13secquatermile

Hi could someone explain the operation and purpose of the amal valve on the porsche 944t 1987 model .

Thanks
Stephen

lart951

that's a new name for me but I think you are referring, to the cycling valve here from clark's garage

4.3 Cycling Valve

Cycling Valve 1 The cycling valve on the 951 is located underneath the intake manifold. It has three ports. One port is connected to the inlet side of the turbocharger between the air flow meter and the turbocharger, one to the discharge of the turbocharger via a banjo bolt on the discharge pipe to the intercooler, and the aforementioned line going to the wastegate diaphragm. Normally, the cycling valve is "open" which allows the pressure from the turbocharger discharge to be bled back to the turbocharger inlet. This is possible because the port on the cycling valve coming from the turbocharger discharge has an orifice in it. When the cycling valve moves toward the "closed" position, it is closing off the port to the turbocharger inlet. This allows pressure from the turbocharger outlet to pass through the cycling valve to the line going to the wastegate diaphragm. This causes pressure to build up on top of the wastegate diaphragm. When the combined pressure on top of the diaphragm and exhaust pressure against the valve seat overcome the spring pressure in the diaphragm, the wastegate will open bypassing the exhaust flow around the turbocharger thereby limiting boost pressure.

Cycling Valve 2 The cycling valve is controlled by the KLR Unit (Knock Regulator Unit). The KLR receives signals both directly and from the DME Control Unit to determine how the cycling valve should be controlled. The chips in the KLR have a boost limit which comes preset from the factory. When the actual boost reaches the computers preset limit, the KLR sends a signal to the cycling valve to close which allows exhaust pressure to open the wastegate. If the cycling valve fails, loses power, or a problem occurs in the KLR unit, the cycling valve will fail fully closed. In this mode boost is limited to approximately 1.2 bar. This is essentially the boost at which the force of the exhaust pressure will overcome the wastegate diaphragm spring pressure