Bigger sparks?

[Oliver Sedlacek]

My XFlow doesn't run on the EDIS-Megajolt as well as it did on points, and I suspect the spark isn't as strong as it needs to be.

I'm still using 0.6mm (24 thou) plug gaps, should I try something bigger or smaller?

Is there any difference between coil packs, and are they matched to the EDIS?

Any other ideas?

[Josh_b]

you really need to open the gaps up to 1mm - 1.2mm for a naturally aspirated motors

[flashrs1988]

I would say that 0.6 mm is way to small, using EDIS you get a much bigger spark at higher Rpm’s than with a conventional coil and dizzy, open the gap up to around about 1mm , seems to work well on my turbo setup,


Cheers.

Steve.

[Oliver Sedlacek]

I'll give it a go when I've fixed the noise spikes

[MartinM]

What noise spikes?

I'm intrigued - how do you know you've got them and how are you going to fix them?

[pipinhispop]

I am running EDIS on my 1600 xflow and using 1mm plug gaps. It pulls like a steam train compared to how it was on the points.

[Oliver Sedlacek]

When the coils discharge to produce the sparks you get some sharp current edges which the megajolt sometimes picks up on the PIP line. The runtime display then suddenly shows twice the RPM, and the timing is set appropriately, which may cause poor running. To give me more of an idea of what is happening, I coded a glitch detector into the megajolt firmware which ignores any pulse which would indicate an increase in RPM of over 33% between two sparks. When a glitch is detected the megajolt also lights a LED, so I can easily see the problem. I still don't know how I'm going to fix them though.

[MartinM]

Just got my (V3) MJLJ working fully this morning - but not until I sorted out the incredible noisy PIP signal...but noisy as in superimposed HF noise rather than false high/low transitions.

...which is very clean when the coils are disconnected, but very noisy with them in circuit.

It looks like a simple solution for V3 owners with this problem - well, it changed mine from 'ignition timing all over the place" to "ignition timing is rock solid" anyway

I just put a standard 0.1uF decoupling capacitor between pin 8 (PIP in) and pin 6 (ground) on the MAX-232 - much cleaner PIP signal, rock solid timing advance

Any thoughts Brent?

[SRandle]

Do you think putting a capacitor on the pip line going into the board on main connector will make any difference.

Or is it a new board update?

Have noticed sometimes when using a strobe light to check timings the unit drops the timing back to ten degress.

Steve.

[Oliver Sedlacek]

Not knowing the drive capabilty of the EDIS, I haven't tried anything as big as 0.1uF. As it works for you, I might give that a try. I moved the chassis connection of the external 12V decoupling capacitor from the coil pack mounting to the EDIS mounting which seemed to improve things....

[MartinM]

Oliver

I didn't class 0.1uF as particularly big - it's the standard decoupling capacitor for HF noise reduction used liberally in the MJLJ circuit. It rounds off the corners of the PIP signal a fraction, but it's really hard to tell even using a scope. It gets rid of the superimposed HF a treat though!

Steve

I just soldered the capacitor onto the solder pads underneath the board for pins 8 and 6. My capacitor wires are on a 5mm pitch, and pins 8 and 6 are 0.2" apart so it fits perfectly. Theory says the decoupling should be as close to the IC as possible - it would be difficult to get any closer!! I did put an IC holder on the board for my MAX-232 (I think the build examples have holders for all ICs except the MAX-232), so I just made sure it was taken out before I soldered teh capacitor in.

I certainly observed the timing jumping around a lot pre-fix - it really is rock steady now.

Total cost of solution less than £0.05 !

[SRandle]

Hi

Not sure if you miss understood my question but I am running on the version 2 board. There is no connection to the MAX232 chip.


Steve.

[MartinM]

I don't think I knew that!

There's quite a difference in PIP pre-processing between V2 and V3...

V2 has some 'clean-up' switching, mainly concerned with bringing the 12v PIP signal down to 5v logic so that it can be fed into the processor - using a transistor switch and a potential divider protected with a zener diode. No explicit HF filtering, but the transistor should provide that to some extent

...so no harm in trying the capacitor on the input connector I suppose - it shouldn't break anything (at you risk, obviously!).

V3 has nothing at all - PIP feeds straight into the MAX-232, which is quite happy processing 12v signals - except my capacitor mod that seems to solve my problems, anyway

[Oliver Sedlacek]

0.1 uF is standard decoupling for a supply rail, but it can clobber some signals, dependant on the driver design. If it works, that's fine. I didn't know the V3 uses the MAX232 as a level shifter, which is certainly quite a smart idea.

[strikermk2]

Hi. I'm attampting to install a megajolt on my 1700 x-flow. Do i need to change the spark plugs to a different type than used with the distributor. If so any idea what type??
Thanks Bryan