Basic System Description


Unlike the carbureted 950's, the Fuel Injected 990's only use the Secondary Air Control (SAS) during warm up to get the CATs up to operating temperature (Light off). The ECU handles the emissions with info from the Lambda probes (and others) once up to temperature.

During cold start the engine requires a relatively rich mixture for smooth operation. So, the ECU operates in open loop mode with a fixed fuel map for the first minute or two of engine operation (depending on info from the temperature sensors) until the Lambda sensors have heated to operating temperature. By feeding air into the exhaust (secondary air), CO and HC are oxidized through after burning at temperatures over 600°C to form water and carbon dioxide. The resulting high temperatures also aid in bringing the CATs up to operating temperature more quickly.

To achieve efficient warm up operation, a high secondary air flow rate must be achieved within the first few seconds of engine startup, and the air flow rate must be maintained until oxygen sensor control is in operation. Air flow is maintained by the Secondary Air Control (AKA SAS or SLS). Once the lambda probes and catalytic converters have reached their operating temperatures, the solenoid valve cuts off the secondary air flow and the ECU goes into closed loop mode (ie: ECU adjusts AFR to maintain 14.7:1 ratio).

Air from the SAS during normal operations would result in false readings from the lambda probes. What a can o' worms that would be to factor into the map.

I see no reason to disable the SAS on the 990's.

Lambda probes:
The lambda probes screwed into the exhaust after each cylinder measure the partial oxygen pressure in the emission compared to the ambient air, i.e. the sensors compare the oxygen content in the emission with the fresh air.

A lambda probe basically consists of a ceramic body coated on both sides with a platinum layer. The platinum layer acts like an electrode. The outer layer comes into contact with the emission, the inner layer with the ambient air. The ceramic body becomes electro-conductive from a temperature of approx. 350º C; voltage is generated if the oxygen content between the ambient air (inner electrode) and emission (outer electrode) varies. The higher the difference in the oxygen level, the greater the voltage; the lambda probe voltage can lie between 0 and 1 volt in operation. Normally the lambda probe voltage will fall between 0.2 volt for a lean combustion and approx. 0.8 volt for a rich combustion.

– For lean mixtures (excess air) only part of the drawn in oxygen is required for combustion; a large share of oxygen remains in the emission - resulting in a low lambda probe voltage.
– For rich mixtures (air deficiency) almost all of the oxygen is burned; hardly any oxygen remains in the emission - resulting in a high lambda probe voltage.

The ideal operating temperature for a lambda probe is at approx. 600º C, although up to 950º C is possible for short durations. To reach the operating temperature as quickly as possible, the lambda probes used in this motorcycle are equipped with a heater switched on by the control unit.

NOTE: The ceramic body of the lambda probe is very sensitive to shock which is why it is covered with a slotted sheet-metal sleeve.

The lambda probes used in the LC8 F.I. engines are of the zirconia narrow band type. They are not designed to be used by the F.I. computer to achieve AF mixtures other than stoichiometric (14.7:1). Therefore, expecting to use it for tuning the engine map for performance is not practical (nor possible). It is there, for all intents and purposes, only to keep the emissions in check. They are used only for operation below ~5000 rpm.

Catalytec Converter (CAT):
KOTH: The catalytic converter is installed in the main silencer and transforms most of the main toxic constituents into non-toxic compounds. It is designed as a three-way catalytic converter and consists of a coiled metal support whose surface is coated with precious metals such as platinum and rhodium; the coating only weighs 1 to 2 grams.

Similar to the lambda probe, the catalytic converter is not activated until a temperature of approx. 300º C is reached; it operates best between 400º C and 800º C. Thermal aging accelerates at a temperature of 800º C. Much higher temperatures occur if the ignition/injection system (e.g.: ignition faults) malfunctions, which can destroy the catalytic converter. The main constituents in the emissions are nitrogen (N2, not involved in combustion), carbon dioxide (CO2, the result of complete combustion) and water or steam (H2O, is bound in the fuel and released during combustion); together they comprise approx. 90% of emitted exhaust gas and are considered harmless. The rest mainly consists of carbon monoxide and hydrocarbon (CO and HC, both the result of incomplete combustion) and nitrogen oxide (NOx, the result of high combustion chamber temperature); all three are toxic.

To effectively convert these 3 components into harmless carbon dioxide, water and nitrogen in the catalytic converter, the engine must be operated close to lambda 1 (1:14.7 AFR), i.e. the efficiency of combustion is greatest close to lambda 1. But lambda 1 is almost impossible to achieve by control engineering, which is why the control unit continuously (several times each second) produces mixtures alternating between lambda 0.97 (rich mixture) and 1.03 (lean mixture). Under these conditions the voltage generated by the lambda probe varies between 0.2 volt and 0.8 volt depending on the exhaust gas composition.

The 15 minute Idle Trick
Superduke: It seems there's a little confusion about the so called “15 min idle trick”
If the dealer changed the mapping (maybe for a different exhaust ) he had also also to do the 15 min idle run. But we don’t want to change the mapping, we only want the EFI to “re calibrate. Because of the self learning EFI the “actual” parameters of the engine are measured and stored into the EFI as new basic information, if you do a 15 minute idle run.There is a good information about this in a document from KTM Sommer.
I will try to translate the most important things you have to do.

Enough gas in the tank !
Do it outside , not in a closed garage and somewhere in the shadow.
You need also a stop watch.

What to do:
The bike must be in a vertical position – so don’t use the side stand for the procedure.
The engine must be cold.
Start the engine and let it idle for 15 minutes.
You are not allowed to use any functions of the bike in this time.
The time must not be less then 15 minutes and not more then 16 minutes.
If the engine stops running during this time, just restart it and let it run for the rest of the time.

Error Codes:


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