output,so possibly you might be able to get 100/200 Watt,with a generator hookup.It would be difficult (and expensive) to come up with a small very high rpm (100/200 krpm) turbine design for such a small gas flow and also the generator which would be running at this speed.May be something more modest could be used to generate auxiliary electrical power,but I think it would be inordinately expensive and therefore inpractical,too bad.By the way for 2 strokes turbo's are not a good idea,they don't care for back pressure at all!.
  6. JemmaUK

    JemmaUK Guest

    The whole point in this is there wouldnt be any backpressure - excepting the small friction losses from turning the generator.

    Backpressure in a turbo/supercharger only comes from the fact you are compressing air in the intake stage.

    And lets say we get 15% of the IC motors energy back though the generator and to a hub motor - thats effectively 15% free energy without drag on the bike or drain on the engine.

    The only losses to the engine would be a minute increase in exhaust pressure and with a tuned pipe that might actually help the engine a little by giving a little more exhaust pressure in the cavitator for the pressure waves to travel through.

    If I had the money I'd do it on mine - but its just a thought at the moment.

    Jemma xx
  7. fastboy9

    fastboy9 Member

    I like it, very clever,
    jemma you really do come up with some great "out of the box" ideas, thats such a good character trait. I am very interested in the whole idea, I will have to look into it

    Good on you :)

  8. duivendyk

    duivendyk Guest

    I don't buy the "no back pressure notion",but that apart, coming up with a high rpm 100k plus generator will be very difficult, the losses in ordinary transformer steel will be excessive at 1500 hz or so and ferrite material would have to be used.The overall efficiency would be less that 5 % and the cost prohibitive Dreaming things up is easy,remember 1% inspiration,99% transpiration (T A Edison I believe).What might possibly work is a some kind of bellows type chamber in the exhaust attached to a inverse mode"speaker" arangement the bellows drive the vibrating magnet which induces a voltage into the "voice" coil (or you drive the coil and keep the magnet stationary) the whole affair is broadly tuned to the exhaust (about 100 Hz).The exhaust pulses excite this resonator.I have seen generators based on that principle.This would be a lot cheaper to build and could be part of a tuned exhaust system.The problem I see is to keep it from getting too hot.
    Last edited by a moderator: Oct 21, 2008
  9. unfortunatly it would never work,
    for eg. a TO4 garrett which is big enough for 4 litre motor has a compressor wheel that weighs 0.25 kg, and the exhaust turbine wheel and shaft weighs 0.50 kg.
    if you removed the compressor wheel and hung a 1 kilo armature off it there would never be enough torque in the shaft to turn it fast enough to make a charge, if it did charge soon as you put load on it (with lights or what ever) you would probably stop the shaft in its tracks.
    So a turbo with a small enough exhaust wheel to actually turn on a 60cc motor probably wouldn't even have enough shaft torque to turn a 6v magneto.