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So close but yet so far!


mikec

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Using the minus ten setting will make it follow the intended ignition map. If your base timing is correct (I.e it idles at a physically confirmed 10 btdc if you were to set the entire table to 10's) then you will be seeing *squints at phone* around 10-12 degrees advance at idle from the picture above. This should be fine, but you must confirm your base timing is OK with a "dumb" timing light. I have a bit more, as I adjusted timing to get max rpm/lowest map and then backed it off a few degrees.

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Sorry ignore the above! Just realised you said Trim angle!

So if you set fixed angle to 10, and then have your trim angle set as you do, what do you see with a timing light?

Fixed angle is set as -10, trim angle also at -10 it shows no.1 firing around tdc. It's blooming hard to see exactly because the timing pointer is obscured by the ps pump!

With the fixed angle set at -10 and trim angle at 0 it shows no.1 firing at roughly 10 btdc

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Trim angle only affects the spark map values, it does NOT affect fixed values. To get the timing/trim correctly set I set my spark map to all 10's, then adjusted the trim angle until it was showing 10deg advance with the timing light. Get that right before you do ANY other fiddling or start to think about tuning.

To run from the spark map set "fixed angle" to -10. Your timing should then be whatever is in the box on the spark map the engine is running in, highlighted by Megatune when it's running, in your screenshot it's the top left box as (presumably) your engine is not running.

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Trim angle only affects the spark map values, it does NOT affect fixed values. To get the timing/trim correctly set I set my spark map to all 10's, then adjusted the trim angle until it was showing 10deg advance with the timing light. Get that right before you do ANY other fiddling or start to think about tuning.

To run from the spark map set "fixed angle" to -10. Your timing should then be whatever is in the box on the spark map the engine is running in, highlighted by Megatune when it's running, in your screenshot it's the top left box as (presumably) your engine is not running.

So in the screen shot above I change every box to 10, then I put the timing light on no1, and adjust the value in the trim angle box until I see 10btdc on the pulley. Is that correct or have I misunderstood. How is the rest of the spark map changed then? Is that changed when I start tuning? Here was me thinking I was nearly there :0

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So in the screen shot above I change every box to 10, then I put the timing light on no1, and adjust the value in the trim angle box until I see 10btdc on the pulley.

Correct. Before you do that, save your spark map (File->Table Export) you'll see why in a sec...

How is the rest of the spark map changed then? Is that changed when I start tuning? Here was me thinking I was nearly there :0

Once you have your trim value correct, you can put the proper spark map back in (File->Table Import ... told you you'd see why!) then you can tweak it from there. BUT, if Nige has done you a map I would be inclined to leave it alone unless you're really sure you know all about ignition tuning and the risks of getting it wrong. What Nige provides should be plenty good enough.

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Mike,

You over complicating fings again chap :D:lol:

OK

What you ate trying to do is to check your timing is "Spot On" ?? Yes ?

If so then .....

The trigger wheel is set up with say 1 .5-1.0mm gap.

The trigger wheelis bolted in place

The engine runs

What you need to do is check what the ENGINE actual Timing is with the trigger wheel VS what Megatune is saying

In other words, Megatune my have the engine tick over is a cell saying 13 degress,

BUT

The actual engine timing is 5 degrees, as the Trigger wheel in this instance is set wrong.

You have 2 x choices

Alter the trigger wheel

Each "tooth" on the trigger wheel is roughly speaking 10 degrees, the middle of a tooth is thus 5 degress,

so, you COULD lossen and turn the TW on the slots to get it more where it should be, ie in this instance the MT says 13

and the engine is 5, that -8 degrees out or 8/10 of a tooth to be moved.

This way is best, piddling about with the trigger wheel so that MT and the timing light BOTH MATCH means the system is set up properly

You do NOT need to change the entire Spark map to do this,

You will find that Tickover will be in prob no more than say 9-12 cells, just set ALL those cells to 10 degrees, and check No 1 Light with Strobe

fiddle with TW until BOTH match, then reset the cells changed to 10 back to where they should be.

The other way is quicker but a Bit of a bodge.

In the instance above change Spark>spark setting>Trim to -8

DO NOT take -10 out of the Fixed angle setting, or change any other settings, you'll just screw it up royally as fridge says !

NOW the SOFTWARE compensates for the TW being wrong, it will simply deduct -6 from ALL 144 Spark cells, so that whatever

spark in fires is -6 cos the TW is -6 out so it makes it "Correct".

However this way the spark angle guage will ALWAYS read wrong

Hope this helps

Nige

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Gonna have a go at this again today, think the problem is when I originally checked the timing on the pulley, I just checked it was about 10btdc thinking that the fixed angle figure (-10) was the one I should be checking against. Rather than the actually timing figure the engine is running in the spark table. Gonna try the bodge method for now, hopefully it sorts the hunting out. Cheers mike

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  • 2 weeks later...

Ok been trying the timing etc, ms and the actual pulley timing seem pretty much the same. Can't tell exactly as its impossible to see the pointer exactly because of the ps pump.

Anyway I need to sort out the hunting, not that it probably matters but it only does it when it's warm.

So next question is what exactly is the rear bank O2 voltage guage measuring? Can't seem to find an answer on the web, but I'm wondering if whatever this measures is contributing to the hunting.

I took a vid of the gauges at idle

http://i49.photobucket.com/albums/f257/little_landy/0826E708-3440-4CAB-A265-A928578DC46D-8858-00000AE0762402AD.mp4

It's might not be easy to tell on the video but the O2 voltage guage reacts exactly the same as the engine noise.

Any ideas ? Cheers mike

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Ok hopefully may have sorted the hunting, although I have thought it solved before but wasn't :0

Anyway quagmire suggested I alter the ve table at idle hers the old table

2D9C6481-1CA0-4C30-BF7E-64CC9262FFDD-822

And the new

AAEF46EF-E7C0-44A7-8A7B-48D6AE45B5A5-822

You can see where I changed the four cells to 56.

Hopefully this fixes the issue (everything crossed!)

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Er

Wtf is that be table - that's not anything of mine

Fuelling is all over the place ????

N

Exactly why I asked what required fuel is, in this case I shall refer you to the Megamanual, you really should read it, and evidently have not.

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Er

Wtf is that be table - that's not anything of mine

Fuelling is all over the place ????

N

I've not had much choice other than go out and try tuning it hoping its sort the idle. But at the minute it idles better than it did using the map you sent me.

The required fuel value I'd imagine would be whatever it was in the map you sent me, unless tuning ms allows it to change it.

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As a starter try to make all the values in the VE table 600-1000 rpm 20-50 Kpa the same. About 40 should do it.

Sort of did that but over a smaller range, changed them to 56, but just the cells that were lighting up when it was idling. It seemed to work, that day it worked and the next day it worked, but then a week later its started doing it again. I can't help but think its something really silly and simple, but really struggling for ideas.

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Hunting can be a number of things, it's like an unstable PID loop where some factor is causing the system to oscillate... wait, come back, don't fall asleep!

The basic idea of setting your idle is to slope the fuel map down to the bottom left corner slightly; so if the revs drop, it goes slightly leaner, which causes the revs to pick up slightly. Likewise, if the MAP drops (load) it leans slightly and picks the revs up a bit. Get it right and it will act as self-correcting and idle smoothly - but get it too far either way (too flat or too slopey) and it will hunt.

There are similar things you can do with the ignition map but for now let's not complicate things.

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