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Re:Fuel Injection Facts and Tips
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TOPIC: Re:Fuel Injection Facts and Tips
#852116
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Re:Fuel Injection Facts and Tips 3 Years, 1 Month ago  
They generate they're own voltage based not the amount of heat. The hotter they are, the more voltage... and the cooler the less. That's how they read the state of the exhaust gases, based not the amount of voltage the O2 sensor sends to the ECU; then the ECU adjusts the amount of fuel injected accordingly. If the O2 sensor is failing, they don't generate enough voltage. Think of it this way, if they bike is running lean, the exhaust temp will be hotter and the O2 sensor, via the ECU, will adjust the fuel mixture accordingly, there by making it more rich and cooling the exhaust gases. If the exhaust temp is too cold, the voltage level is too low and the ECU thinks it's running too rich and leans out the fuel mixture in the injectors. Get it?
 
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Last Edit: 2015/01/24 09:18 By Doc_V.
 


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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
They're called O2 sensors for the purpose of monitoring oxygen present in the spent gasses.

The zirconia sensors, once they reach operating temperature, do just that.

I with a richer than normal mixture, not enough oxygen on the O2 sensor will drop the voltage telling the ECU to lean it out, and vice versa.




Closed Loop

The computer uses the oxygen sensor's input to regulate the fuel mixture, which is referred to as the fuel "feedback control loop." The computer takes its cues from the O2 sensor and responds by changing the fuel mixture. This produces a corresponding change in the O2 sensor reading. This is referred to as "closed loop" operation because the computer is using the O2 sensor's input to regulate the fuel mixture. The result is a constant flip-flop back and forth from rich to lean while keeping the average overall fuel mixture in proper balance to minimize emissions.

When no signal is received from the O2 sensor, as is the case when a cold engine is first started (or the 02 sensor fails), the computer orders a fixed (unchanging) rich fuel mixture. This is referred to as "open loop" operation because no input is used from the O2 sensor to regulate the fuel mixture. If the engine fails to go into closed loop when the O2 sensor reaches operating temperature, or drops out of closed loop because the O2 sensor's signal is lost, the engine will run too rich causing an increase in fuel consumption and emissions. A bad engine temp sensor can also prevent the system from going into closed loop because the computer also considers engine temperature when deciding whether or not to go into closed loop.

Closed loop mode is during cruise engine demands, for better fuel efficiency and emissions, and at higher throttle settings the ECU goes into open loop to a pre determined [richer] mixture setting for better power.
 
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Last Edit: 2015/01/24 08:20 By BikerRon.
 


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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
On our bikes the system is always in open loop during idle because the AIS is turned on during idle. During closed loop cruise the AIS is turned off because the extra air would cause false readings. During open loop and coast it's back on again so any unburned hydrocarbons can be reignited.
 
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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
Oh, this AIS?

 
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Last Edit: 2015/01/24 09:45 By BikerRon.
 


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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
Such a simple looking thing to be so important.
 
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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
(From the 2008 service manual)

Air injection
The air induction system burns unburned exhaust gases by injecting fresh air (secondary air) into the exhaust port, reducing the emission of hydrocarbons. When there is negative pressure at the exhaust port, the reed valve opens, allowing secondary air to flow into the exhaust port. The required temperature for burning the un- burned exhaust gases is approximately 600 to 700 °C (1112 to 1292 °F)

Air cut-off valve

"The air cut-off valve is controlled by the signals from the ECU in accordance with the combustion conditions. Ordinarily, the air cut-off valve opens to allow the air to flow during idle and closes to cut-off the flow when the vehicle is being driven. However, if the engine temperatureis below the specified value, the air cut-off valve re- mains open and allows the air to flow into the exhaust pipe until the temperature becomes higher than the specified value."


Pretty much tells me the ECU should be in open loop (O2 sensors has no input) when ever the cut-off valve is open.

Warming up, idle, WOT (I couldn't see having a negitive pressure situation at the exhaust port during this event), and decelerating. The mechanical reed valves will only open during the negative pressure event even tho the solinoid valve is open.
 
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Last Edit: 2015/01/25 07:43 By BikerRon.
 


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#852507
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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
Since there are no temperature sensors in the exhaust I'm not sure what they mean by temperature below a specified value. Maybe the engine temperature but the air flow would only affect the exhaust temperature. Maybe they mean while the engine is warming up and before it transitions to closed loop. But you're correct, the AIS will only be on during open loop - idle and acceleration.

It will be off during high throttle settings because of what Yamaha terms as "self EGR". The two way valve on the carbed bikes shuts off the AIS during full throttle for the same reason.

The valve will open though during less than full throttle acceleration when the system changes to open loop. One would think there wouldn't be any negative pulses with a stock setup at 75+ mph but there are. I can put my fingers on the AIS pipe and it's not even hot.

The only neat thing I've seen about the PC add-on is its ability to lower the cut rpm's. I don't know at what rpm's Yamaha turns the injectors back on but to be able to lower it can increase fuel mileage and probably stop the popping even with the AIS still connected. They say that there is a hesitation if the cut rpm is fairly low but with the injectors on the Road Star pulsing once every revolution I don't think it would be too bad. Be interesting to see someone come out with a module that did only that. Kind of like the low cost one for the earlier bikes that only raised the rev limit.
 
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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
Since there are no temperature sensors in the exhaust I'm not sure what they mean by temperature below a specified value. Maybe the engine temperature but the air flow would only affect the exhaust temperature.

I assume the head temp sensors would be the triggering denominator here, unless the O2 sensors, being online after reaching a certain temp, would be talking to the ECU and letting it also know that "Yea, it's hot in here!"
 
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Last Edit: 2015/01/25 09:23 By BikerRon.
 


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#852538
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Re:Fuel Injection Facts and Tipsy 3 Years, 1 Month ago  
I only know of one temperature sensor and I thought I remembered it being screwed into the front cylinder, left side. But you've got the bike right there, easy enough to look.

The O2 sensors are heated so they come up to temperature real quick. They'll be working even before the exhaust gets up to the higher temps. The ECU will only know that it's getting a signal. Barring contamination the heated O2 sensor should be good for about 100k miles. They might slow down before that time though. Make sure any additives put in the fuel are O2 sensor safe. Don't use any silicone around the intake or exhaust system, that kills them real quick.
 
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#857291
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Re:Fuel Injection Facts and Tipsy 3 Years ago  
what year did the roadstar start with FI ?
 
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