What sensors

[DavidR8]

I was doing a bit of tidying on STella today.
Part of this included pulling the Tupperware so I could wash the inside of it as I've been riding in really crappy weather.
I pulled the plugs and noticed they were wet with gas.
I didn't ride today, the last time was yesterday to warm up the engine for the oil change. Started her up again after the change to make sure all was nice and tight.

But I got thinking about the plugs and wonder what sensors are sending signals to the ECU to alter the A/F ratio from cold running to hot.

Obviously the engine coolant sensor is involved as are the O2 sensors but is there some other sensors involved?


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[Jim Van]

You got it - the coolant temp sensor and probably a timer that determines how long the bike has been running from a cold start-up. It runs in "open loop" until the ECM knows the bike has warmed up enough to switch over to " closed loop". In "closed loop" the signal from the O2 sensors are used to determine the pulse width sent to the fuel injectors to adjust/determine the A/F ratio.

Before warm up, and while in "open loop", the signal from the O2 sensors is ignored. They should stay "high" in "open loop" , anyway.

On cages, how many times the O2 signals switch from "high" to "low" in a given time period, is a measure of how "tight' the mixture is being controlled. It works exactly the same way on a MC .

FYI : http://www.autotap.com/techlibrary/understanding_oxygen_sensors.asp http://www.autotap.com/techlibrary/understanding_oxygen_sensors.asp

 

[DavidR8]

Thanks for the link Jim. That was very informative.

So in theory if I were to pull over on the highway and pull the plugs they should all be dry and a nice tan colour.

I think I may have a go at testing my O2 sensors.
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[SupraSabre]

Some people OVER worry/think too much about things that are working just fine!

 

[DavidR8]

Some people OVER worry/think too much about things that are working just fine!

Thanks


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[Don B]

So in theory if I were to pull over on the highway and pull the plugs they should all be dry and a nice tan colour.

PLEASE don't remove the plugs from a hot (ie, normal operating temp) engine. You could do that on car engines back in the day when they had cast iron heads, but not on aluminum cylinder heads.

Obviously the engine coolant sensor is involved as are the O2 sensors but is there some other sensors involved?

If either of the above were faulty, the instrument panel would let you know (coolant temp bar indicator and/or FI light).

 

[DavidR8]

PLEASE don't remove the plugs from a hot (ie, normal operating temp) engine. You could do that on car engines back in the day when they had cast iron heads, but not on aluminum cylinder heads.



If either of the above were faulty, the instrument panel would let you know (coolant temp bar indicator and/or FI light).

Yes, that was the reason for the in theory part


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[Al st1100]

it all matters , throttle position sensor, map sensor, intake air, coolant , baro sensor. don't look just at o2 sensors for fuel compensation.

 

[Jim Van]

If your gas mileage hasn't changed (decreased ) and seems OK, your O2 sensors are probably working just fine. But it would be interesting, as a data baseline to connect a DVM to the O2 sensor, or better yet an oscilloscope and see how many alterations from about 0.1 volt to 0.9 volt you see after the bike has warmed up and running at say, 2,500 RPM over 30 seconds. You and SuperSabre could compare data.

EDIT : Code 21 ( Cylinders 1/3 ) & 22 ( Cylinders 2/4 ) are for a bad O2 sensors. Probably for a sensor that isn't cycling at all between 0.1 and 0.9 volts , or sluggish.

 

[DavidR8]

If your gas mileage hasn't changed (decreased ) and seems OK, your O2 sensors are probably working just fine. But it would be interesting, as a data baseline to connect a DVM to the O2 sensor, or better yet an oscilloscope and see how many alterations from about 0.1 volt to 0.9 volt you see after the bike has warmed up and running at say, 2,500 RPM over 30 seconds. You and SuperSabre could compare data.

To be honest my city mileage is pretty awful. Last fill up was 24.3mpg with 85% city vs highway.

The bike is new to us in Sept and we haven't had much time for pure highway miles.

I've done starter valve sync, cleaned the 5-way T after getting a code 2 and replaced the thermostat.

Mileage hasn't improved terribly much, maybe 2mpg since the sync.


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[Don B]

To be honest my city mileage is pretty awful. Last fill up was 24.3mpg with 85% city vs highway.

David, as I recall one of your posts in another thread indicated that most of your city riding is in 2nd and 3rd gear. I hate to be the one to burst your bubble, but if you have to ride at a low speed that requires 2nd and 3rd gear to keep the engine RPMs in a desirable range, 24-25mpg is all you should expect. You have to ride it out of the city in 4th and 5th gear at fairly constant speed for reasonably long distances to expect the good mileage numbers that you see some STO members post.

quote=Jim Van;2052316]Your mileage sounds low to me, even with all that city riding. But I don't own a ST1300. Maybe a real ST1300 owner can give you their opinion.[/quote]

I am a a real ST1300 owner, and I've already expressed my opinion, but I can't back it up with real numbers as I never bother to check my mileage after burning a tank of gas in mostly "city" riding around the neighborhood. However, in a reasonable mix of city/freeway riding my mileage is in the mid-30's range, which meets my expectations most of the time.

 

[Jim Van]

Your mileage sounds low to me, even with all that city riding. But I don't own a ST1300. Maybe a real ST1300 owner can give you their opinion.

The coolant temp (ECT) sensor resistance at 68F should be between (2.3K and 2.6K) Ohms.

The air temp ( IAT ) sensor resistance at 68F should be about 1K Ohm and at 86F be about 4K Ohms.

With both sensors connectors disconnected, you should measure (4.75 - 5.25 ) Volts at the connectors.

If any of the sensors are bad, that could prevent going into "closed loop" mode and your gas mileage would be low.

 

[Don B]

If any of the sensors are bad, that could prevent going into "closed loop" mode and your gas mileage would be low.

If any of the sensors are bad, wouldn't the instrument panel indicators tell you, once you determine the failure code?

 

[DavidR8]

David, as I recall one of your posts in another thread indicated that most of your city riding is in 2nd and 3rd gear. I hate to be the one to burst your bubble, but if you have to ride at a low speed that requires 2nd and 3rd gear to keep the engine RPMs in a desirable range, 24-25mpg is all you should expect. You have to ride it out of the city in 4th and 5th gear at fairly constant speed for reasonably long distances to expect the good mileage numbers that you see some STO members post.

Yeah that's what I'm coming to realize.
I think my city diving is different from what others classify as city. Speed limits are 30-50 kmh.

It's the stopping and starting that's killing the mileage I think.

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[Kevin_56]

I think my city diving is different from what others classify as city. Speed limits are 30-50 kmh.

It’s the stopping and starting that’s killing the mileage I think.

You are talking 18 - 30 MPH. I can only say if I do a lot of start and stop riding the back roads in my neck of the woods, my mileage suffers. and that is doing 55 once up to speed. Talking upper 30's in stead of mid 40's. Take that to your city speed and I bet mine will be near yours.

 

[DavidR8]

You are talking 18 - 30 MPH. I can only say if I do a lot of start and stop riding the back roads in my neck of the woods, my mileage suffers. and that is doing 55 once up to speed. Talking upper 30's in stead of mid 40's. Take that to your city speed and I bet mine will be near yours.

Yup that what I’m thinking. Between lights the instant reading goes up quickly at a steady throttle but not enough to offset the start/stop.

Just back from a two-up ride and we saw 23kms/l (54 mpg) on the instant readout (I know it’s not to be relied upon) so I think all is well with the mighty V-4.

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[Kevin_56]

instant readout (I know it’s to be relied upon)

To say the least. It takes a (my estimate) 10 second reading and computes a MPG. Going down hill, great MPG, uphill bad MPG. The Average takes several miles to be anything close to usable, but still not close to calculated.

It is a gage to see that it is capable of decent mileage, that you saw with your 54.

 

[DbleDutch]

Yup that what I’m thinking. Between lights the instant reading goes up quickly at a steady throttle but not enough to offset the start/stop.

Just back from a two-up ride and we saw 23kms/l (54 mpg) on the instant readout (I know it’s to be relied upon) so I think all is well with the mighty V-4.

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Yes in town commuting the ST mileage is :no1:. My 6 mile commute has the highest limit of 45, most is less than 30mph and stop lights every 2 blocks. When the tank is mostly this commuting, I do not even consider the mileage, just at the joy of riding the ST.

 

[drtyrrel]

I've used my bike for demos coaching the MSF BRC2. I never get out of 2nd gear and burn through 1/4 tank or more. I took a Prorider class in Dallas Texas last July. I did a couple of 3rd gear 35 mph plus quick stops but was in 1st gear doing slow speed maneuvers most of the day. I used well over 1/2 half a tank of gas and never left the parking lot. It looks like you have a perfect excuse to take a road trip.

 

[Jim Van]

If any of the sensors are bad, wouldn't the instrument panel indicators tell you, once you determine the failure code?

If the sensors were open , or go way out of range, a trouble code would be displayed. Same with the voltage being applied to the sensors. But it's also possible the sensor could shift value and the ECM would have no idea that happened, but then the ECM would think the bike isn't warmed up and that would keep it in "open" loop mode.

Once the plastic is off, it only takes a few minutes to check the sensor resistance, to determine if it's in the ball park or not, and to check the voltage being fed to the sensors.