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.
Misc: Everything Else Air Fuel Gauge 02 Sensor Lambda Sensor
- Thread starter Cyborg
- Start date
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.
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?
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
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
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.
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.
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.
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.