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Don Mega
Join Date: Dec 2008
Location: Utopia
Posts: 1,688
Rep Power: 17
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0 to100 m.p.h. in 14 seconds in a HR Holden
by Eldred Norman
Chapter 6 - Water As An Anti-Detonant
A British Thermal Unit, B.T.U. for short, is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit. To completely vaporize a pound of water requires about 800 B.T.Us. A pound of methanol requires about 450 B.T.Us. and a pound of petrol about 130 B.T.Us.
Now the colder we can keep the charge density being introduced into the cylinder the greater will be it's density, through contraction, and the more we will get into the cylinder prior to compression.
One of the disadvantages of supercharging is that it tends to pre-heat the mixture which results in some loss of volumetric efficiency, but in any case, from the time that the charge enters the cylinder head until it is finally compressed the charge increases in temperature.
After it leaves the supercharger or in the case of the unblown motor, the carburetor, there are only two sources which can be responsible for this increase. First, friction in negotiating tortuous passages and second, by conduction from the heated walls of these passages. Some of this heat is communicated to the air and some to the fuel in the air/fuel mixture. But the petrol only represents one thirteenth of the weight of the total mixture and since it can absorb only 130 B.T.Us. per pound before vaporization a considerable portion of it does become vaporized during this period. This of course results in expansion and loss of efficiency.
Now turning to methanol as a fuel. In this case the combustible mixture consists of about five parts of air to one of fuel by weight. This means that there is two and a half times as much fuel to absorb the heat, but in addition methanol requires three times the number of B.T.Us. per pound to vaporize it. In all it proves to be more than seven times as effective as petrol in controlling temperature rises in the induction.
It is generally recognized that a change to methanol fuel in the right air/fuel proportions, will increase the power of any engine by about 10% and this with no other changes. With the supercharged engine, it can give power increases up to 25% because as I said earlier, all superchargers, by compression, raise the temperature of the charge.
So effective is methanol in reducing temperatures that it is quite common under humid conditions, to see a supercharged car come in after a hard race, with the entire supercharger and manifold encased in ice. I said earlier that the latent heat value of water is again double that of methanol, but of course it is not a fuel and can play no part in the combustion process. It has been suggested that water admitted in droplet form would be instantaneously converted to steam by the 2300 degree C temperature of the combustion, and, as steam, would combine any red hot carbon particles to form carbon-monoxide, thus preventing the depositing of carbon on the walls of the combustion chamber.
This may or may not be so. I am not competent to pronounce on such a matter. I do know this, however. The combustion chambers of engines using water inhalation are remarkably free from carbon deposits when compared with those where water is not used.
In the late nineteen forties a certain petrol company in the U.S.A. carried out a number of tests which involved the introduction of appreciable quantities of water in atomized form, into the air/fuel mixture. In conclusion they decided that if water could be correctly introduced in the ratio of one volume of water to three of petrol, it was possible to operate satisfactorily two units of a compression ratio higher than with petrol alone. That is that a petrol which would operate on a ratio of say eight to one, could be used on ten to one if water was introduced in the above proportions.
The findings of this company have been confirmed by my own experiments except that I find that with the supercharged car it is necessary to use water at slightly higher rate than this.
It might be thought that the introduction of water would lead to misfiring. I have passed a gallon of water through a three litre motor in seventy seconds at 5000 r.p.m. without a trace of misfiring.
Unfortunately the use of water raises two problems.
First, where to carry the water in sufficient quantity, so that re-watering will not be an intolerable nuisance. And second, how best to introduce it to the motor.
There is no real solution to the first of these problems. A five gallon tank of water is quite bulky and occupies an appreciable amount of space in the boot of an average sedan. A two gallon tank can be fitted under the bonnet of most cars today ( together with the supercharger) but is only good for about 100 miles of hard driving.
With regard to the second part of the problem there are many difficulties. I have tried many methods, none of them entirely satisfactory, since some consideration must be given to cost. At first glance the problem seems simple enough. Use a small water carburetor in parallel with the fuel carburetor and interconnect them so that they open together and make the fuel carburetor slightly over rich to compensate for the extra air introduced by the water carburetor. But, we don't want to take in any water unless we have a positive boost in the manifold. This is where the first of the complications arise. We must introduce a valve between the water carburetor and the supercharger inlet manifold and which is opened by a positive manifold pressure from the outlet manifold , acting on a diaphragm. This is well enough but still not satisfactory , because we find that if we open the throttle fully at say 25 m.p.h. we get a positive boost which opens the valve between the small water carburetor and the intake manifold but because the main petrol carburetor is wide open there is not sufficient vacuum to introduce much water just when we want it most. Also the more the speed increases the lower become the compression pressures but the amount of water being introduced is increasing as the pressure falls in the induction manifold. Clearly the small water carburetor is not a satisfactory method.
As I have said I have tried many methods, but only two are reasonably satisfactory. The least complex of the two is to use the backpressure of the exhaust to pressurize a water tank and to force water from a tank via a small jet into the throat of the petrol carburetor. The water tank must be arranged or located below the level of the carburetor so that water cannot feed by gravity into the engine. If it is located in the boot it is as well to provide a tap in the line in case the car has to be parked nose down on a steep hill, in which case the carburetor might be lower than the tank. A filter of reasonable capacity should be provided in the line from the tank as the gas from the exhaust which pressurizes the tank can contain particles of carbon. If the water passes through a jet of about .025 this will be approximately the right size. It can be introduced into the carburetor via one of the choke spindle holes if the choke assembly is removed, this latter being superfluous with all carburetors fitted with an accelerator pump.
The pipe from the exhaust manifold to the tank should be fairly large, say about five sixteenths O.D. It should be passed through the manifold where the various branches have united, and the end should be directed by means of a slight bend inside the manifold, so that it faces into the exhaust flow.
The reason for the large pipe is so that the air cavity in the tank responds quickly to variations in the exhaust pressure. The tank of course must have a sealed filler. This very simple system has faults, the chief of which is the delay in response to pressure variations particulary when the tank is fairly empty. For this reason a small tank works better than a large one. Naturally it is impossible in this way to get instantaneous responses and throttle opening must thus be a rather gradual process if pinking is to be avoided.
The system at present employed by me makes use of the supercharger manifold pressure and operates much like a paint spray gun with the atomized water directed into the throat of the carburetor. The spray or injector unit consists of two small nozzles. The water nozzle has an aperture of .050 diameter, and the air jet of .060. They are arranged at right angles so that the tip of the water nozzle slightly intersects the jet of air through the air nozzle. It must be kept as close as possible to the tip of the later so that the velocity of the air is as high as possible when it passes over the water nozzle.
This unit will cause quite a fine spray with pressures as low as 2 p.s.i. The water tank, usually of about two gallons capacity is mounted under the bonnet and as close to the injector unit as possible. It must be arranged so that the water level when the tank is full is about three inches below the tip of the water nozzle. This unit is very effective in operation and also economical of water since it will not operate at all unless there is a positive manifold pressure. With low manifold pressures there is some variation in delivery rate of water, as the level in the tank falls, but it is not very great and it is very slight with the higher manifold pressures which of course are primarily the problem.
With this system it is necessary to use a small non-return valve in the air delivery pipe from the pressure manifold, otherwise there would be an air leak into the manifold when the engine is idling.
When mounting the water tank, it is advisable to so locate it that the water level in its relationship to the water jet does not vary when the car is parked on a steep hill. For instance if the tank is put in the boot and the car is facing downhill the water would flow out of the water jet by gravity.
If twin carburetors are employed on the supercharger it is advisable to use two of the injector units otherwise some cylinders are likely to be more favored than others in respect of water droplets.
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Probably the pinion to crown wheel contact has changed (noticeable at 60mph) so I want to change the rear end ratio anyway as the car has soooo much power that it can easily push a much taller gear set. When I go to the effort of doing that I most probably will update the whole drive line at the same time.......... nice dream, only if I want to waste the money on it though *cough tight arse cough* 
Real tests
but its tight as now, so good touch typing can't do it justice 
fucken cool to just reach in turn the key, warm the bad boy up and affect the earths rotation as I accelerate down the road 
Gag factor rice magic dominates cunts!@!!@@!
Makes sense to me that most of the cooling is happening where it is needed most (during the compression phase), as you say though I wonder what the effects are at Lambda 0.65. It is beyond my realm of experience really. In my own case I just went with a system that is basic and works at conventional setting ranges and gives a measurable performance benefit.
Linear Mode
