Improved cold weather running

[NPS]

I have a Breva 1100 which is fitted with wide-band lambda.

The bike runs ok in closed loop mode using the lambda signal to run around 14.7 AFR.

However, in open loop mode when warming up the engine runs rich at about 12 - 13 AFR. Below 8C the ECU never goes into closed loop mode. Between 8-10C it may take as long as 30 minutes to switch to closed loop mode.

In wide open throttle it goes to open loop and the AFR can drop to 11.

 

A solution that appears to work quite well is to place a 2400 ohm resistor in parallel across the inlet air temperature thermister located in the airbox. This fools the ECU to thinking that the air temperature is around 38C warmer. The result is that the ECU switches to closed loop within a minute or so of starting (could be longer to warm up more). In addition, the wide open throttle AFR is now around 12.5 - less lickley to hesitate as it did before being over rich. This due to hotter air being less dense and requriing less fuel.

 

I'm sure this has been done before but just thought others might benefit from my experience, especially in colder climates. To lessen the effect a resistor of 4k or 6k could be used for 28C and 20C, respectively.