Cheap supercharging – induction mods

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    GSX Rat

    Comments and suggestions welcomed, any other ideas? Anybody tried these?

    The idea of the turbo or supercharger in a nutshell, is to get more air and fuel into the cylinder to produce more power per combustion cycle. The main drawback to this is the cost of these systems so it set me thinking are there any alternatives?

    Some ideas that I came up with and am going to attempt in one form or another are:

    Water injection: This is used on high end turbo and nitrous systems to stop detonation, but you may also have noticed that your bike/car runs better on cold damp mornings (or is it just me that gets em out the garage in this weather) , this is because the water in the air help atomize the fuel droplets before combustion, also helping to reduce the temperature of the intake charge which gives greater density and therefore more air/fuel. Googling around, there are several systems but this one ( is basically free to construct and reading through does make sense. What sort of power improvements would be gained I am unsure of but is worth a try.

    Ramair: Obvious really – big funnel on the front of the bike, piped straight into the airbox. Theoretically should work as long as you can get more air in than you use, therefore should be more effective on smaller machines (the honda cub perhaps!) as the volume of air through the engine is less.

    Electric fan: I have seen these on Ebay with various claims as to their efficiency and power improvements, and again it sounds reasonable. You take a large cfm flowrate fan and enclose it in a housing, suction end pointed towards the front to gain a little ram air effect, and run the fan to your airbox. This should generate a pressure inside the airbox, the same as a supercharger. Obviously the pressures attained won’t be as high as a screw or vane type compressor but there must theoretically be some improvement. My thoughts were a cooling fan off a car radiator channeled to the airbox through some smoothwall pipe (ribbed pipe would create turbulance and destroy any improvements that the fan made because of reduced airflow)

    Venturi: If you create a venturi shape and pass air through it, you create a mild vaccuum behind it, basically the same as thrust augmenters on a jet. If you was to fix a venturi on to the end of the exhaust, air moving over it will create a pressure drop in the exhaust pipe at speeds (higher speed the more air passing over and therefore the greater the pressure drop) and this effect could suck waste gas out of the cylinder bore when the valve opens (4 stroke) or piston drops (2 stroke). This would mean better scavenging of waste gases from the cylinder which means more room for a fresh charge, hence more power but possibly also means a lower pressure in the cylinder when it comes to introducing a fresh charge which again means more flow – more power.

    Cooling: The colder the air and petrol the denser it is – this means for a given volume eg cylinder volume, the cooler the petrol/air the bigger the bang , and more power. This is born out by intercoolers on turbos and superchargers, as well as other types of compressors as after compression the charge is cooled to increase density again. So, how to cool the air/fuel. The easiest way is to pack take a tube the same size as your petrol line (metal for better heat transfer), take a bigger tube (drainpipe whatever) , seal one end up, drill a hole in the bottom and pass fuel line through, fill with water and freeze it. Any petrol passing through this line would be cooled by the ice in conntact with the tube (this is a very basic shell and tube heat exchanger) This would work for quite a while as until all the ice melts, the water would retain a temperature of zero degrees. The same principle could be applied to the airbox, passing air over the frozen ice would cool it and have the same effect.

    The Daddy: Bearing in mind the above, how about a small fridge system to cool the air and petrol. Take for example R717 (ammonia), at atmospheric pressure liquid ammonia is approx –35 degrees c( – pressures are absolute therefore atmosperic pressure is one bar). If you were to cool the petrol using a small shell and tube heat exchanger and cool the air using a normal evaporator you would, in theory gain significant improvements! There is a little more to it, you need a condenser (radiator), a compressor and a TEV but this is not impossible, nor is it rocket science… I realize liquid ammonia is out of the reach of many but there must be mods that can be made to home and car air con systems that would work! , also propane is a very good refrigerant – look at a bottle after you’ve been using a blowtorch for a while – the outside is cold and sometimes covered in ice, the only drawback is it goes bang if it leaks.

    Any other ideas, you think this will work – if you’ve read this far you must be slightly interested!

    GSX750 Ratfighter / SR125 Rat / GSX600F / Beamish250 / Honda70 Rat

    Blackboard paint – Covers a multitude of sins!

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