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Misc: Everything Else Air Fuel Gauge 02 Sensor Lambda Sensor


Magnetoman

Well Known and Active Website User
VOC Member
I have a Mikuni Flat Slide
Oh, that's right. I'd forgotten. A Mikuni is essentially the same as fuel injection so I'm pretty sure all you need to do is hold your AFM near it -- it doesn't even have to be plugged in -- and from then on the mixture will be perfect.
 

Cyborg

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VOC Member
Actually one of my fears is the thought of you riding down the street with your engine ticking over every second lamppost in a UHCs free euphoria while I'm linishing away in my dingy basement because of this flat side's limited choice of needles.
 

Mike 40M

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VOC Member
All very interesting. Decided I'll try myself. I understand that the sensor should not be to close to the exhaust port, but how far away can it be? I would love some pictures on how you have fitted the sensor. What works and what don't. Has anyone of you ever measured temperatures in the exhaust?
 

vibrac

Well Known and Active Website User
VOC Member
Yes the ECU world is a different place watching Ben with his vmcc eligible brick adding 500 rpm for snetterton or richening up because of the weather is a revelation.
We just used the lamba on the racing comet in the bung on the side of the curve of the exhaust pipe when on the Dyno because the probe stick up the silencer was a bit too inaccurate. On the track it just has a m8 bolt up it
 

Cyborg

Well Known and Active Website User
VOC Member
Oh, that's right. I'd forgotten. A Mikuni is essentially the same as fuel injection so I'm pretty sure all you need to do is hold your AFM near it -- it doesn't even have to be plugged in -- and from then on the mixture will be perfect.
Actually I think a Keihin CV is a step closer than my flat slide, but I'm not having one of those on a cranky old Comet with MK2 cams from heavens knows where. The slide would be acting like a cornered rat.

So...kind sir... when you change a pilot jet... what does your data tell you with regards to throttle opening/AFR? I have found that in some cases (different brand than yours) a pilot jet seems to have an effect well beyond what is considered normal. Yes it obviously has less of an effect as throttle opening increases, but still seems to come into play.

More on the "only one thing at a time rule" I have the same mantra when trouble shooting because it has its obvious advantages... so unless its a situation where it takes hours upon hours to get to the source, I wouldn't ever be inclined to consider just throwing parts at something. However... with your ability to record the data, I could see you being able to do more than one change at a time. As in whats to stop you from swapping a pilot and a main at the same time for example if you can read exactly whats going on and compare history.
 

Magnetoman

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VOC Member
So...kind sir... when you change a pilot jet... what does your data tell you with regards to throttle opening/AFR? I have found that in some cases (different brand than yours) a pilot jet seems to have an effect well beyond what is considered normal. Yes it obviously has less of an effect as throttle opening increases, but still seems to come into play.
Stop me if I've already mentioned this...

I spent some time last month messing with carburetors on my flow bench motivated by wanting to understand the effect the shape of the spray tube has on the pressure difference that pulls fuel into the airstream. It turns out an Amal Concentric intended for 2-strokes has a different shape spray tube, which is well known, but also a hidden restriction inside the compensating air passage that I've never seen written about before. However, hoping to make a very long story short, concentrate on the blue/red dashed curve and the purple 'pilot circuit' curve.

As can be seen, at 5 CFM (~1/8 throttle) the depression over the pilot jet is 3.06x greater than that over the needle jet. A #25 pilot jet has diameter 0.0175" for an area of 2.40x10-4 sq.in. The annular area of a 0.1065" needle jet with a 0.0984" needle is 13.0x10-4 sq.in., which is 5.4x greater. What this means is that at ~1/8 throttle, where Amal's simplified tuning description says the pilot jet is only just losing its influence, already the main circuit is supplying 5.4x/3.06x = ~1.75x more fuel than the pilot circuit.

At larger flows the depression in the pilot circuit saturates at ~0.150 psi whereas that of the spray tube of a 2-stroke body (dashed blue/red curve) continues increases to 0.340 psi at full throttle. Further, by that point the needle is essentially out of the needle jet and flow out the spray tube is determined by the main jet. Assuming a #300 main jet (dia. 0.059"; area =27.3 x10-4 sq.in) the relative flow of fuel through the spray tube will be greater than through the pilot circuit by (27.3 x10-4 / 2.40 x10-4) x (0.340 psi / 0.140 psi) = 27.7x. That's a pretty large factor, but it shows the pilot circuit is still responsible for nearly 4% of the fuel supply even at full throttle. For comparison, in the range where the taper matters, moving the needle by one slot in a Mikuni change the mixture by 4.5%, which indicates even at full throttle the ~4% effect of the pilot circuit isn't completely negligible.

Pilot04.jpg
 

Cyborg

Well Known and Active Website User
VOC Member
Nice to know I'm not completely mad after all. Thank you for that. I'm starting to get the urge to drag that T/A sensor out from under the bench so it would appear that you have spawned some sort of desire for more data.
 
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Magnetoman

Well Known and Active Website User
VOC Member
some sort of desire for more data. ... see if I can prevent it from getting out of hand.
I have three empty inputs for my data logger so I easily could add an exhaust temperature sensor. However, I've resisted the urge because it would give me an additional curve that went up and down in some fashion but, unlike AFR, the data wouldn't be "actionable." The AFR tells me to turn a screw to the left, drop the needle a notch, or whatever, but the exhaust temperature is just a much less sensitive way of telling me it's too rich or too lean so I can't think of any reason to have that data in addition to AFR.

Like Goldilocks, for the task at hand there can be too little data (the usual case), too much data (not often the case, but certainly possible), or just the right amount of data.
 

Cyborg

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VOC Member
I'd like to install a ETS just so I'd know how close I could get to the exhaust port without exceeding the 800 C. Did your voltmeter arrive yet and have you had a chance to connect to your LM-1's analog output?
 
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Magnetoman

Well Known and Active Website User
VOC Member
Did your voltmeter arrive yet and have you had a chance to connect to your LM-1's analog output?
It's all installed and ready to go. Unfortunately, my Chief Mechanic screwed up when he installed the magneto's pinion and the timing slipped. I've had words with him and I can safely say he was every bit as chagrinned by this turn of events as I was. It took swapping a 1038 Concentric for the 1036 to re-corroborate for the Nth time the axiom that 90% of carburetor problems are electrical.

Anyway, the bike is on the lift waiting for me to reset the timing. I won't have time to do this tomorrow but hope to on Saturday.
 

JustPlainBill0

Website User
Non-VOC Member
Welcome to the forum and welcome to this thread.

As mentioned previously in this thread, my instructions also say to mount the bung at least 18" from the port, but it goes on to say "if you expect EGT over 800 C". I'm still thinking that less than 18 is ok if Ducati can do it. Farther from the tail pipe would be good in my case because I'm using a relatively short reverse cone setup.

Can't say I'm in the mood to buy another (EGT) gauge after my recent fiasco with "Smiths" or should I say "the Smiths"..as in plural.
You probably don't want to drill a lot of holes in your exhaust header, but maybe you could take a length of 1 5/8" OD x 18" exhaust pipe (straight if possible, or with a bend if needed) to use as a stationary EGT testing pipe. You will have to buy an EGT meter (as cheap as $17 US on eBay) for measurement. If you don't weld, make a series of shallow cuts to form tabs around the end of the pipe fitting into the head. Bend the tabs outward to make a shallow flange for the exhaust nut. When you have the flange fitting into the exhaust port and secured with the nut, start from the furthest away part of the tube, drill a hole for the EGT probe, determine exhaust temp there, and continue the process, making new holes a few inches apart and higher each time until you get a reading of 800 C (1472* F) or higher. You can position your O2 sensor below that point on your actual exhaust header.
 

stu spalding

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VOC Member
If your silencer is shy of baffles, what's to prevent pushing a piece of small bore copper tube up the exhaust pipe to the required spot and sticking sensors on the outer end. Just a thought. Cheers, Stu.
 

Cyborg

Well Known and Active Website User
VOC Member
If your silencer is shy of baffles, what's to prevent pushing a piece of small bore copper tube up the exhaust pipe to the required spot and sticking sensors on the outer end. Just a thought. Cheers, Stu.
That is a thought. For now I'm using a reverse cone contraption. It does have a baffle blocking the way, but its removable or I don't mind modifying it so a probe could be slid through it (not much of a baffle). I really need to find a used Comet pipe so I don't turn mine into an ugly looking mess since I'm starting from scratch. Bit of a catch 22 wanting to use the A/F gauge to get me into the ballpark, but also wanting an EGT reading to locate the bung. If my fuel mixture is way off, then presumably EGT would be off as well. The gauge will only be on the bike to sort the jetting, so I could try going the bunsen valve route. If Magnetoman needed to invent one for his Gold Star, then with my shorter muffler, I'm even more likely to experience reversion.

Anyone in the Vancouver section have a Comet pipe that they can part with?
 

genedn

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VOC Member
That is a thought. For now I'm using a reverse cone contraption. It does have a baffle blocking the way, but its removable or I don't mind modifying it so a probe could be slid through it (not much of a baffle). I really need to find a used Comet pipe so I don't turn mine into an ugly looking mess since I'm starting from scratch. Bit of a catch 22 wanting to use the A/F gauge to get me into the ballpark, but also wanting an EGT reading to locate the bung. If my fuel mixture is way off, then presumably EGT would be off as well. The gauge will only be on the bike to sort the jetting, so I could try going the bunsen valve route. If Magnetoman needed to invent one for his Gold Star, then with my shorter muffler, I'm even more likely to experience reversion.

Anyone in the Vancouver section have a Comet pipe that they can part with?
Where on Pender is your cabin? My cabin is at hope bay, we are on port washington rd.

Ill take a look for a pipe. I might have one. I have put 7K miles on my comet since Robert and I played with the sniffer. The carb settings seem to be fine and could probably be checked again.

John McDougall had the bungs welded into the exhaust on his shadow and had a sensor on his handles to indicate the ratio. Someone might know how far down the pipes they were welded or have a photo that would give a sense of where they were located.
 

stu spalding

Well Known and Active Website User
VOC Member
Or even a length of the spiral wound metal covering that shower unit makers use, after the liner has been removed. It might even be possible to attach a length of piano wire to one side of the end that's up the exhaust and persuade it to go up the rear downpipe. Just a thought. Cheers, Stu.
If your silencer is shy of baffles, what's to prevent pushing a piece of small bore copper tube up the exhaust pipe to the required spot and sticking sensors on the outer end. Just a thought. Cheers, Stu.
 

Cyborg

Well Known and Active Website User
VOC Member
My cabin is attached to an old wood boat floating in Otter Bay. They call it Otter Bay for a reason and they love using my boat. At times it more closely resembles an outhouse or the movie set from Animal House after the food fight.

Even a knackered front pipe from a twin would do. With TIG brazing I could nurse some bungs into it and cap off the rear cylinder bit even if its a tad rusty.

I never had the pleasure of meeting John, but recall seeing a Shadow at the Tsawwassen Swap Meet with the O2 sensors.

When discussing location of the sensor bung, it was Magnetoman (over on Oldhaven's kickstart ignition advance thread) that said he needed a bunsen valve to keep air from finding its way back up the exhaust and wreaking havoc with the sender. That should have dawned on me because when assembling an exhaust system for the aforementioned boat you have to account for the possibility of reversion. More important because it can draw water back through the exhaust manifold and down into the exhaust port.

Here are two links that have to do with exhaust. WARNING both contain content that you may find disturbing.

The first has to do with anti reversion cones installed in the pipe at the exhaust port. Its not a glowing review, http://www.nrhsperformance.com/tech_arcones.shtml

The second has to do with drag pipes, but has some interesting bits mixed in about reversion and it does show dyno runs.


Maybe Magnetoman could put a thumbscrew in his tailpipe and go for a ride without the bunsen valve and see what the A/F sender has to say about that?
 

Cyborg

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VOC Member
Those are close to the port. Did he just leave them in there?
 

MSVH Y3

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VOC Member
John put these on and left them on. I have no Idea if he intended to remove them but they were on his bike for a few years. These pictures were taken at the NA Rally at the Gorge in 2013.
 

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