Join Date: Aug 2010
Location: N-East Central USA
X180 UFO Capsule
The CIS momentary enrichment is executed by the "UFO" capsule, and not the WUR.
This capsule looks like a small metal UFO with a vacuum line at the bottom and has a square electrical terminal at the top. Some Esprits have just an empty square two prong male plug and no sign of the capsule. This part does not show anywhere in Parts List, Lotus Notes or anywhere else. Most of the owners don't even know of its existence or purpose. However, on the sheet 7 section MG of 1988 Onwards Service Notes there is a "Differential Pressure Valve" connected between the earth and pin #11 of the ECU. Pin 11 of the ECU controls the fuel enrichment. The UFO capsule is a momentary Hobbs switch and its vacuum line connects to a tee plumbed into the black w/white stripe hose connected to the bottom of the square module (an over-boost sensor) located on top of the RH rear wheel arch, (right buttress). Black w/ white stripe vacuum line runs directly from the over boost cutout switch to the intake manifold at the back of the engine and on the downstream side of the throttle plates. So it's measuring true vacuum/boost at the input to the valve.
The two pins of the connector are shorted together for about 1.5 second each time there is a quick decrease in the vacuum level (100mB jump, i.e. the throttle plates are opened quickly). The device only works with a vacuum applied, no connection between the two pins occurs during gradual increase or decrease of boost. One pin of the connector is grounded and the other goes to the ECU. So each time the throttle is pressed quickly to increase speed a ground signal is sent to the ECU. It has been confirmed that the function of this device, in conjunction with the ECU, is to act as the K-Jetronic equivalent of an accelerator pump. When the ECU receives the ground signal from the UFO device it adjusts the frequency valve to DC=95% to provide extra fuel for acceleration (momentary action). It has been confirmed empirically, that this capsule dramatically improves throttle responsiveness.
To achieve continuous enrichment under boost, the Control Pressure has to be manipulated via continuous WUR adjustment in function of the rpm and MAP. It can not be done by grounding pin #11. However, it can be done either digitally, with an application of the UTCIS "PT" Digital WUR, or mechanically by applying the IM plenum pressure signal to one side of the diaphragm in the WUR lower chamber. Boost sensing WURs were used on 1980-s Volvo turbo, Audi TQ, MB, Saab, Porsche, BMW, etc., but (mysteriously) not on Lotus.