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83958 Major - 2016 - Cam Timing

Discussion in 'Boxers/TR/M' started by vincenzo, Feb 13, 2016.

  1. vincenzo

    vincenzo Formula 3
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    #1 vincenzo, Feb 13, 2016
    Last edited: Feb 13, 2016
    This vid shows the TR's piston travel per degree of rotation. By calling out the degrees, I could maintain the clockwise pressure and not introduce needless error. When you release the clockwise pressure, the system wants to retract a half degree or so... this retraction varies over the rotation because of varying valve spring pressure and belt tension etc.

    You can clearly see the piston rising in the readout and see the pause as it first reaches the top of its travel at the zero degrees callout. As the rotation continues, you can clearly see the next two to three degrees of piston dwell as the piston travels over the top.

    TDC per Rifledriver (Brian Crall) is defined as the start of the dwell period - i.e. the first moment that the piston reaches its peak height. He points out that this is his first hand experience and is not explicitly defined in Ferrari literature. This 'start of dwell' point is called out as Zero on this vid.

    Rgds,
    Vincenzo
    PS: once the Zero point was passed, I should have been calling out negative numbers to clarify that the clockwise rotation was maintained.
    [ame]http://www.youtube.com/watch?v=G2QoNYlYPJg[/ame]
     
  2. vincenzo

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    #2 vincenzo, Feb 13, 2016
    Last edited by a moderator: Sep 7, 2017
    This is the flywheel mark when the piston is at the start of the dwell.

    The mark is: PM | 1-6

    The "|" designates the exact location.

    NOTE that the OEM flywheel mark for TDC is NOT aligned with the start of dwell!

    The studs are symetric, and thereby indicate that there is no parallax error introduced by the viewing angle.
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  3. vincenzo

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    #3 vincenzo, Feb 13, 2016
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    This is the flywheel mark when the piston is mid dwell.

    NOTE that the OEM flywheel mark for TDC IS aligned with mid dwell!

    This corresponds to the American standard for the definition of TDC (mid dwell).

    Perhaps the OEM pointer is off....
    Perhaps I misunderstood Brian Crall (Rifledriver)...
    Perhaps my technique is flawed...

    Hopefully Rifledriver and/or our other experts could chime in.

    Tomorrow I'll see what I might be able to do with a piston stop to determine TDC per the American standard.

    rgds,
    Vincenzo
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  4. vincenzo

    vincenzo Formula 3
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    #4 vincenzo, Feb 13, 2016
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  5. vincenzo

    vincenzo Formula 3
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    #5 vincenzo, Feb 13, 2016
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  6. Rifledriver

    Rifledriver Two Time F1 World Champ

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    Not my definition. It is the definition of the guys who built them as told by them directly to me and a lot of other people..

    Pointers are adjustable. If people like to do otherwise, or believe otherwise, fine by me.
     
  7. vincenzo

    vincenzo Formula 3
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    Thanks for the clarification!

    rgds,
    Vincenzo
     
  8. vincenzo

    vincenzo Formula 3
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    #8 vincenzo, Feb 14, 2016
    Last edited by a moderator: Sep 7, 2017
    After Brian reconfirmed... I worked hard on my technique and completed multiple runs to confirm consistency. After plotting the data some new info fell out:

    1) My initial estimate of TDC (Zero Degrees on the plot) moved a degree further out to the right
    2) This 'new' TDC (1 Degree to the right of Zero) MATCHES THE OEM FLYWHEEL (Cheers!)
    3) My dial indicator reads out in thousandths - note that I had to estimate the tenth of a thou!

    Most importantly, EXTREME care is required for any kind of precision at the tenth of a thou level. There are FOUR degrees of spread with piston movement of less than a thou!

    The 'over the top' data (to the right of zero - piston moving downstroke) had some inconsistency of up to 001". Presumably this is unpredictable lash uptake (bearing clearance) or perhaps a bit of stiction/ rubbing against the spark plug threads by the plunger rod. Over the top data does not matter for TDC determination.

    I believe these results are sufficiently accurate to determine TDC per Brian's understanding of the Ferrari methodology. In a production shop, a dial gauge that reads to the tenth of a thou would be recommended. In addition, if a tenth of a thou is routinely required, a tool such as this ought to be in the arsenal:

    TDC-KIT-01 Top-Dead-Center Tool Kit - Ricambi America, Inc.

    Next time!

    Brian - Thanks again - as always, input and suggestions are appreciated.

    Rgds,
    Vincenzo
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  9. vincenzo

    vincenzo Formula 3
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    #9 vincenzo, Feb 25, 2016
    Last edited by a moderator: Sep 7, 2017
    Splurged a bit and invested in the Hill Engineering TDC kit with a 0.01mm dial indicator. The pic shows the results.

    The new tool improved both the accuracy and precision of the results. The final TDC outcome however, was unchanged.

    Note that the new results have a 'lazy' peak that spans ONE DEGREE (from zero to one degree to the right).

    The prior graph (with a .001" dial indicator and mag mount) had a 'lazy' peak that spanned TWO DEGREES.

    The HE kit is reassuring and more foolproof and quicker to use. It is a 'nice to have' tool, but is not required. A mag mount dial indicater provides adequate results -IF- you are VERY careful. Minor complaint: the dial indicator does not have our US standard 4-48 threads on the tip. Don't plan to use it with your existing accessories.

    Bottom line: TDC MUST BE RIGHT before anything else! Glad to have the HE tool in my kit.

    Life Is Good,
    vincenzo
    PS: The 'noise' on the downside of the graph remained with the HE kit - this points to a lash issue rather than a tool issue.
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  10. vincenzo

    vincenzo Formula 3
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    #10 vincenzo, Feb 25, 2016
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  11. vincenzo

    vincenzo Formula 3
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    #11 vincenzo, Feb 25, 2016
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    The intake valve clearance was set to 0.5mm via a thinner shim. Shims vary by 0.05mm.

    The overall setup is shown in the pic.

    Actual results:
    Valve opens at 11.5 degrees BTDC, closes at 50.5 degrees past BDC.
    Total duration 242 degrees - mid point at 109.5 degrees after TDC.

    Ferrari specifications:
    Valve opens at 13 degrees BTDC, closes at 51 degrees past BDC.
    Total duration 244 degrees - mid point at 109 degrees after TDC.

    Total degrees will vary with ACTUAL valve clearance. I know of no way to EXACTLY get 0.5mm of clearance. My 0.5mm feeler gauge will pass (tightly) but my 0.508mm (0.02") will not. The clearance is VERY close to the 0.5mm spec. I believe that this VERY small variation accounts for the difference between actual and specified open/close.

    Based on the mid point difference, I believe that this cam is 1/2 of a degree retarded.

    Input requested! Where is my logic off base?

    Life Is Good,
    vincenzo
    PS: 3 cams to go.
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  12. vincenzo

    vincenzo Formula 3
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    #12 vincenzo, Feb 25, 2016
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    Here is a pic of the pickup point on the valve shim.

    The dial indicator rod is in-line with the valve stem (more or less).

    Please read the next post and weigh-in with your expertice!

    Life Is Good,
    vincenzo
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  13. bpu699

    bpu699 F1 Veteran
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    You are going through the same mental head banging I went through. Depending on how I checked, it was either spot on or up to 1.5 degrees off as best as I can tell... Ferrari was happy with +\- 1 degree. Worse case scenario, I can live with 1.5 degrees... The last two dealers were ok with it too... I suspect few can hit dead zero with any degree of confidence, unless they do this for a living...

    In the end, that's good enough for 99% of the population. Honestly, I suspect 90% of folks don't ever check. If the car runs great, and passes emissions, it's fine.

    I wanted to do it right. So I did. Next time, I am just popping on the new belt.
     
  14. vincenzo

    vincenzo Formula 3
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    do you think the 1/2 degree off (based on mid-point) is a valid conclusion?
     
  15. bpu699

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    I ended up just visually using the TDC marks on the flywheel...

    Using the piston lock was wrong per the experts...

    I think if you measure and you are 5 degrees off...that's a huge deal...

    3 degrees I would be scratching my head and adjusting the cams...

    2 degrees, I do some soul searching...

    1.5 degrees, I can live with. And, for all I know, it's spot on. 3 of my cams were well within a degree. 1 seemed slightly over but I am not quite convinced...

    I plan on being anal and rechecking that 1 cam one more time, as soon as it warms up... It's really cold here in wisconsin...

    See my long other post...
     
  16. qwazipsycho

    qwazipsycho Formula 3

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    I argued this point a while ago. I've owned my car 16 years. I've done 3 majors and always just swapped the belts because it runs great. I just don't see how going through all this brain damage improves anything. If it was done right in the first place, doing it again only verifies that it's right and improves nothing.

    This is like the "diff argument". So let's just agree to disagree before anyone starts lobbing grenades in my direction.
     
  17. ago car nut

    ago car nut F1 Rookie
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    I think I will make that TDC. tool, thanks for posting.
     
  18. vincenzo

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    This particular car sat for four years and then had the belts changed per your theory. It did not run well and the gas analysis was not right. It was theorized that cam timimg was off. Then the car went into storage once again.

    The cams may be off from the day I bought the car in 1997 and had a belt change done in an independent's shop. It never went through a gas analysis nor smog check after that service.

    Anyway, I need to go through this car with a fine toothed comb and leave nothing unchecked.

    Once I have personally established that the cam timing is right - I may be inclined to agree with you. This however, is a 'special circumstance'.

    Life Is Good,
    vincenzo
     
  19. vincenzo

    vincenzo Formula 3
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    #19 vincenzo, Mar 3, 2016
    Last edited by a moderator: Sep 7, 2017
    So far, I have baselined bank 1-6. The intake was easy and spot on to the factory specs. The exhaust proved a bit more difficult - repeatability was an issue - it was difficult to read the Dial Gauge.

    Fixed the Operator difficulties with the HUGE gauge/ monitor! It looks a bit strange - perhaps even surreal - but it works GREAT!
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  20. vincenzo

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    #20 vincenzo, Mar 3, 2016
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    The exhaust valve was a bit more difficult to interpret. This is the raw, collected data after the repeatability issues were brought under control. Remember - we are talking some extremely small distances and variation here! 0.005mm = 0.0002inches!

    The table shows the Exhaust Valve opening late, and closing early. Since these cams are symmetric, this variable is attributed to an inexact clearance rather than a timing issue. Even then - THESE NUMBERS ARE WITHIN SPEC (+/- 1 DEG).

    For reference:
    An 0.5mm feeler passed and a 0.508mm (0.02") would not pass.
    Spec calls for 0.5mm clearance and shims come in 0.05mm increments

    Initially, the dial gauge would 'jump' about .03 or .04mm as the lash was taken up. Hell... it would even travel 'up' for an initial jump before it reversed and traveled down with the valve! Really bad lab results!

    The best repeatability required that the valve shim/bucket be nudged to a lash free location before the rotation began. Effectively, I use the shim replacement tool lightly wedged in between the bucket and cam to snuggle the bucket down and tight against the valve spring. Then, a relatively consistent (AKA: not impressively repeatable) bucket height could be established before each rotation. Without doing this - the numbers were all over the map.

    Looks to me like the cam timing on bank 1-6 is well within spec. The intake was spot on and the exhaust is shown in the table. I consider the exhaust cam spot on as well (open 1 deg late, close 0.8 deg early). Correct cam timing is my 'expected case' on this bank since the gas analysis was also in spec on bank 1-6.

    Tomorrow, I move to bank 7-12 with a relatively refined technique. The gas analysis was off for this bank and I expect to find the cam timing off as well.....

    Stay tuned for more,
    Vincenzo
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  21. Newman

    Newman F1 World Champ
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    Fantastic attention to detail. What I would like to see is a dyno pull on the engine with your method vs a less anal method and see if there's a measurable difference. The other thing that comes to mind is if you take a step back and look at the fact the liners aren't dead straight, neither is the crank and the block will grow in width advancing cam timing (unless the timing belt grows at the same rate of aluminum) one has to wonder how carried away we really need to be. I dynoed a US spec 90 testarossa with 90000 kms on it with 24% leak down loss on 2 cylinders past the rings and it made 379HP. And if you want to do it right (and go insane) you would check all 48 valves to make sure the lobes were all ground in the proper positions relative to crank position not just for number 1 and 7. Your method just says 2 of 12 cylinders are timed right. Just food for thought, not trying to be a knob.
     
  22. vincenzo

    vincenzo Formula 3
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    I fully agree. My 'anal' nature on this job so far, is to develop a reasonable technique. There are MANY sources for error to be introduced.

    Just one example:
    When the engine rotation is stopped, the crank 'settles' backwards from 1/2 to 1 degree or so. The amount changes at every location on the dial!

    Solution:
    Read the crank with rotational torque still applied and in motion (for TDC). This is where the HUGE dial gauge screen really helps. The HUGE handle on the crank is really needed to SLOWLY and EVENLY rotate the crank.

    Without working through all these variables, the resultant data is trash. Chasing one's tail can continue forever!

    From what I've seen so far, +/- 1 degree is about the best (?) one can expect.

    Life Is Good!
    vincenzo
     
  23. vincenzo

    vincenzo Formula 3
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    #23 vincenzo, Mar 5, 2016
    Last edited by a moderator: Sep 7, 2017
    Cylinder No. 7 - Intake:

    Changed out the 3.95mm shim for a 3.65 and have an estimated final clearance of 0.507mm.

    The spec calls for exactly 0.5mm - there is no such thing in the real world!
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  24. vincenzo

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    #24 vincenzo, Mar 5, 2016
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    This is the raw data. Very consistent values that look good.

    BUT!

    What's up with the THREE Deg early opening and FIVE Deg early close!?!
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  25. vincenzo

    vincenzo Formula 3
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    #25 vincenzo, Mar 5, 2016
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    Here is a sketch to visualize what is happening.

    The actual clearance at 0.507 is slightly more than 0.5mm. The actual data is measuring the symmetric profile further up the curve from the factory spec. The actual data measures a calculated duration of 242.1 deg rather than the spec 244 deg.

    Split the difference for the symmetric lobes and each event must be adjusted as shown by 0.95 degrees.

    NOW the data looks good!

    INTAKE OPENING:
    Adjusted spec = 12.05 deg BTDC
    Actual Value = 16 deg BTDC
    THE VALVE IS OPENING 3.97 DEG TOO EARLY!

    INTAKE CLOSING:
    Adjusted spec = 50.05 deg ABDC
    Actual Value = 46.1 deg ABDC
    THE VALVE IS CLOSING 3.94 DEG TOO EARLY!

    NOW THE DATA MAKES SENSE!
    The timing is 4 deg early on BOTH events.
    NOT 3 deg early on opening and 5 deg early on closing!
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