The post is about a little gadget I made to make real-time air/fuel adjustments to the bike.
So, here it goes:
THE PROBLEM:
My typical riding weekend excursion consists of riding into the mountains with friends, having lunch or coffee and then returning home. The problem is that especially in summer, due to the accumulated heat of the engine, when the bike sits after the first leg of the trip, the heat of the engine creeps upwards, the temperature sensor gets hot itself and when the return leg commences, it gives false temperature readings (higher than normal) to the ECU. With those false high temp readings the ECU leans-out the mixture and so the bike becomes nervous and unpleasant to ride.
And beyond that, in general the bike fuelling-wise is very finicky. Depending on temperatures, humidity, how long it's been since the TPS has been baselined etc it can be smooth as butter or vicious as a divorced mamba. Very temperamental and I don't like that - 15 years on japanese bikes made me demand otherwise.
So I had to do something about it.
THE SOLUTION IN THEORY:
Fuelling is taken care of by the ECU. What it does is control the amount of fuel injected into the cylinders depending on the amount of air it thinks is entering into the cylinders. This depends on three parameters:
1. How open the throttle is
2. The fuelling table
3. The air temperature
In order to manually trim the fuelling while on the go, the only possible way to do it is to fiddle with the air temperature readings. If the temp sensor says "It's X degrees" and it is actually less than that I need to correct that reading. But how to change that reading?
Somewhere here in the forum I learned that the temp sensor is simply a variable electrical resistance, with inverse relation: the higher the temperature, the less the resistance. So, it is actually pretty simple: I can just add a resistance in series with the sensor and then the increased resistance will result in a lower temperature reading to the ECU. Of course, in order to have adjustability, it will need to be a variable resistance, i.e. a potentiometer.
However, there is a question: what range of ohm resistance should the potentiometer have? The function boundaries of the temp sensor should be known. Again ,somebody here in the forum provided with the information - the temp sensor reads about 200 Ohms at 50 degrees C whereas it reads something like 2K Ohm at 0 degrees.
The amount of temperature correction I would need to be able to make was in the range of 10-20 degrees Celsius, which accounts for up to 6-7% of fuelling difference. (A 10 degree C difference at usual temperatures equals to about 3% fuelling difference). The potentiometer range had to be chosen carefully because the relation between temperature and resistance of the sensor is not linear, so it would have to be narrow enough to allow for enough sensitivity for hotter days, and wide enough for the colder days. Eventually I figured out that a 2K Ohm potentiometer would be perfect for what I needed (and it proved correct).
In the first picture you can see the stock configuration, and in the second the configuration with the adjuster interjected between the sensor and the ECU. The switch is not necessary but I thought that while riding I wouldn't want to fiddle with the adjuster itself and the switch would allow me to easily revert to stock. Actually what the switch does is bypass the potentiometer, so in order for the potentiometer to work the switch needs to be in open position.
Essentially what it is is a "booster plug" but with adjustability.
THE SOLUTION IN PRACTICE:
So what I needed was (as shown in the third picture):
- The potentiometer,
- a switch
- a small box to put everything inside
- proper connectors, which are "TE/Amp Junior Power Timer Connectors" bought from www.cycleterminal.com
- cable
- intermediate waterproof connector to easily remove the device if need arises.
- a clamp to mount the device on the handlebar
In the rest of the pictures you can see how the device was made. Eventually the epoxy putty I used to attach the little bolt that would hold the lid of the box in place didn't hold out so eventually I used a zip-tie.
Installation was very easy. I only had to remove the tank in order to connect to connectors and tidy-up the cables.
DOES IT WORK?
Hell yeah! take a look at this:
(sorry for the glaring flashlight - without it the camera just wouldn't focus properly)
(readings taken through Bluetooth OBDII connection and the "Torque Pro" app)
THE BEAUTY OF IT:
1. It's foolproof #1: The non-linear temperature-resistance relation of the sensor means that even if the device is forgotten at the "active" position, a reduction in the reading of the sensor itself will move the function to the much less sensitive part of its range and the effect of the added resistance will become negligible.
2. It's foolproof #2: It can only add resistance which means it can only lower the temp reading which means in turn that it can only add fuel, not remove. So no danger of overheating the engine or burn valves etc.
3. It's short-proof. If for whatever reason there is any short anywhere in the circuitry of the device, the only result will be that the bike will be functioning as stock. Remember: the device just adds resistance to the sensor's so if there is a short the only effect is that the additional resistance just isn't added, nothing more.
4. It can be easily removed: The device can be easily removed via the intermediary connector if a shorting plug is added to this connector. And of course I have already made such a plug, stored in the underseat space of the bike.
DOES IT AFFECT RIDING:
Yes. It's winter now and I can't test it properly as the bike more or less works properly. But still, lowering the temperature for 10 degrees (i.e. adding ~ 3% more fuel) induces a slight reduction in engine brake and slightly softens-up throttle response. (There's no change in power output). I wouldn't go below that as I don't want to over-enrich and start fouling my plugs. Anyway, summer is near and it'll be tested for real benefit then.
So that's it. I'd like to thank all people who offered input for this project either directly or indirectly. I can't remember nicknames but whoever you are - thank you.
So, here it goes:
THE PROBLEM:
My typical riding weekend excursion consists of riding into the mountains with friends, having lunch or coffee and then returning home. The problem is that especially in summer, due to the accumulated heat of the engine, when the bike sits after the first leg of the trip, the heat of the engine creeps upwards, the temperature sensor gets hot itself and when the return leg commences, it gives false temperature readings (higher than normal) to the ECU. With those false high temp readings the ECU leans-out the mixture and so the bike becomes nervous and unpleasant to ride.
And beyond that, in general the bike fuelling-wise is very finicky. Depending on temperatures, humidity, how long it's been since the TPS has been baselined etc it can be smooth as butter or vicious as a divorced mamba. Very temperamental and I don't like that - 15 years on japanese bikes made me demand otherwise.
So I had to do something about it.
THE SOLUTION IN THEORY:
Fuelling is taken care of by the ECU. What it does is control the amount of fuel injected into the cylinders depending on the amount of air it thinks is entering into the cylinders. This depends on three parameters:
1. How open the throttle is
2. The fuelling table
3. The air temperature
In order to manually trim the fuelling while on the go, the only possible way to do it is to fiddle with the air temperature readings. If the temp sensor says "It's X degrees" and it is actually less than that I need to correct that reading. But how to change that reading?
Somewhere here in the forum I learned that the temp sensor is simply a variable electrical resistance, with inverse relation: the higher the temperature, the less the resistance. So, it is actually pretty simple: I can just add a resistance in series with the sensor and then the increased resistance will result in a lower temperature reading to the ECU. Of course, in order to have adjustability, it will need to be a variable resistance, i.e. a potentiometer.
However, there is a question: what range of ohm resistance should the potentiometer have? The function boundaries of the temp sensor should be known. Again ,somebody here in the forum provided with the information - the temp sensor reads about 200 Ohms at 50 degrees C whereas it reads something like 2K Ohm at 0 degrees.
The amount of temperature correction I would need to be able to make was in the range of 10-20 degrees Celsius, which accounts for up to 6-7% of fuelling difference. (A 10 degree C difference at usual temperatures equals to about 3% fuelling difference). The potentiometer range had to be chosen carefully because the relation between temperature and resistance of the sensor is not linear, so it would have to be narrow enough to allow for enough sensitivity for hotter days, and wide enough for the colder days. Eventually I figured out that a 2K Ohm potentiometer would be perfect for what I needed (and it proved correct).
In the first picture you can see the stock configuration, and in the second the configuration with the adjuster interjected between the sensor and the ECU. The switch is not necessary but I thought that while riding I wouldn't want to fiddle with the adjuster itself and the switch would allow me to easily revert to stock. Actually what the switch does is bypass the potentiometer, so in order for the potentiometer to work the switch needs to be in open position.
Essentially what it is is a "booster plug" but with adjustability.
THE SOLUTION IN PRACTICE:
So what I needed was (as shown in the third picture):
- The potentiometer,
- a switch
- a small box to put everything inside
- proper connectors, which are "TE/Amp Junior Power Timer Connectors" bought from www.cycleterminal.com
- cable
- intermediate waterproof connector to easily remove the device if need arises.
- a clamp to mount the device on the handlebar
In the rest of the pictures you can see how the device was made. Eventually the epoxy putty I used to attach the little bolt that would hold the lid of the box in place didn't hold out so eventually I used a zip-tie.
Installation was very easy. I only had to remove the tank in order to connect to connectors and tidy-up the cables.
DOES IT WORK?
Hell yeah! take a look at this:
(sorry for the glaring flashlight - without it the camera just wouldn't focus properly)
(readings taken through Bluetooth OBDII connection and the "Torque Pro" app)
THE BEAUTY OF IT:
1. It's foolproof #1: The non-linear temperature-resistance relation of the sensor means that even if the device is forgotten at the "active" position, a reduction in the reading of the sensor itself will move the function to the much less sensitive part of its range and the effect of the added resistance will become negligible.
2. It's foolproof #2: It can only add resistance which means it can only lower the temp reading which means in turn that it can only add fuel, not remove. So no danger of overheating the engine or burn valves etc.
3. It's short-proof. If for whatever reason there is any short anywhere in the circuitry of the device, the only result will be that the bike will be functioning as stock. Remember: the device just adds resistance to the sensor's so if there is a short the only effect is that the additional resistance just isn't added, nothing more.
4. It can be easily removed: The device can be easily removed via the intermediary connector if a shorting plug is added to this connector. And of course I have already made such a plug, stored in the underseat space of the bike.
DOES IT AFFECT RIDING:
Yes. It's winter now and I can't test it properly as the bike more or less works properly. But still, lowering the temperature for 10 degrees (i.e. adding ~ 3% more fuel) induces a slight reduction in engine brake and slightly softens-up throttle response. (There's no change in power output). I wouldn't go below that as I don't want to over-enrich and start fouling my plugs. Anyway, summer is near and it'll be tested for real benefit then.
So that's it. I'd like to thank all people who offered input for this project either directly or indirectly. I can't remember nicknames but whoever you are - thank you.
