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17-12-2009, 02:51pm
I'm not sure how to link to a specific post, so I'll just cut and paste it. Here's what I found recently:
For the entire run I had my air/fuel ratio meter mounted on the top triple clamp giving me the good news in real time. The data comes from a Bosch LSU 4.2 wideband oxygen sensor which has a laser trimmed calibration chip and is managed by a Tech Edge WB0 datalogger. The datalogger is also calibrated to air.
The K8 is dead stock, including the ECU maps, apart from removal of 1st-4th gear and top speed restrictions and a switch that allows me to turn off the stock HO2 sensor without invoking a fault code.
We all rode responsibly at normal Hayabusa cruising speeds for the duration of the trip and all paid for it at the pump.
Saturday was stinking hot (high ambient air temperature) and Sunday morning cool.
Here's what I found.
As per ECU code research, the Gen II Busa has a 'window' in which the HO2 sensor operates in closed loop. It starts at 2000 rpm and ends at 6000 rpm. Within this window the ECU doggedly holds the air/fuel ratio at lambda (14.7 parts air to 1 part of fuel). Outside the window, with high ambient air temp the bike runs excessively rich; ranging between 11.8:1 to 12.4:1. When cool (approx 18 degrees celcius) it sits around 13.1:1 to 13.4:1 - prime power territory.
With the HO2S switched off, the bike again runs excessively rich (avg 12.6:1) all the way from low rpm through to high rpm. Actually, the faster I went the richer it got. I got the impression the ram air compensation formula is not right for Australian conditions, (and neither is the 'rich' margin). I also noted that the engine coolant temperature dropped the faster I went!
What's going on? Well, at this stage it's just conjecture, (logging to commence this week) but I reckon Suzuki went for a big fat margin of error to accommodate fitment of aftermarket pipes. It also went rich because a rich mixture provides lower noise emissions, (PAIR, catalytic converters and the HO2S fix the exhaust emissions). The third reason I believe Suzuki went for a rich margin was to help prevent detonation. The Hayabusa doesn't have a knock sensor, therefore having a rich mixture helps reduce the potential for pre-ignition or detonation.
It all equals higher fuel consumption and less power.
It ran better when it was cool.
Camel
For the entire run I had my air/fuel ratio meter mounted on the top triple clamp giving me the good news in real time. The data comes from a Bosch LSU 4.2 wideband oxygen sensor which has a laser trimmed calibration chip and is managed by a Tech Edge WB0 datalogger. The datalogger is also calibrated to air.
The K8 is dead stock, including the ECU maps, apart from removal of 1st-4th gear and top speed restrictions and a switch that allows me to turn off the stock HO2 sensor without invoking a fault code.
We all rode responsibly at normal Hayabusa cruising speeds for the duration of the trip and all paid for it at the pump.
Saturday was stinking hot (high ambient air temperature) and Sunday morning cool.
Here's what I found.
As per ECU code research, the Gen II Busa has a 'window' in which the HO2 sensor operates in closed loop. It starts at 2000 rpm and ends at 6000 rpm. Within this window the ECU doggedly holds the air/fuel ratio at lambda (14.7 parts air to 1 part of fuel). Outside the window, with high ambient air temp the bike runs excessively rich; ranging between 11.8:1 to 12.4:1. When cool (approx 18 degrees celcius) it sits around 13.1:1 to 13.4:1 - prime power territory.
With the HO2S switched off, the bike again runs excessively rich (avg 12.6:1) all the way from low rpm through to high rpm. Actually, the faster I went the richer it got. I got the impression the ram air compensation formula is not right for Australian conditions, (and neither is the 'rich' margin). I also noted that the engine coolant temperature dropped the faster I went!
What's going on? Well, at this stage it's just conjecture, (logging to commence this week) but I reckon Suzuki went for a big fat margin of error to accommodate fitment of aftermarket pipes. It also went rich because a rich mixture provides lower noise emissions, (PAIR, catalytic converters and the HO2S fix the exhaust emissions). The third reason I believe Suzuki went for a rich margin was to help prevent detonation. The Hayabusa doesn't have a knock sensor, therefore having a rich mixture helps reduce the potential for pre-ignition or detonation.
It all equals higher fuel consumption and less power.
It ran better when it was cool.
Camel