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Old 12-26-2012, 02:18 PM   #51
wrxadam05
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That is block height, he is trying to measure the head.
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Old 12-26-2012, 02:29 PM   #52
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Quote:
Originally Posted by kellygnsd View Post
No you will have the correct centerline but if you have done any head or block decking and use the stock thickness HG your stock timing marks can be slightly off. The LIC/Crawford adjusters are made for just this reason. I made up the decking difference with a thicker HG.


And by off slightly I mean 1/2 degrees or maybe a degree or two.
ok ok.. I follow. no decking on my build, although, for my setup Im going to be running .039(1mm) cometic head gaskets (100mm bored over block) compared to the oem gasket .023(.6mm). I guess we shall see if a difference in HG thickness of .016 will throw my timing off..
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Old 12-26-2012, 02:30 PM   #53
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You will be fine, that is minimal.
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Old 12-26-2012, 02:45 PM   #54
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for some measurements, that would be considered alot.. been deep into measuring piston to wall clearances.. (.0035"-.0045") has been my magic numbers recently.. lol.. As soon as i finish the valve grind on my LH head, ill be mocking the longblock up and checking timing.. but yeah didnt think as far as timing is concerned my setup would be a big jump..
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Old 12-26-2012, 03:07 PM   #55
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Quote:
Originally Posted by Soarer View Post
Does anyone know the procedure to measure a head to see if has been decked and if so, by how much?
You'll need a FSM to find out the exact procedure but in the deck of the heads there is a relief point that you can measure from to see how much material has been removed from the deck. If anyone has a pic of the bottom of a head post it up for reference.
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Old 12-26-2012, 03:16 PM   #56
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Quote:
Originally Posted by 99imprezd View Post
for some measurements, that would be considered alot.. been deep into measuring piston to wall clearances.. (.0035"-.0045") has been my magic numbers recently.. lol.. As soon as i finish the valve grind on my LH head, ill be mocking the longblock up and checking timing.. but yeah didnt think as far as timing is concerned my setup would be a big jump..
What would be considered a lot? .4mm head gasket difference?
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Old 12-28-2012, 08:45 AM   #57
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can someone please tell me what are the numbers or letters stamped on the camshafts are for? i have a damaged v7 left intake camshaft with avcs oil ports and i want it repplaced but unsure about the part#. my camshaft has "G3" on it and i have one im looking to purchase but it is stamped "LD"
whats the difference? are all avcs camshaft stamped with the same digits?
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Old 12-28-2012, 08:53 AM   #58
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anyone please share some info with me. pm me or something
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Old 12-28-2012, 09:09 AM   #59
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arent they just casting numbers.. by year and batch or something along those lines.. Im guessing there is a difference between Dual AVCS and single AVCS as well..
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Old 12-28-2012, 02:31 PM   #60
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You should always check your CAM Timing when the engine has been rebuilt nomatter whether you're running AVCS or not. AVCS isn't a magic trick that calibrates itself and makes timing changes due to HG thickness or whatever go away.

Those with AVCS and/or Adjustable pulleys......... Doing COLD engine centerline settings go out of the window as soon as the engine warms up.... food for thought! Also the difference from COLD to HOT might (very likely) not be equal on both banks.

To give you an idea from my measured and logged values........

COLD :
LH Intake 120*, Exhaust 118*, RH Intake 123*, Exhaust 116*

HOT:
LH Intake 116*, Exhaust 122*, RH Intake 121*, Exhaust 118*

See where I am going with this?

What I did next was Retard the Intake pulleys by a Tooth on the Timing belt since I wanted it to sit at something like 130+ *. After retarding both Intake pulleys one tooth the cams were at LH 131* and RH 136* (HOT). I wanted my Exhausts to sit at around 110* when HOT so I set the Adjustable pulleys COLD to LH 106* and RH to 108*.

Next step was to REDO the AVCS offsets, etc. to have the CAMs read LH 0.0* (Most retarded position) and RH -5.0* (Most retarded position). That way the Intake cams will be sitting at the same Centerline when the Cams go to a certain Advance Target which is mutual for both Cams.

EG. Advance 30* for LH and RH.

LH will be sitting at 131 - 30* = 101*.
RH will be sitting at 136 - 30* - 5* (offset) = 101*

This is my method of getting CAM Timing set properly.
On one of my new racing engines which I am going to build I might use ported to the moon EJ205 heads, Cams and 4x Adjustable Pulleys. However I will also be mounting Triggerwheels + Hall Effect sensors to EVERY Adjustable Pulley to be able to LOG ACTUAL Cam position when the engine is upto real life water/oil/EGT temperatures to calculate back where I should have put the COLD Cam timing in the first place

Cheers,

Jasper.
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Old 12-28-2012, 03:05 PM   #61
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Logged cam position values will have some error just due to the way they are calculated. Engine position is calculated in between crank teeth position and can fluctuate depending on engine acceleration rates. Do you trust your logged cam position values over your measured cam position values?
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Old 12-28-2012, 03:25 PM   #62
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Hi,

There might be error in the calculation as you say but that would be mostly depending on RPM or moreover varying RPM which causes different acceleration rates. I am however checking cam angles at the same rpm but just simply Cold vs. Hot. I simply see the Cam Angles change as Water temp is rising.

If you cannot rely on proper interpretation of cam angles from a proper standalone there is no point to use AVCS in the first place I think.

Jasper.
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Old 12-28-2012, 05:36 PM   #63
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In two complete revolutions of an engine each cylinder fires once. In those two revolution the engine speed is not constant but pulsed as each cylinder fires. With a 36 tooth crank trigger wheel engine position has to be calculated in between known tooth position based on the rate of change of acceleration of the previous teeth. Until we get a 360 tooth crank trigger the best we can get is an estimation of cam timing relative to engine position but its a pretty good and reliable estimation of position.

With a 36 tooth crank wheel engine position is updated every 10 degrees

With a 360 tooth wheel we would have accurate engine positioning down to the degree and a good approximation in between degrees but getting electronics that can process a 2.52 MHz signal properly would not be easy or cheap.
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Old 12-29-2012, 02:20 AM   #64
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^^^ As far as the math and theory goes you are correct. Below are some pics to show you it can certainly be done and I might even have some discs lasercut when I'm getting too boring sorting other priorities first ;-)

LH Variable Cam Trigger using a 12-1 wheel


RH Variable Cam Trigger using a 12-1 wheel


One could do the same ofcourse for the LH and RH Exhaust Pulleys but since I am not running AVCS there nor can be @rsed to check actual Exhaust timing now I didn't include that

And......... a 359 Tooth Crank Trigger as you would like (360-1 so it can do 360* on Crank Trigger alone but can key off of the LH Cam to go 720* full sequential)


Such a Crank Trigger however would be HUGE otherwise it wouldn't work physically with most sensors when gap widths are getting too small to be picked up. The only proper way would be to run one off of the back of the Flywheel in the Bellhousing which I might consider.

As I said I don't think one needs to go that ridiculously accurate to see and understand that aluminium engines, etc. simply expand as all alloys/metals do when getting hot. Cam Belt could be stretching as well which is counteracted by the Belt Tensioner hence the LH side show the largest differences.

I have seriously considered mocking up a hot water/pump solution to be able to heat the engine up to normal operating temps whilst the engine is on the stand to do actual measurements with watertemps at say 90~95*C with a degreeing wheel and dial gauge. I might do it next time round but will keep with what I have seen for now.

Cheers,

Jasper Kopinga
CS Racing
Taiwan.
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Old 12-29-2012, 07:31 AM   #65
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Kelly,

Would you enlighten me where you got the 2.52 MHz figure from?

If we take an EJ25 spinning at 10.000 rpm the crank rotates at a speed of 10.000 / 60 = 167 revs per second. Each rev has 360 teeth passing by the sensor if one would use such a huge crank trigger. So 360 * 167 = 60.120 Hz

As you see it is not THAT exciting from an ECU point of view.

Cheers,

Jasper.
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Old 12-29-2012, 01:34 PM   #66
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My bad, my quick math was of by a factor of 60. I was thinking rps instead of rpm.
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