Trigger Offset: is it persistent, cumulative-I can't read it

[Jeffs_Alpine]

Hey all,

I'm hoping to get a bit of insight into how the trigger offset works. I've got my mj working on my Alpine but the Lucas disty still works better, so I still have a little ways to go.

I'm thinking that the trigger wheel may not be precisely tdc and that the 'trigger offset' might be worth twiddling with. When I 'Read options', it comes back zero. If I set it to any value between -5 and +5 and write options, it appears to do something, but when I perform a subsequent 'Read options', it again comes back zero.

So where does this value go and does it get overwritten or summed if I perform multiple write options? I've looked through the advanced memory list but I'm not sure I know what I'm looking at.

And finally, what happens if I have a value greater or less than +5 or -5 respectively?

Thanks!

Jeff

[Jeffs_Alpine]

Is anyone using the Trigger Offset?

[brentp]

Hi Jeff,

When you connect your computer to a freshly power-cycled Megajolt, go into "Global Controller Options", and click "Read Options", what values show in the various items in the dialog box (Cylinders, cranking advance, trigger wheel offset, EDIS PIP filter level)

To answer your specific question, it is supposed to retain the value, yes- and is what one would expect- a absolute correction value for slight misalignment of trigger wheels.

To confirm- when you change a value, you definitely need to click "Write Options" to send the values back (not 100% sure if you're doing this based on how I read your post, apologies in advance) The global controller options reads/writes directly to controller flash- it's not part of the "Ignition Config" held in RAM during normal operation.

Before, you were having general issues communicating with the unit. Generally speaking, are you able to read, write and flash Ignition Configs now? What did you do to resolve that problem?

[Jeffs_Alpine]

Hi Brent,

My apologies for my poorly written post earlier today.

Yes, I believe I am communicating with the MJ - thanks to you and your help.

When I connect to the MJ and start the car, it runs, but runs rather badly. I'm using the default timing file as a starting place. My operating premise is that no matter how hard I tried to align the hall sensor to the correct tooth, that it would be off some amount - hence the badly running engine. (should the sensor be aligned to the leading edge of the tooth, center, or trailing edge?)

But with it running, I can see the vacuum (KPa gauge) bouncing around, which I believe confirms that the the MJ is communicating with the laptop.

To answer your question - "... what values show in the various items in the dialog box":

Cylinders = 4
cranking advance = 0
trigger wheel offset = 12
EDIS PIP filter level = 10

Now, in this state, I select the 'Global Controller Options' menu and then the 'Trigger Offset' value is zero. I'll change the value in the text field to 5, then press 'Write options' button, then re-press the 'Read options' button and the field is zero.

I assume that it should retain the value I enter into the 'cranking advance'? And for my original question, is +5 and -5 the max values?

Thanks Brent!

Jeff

[brentp]

Yes, it should definitely retain the value If you change one of the values, say cranking advance to 11 degrees, or trigger wheel offset to something else, like -2 degrees, and then click "write options" it should retain that value.

Try:
1) "Read Options"
2) Changing a value
3) "write options"
4) Power cycle controller
5) "Read Options"
6) Verify correct values

yes, the trigger offset range is +/- 5 degrees.


For sensor alignment, it should be aligned to the center of the tooth. Slight misalignment is not a big deal for how well the engine runs- it simply skews the base timing off by that small amount- it should still run smoothly. By the way, what does "badly" mean? does it mis-fire? does it run unevenly? how does the engine run with the Megajolt disconnected, with the EDIS module in "limp home mode"? It should run *smoothly*, but down on power (of course).

[Jeffs_Alpine]

Brent, I followed, last night, the steps you outlined below and could not get the values to be persistence. But I'm now seeing (self-healing?) them working fine.

My conclusion: I suspect that I was performing some voodoo inspired tuning adjustments making it appear that my changes were not sticking, when in fact they were. Sorry for the drill.

Now for the engine running bad - it ran, but just badly. It ran well enough seemed close enough so I the tooth count and the sensor/missing tooth positioning and sure enough, it was off by a tooth. Silly me.

So the good news is, that the MJ now works as well as the Prince of Darkness (Lucas) (woo-hoo). I'm very optimistic that within the days ahead we'll be experiencing a whole new domain of precision and tuning quality unseen by at least me on this machine.

(please excuse my writing tonight. I had a tooth extracted this afternoon (mj solution coincidence?) and they gave me something which is causing me to feel just a little floaty. )

So now I just need to find or craft a timing file for a 67 Sunbeam Alpine with dual Weber dcoe 40s and an aggressive cam. I've looked throughout the board and didn't see one, but if you happen to recall such a timing file, and could point me in teh general direction, that would be super!

Thanks! Jeff