Author Topic: Question about shifting ignition order  (Read 310 times)

Offline nmerrill

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Question about shifting ignition order
« on: February 23, 2019, 10:14:42 pm »
5 cylinder, VAG Hall 60-2 trigger, and distributor secondary.
TDC after trigger set to 78, corresponding with Hall at tooth 13.

Timing light fires on cylinder #4 TDC (marks on crank pulley)

Since I only have a single ignition output (Pin 35) I can't shift the ignition order in the ignition outputs visual window, correct?
So, the way to adjust the ignition order would be to shift the trigger reference tooth table order, correct?

Or, could this be done by adjusting the FTT in the primary trigger visual?


Offline nmerrill

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Re: Question about shifting ignition order
« Reply #1 on: February 24, 2019, 07:18:29 am »
Well, now I'm stumped.
I shifted the reference tooth table three different times, maintaining the order, but shifting the locations
0, 24, 48, 72, 96
24, 48, 72, 96, 0
96, 0, 24, 48, 72  etc.

The timing light still flashes at #4 TDC - no change.  I don't understand this!

Rotating in the ignition visual makes no change either, as it shouldn't.

Shifting FTT moves timing of light flash as expected.  This isn't an option for this problem though.

So, how do I change ignition timing order?

Offline nmerrill

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Re: Question about shifting ignition order
« Reply #2 on: February 24, 2019, 08:59:37 pm »
Actually, adjusting FTT *was* able to correct this.
I shifted FTT to 12, adding 72 deg. of rotation, and timing light now flashes correctly on #1 TDC with ignition lock on 0.25 deg.
Left TDC after TT the same = 78.

Not sure if there is another way to approach this.
I'm still not sure why shifting the trigger reference table does not affect the firing location.

Offline nmerrill

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Re: Question about shifting ignition order
« Reply #3 on: April 14, 2019, 04:51:47 am »
Seems mighty quiet around here... If anyone is listening, I'd appreciate an explanation of this!

As mentioned above, the only way I could make the ecu trigger in time with #1 was to shift FTT...

I can't shift ignition outputs, because I'm running a distributor off 1 output, thus, nothing to shift.

I moved FTT to 12, from 0.  I left TDC after trigger at 78 deg.
Now it flashes #1 TDC correctly

So, Id like to understand this!  Just reading the help pages about TDC after trigger setting, and FTT, would lead me to conclude that moving FTT to 12 would reduce the TDC after Trigger degrees to just 2 teeth, since TDC after 0 tooth was 78 deg - mechanically fixed.

I was able to use the ignition lock to set the ignition to advance all the way to 63, and predictably, it fired #1 almost all the way back to #4.

So, the ECU still is able to advance timing, meaning that the TDC after trigger is still large, presumably still 78 deg.

My *guess* is that moving FTT actually just shifts when the ECU begins its count, but it still counts based on the trigger reference table- that is tooth 0, 24, 48, it just starts someplace other than 0...?



Can anyone explain this?
Thanks!


Offline Kamuto

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Re: Question about shifting ignition order
« Reply #4 on: April 14, 2019, 01:59:43 pm »
Seems mighty quiet around here... If anyone is listening, I'd appreciate an explanation of this!

As mentioned above, the only way I could make the ecu trigger in time with #1 was to shift FTT...

I can't shift ignition outputs, because I'm running a distributor off 1 output, thus, nothing to shift.

I moved FTT to 12, from 0.  I left TDC after trigger at 78 deg.
Now it flashes #1 TDC correctly

So, Id like to understand this!  Just reading the help pages about TDC after trigger setting, and FTT, would lead me to conclude that moving FTT to 12 would reduce the TDC after Trigger degrees to just 2 teeth, since TDC after 0 tooth was 78 deg - mechanically fixed.

I was able to use the ignition lock to set the ignition to advance all the way to 63, and predictably, it fired #1 almost all the way back to #4.

So, the ECU still is able to advance timing, meaning that the TDC after trigger is still large, presumably still 78 deg.

My *guess* is that moving FTT actually just shifts when the ECU begins its count, but it still counts based on the trigger reference table- that is tooth 0, 24, 48, it just starts someplace other than 0...?



Can anyone explain this?
Thanks!
shift ignition wires on your dizzy
Vems installer in Lithuania
valdas.sunokas@gmail.com

Offline nmerrill

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Re: Question about shifting ignition order
« Reply #5 on: April 14, 2019, 11:07:21 pm »
ok, but why?
 I'm not really looking to make random mechanical botches to help out my fancy EFI.


Offline gunni

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Re: Question about shifting ignition order
« Reply #6 on: April 17, 2019, 01:07:18 am »
You demonstrated how to setup your car to get ignition to align with TDC of cylinder 1 by using the first trigger tooth value.

You have adjusted the starting point, any reference tooth after that is a countr from that 0 point

So 0 refers to TDC on cyl1 in this case now.

0 is not the right value ever to set for FFT, its just a helping mechanism for VEMS to do counting
Say your missing tooth passes the TDC mark on your engine 100deg before the engine reaches TDC.

You have two variables to play with to get the alignment right.
On a 60-2 each tooth represents 6 degrees.
So you could do FFT at 16 (16*6=96) and then the reference angle would need to be 4
4 + 96 = 100

You could also do
FFT 10 > 60
then reference angle needs to be 40
60+40 = 100

The highest value the reference angle can be is 127.5 which in hex is FF or in decimal 255, this will give an angular accuracy of 0.5deg out of 255 possible values (0,0.5,1.0,1.5 etc)
So if your actual value needed is 78deg reference and 12 FFT then  your total angle is
12*6 + 78 = 150deg total angle.






Offline nmerrill

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Re: Question about shifting ignition order
« Reply #7 on: April 17, 2019, 07:24:39 pm »
Ok, thanks for the reply!

I think I follow what you are saying, and that is why I'm still confused...

To clarify: My 60-2 wheel is set so that the sensor is pointing at the 14th tooth after the missing teeth when Cyl 1 is at TDC.
So 84 degrees of crank rotation from the missing teeth (14 teeth), and 78 deg. if you measure from the first tooth after the missing teeth.

you wrote:
"So if your actual value needed is 78deg reference and 12 FFT then  your total angle is
12*6 + 78 = 150deg total angle."

This is what confuses me- because I get timing light confirmation on #1 with FTT =12 *and* TDC after Trigger is 78 deg. (you call this "reference")

But the "total angle" in my configuration is 84 deg, no? 

Which means If I set FTT to 12, then the reference angle (TDC after..) should only be 12.

Unless, the computer is only looking for *any* cylinder TDC, and I'm hung up on Cylinder #1.   If that were true, then I don't understand what information the CPU has to actually identify which cylinder it is at in order to fire the coil or injector for.



Offline gunni

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Re: Question about shifting ignition order
« Reply #8 on: April 17, 2019, 10:46:19 pm »
It sounds like either the missing tooth is not 14 teeth away from TDC or that your distributor is clocked incorrectly.
I can´t see any other way for you to be off like that.

Offline Kamuto

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Re: Question about shifting ignition order
« Reply #9 on: April 18, 2019, 02:48:28 pm »
It sounds like either the missing tooth is not 14 teeth away from TDC or that your distributor is clocked incorrectly.
I can´t see any other way for you to be off like that.
you are right :D
Vems installer in Lithuania
valdas.sunokas@gmail.com

Offline nmerrill

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Re: Question about shifting ignition order
« Reply #10 on: April 18, 2019, 08:22:11 pm »
Well, ok.  The VAG 60-2 trigger is a rear mainseal type, and was installed with the lock device.  I'm pretty sure that puts the sensor at the 14th tooth.

I re-checked the distributor, and confirmed that the marks on the hall wheel and housing are in alignment, with the rotor facing #1.  Rechecked the wires to confirm they are attached to the correct cylinders.

Here are two trigger logs showing the two results.  One shows FTT = 0, the other shows FTT= 12

Hope the picture show...







Doesn't this show that with FTT= 0 VEMs is triggering the coil at the incorrect times, and the distributor clock is irrelevant?
Additionally, it also shows that the MT are about 14 teeth before TDC #1.
Or am I wrong?
« Last Edit: April 18, 2019, 09:01:01 pm by nmerrill »

Offline nmerrill

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Re: Question about shifting ignition order
« Reply #11 on: April 24, 2019, 12:21:16 am »
bump!
Anyone?