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I found this article in the VN1600 yahoo group's page. I can e-mail you charts if ya want. Enjoy =) PB


CHEAP FIX OF A FI ENGINE PINGING CAUSED BY A LEAN AF MIXTURE

Usual disclaimer first. The facts and opinions in this article are for information only and I take no responsibility for any possible problems or damage caused by modifying your bike based on this article.
This write-up is not intended to be a technical article but rather some basic facts on causes of pinging of four stroke motorcycle engines with focus on fuel injected (FI) engines, specifically the Kawasaki V-twins. Simple solution is explained that worked well on two of my FI bikes, the 2002 Suzuki V-Strom DL1000 and 2003 Kawasaki VN1600 Classic.

Causes of pinging/knocking on 4-stroke engines.
The pinging is usually caused by some kind of uncontrolled ignition that occurs too early in the engine’s compression cycle. Apart from running with no oil, the engine ping/knock is probably the second worst thing that can affect the longevity of an engine. There can be quite a few reasons for the engine pinging/knocking like a lean air/fuel (AF) mixture, too advanced spark timing, wrong spark plugs, engine overheating, carbon deposits, high compression ratio, poor fuel and possibly others. The only cause that I want to address in this article is the lean AF mixture, as this can be corrected by simple (or complicated and expensive) modification of the bike’s FI system.
The useable AF mixture on which the 4-stroke engine can run is quite wide. It can be as high as 17:1 for the most complete combustion, minimum emissions and best fuel economy and as low as 12:1 for the best engine power. An optimum AF ratio is usually considered to be 14.7 : 1 or 14.7 pounds of air for 1 pound of fuel. Running lower AF mixture not only gives you more power, but it is safer for the engine as the extra fuel is cooling the cylinder and cylinder head components. Different engine operating conditions and load may require different AF mixture, so on carbureted engines, where the mixture cannot be precisely controlled, the manufacturers tend to set it overall a bit richer and you seldom have a pinging problems.
On the FI engines, there is much better control of the AF mixture as the bike’s sensors supply the ECU (electronic control unit) all the needed information like the engine and air temperature, air/ambient pressure, throttle position, engine load and others. This, combined with the environment protection concerns, is making the manufacturers to push the limits of engines combustion setup towards more lean AF mixtures = more complete, less emissions combustion.
Unfortunately, some manufactures seem to program/map their ECUs towards excessively lean mixtures (especially on liquid cooled bikes where it is more safe) which inevitably results in pinging/knocking usually under low RPM, heavy load and hot operating conditions. Instead of optimizing bike’s sensors and ECU program/map the manufacturers make the owners solve the problem - pay a premium for a high octane gasoline.
This is especially true about the large FI Kawasaki V-twins. As far as I know, all the 1500+ cc Kawasaki V-twins have 9:1 compression ratios, which in no case should require high octane gas. There is quite a few FI bikes with 11:1 or more compression ratios which are rated by manufacturers for a regular 87 octane gas. An example is the above mentioned Suzuki V-Strom with 11.5 : 1 compression ratio.
Most of the V-twin cruiser owners are making the AF mixture issues worse by installing open pipes and air kits that tend to lean out the AF mixture further and make the pinging worse. The only solution for situations like this is some kind of ECU program/map modifying devices like the Power Commander (PC) or Techlusion’s TFI. The cost of these “gizmos” is quite substantial, usually $400+ in Canadian dollars. I am not familiar with the design of these devices and I do not know if they modify the AF mixture only or if they modify things like the spark advance as well, and I am not going to comment on their pros and cons.

Solving the pinging/knocking with air temperature sensor modification.
Your FI bike’s ECU has a certain program/map which tells it how much of fuel should be injected depending on operating conditions. One of the most important “condition” is the temperature of the air, which mixed with the fuel facilitates the combustion. The air (including the oxygen in it) is a weird yet predictable “animal”. Depending on pressure (and that depends on elevation) and temperature, the same mass/weight of the air will have a different volume. As we are going to tinker with the air temperature sensor, the air temperature effect is what I will try to explain a bit more. Have a look at the graph below showing the relationship between the air density (mass/volume) and the temperature.
 

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As the temperature goes up, the air gets “thinner” and there is less oxygen in it to facilitate the combustion. To keep the proper AF mixture, your FI bike has an air temperature sensor and at higher temperature (= lower air density) it will tell the ECU to correct/lower the amount of fuel added per volume of the combustion air and vice versa.
The air temperature sensor on Kawasaki FI bikes is a thermistor that is changing its resistance depending on temperature. I have the resistance data for the 2003/2004 VN1600 Classic and they are identical for the Mean Streak. I would assume that the sensors are the same on the other Kawasaki FI bikes but I cannot guarantee it. The graph below shows the sensor’s resistance versus temperature:



As you can see, at low temperatures the resistance is as high as 6000 Ohms while at higher temperatures it is as low as 500 Ohms. For us the most important resistance range is somewhere between 1500 and 2500 Ohms, corresponding to 20 to 40 deg.C engine inlet air temperatures as measured by the sensor. I am assuming that the engine inlet temperature will be some 10 deg.C higher than the actual ambient temperature as the air will warm up going in between the cylinders before it hits the sensor – your guess is as good as mine.
Our objective is to eliminate/reduce the pinging by making the AF mixture richer. This can be achieved by a simple trick – adding the resistance to the air temperature sensor. If we add the resistance, we are fooling the ECU into thinking that the engine inlet air is cooler (= more mass and oxygen per volume) and the ECU will increase correspondingly the addition/injection of fuel. Unfortunately, there is one issue here with adding a fixed value resistor in series with the air temperature sensor (thermistor). Both the air density vs. temperature and the sensor resistance vs. temperature curves are not linear, so the same resistor (say 500 Ohms) will have a different effect at different air temperatures. As I will demonstrate in next two examples, that might actually be to our benefit. The two examples are exact calculations for 500 Ohms resistor with an air at 80% humidity at elevation of 800 meters above the see level (most of Alberta).
Example 1. Ambient temperature is 10 deg.C, engine inlet is 20 deg.C. The sensor/ECU is reading 2560 Ohms, air density 0.06813 lb/ft3. Added 500 Ohms - the ECU is now reading 3060 Ohms, corresponds to 15.4 deg.C = air density 0.06925 lb/ft3. Air density increase is 1.7% the ECU adds 1.7% more fuel.
Example 2. Ambient temperature is 30 deg.C, engine inlet is 40 deg.C. The sensor/ECU is reading 1210 Ohms, air density 0.06245 lb/ft3. Added 500 Ohms - the ECU is now reading 1710 Ohms, corresponds to 30.4 deg.C = air density 0.06530 lb/ft3. Air density increase is 4.5%, the ECU adds 4.5% more fuel.
Evidently, the higher the ambient/engine inlet temperature, the bigger the effect of the 500 Ohms resistor will be. As mentioned before, that might work OK for us as at higher temperatures the engine is much more prone to pinging and it needs richer AF mixture to eliminate the pinging.

Bottom line facts.
Assuming that the Kawasaki FI engines are as stock rather on a lean side in the AF mixture, they can make use of the fuel ratio increase by up to 20%; let’s be conservative and say 15% max (and this is with the stock exhaust). Based on the data presented above, I would say that a fixed resistor in range of 500 to 1500 Ohms (added in series with bike’s temperature sensor) would work best for the most common operating temperature range to eliminate the pinging. I am using presently the 500 Ohms resistor and planning to go to 700 Ohms. Ideally, a 1500 Ohms potentiometer could be installed to vary the resistance for an optimum performance. Remember, too rich AF mixture will not harm the bike, too lean mixture will.
I have not seen any deterioration in fuel consumption with the 500 Ohms resistor, in fact I think it got about 5% better. Going to 1000 or 1500 Ohms you might see some fuel consumption increase, but your bike will not “complain” for sure.
You can buy resistors in Radio Shack, they come in values 470, 690, 1000 and 1500, there might be some values in between, I am not sure. The cost is less than $1 per couple. Buy preferably the ¼ Watt ones, but the miniature 1/8 Watt are OK as well.
Now, how to do it. I have the info, wiring diagrams, for 2003/04 VN1600 Classic and Mean Streak only, they are identical. I would suspect that other Kawasaki FI V-twins use the same wire harness and the same wire coding.
The air sensor is located under the right hand side “air cleaner”, near the throttle body inlet. It is mounted in the base plate and you probably have to remove the plate to get access to the wires. The other option to get to the right wire is on the ECU unit connector and this is where I cut the lead and soldered in the resistor. The lead/wire that you are looking for is pink in color and connected to pin #31. The ECU unit is just next to the battery and can be fished out after removing the bracket holding the battery. I just cut the wire about an inch from the connector and soldered the resistor in, I put some shrink tubing on it, but I actually did not shrink it as I may try different resistor in a near future.
As I have already mentioned I did the same mod on my 2002 V-Strom with a fair success using the 690 Ohms resistor. I’d suggest that you do not attempt this fix unless you have at least basic skills with the soldering gun, ask a friend for help if this is a case. If you have further questions you can e-mail me at ‘[email protected]’, I will be glad to answer, time permitting.

Lumir F. BAKOTA, Crowsnest Pass, Alberta
 

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Discussion Starter #3
Hey in a few more posts I'll be in quadruple digits =) Almost to 1000 :razz: :razz:
 

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Hmm, resistor tricks have been around for a while for FI cars. They are supposedly designed to increase HP, but they usually just screw with the engines PCM causing more problems than they're work.

However, in our particular example where we're not necessarily looking for more power, rather trying to trick the computer into richening out the bike, this might actually work. I would be willing to be a guinea pig here and try this, however, I am leaving for the Smokey Mountains this weekend and I dont want to do this then go on a huge trip like that. I'd much rather be closer to home.

So unless someone else is willing to give this a shot before I get back, I can do it the first weekend of August and I'll report back my findings....
 

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I once put a potentiometer on my temp sensor on a car that would not idle correctly when it was warmed up. I could make it idle ok by adjusting the pot which makes me believe that in theory this would indeed work to change the fuel mixture. It made my fuel mileage so bad that I took it off and went back to left foot braking while toeing the gas a little at stop lights. I think I had a malfunctioning computer though, and it may have overcompensated. I will be interested to see how it works for Constrictor. Just curiosity on my part since my Classic hasn't pinged much yet.
 

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Woot!! I found a guinea pig!! If it works good enough you want to change the intake too?? There's a couple 800 guys who have put S&S covers onto thunder hypercharger backplates with good success and it should work for the 1500/1600's too. I'll have to do some more research if you're interested :twisted: :twisted:

Does your Meanie knock or ping?? I'd like to see somebody with a pinging problem try this to see the results.
 

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oldodge said:
I once put a potentiometer on my temp sensor on a car that would not idle correctly when it was warmed up.
I was wondering as I was reading if a potentiometer would work. By using a pot, you would effectively have an idle adjustment like a carb'd bike. We have several at work that aren't much bigger than 5 or 6 stacked quarters with a post in the 1500-2000 ohm range. I'll check them out today and let you know.

Russ
 

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Ping

....and what can one do with an 03 carb model that pings?

Have done the seafoam thing
now rev her higher before shifting
down shift on hills
but on a 3 hr highway run in 90 deg temps yesterday she did it several times

Suggestions?

Growler
 

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jet the carbs. fatten the mixture a little. should be alot cheaper than an FI bike
 

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ping

I believe there is a mixture adjusting screw on the carb somewhere?

Got to get me a service manual.

Thanks
Growler
 

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Constrictor said:
Hmm, resistor tricks have been around for a while for FI cars. They are supposedly designed to increase HP, but they usually just screw with the engines PCM causing more problems than they're work.However, in our particular example where we're not necessarily looking for more power, rather trying to trick the computer into richening out the bike, this might actually work.I would be willing to be a guinea pig here and try this, however, I am leaving for the Smokey Mountains this weekend and I dont want to do this then go on a huge trip like that. I'd much rather be closer to home. So unless someone else is willing to give this a shot before I get back, I can do it the first weekend of August and I'll report back my findings....
Isn't that the same "trick" used with the Caddman mod you posted (ie, 500ohm resister at the inlet air temp sensor)?
 

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NY_Guy said:
Isn't that the same "trick" used with the Caddman mod you posted (ie, 500ohm resister at the inlet air temp sensor)?
Yep, but this thread is from '05, so that post was made before he did the mod.;)
 

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As the temperature goes up, the air gets “thinner” and there is less oxygen in it to facilitate the combustion. To keep the proper AF mixture, your FI bike has an air temperature sensor and at higher temperature (= lower air density) it will tell the ECU to correct/lower the amount of fuel added per volume of the combustion air and vice versa.
The air temperature sensor on Kawasaki FI bikes is a thermistor that is changing its resistance depending on temperature. I have the resistance data for the 2003/2004 VN1600 Classic and they are identical for the Mean Streak. I would assume that the sensors are the same on the other Kawasaki FI bikes but I cannot guarantee it. The graph below shows the sensor’s resistance versus temperature:



As you can see, at low temperatures the resistance is as high as 6000 Ohms while at higher temperatures it is as low as 500 Ohms. For us the most important resistance range is somewhere between 1500 and 2500 Ohms, corresponding to 20 to 40 deg.C engine inlet air temperatures as measured by the sensor. I am assuming that the engine inlet temperature will be some 10 deg.C higher than the actual ambient temperature as the air will warm up going in between the cylinders before it hits the sensor – your guess is as good as mine.
Our objective is to eliminate/reduce the pinging by making the AF mixture richer. This can be achieved by a simple trick – adding the resistance to the air temperature sensor. If we add the resistance, we are fooling the ECU into thinking that the engine inlet air is cooler (= more mass and oxygen per volume) and the ECU will increase correspondingly the addition/injection of fuel. Unfortunately, there is one issue here with adding a fixed value resistor in series with the air temperature sensor (thermistor). Both the air density vs. temperature and the sensor resistance vs. temperature curves are not linear, so the same resistor (say 500 Ohms) will have a different effect at different air temperatures. As I will demonstrate in next two examples, that might actually be to our benefit. The two examples are exact calculations for 500 Ohms resistor with an air at 80% humidity at elevation of 800 meters above the see level (most of Alberta).
Example 1. Ambient temperature is 10 deg.C, engine inlet is 20 deg.C. The sensor/ECU is reading 2560 Ohms, air density 0.06813 lb/ft3. Added 500 Ohms - the ECU is now reading 3060 Ohms, corresponds to 15.4 deg.C = air density 0.06925 lb/ft3. Air density increase is 1.7% the ECU adds 1.7% more fuel.
Example 2. Ambient temperature is 30 deg.C, engine inlet is 40 deg.C. The sensor/ECU is reading 1210 Ohms, air density 0.06245 lb/ft3. Added 500 Ohms - the ECU is now reading 1710 Ohms, corresponds to 30.4 deg.C = air density 0.06530 lb/ft3. Air density increase is 4.5%, the ECU adds 4.5% more fuel.
Evidently, the higher the ambient/engine inlet temperature, the bigger the effect of the 500 Ohms resistor will be. As mentioned before, that might work OK for us as at higher temperatures the engine is much more prone to pinging and it needs richer AF mixture to eliminate the pinging.

Bottom line facts.
Assuming that the Kawasaki FI engines are as stock rather on a lean side in the AF mixture, they can make use of the fuel ratio increase by up to 20%; let’s be conservative and say 15% max (and this is with the stock exhaust). Based on the data presented above, I would say that a fixed resistor in range of 500 to 1500 Ohms (added in series with bike’s temperature sensor) would work best for the most common operating temperature range to eliminate the pinging. I am using presently the 500 Ohms resistor and planning to go to 700 Ohms. Ideally, a 1500 Ohms potentiometer could be installed to vary the resistance for an optimum performance. Remember, too rich AF mixture will not harm the bike, too lean mixture will.
I have not seen any deterioration in fuel consumption with the 500 Ohms resistor, in fact I think it got about 5% better. Going to 1000 or 1500 Ohms you might see some fuel consumption increase, but your bike will not “complain” for sure.
You can buy resistors in Radio Shack, they come in values 470, 690, 1000 and 1500, there might be some values in between, I am not sure. The cost is less than $1 per couple. Buy preferably the ¼ Watt ones, but the miniature 1/8 Watt are OK as well.
Now, how to do it. I have the info, wiring diagrams, for 2003/04 VN1600 Classic and Mean Streak only, they are identical. I would suspect that other Kawasaki FI V-twins use the same wire harness and the same wire coding.
The air sensor is located under the right hand side “air cleaner”, near the throttle body inlet. It is mounted in the base plate and you probably have to remove the plate to get access to the wires. The other option to get to the right wire is on the ECU unit connector and this is where I cut the lead and soldered in the resistor. The lead/wire that you are looking for is pink in color and connected to pin #31. The ECU unit is just next to the battery and can be fished out after removing the bracket holding the battery. I just cut the wire about an inch from the connector and soldered the resistor in, I put some shrink tubing on it, but I actually did not shrink it as I may try different resistor in a near future.
As I have already mentioned I did the same mod on my 2002 V-Strom with a fair success using the 690 Ohms resistor. I’d suggest that you do not attempt this fix unless you have at least basic skills with the soldering gun, ask a friend for help if this is a case. If you have further questions you can e-mail me at ‘[email protected]’, I will be glad to answer, time permitting.

Lumir F. BAKOTA, Crowsnest Pass, Alberta
As the temperature goes up, the air gets “thinner” and there is less oxygen in it to facilitate the combustion. To keep the proper AF mixture, your FI bike has an air temperature sensor and at higher temperature (= lower air density) it will tell the ECU to correct/lower the amount of fuel added per volume of the combustion air and vice versa.
The air temperature sensor on Kawasaki FI bikes is a thermistor that is changing its resistance depending on temperature. I have the resistance data for the 2003/2004 VN1600 Classic and they are identical for the Mean Streak. I would assume that the sensors are the same on the other Kawasaki FI bikes but I cannot guarantee it. The graph below shows the sensor’s resistance versus temperature:



As you can see, at low temperatures the resistance is as high as 6000 Ohms while at higher temperatures it is as low as 500 Ohms. For us the most important resistance range is somewhere between 1500 and 2500 Ohms, corresponding to 20 to 40 deg.C engine inlet air temperatures as measured by the sensor. I am assuming that the engine inlet temperature will be some 10 deg.C higher than the actual ambient temperature as the air will warm up going in between the cylinders before it hits the sensor – your guess is as good as mine.
Our objective is to eliminate/reduce the pinging by making the AF mixture richer. This can be achieved by a simple trick – adding the resistance to the air temperature sensor. If we add the resistance, we are fooling the ECU into thinking that the engine inlet air is cooler (= more mass and oxygen per volume) and the ECU will increase correspondingly the addition/injection of fuel. Unfortunately, there is one issue here with adding a fixed value resistor in series with the air temperature sensor (thermistor). Both the air density vs. temperature and the sensor resistance vs. temperature curves are not linear, so the same resistor (say 500 Ohms) will have a different effect at different air temperatures. As I will demonstrate in next two examples, that might actually be to our benefit. The two examples are exact calculations for 500 Ohms resistor with an air at 80% humidity at elevation of 800 meters above the see level (most of Alberta).
Example 1. Ambient temperature is 10 deg.C, engine inlet is 20 deg.C. The sensor/ECU is reading 2560 Ohms, air density 0.06813 lb/ft3. Added 500 Ohms - the ECU is now reading 3060 Ohms, corresponds to 15.4 deg.C = air density 0.06925 lb/ft3. Air density increase is 1.7% the ECU adds 1.7% more fuel.
Example 2. Ambient temperature is 30 deg.C, engine inlet is 40 deg.C. The sensor/ECU is reading 1210 Ohms, air density 0.06245 lb/ft3. Added 500 Ohms - the ECU is now reading 1710 Ohms, corresponds to 30.4 deg.C = air density 0.06530 lb/ft3. Air density increase is 4.5%, the ECU adds 4.5% more fuel.
Evidently, the higher the ambient/engine inlet temperature, the bigger the effect of the 500 Ohms resistor will be. As mentioned before, that might work OK for us as at higher temperatures the engine is much more prone to pinging and it needs richer AF mixture to eliminate the pinging.

Bottom line facts.
Assuming that the Kawasaki FI engines are as stock rather on a lean side in the AF mixture, they can make use of the fuel ratio increase by up to 20%; let’s be conservative and say 15% max (and this is with the stock exhaust). Based on the data presented above, I would say that a fixed resistor in range of 500 to 1500 Ohms (added in series with bike’s temperature sensor) would work best for the most common operating temperature range to eliminate the pinging. I am using presently the 500 Ohms resistor and planning to go to 700 Ohms. Ideally, a 1500 Ohms potentiometer could be installed to vary the resistance for an optimum performance. Remember, too rich AF mixture will not harm the bike, too lean mixture will.
I have not seen any deterioration in fuel consumption with the 500 Ohms resistor, in fact I think it got about 5% better. Going to 1000 or 1500 Ohms you might see some fuel consumption increase, but your bike will not “complain” for sure.
You can buy resistors in Radio Shack, they come in values 470, 690, 1000 and 1500, there might be some values in between, I am not sure. The cost is less than $1 per couple. Buy preferably the ¼ Watt ones, but the miniature 1/8 Watt are OK as well.
Now, how to do it. I have the info, wiring diagrams, for 2003/04 VN1600 Classic and Mean Streak only, they are identical. I would suspect that other Kawasaki FI V-twins use the same wire harness and the same wire coding.
The air sensor is located under the right hand side “air cleaner”, near the throttle body inlet. It is mounted in the base plate and you probably have to remove the plate to get access to the wires. The other option to get to the right wire is on the ECU unit connector and this is where I cut the lead and soldered in the resistor. The lead/wire that you are looking for is pink in color and connected to pin #31. The ECU unit is just next to the battery and can be fished out after removing the bracket holding the battery. I just cut the wire about an inch from the connector and soldered the resistor in, I put some shrink tubing on it, but I actually did not shrink it as I may try different resistor in a near future.
As I have already mentioned I did the same mod on my 2002 V-Strom with a fair success using the 690 Ohms resistor. I’d suggest that you do not attempt this fix unless you have at least basic skills with the soldering gun, ask a friend for help if this is a case. If you have further questions you can e-mail me at ‘[email protected]’, I will be glad to answer, time permitting.

Lumir F. BAKOTA, Crowsnest Pass, Alberta
I stripped and rebuilt my 2001 vn1500 Classic after 6 years under a blanket, once going I realised that the bike was running lean, lots of backfiring out the exhaust and pinging, engine clunking etc etc. I put a 1500 ohms resistor in and all fixed, thanks for the information 👍👍
 
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