Individual power not correct, trigger related ?

[Mads Lund]

Hi

My engine (Jaguar S 3.0 V6 Duratec) is running smoothly in idle, but the individual power is showing large variations on cyl 3 and 6 (360deg apart). Further do the triggerlog seems a little different than what I can find on google. Please have a look:
|http://thumbsnap.com/uHbdwkMC[/img]

[mattias]

Variations cam come from bad valve seats, poor injector spray pattern, piston rings, .. 
Ever done a leak-down test? Or just a basic compression test?

[Mads Lund]

Engine is fine and ideling very smooth. Rpm steady at 760 rpm +/- 10 rpm

From a trigger result do the tooth sequence and timing look very steady, only thing that seems strange is that tooth 0  have a diff of 103% (assuming that the gap is = average tooth width) and tooth 1 have a diff of 95%, all the other is diff 100% +/-1%. This could indicate that the rising edge of tooth 0 is misplaced by 0,4 deg (that the gap is a little to wide) 

Could this me a manufacturing error on the wheel ? Problem is that the trigger wheel is burried inside the engine with the cam chains on a V6 duratec, so getting is out for a measurement is a 2 day task.

Another question ? what's the measuring points for the individual power, the trigger tooth (0-12-24) in my case, or the ignition events ? If it's measured between the trigger teeth's can it explain what I'm seeing, if it's between ignition events, should the misplaced edge of tooth 0 not affect the total time of ignition 3 (that run from angle 280 to angle 40, 0 = edge of tooth 0, tdc = 50 deg after tooth 0, ignition static 10 deg btdc )

      ms   % rev
   tooth 0-11'   26.012   33,17%
   tooth 12-23   26.132   33,32%
   tooth 24-35   26.280   33,51%
   1 ignition   26.084   33,26%
   2 ignition   26.152   33,35%
   3 ignition   26.188   33,39%
   Avg tooth   2.178   
   one rev time   78.424   
tooth   Primary Diff (ms)   Primary Diff Ratio   Diff to avg
Gap   2.178   1.00   100%
0   2.254   1.03   103%
1   2.076   0.95   95%
2   2.156   1.04   99%
3   2.172   1.01   100%
4   2.184   1.01   100%
5   2.200   1.01   101%
6   2.200   1.00   101%
7   2.192   1.00   101%
8   2.188   1.00   100%
9   2.180   1.00   100%
10   2.164   0.99   99%
11   2.152   0.99   99%
12   2.148   1.00   99%
13   2.148   1.00   99%
14   2.156   1.00   99%
15   2.172   1.01   100%
16   2.188   1.01   100%
17   2.200   1.01   101%
18   2.208   1.00   101%
19   2.192   0.99   101%
20   2.196   1.00   101%
21   2.184   0.99   100%
22   2.168   0.99   100%
23   2.164   1.00   99%
24   2.156   1.00   99%
25   2.152   1.00   99%
26   2.164   1.01   99%
27   2.180   1.01   100%
28   2.192   1.01   101%
29   2.200   1.00   101%
30   2.208   1.00   101%
31   2.196   0.99   101%
32   2.196   1.00   101%
33   2.188   1.00   100%
34   2.172   0.99   100%

[VEMS]

Hello Mads Lund,

Could you upload the original triggerlog file so i can review ? Thanks,
Best regards,

Dave

[Mads Lund]

Sure

Here's an example

http://shares.vejnoe.com/s#5e9ad216-62ea-469a-9373-64888deee9df/tvr.clouddrive.vejnoe.com/shared/

[VEMS]

Hello Mads Lund,

Thanks for the triggerlog, i have reviewed; There is indeed a slight deviation around the missing tooth, this does however not account for the cylinder to cylinder variance which is also clearly visible in individual power. I suspect this might be caused by a mechanical cause like Mattias already outlined/hinted.

Individual power is measured from trigger tooth to the next trigger tooth like you suspected (reftooth 0-12-24 + trigger_tooth) but take care the scaling is variable (is relative diff against previous period).

Best regards, Dave

[Mads Lund]

Hi Dave Thanks

I have tried swiching injectors coils etc beteen cylinders, and have pressure/leak tested the cylinders as well. and the problem stick to cyl 3 and 6.

Just to eliminate my suspision of a problem with the trigger wheel geometry do I have the following idea - please comment.

Currently is trigger 0-12-24, with ignition sequence 123456, (front right, front left, middle right, middle left, rear right, rear left). Tdc after trigger is 50 deg

If I swap to numbering front left as #1 (currently #2) will I still get same ignition sequence, everythin delayed 120 deg. with the oprion of tetting the gap + tooth 0 and 1 inside the same frame. HAving trigger tooth set @ 6-18-30 with tdc 110 deg after trigger and all cylinders will be #1 lower, ignition sequence (front left, middle right, middle left, rear right, rear left, front right)

And in this way should it be possible to move the trigger teeths around to eliminate the problem if a single tooth is sligthly off position.

btw, I am aware of the way the individual power is allways a relative figure. But isn't it relative to last ignition sequence average ? In my case trigger event (1+2+3+4+5+6) / 6 = avg trigger event time, then shoving trigger event 7 - avg trigger event time as Cyl1 delta, trigger event 8 time / avg as cyl 2 delta etc...

In case its simply trigger event 2 time - trigger event 1 time = cyl 2 delta, etc. will I be very dificult to read as a "slow" cylinder ofcause will show as slow, but the following healty/avg cylinder will show as fast compared to the other ?

Perpahs if you have the math/code will it be easy to understand 

[lost]

I also had problems on V6 with individual power two cylinder "offset" Setup was correct, but vems for unknow reason had offset on two cylinders.. Like it didnt count correctly 60-2 wheel, and missed one pair of cylinders. Maybe a firmware problem?
http://www.vemssupport.com/forum/index.php/topic,839.270.html

I will be replacing engine soon and have upgraded vems to new firmware, and will try to make better ground. And test it again.

[VEMS]

Hello Mads,


Swapping the reftooth table (or actually adding 6 to) would not work well, the first tooth always has to be 0 in reftooth table (or actually the reftooth table should contain at least one 0 position).
If you would like to move away from the missing tooth you could specify a different trigger tooth and correct tdc after trigger. Example: change from trigger_tooth = 0 and tdc after trigger = 50 to trigger_tooth = 1 and tdc after the trigger = 40. However this would only work in recent firmwares (1.2.25 and up) in which rpm period is dependent on trigger_tooth.

Individual power is relative (to previous rpm period) time difference. Like: prev_rpm_period (time) - current_rpm_period (time) = power for that cylinder.
No averaging sums or divisions (very time consuming) involved.

The individual power indicator is useful for trimming injector trim or identifying misfiring cylinder; in which case there is a big difference from mean.
You are correct regarding the "slow" cyl showing slow and the next following "normal or average" showing fast (compared to previous slow). But its only ment to provide a tool to even the cylinders out or identify difference from even.


Best regards, Dave

[Mads Lund]

Hi Dave

Problem solved, and root cause identified. As expected was the time difference due to the period of tooth 0 beeing less tand the period time of the other teeths. I found a usefull way of identifing the geometry for the trigger wheel. Simply go downhill at 60 mph, and release the throttle. Under engine breaking shall the individual power time be absolutely flat (or at leas very close) if there are a repeated pattern (like mine above) are there a geometrical, og analogue irregularity of the trigger pulses.

My problem, must be present on many installs, or at least every one using the original triggerwheel and sensor of a Ford. Looking at the analogue signal from the sensor, with the engine running look like this:



It clearly shows that the aditional positive mplitude of tooth 0, have the side effect that the crossing point is slightly delayed (4% of periodtime), giving a "wrong" timing of tooth 0's falling edge, equal to 0,5 crank deg.
So lesson from this, is to avoid using "first trigger tooth = 0" if possible.
I changed my ignition sequence from 1-2-3-4-5-6 to 2-3-4-5-6-1 used first trigger = 6, and TDC after trigger = 110 (was 50), not really a super solution but it works. I'll rotate the trigger wheel 60 deg, when I get the chance. Final result, idle with cold engine:


Then on to the nex issue, my VR-Hall converter for the gearbox speedo sensor don't work past 10 mph, and the sinal is top notch.