Thanks......

That said there's a 99% chance the sensor is not the problem. That's how Murphy works around here. Removing the epoxied sensor is not hard enough to have been the problem, getting a replacement CDI box from Taiwan is much more difficult. They'll probably want a video for proof and delay the return process. That would be more in alignment with my luck.

I've delayed replacing a radiator cap on my auto for fear the tranny would immediately stop working.

maybe he can redesign his bracket to use a zip tie instead of epoxy

Then it wouldn't look professional and pretty. It is a nice looking cnc'd piece.

BTW, using CDI ignitions for 6 or so years now I have never had a CDI module or hall sensor fail. I have received preowned engines with non functioning modules and sensors, just have never had one of mine go poopoo on me.

Dave, Do you use the RCExl tach output for an RPM feed into OpenXsensor? I seem to be having trouble with getting a good signal there - Its very noisy (high frequency). If I Play with the scope settings I can see the pulse for the ignition but lots of noise on top of it.. Is a filter required?

Im was assuming the signal is an +5v / 0V situation like the Trigger Hall but it seems to be A weak (low voltage/current?) signal. Should be signal to pin 8 and ground to ground correct...

Strange... I get a pretty good readout from the tach output with the FrSky temp/rpm board, and that board is not even made for use in combination with ignitions (it is ingended for brushless electrics).
Meaning, the signal is probably OK, because plenty people use that set-up.
https://www.rcgroups.com/forums/show...1&postcount=18

I've never looked at it on one of my oscilloscopes because it always works. I just run only the signal wire from the ignition directly to (I think) pin 8 on the nano. I do not attach the ground on the rpm wire when using an rcexl ignition kill switch (which is always) as I'd prevents the kill switch from working.

The new hall sensor didn't help.

I think the auto advance is not working correctly, the fuel mixture demands are changing as throttle is reduced, needing a richer and richer mixture from 4000 on down to idle. Attempts to adjust the mixture for idle result in a waaaay overly rich midrange, causing a cylinder to flood and drop out.

Spend more money time!

On a side note: I spoke to Adrian at CH today, he said that the Rcexl ignitions sold for the last 5 years or so have just as hot of spark as the CH ones. The only difference is a slight change in the timing curves between them. Even that, he said, is unnoticeable to all except the most discerning ear.

Likely there is almost no current flowing so any external noise has a relative big influence.
If you place a resistor between the pulse and ground then that resistor will "short" the noise but not the signal.
The sensor is designed to be able to give a current high enough to still have a good output pulse.

more theory and how to choose resistor value

I found my issue and its a Goodie !! Its Almost a Lonnie one.....

The ignition box I was testing with has an issue with the tach lead - it produced an odd low voltage noisy signal. - I changed ignition boxes and all of a sudden the RPM readout worked. It does need a small cap to filter some of the noise (power supply?) out to prevent a bouncing reading but on the scope it has a very normal looking pulse - Will look into it further but its an old ignition and i'm not sure if it might have been previously mistreated..

Anyways - A successful trip down the OpenX Rabbit hole and we will have telemetry from the boxer when it runs..

EDIT: sorry - testing was early this morning and I forgot that it was connecting the ground that solved the issue not a cap ... I am assuming if you use a Cutoff switch the ground gets through to the radio (and OpenX) via the cutoff when its set to run. I had to connect the ground to get a normal reading.

Which ignition cutoff board are you using?

The Rcexl Kill switch switches the ground connection to the battery. When you install an Arduino, it provides another ground path via the rpm ground. As a result, the kill switch is bypassed through the Arduino. An opto-isolator would solve the issue but removing the ground from the rpm plug works too as the kill switch provides the needed ground reference when the ignition is enabled. Of course, when the ignition is disabled, the RPM is zero.

Important info: I mod my kill switches to use one battery. If you don't your ignition will not be tied to the radio's ground so you will still need the rpm signal ground connected.

In the Bold ... I would hope so, otherwise you have a very unique ignition system.

How is it getting a multi path to ground, from the KS ign BEC modification, or from the arduino.

I use a RCexl kill switch setup so the ign has its own battery... the kill switch is opti-isolated from the receiver... signal wire controls ign arm / disarm... how I know is I have the kill switch receiver lead plugged into the output channel of the servo buss ( kill switch channel ), and the servo buss only has the signal wires coming from each of the receiver channels and plugged into the channel inputs of the servo buss, the servo buss has its own battery separate from the receiver, and ignition.

Just bench testing Lonnie and no ignition cut-off used yet and I discovered (the harder way) that I needed to have the ground hooked up - After I did- I re-read Dave and Bert's commentary on the kill switch item and deduced it does get a ground from a "turned on" kill switch.

Grounds through the ign power source not through the receiver unless you have done the BEC mod... with the STD setup using a dedicated ign battery the receiver powers the kill switch logic, and the kill switch then switches the ground of the ign power source.

Well guys... Shop night watching my football team suffer a loss.... but I got the Boxer on the stand. Couldn't resist the urge to "light her up" and I think "all is going to be wonderful".

Just idle and not on a curve yet - Just a quick study on where the jet seems to be - Idle is right at the bottom of the pulse range so it might need a bleed but will wait until I see where the jet is at for the top end.

Didn't throttle up to preserve neighbourhood peace as it was 11pm... in the video I add little throttle at the end and play with the mixture which responds very crisply to changes.. it will sustain a 1000 rpm idle when set a little rich...

Might start tuning tomorrow...It sure makes a pretty sound

Whoo hoo! That sure sounds healthy!

Keep a bit of margin above the 1000 RPM idle, because to the best of my knowledge, below 1000 RPM the retardation curve ends and the timing falls back to "set angle" AKA 28 deg BTDC.

You won't notice much in a change in running behaviour, but the early ignition will hammer the rods a bit, and due to the low RPM there is not much hydrodynamic pressure in the big ends.

I have never tested to destruction so I can't say for sure if it will do harm, but my gutfeeling says to keep RPM above 1000 (I run between 1200 and 1400).
It also is pointless to go that low, the APC 18 x 6W allready becomes a very effective airbrake below 2K

But the stability of the idle shown, is exemplary! Kudos!

Thanks for the tip Bert, didn't know this. I think I can hear this happen and its as the reading drops below 1000 on my tach - sound changes like its ignition related and the idle falters a bit.

Another thing I noticed as I tend lean I can hear an odd little exhaust "popping echo" sound. Is this common and is it a lean indication. I looked back at your boxer running on you tube and don't hear it but your probably set on the curve. Listen as I lean to shut off at the end and you can hear it well.. I can get it to make this sound when running and just wonder if its a good lean indication.

I also noticed you run mufflers - What are they off of?

Chris, does that popping sound like poyt, poyt, poyt. If it does you're very close to a perfect mixture at idle but slightly on the rich side, at least when running methanol. Not sure about gas yet. Anyway, the poyt sound is much more prevalent using straight header pipes than when using mufflers.

well done, once again, chris. looks like you have a winner there.

Engine sounds good Cat... that wet hollow plop, plop sound at idle is the valve over lap, when the valves open there is pressure released across the exhaust / intake... like putting your finger in your mouth and quickly popping your finger out one side, you get that wet pop sound.... it happens when the exhaust pressure pops back across the intake... when the exhaust gas flow velocity increases, scavenging pulls fresh fuel across the overlap from the intake, and you get a pressure wave that bounces back and forth across the overlap, and you hear that plop, plop, plopplop plop. sound in the exhaust headers.

In regards to the ignition timing reverting to the "base timing" full advance below 1000rpm, I have not experienced that with CH ign... there is a start rpm argument that initiates spark between 150-200 rpm for startup, and once the engine is running, its on the ign map curve... I know with the early rcxel ign sys you can turn the engine over very slowly, and you will get a spark to occur.

When Idle drops below 1000, on mine I start hearing the camgears chatter a bit.

As John said, the wet popping sound is not becaue of lean or rich, it is because the valves are timed for higher RPM, so the exhaust stays open a bit too long at idle. This causes the pressure in the exhaust to reverse when the piston starts going down but the exhaust valve is still open. A richer mixture camouflages it a bit because of the afterburning going on in the muffler or header.

The mufflers that I use are JustEngine "baffled mufflers", externally a direct copy of the original OS FS91 Surpass muffler, but they make them with a baffle, which changes the soundcharacteristics very slight but noticable. People say they can hear my engines run on gas because they sound different than glow fourstrokes, but I think it is the baffled mufflers that I use on all of them.

I think, JustEngines still makes them if you order them, but in all fairness, I think with your machining skills you can make them cheaper yourself.
You will need 90 degree knuckles though.

The way it was explained to me, the "poyt" sound at idle is caused at the instant the intake valve opens during the valve overlap period and can be heard through the exhaust. Just like with the popping noise one can make with their finger/mouth it requires a sudden change in pressure. It takes a valve opening with a lower pressure on one side than the other to create that popping sound. Keeping in mind that the velocity of the exhaust gasses leaving cylinder does create a lower than atmospheric pressure in the cylinder just before the intake valve opens makes sense, otherwise exhaust scavenging wouldn't work at all.

In addition, the richer the mixture, the wetter the intake valve, the more frequent the popping sound will occur.

Anyway, that's what I've heard, so please don't throw fireballs at me.

When idling, the pressures and velocities involved with the scavenging period of a fourstroke are pretty low. At the time the intake opens (begins to open, to be more precise), at idle the exhaust period is almost ending, and because of low combustion pressure and low RPM (longer duration or the same upward piston movement) the pressure in the cylinder at the moment of opening of the intake valve is basicallly equal on both sides. So not much going on there.
Because of the low combustion pressure and the slow piston movement, there is not much velocity in the exhaust gas either. So very little inertia.
So the intake opens, and basically "nothing" happens.
Now the piston passes TDC, and begins its downward movement, Both valves are open at this moment. The piston begins to draw in gas, through both valves. BUT.... the throttle is closed to idle position so the intake offers great resistance, and the gas that can flow in easiest is that from the exhaust. So there, the flow reverses. Then the exhaust valve closes, and the inrushing gas "bounces" against the closed exhaust valve.
The "poyt" sound is the reversal of the gas in the muffler followed by the bounce of the pressure wave when the valve closes.

When the engine picks up speed because the throttle is opened, there will be more velocity in the exhaust port and because the restriction in the intake tract is gone, the gasflow will be unidirectional as long as the exhaustvalve is open, There is no more reversal of gasflow after TDC, no more bouncing of the pressure wave against the closing exhaust valve, and the "poyt" sound dissapears.

That is how I can figure things out if I play the movie of the process in extreme slo-mo in my head.