Inside the "Triple Nickel"

[Chris-PA]

prevent? ... when air velocity increases.... quicker transition over to main ...helps pick up fuel from main sooner

The air velocity that matters is that passing the fuel outlet ports. When the throttle plate is closed those notches are far away from the main venturi and outlet, and the carb should be designed such that it does not create enough pressure drop to pull fuel from the main circuit.

The air passing around the edge of the throttle plate forms a venturi, with the idle outlets located there. Putting notches in it shifts the air flow around, and can be used to redirect air towards or away from outlets (including the idle transfer outlets at part throttle). Given how these are located it would appear they are placed to avoid the fuel ports. But regardless it should not activate the main.

 

[dbittle]

The air velocity that matters is that passing the fuel outlet ports. When the throttle plate is closed those notches are far away from the main venturi and outlet, and the carb should be designed such that it does not create enough pressure drop to pull fuel from the main circuit.

The air passing around the edge of the throttle plate forms a venturi, with the idle outlets located there. Putting notches in it shifts the air flow around, and can be used to redirect air towards or away from outlets (including the idle transfer outlets at part throttle). Given how these are located it would appear they are placed to avoid the fuel ports. But regardless it should not activate the main.

Ok, I keep coming back to Mastermind's idea that fuel puddling behind the throttle valve is causing a rich bog condition when the throttle is opened. If I understand the patent literature description correctly, the system can restrict the flow of fuel through the system, but it cannot add more fuel than the carburetor would put in if the autotune system was not there. In other words, they would set up the carburetor to be too rich and use the electronic controls to lean it out. That would be true at idle, transition and WOT, right? If that is the case, what would be the result if we introduced a deliberate air leak into a saw that is showing the bog? Would the bog get worse or get better? What I'm trying to drive towards is an absolute conclusive certainty of whether the transition bog is a lean condition bog or a rich condition bog. With the explanation of the TPS system, I'm not sure how it is participating.

 

[Chris-PA]

Ok, I keep coming back to Mastermind's idea that fuel puddling behind the throttle valve is causing a rich bog condition when the throttle is opened. If I understand the patent literature description correctly, the system can restrict the flow of fuel through the system, but it cannot add more fuel than the carburetor would put in if the autotune system was not there. In other words, they would set up the carburetor to be too rich and use the electronic controls to lean it out. That would be true at idle, transition and WOT, right? If that is the case, what would be the result if we introduced a deliberate air leak into a saw that is showing the bog? Would the bog get worse or get better? What I'm trying to drive towards is an absolute conclusive certainty of whether the transition bog is a lean condition bog or a rich condition bog. With the explanation of the TPS system, I'm not sure how it is participating.

I don't have enough information. The discussion upthread between Hamish and Mastermind about the TPS sensor/linkage slop seemed like a reasonable explanation.

 

[dbittle]

I agree with that. Hamish and MM both arrived at that conclusion. I'm not smart enough to understand how it is playing, but it is clear that it is. I guess my realization of the day was that to make a system run like AT runs, you have to make the baseline carb settings too rich, because the controls only can make it leaner. I do think it is important to nail down whether the system has a rich spike or a lean spike when the throttle is snapped open.

 

[Mastermind]

I'm reading along....

 

[Chris-PA]

Again, lacking first hand experience and parts to play with I really don't know much. It is not closed loop under acceleration, but I don't know things like if it has an accelerator pump. Still, it clearly must have a different routine for acceleration, and if the throttle plate opens and the system doesn't see it it's not going to respond properly.

 

[dbittle]

Again, lacking first hand experience and parts to play with I really don't know much. It is not closed loop under acceleration, but I don't know things like if it has an accelerator pump. Still, it clearly must have a different routine for acceleration, and if the throttle plate opens and the system doesn't see it it's not going to respond properly.

That may be how the TPS issues play into it, right there.

I want to pull on the thread a little more though. I don't have one of these saws either, so I'm just asking questions and trying to put the pieces together in my mind. My read of the patent references is that the electronics are always leaning out the mixture by restricting the flow of gasoline into the carburetor. It can't force gasoline into the carburetor, it is not an injector. The carburetor is set rich enough to cover substantial air leaks - we know that already. There is some kind of fuel map too, or target mixture map, or something like that, because without the map there is no need for a TPS. Tightening the TPS connection as suggested by Hamish may be a big step forward, along with improving the TPS signal quality as MM has been doing. I have to go put kids to bed, so good night all.

 

[one.man.band]

I agree with that. Hamish and MM both arrived at that conclusion. I'm not smart enough to understand how it is playing, but it is clear that it is. I guess my realization of the day was that to make a system run like AT runs, you have to make the baseline carb settings too rich, because the controls only can make it leaner. I do think it is important to nail down whether the system has a rich spike or a lean spike when the throttle is snapped open.

TK and mweba worked out a mechanical remedy for rich version of the bog/idle issue.
Brad's mechanical remedy was for the lean out issue. Terry Syd as well.
Mastermind found a electro/mech rich condition fix to adjust TPS.
Hamish explained how the TPS system interacts w/fuel curve.
tlandrum described electronic changes/similarities between these different versions of carbs.

good stuff guys.. ty.

cannot remember who stated that there were 10 or so updates to software?
don't know what the updates were, but i suspect that the updates
were changes to the way the TPS reading interacts with the fuel curve.

rich or lean?
your saw may have a chance of either, probably... depending on what update
version # of the software fuel curve your saw has, is my guess. and just a wild guess at that.
maybe some folks could shed some light on this.

lots of good information gets lost forever quickly on this site because of the way it goes
to page 6 of the chainsaw forum, buried under countless new posts. another, is the way posts are thrown
into a giant fish barrel. not going to do the legwork to find where, and what threads the good info above was posted,
but great info if you can find it.

 

[one.man.band]

The air velocity that matters is that passing the fuel outlet ports. When the throttle plate is closed those notches are far away from the main venturi and outlet, and the carb should be designed such that it does not create enough pressure drop to pull fuel from the main circuit.

The air passing around the edge of the throttle plate forms a venturi, with the idle outlets located there. Putting notches in it shifts the air flow around, and can be used to redirect air towards or away from outlets (including the idle transfer outlets at part throttle). Given how these are located it would appear they are placed to avoid the fuel ports. But regardless it should not activate the main.

agree that it's based on the where the location of the holes in the butterfly are located.

maybe we can agree on this:
if the hole(s), notches or whatever is/are located adjacent to the idle progession holes, more fuel is drawn from the idle circuit, but only when the butterfly is ator near idle position. if holes are located away from the idle circuit, opposite is true.

now the air, lots of vacuum through the idle circuit at idle, as the throttle plate opens, air velocity increases, at some point there is enough to get the main flowing. nothing new there. but when when the throttle is opened quickly from idle to wfo, there is a lag in pressure differential. ie. motor is at too low of an rpm to take advantage of wfo airflow. bog or hesitation. due to lean out or rich condition.

notches: holes located anywhere away from the progression holes promote air velocity. there is initially greater air velocity in the carb throat with the additional holes, at idle and part throttle. compare to the case where no additional holes were added. the additional holes help to increase the air velocity which in turn, flow the main sooner, thus changing the fuel curve mechanically.

at least that is my take on it. did many hours of testing on an non-electro carb over a few days using this idea many months ago. not going to rehash my posts from another forum, here too.

 

[blsnelling]

My 2260 was most definitely lean when coming down to idle from WOT, just like a lean L does. The hesitation from idle, I can't say for sure, but would assume it's a lean condition as well. The EL48 carb did wonders for it.

 

[gunrush128]

My 2260 was most definitely lean when coming down to idle from WOT, just like a lean L does. The hesitation from idle, I can't say for sure, but would assume it's a lean condition as well. The EL48 carb did wonders for it.

Did you ever find someone to upload the firmware for you, or did you just swap the electronics from the EL46? I called 2 dealers yesterday... The closest one doesn't have the programmer, and the other one(an hour away) gave me a big run-round. He says he needs the serial number from the saw, and part numbers from the flywheel and coil. He says they all need to be matched specifically to the carb.... Oh, and he says he'll charge me $80/hr to upload the firmware with a minimum charge of 1/2 hour, but thinks it'll take him longer than that. [emoji35]


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[tlandrum]

he needs the model and serial number from the saw, part number on the coil and the carb in hand to upload the info to the carb. ive done it in 5 minutes and its took as long as an hr to get it done. sometimes the job is really easy, sometimes not so much ,when the reader wont pick up the carb like it should or the download fails over and over.it can get aggravating to say the least.

 

[gunrush128]

I guess that makes sense, but paying $80 to plug it in seems crazy to me. Honestly, the hesitation on my saw is very minimal since I went through the reset process again (WOT in a log for 5 min). Sometimes it's not even there. I guess I must have OCD, I just like it to be perfect all the time. This saw is an animal with a sharp chain and 20" bar. I just don't like the fact that these little problems are out of my control. I miss my H-L screws!


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[DeckSetter]

Has anyone adapted a conventional carb to one of these? I'd be curious to see how a conventional well tuned carb ran compared to an auto tune saw.

 

[dbittle]

TK and mweba worked out a mechanical remedy for rich version of the bog/idle issue.
Brad's mechanical remedy was for the lean out issue. Terry Syd as well.
Mastermind found a electro/mech rich condition fix to adjust TPS.
Hamish explained how the TPS system interacts w/fuel curve.
tlandrum described electronic changes/similarities between these different versions of carbs.

good stuff guys.. ty.

cannot remember who stated that there were 10 or so updates to software?
don't know what the updates were, but i suspect that the updates
were changes to the way the TPS reading interacts with the fuel curve.

rich or lean?
your saw may have a chance of either, probably... depending on what update
version # of the software fuel curve your saw has, is my guess. and just a wild guess at that.
maybe some folks could shed some light on this.

lots of good information gets lost forever quickly on this site because of the way it goes
to page 6 of the chainsaw forum, buried under countless new posts. another, is the way posts are thrown
into a giant fish barrel. not going to do the legwork to find where, and what threads the good info above was posted,
but great info if you can find it.

I think that post sums it up pretty well. There have been several iterations of the carburetor hardware and software, which means that different version combinations have different hardware and software bugs that pop up during operation. That has probably contributed to the confusion about what fixes work and what the manifestations of the problems are. A fix that works on a combination with a lean bog doesn't work on one with a rich bog..... I think the TPS information was new though, and seems to be perhaps the dominant issue with the current (or fairly recent) saws.

 

[SierraMtns]

Brad,

Thanks for taking us a long your journey on building the 555. I had fun reading all 35 pages today at work.

But now I am so confused on what mods if any to do on my long bar 555...

I did perform a complete gut job on the muffler. It lowered the exhaust temps down to 210-214*F and seemed to wake her up.

Nick