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Reply to: leaning-leaking (scottie) with respect! (archive)

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Posted by Paul S. on February 04, 2001 at 08:32:46:

Dear Scottie,

Conventional combustion theory is based on the smooth flow of induction and exhaust gasses. In the old days if you wanted to improve your cars performance you might have your head ‘gas flowed’ – this basically involves polishing the inlet and exhaust ports to make the gasses flow faster. More recently however, F1 engine development has involved what has become known as ‘swirl’ technology. This contradicts old notions by suggesting that turbulence in the induction gasses creates a better suspension of fuel molecules and thus more effective combustion.

The Ecotek CB-26P is a non return valve with a Venturi construction which injects minute quantities of agitated air into the manifold at certain specific pressures. Whilst this will lean the mixture very slightly the quantities of air are so tiny that it can in no way be construed to constitute a large enough 'air-leak' to be considered detrimental to the normal functionality of the (I.C.E.) internal combustion engine. Approx. 5% is sufficient to create the turbulence necessary to produce such a dramatic improvement in combustion efficiency, such improvements more than compensate for the slight leaning of the mixture.

This revolutionary device works by taking advantage of an effect involving differential pressures known as the ‘Venturi’ effect. The design of the device, which incorporates two perpendicular tubes with constricted throats conjoined into a T-junction, creates a change in pressure and velocity of the airflow in the centre of the device as the air traverses the tube.

A minute airflow originates via the device and is directed along a connecting pipe via the device into the inlet manifold. As this secondary air source combines with the air drawn through the conventional air intake, a turbulence is created which further combines with dispersed fuel droplets that have been injected by the EFI system.

As a unit amount of air passing through a unit length of tube in a unit time always has to remain constant (the conservation of momentum), the constriction in the cross-sectional area of the tube has the effect of producing a higher flow velocity and a partial vacuum in the vertical down-pipe of the device.

The device acts to mitigate air intake, it is designed so that when the engine is idling, a minute amount of air is drawn in. The air drawn in via this ‘bleed’ serves to reduce emissions at tick over (particularly CO) without affecting smooth running. This 'bleed' occurs throughout the rev range acting to sustain the turbulence initiated by the full operation of the device at higher RPM.

In the case of both periods of moderate acceleration and in the few seconds after hard acceleration, there is a much higher pressure flow of air along the ‘T’ of the device and hence much stronger suction in the vertical down-pipe. The device incorporates a valve attached to a rigid steel spring and at certain engine speeds this is forced open by the partial vacuum, against the resistance of the spring, to allow air to be sucked in and restore the pressure inside the tube.

The valve will then return to its original position and the process repeated. The net effect of this is an oscillatory motion in the down-pipe the frequency of which is governed by the rigidity of the spring (the spring constant), the engine speed and other parameters of the car to which the device is fitted.

It is this oscillatory motion and resultant longitudinal wave of compressed and then rarefied air that enhances combustion efficiency. This wave of air is transmitted along the connecting pipe until it reaches the opening of the inlet manifold where it disperses and greatly improves the mixing process of fuel and air. In normal combustion many of the larger fuel droplets fall out of the mixture and are expelled via the exhaust as unburned Hydrocarbon emissions. Due to the more finely dispersed fuel droplets created a much more efficient burn is produced.

At very high engine speeds the device will remain ‘open’; this improves the air intake into the inlet manifold and, as a result of its design, the effect of the air passing through the open valve causes it to 'swirl'. This again creates improved fuel/air mixing and improved combustion. At high revs this can be at least as effective as the oscillatory effects at lower revs.

Any leaning of the fuel air mixture caused by the opening of the valve is compensated for by the improvements in the suspension of the fuel molecules.

Paul S.


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