It doesn't take long after purchasing your new HD that this is a very hot running engine. One of the most common complaints about the new bikes is the heat that comes off the engine and exhaust system. These high operating temperatures can be mostly attributed to the new closed loop operating mode of the EFI system. The OEM closed loop operating mode relies on narrow band oxygen sensors to keep the air fuel ratio at 14.7:1 at idle, under normal riding circumstances and while cruising on the highway.
Most Riders are also aware that HD engine EFI acts a little differently when the engine even gets hotter than normal. The conditions that trigger a high heat condition include trying to idle for long periods of time, under very slow riding conditions or when the ambient temperature starts getting above 85 degrees. When the ECU senses hot engine temperatures, it goes into a overheat/high temperature mode of operation that is sometimes referred to as "Parade Duty" mode. Knowing that this overheat mode exists and recognizing what is happening as the engine temperature goes up are completely different issues. During development and testing of the Nightrider.com LC1 Wide Band O2 sensor Upgrade, the behavior of the OEM ECU was observed and data logs collected by our laboratory instruments. Listed below is the sequence of events and engine behaviors noted as the engine warms up, gets to normal operating temperature and goes into high temperature mode.
lDuring engine warm up the HD engine runs in open loop mode at a 12.5:1AFR. No matter what the engine temperature, this is the AFR that occurs at starting. If you disconnect the O2 sensors on the engine, this is the default idle AFR for the HD engine until the engine warms up.
Once the ECU determines the engine is warmed up, it goes into closed loop mode and will idle at a very lean (and hot) 14.7:1. Normal idle speed is 1050.
In high temp mode the engine RPMs drops to 950 and the ECU goes to open loop mode, richening the fuel mixture to 12.0:1 in an attempt to cool the engine. As soon as the engine RPMs hits 1200, the ECU goes back to closed loop mode at 14.7:1 which is too lean. This means that the smallest amount of throttle will lean the engine out as long as the ECU is operating in "high heat" mode.
If the bike tries to
accelerate, the engine stumbles and the continuation of the lean AFR
condition can drive engine temperature even higher.
lDuring testing in controlled conditions with data logging instrumentation attached to the engine, the overheating engine behavior was captured. The OEM engine will go into this "high heat" mode in about 10 minutes of idling at 78 degree ambient temperatures in shady conditions. Exhaust pipe temperature will get as high as 750F degrees about 6" down from the cylinder heads as measured by a thermocouple. Temperatures of 194+ degrees were measured at the heat shields of the same location by IR thermometer.
lThe graphs below summarize testing done. The OEM engine (top) ran at 14.7:1 until it overheated and the AFR richened to 11.5:1. Exhaust temperatures peaked at 750 degrees and averaged 600 degrees during the test duration
lThe lower graph represents an engine with the LC1 WBO2 upgrade. The AFR is centered on 13:1 as programmed into the LC1. Temperatures at the exhaust peaked at 660 or 90 degrees less. Average exhaust temperature during the test was 540 degrees or 60 degrees low. Temperatures at the heat shield were 150 degrees or over 40 degrees lower.
lWith the LC1 WBO2 upgrade in place, the HD engine was 15-20% cooler under the same operating conditions and never went into high temperature operating mode.
The ECU forces the engine to idle at a very lean (and hot) 14.7:1 in closed loop mode. Normal idle speed is 1050. In high temp mode the engine RPMs drops to 950 and the ECU goes to open loop mode to richen the fuel mixture to 12:1 in an attempt to cool the engine off. Give the engine some throttle and as soon as the engine RPMs hits 1200, the ECU goes back to closed loop mode at 14.7:1 which is too lean, it drives engine temperature even higher and the engine stumbles.
During testing of the LC-1 WBO2 upgrade, data logs were captured the OEM HD engine/ECU behavior with various test instruments for RPMs, Exhaust Temperature and AFR. The OEM engine will go into this "high heat" mode in about 10 minutes of idling at 78 degree ambient temperatures in shady conditions. Exhaust pipe temperature can get as high as 800F degrees about 6" from the cylinder heads. Temperatures measured by IR Thermometer at the heat shield was 194+ degrees.
With the WBO2 upgrade in place under the same conditions, exhaust pipe temperatures averaged almost 100F degrees cooler after 15 minutes of idle and the ECU never went into high temperature mode. Temperatures at the heat shields were a little over 150 degrees, or 40 degree drop.
While installing the LC1 WBO2 upgrade can not guarantee that the engine will not go into high heat mode, it does make it more resistant to high temperatures. Should the engine go into high temp mode, when the RPMs reach 1200 the WBO2 sensor will make sure the fuel mixture is a richer fuel mixture to prevent stumbling.
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