6 replies to this topic

[GreenMini17]

Im using Omex 200 series ignition system and i need to show the ecu where top dead centre of the crank is. Im using a 36-1 toothed pulley (same as megajolt etc). To do this i will need to get piston 1 to tdc. I understand how to do that but what i dont understand is how to mark tdc on the crank & pulley? Could someone please explain to me how this is done? Once i have it marked i need to attached a timing light. How does the timing light then take a reading? Thanks in advance. This is all very new to me!!

[dklawson]

I have zero experience with Megajolt or other mapped ignition systems so I can only answer in generalities.

 

When you are finding TDC, make sure you have determined this by taking piston height measurements each side of presumed TDC  and then accurately positioning the crank at the exact (averaged) position between the two measurements.  Only turn the crank "forwards" during your measurements and when you finally set the crank to TDC so you do not introduce a backlash error.

 

I don't know the type of sensor used to look at the timing gear teeth.  In industry there are inductive proximity switches and 2-wire magnetic sensors.  The inductive switches can be moved into position until their output turns "on" (they will switch on and off at zero speed).  If you have such a switch you would only need to move it towards the timing pulley tooth with the engine sitting at TDC and lock its position down as soon as it detects the edge of the tooth.  The switch would then be set to turn on at exactly TDC.  

 

For the magnetic sensors, there must be rotation for them to turn "on".  For an initial setting you have to "eyeball" the position of the sensor's tip to be lined up with the leading edge of the gear tooth and lock it down.  Once the engine is started you would then have to tweak the position by moving the sensor slightly while using a timing light.

 

You asked about the timing light.  Here again I only have experience with standard ignition systems.  However. what I can tell you is that if you use an inductive timing light, its pickup would be clamped to the spark plug wire for cylinder #1.  With your mapping set to fire at TDC (no advance at all) you would probably turn the engine over on the starter with all the spark plugs removed (so the engine won't run or have to compress anything).  While pointing the timing light at the engine's (factory) timing marks.  You would move the mapped ignition's sensor forward or back (angularly) until you the 0 degree timing marks line up.  This is much like what would be done with a traditional distributor except you would be moving the mapped ignition sensor to get the timing set instead of moving the distributor.

 

If nothing else... my post should prompt those who really know to post to your thread.

[mini13]

Ok, there are a few things that can cause issues with this,

 

first off, is your system wasted spark? and what timing light will you be using?

 

as above you need to accuratly find and mark TDC, the method I use for this is the "dead stop method" ie an old spark plug with the middle knocked out, I have put a bolt through this so it contacts the centre of the piston near TDC, you can then pop this in to no1 turn the engine over slowly with a spanner till it touches the piston and stops, make a mark in tipex or white paint, wind the engine back the other way til it locks, mark it again..... then put a mark half way between the two, this is the one you use, so wipe the others off.

If you have no marks at all you'll need to make a reference mark on the timing cover when you make the first mark.

I have actuall gone a step furthur than this on my current engine, and drilled a hole in the flyyheel case so I can see the ring gear, I have one tooth painted white, and a white mark on the casing, as the flywheel is a larger diameter its a more accurate mark.

 

 

Timing lights...... you will need an adjustable one, as the ecu will be giving an amount of ignition advance (say 15 at idle) so you set the gun for 15 degrees shine it at the marks and they should line up... if not adjust the gun so they do and this will tell you what the ecu is actually setting the timing to (ie how far the crank trigger is out which can normally be trimmed in the ECU software). You also need to be aware that with wasted spark ignitions electronic timing lights often get confused and read double. On mine with 15 degrees advance on the engine I need to set the light to 30 degrees to get the timing lights to line up. this is due to there being twice the amount of sparks on a wasted spark system, so it thinks the engine is turning at double the speed, so it throws the calculation out.

[GreenMini17]

Ok, there are a few things that can cause issues with this,
 
first off, is your system wasted spark? and what timing light will you be using?
 
as above you need to accuratly find and mark TDC, the method I use for this is the "dead stop method" ie an old spark plug with the middle knocked out, I have put a bolt through this so it contacts the centre of the piston near TDC, you can then pop this in to no1 turn the engine over slowly with a spanner till it touches the piston and stops, make a mark in tipex or white paint, wind the engine back the other way til it locks, mark it again..... then put a mark half way between the two, this is the one you use, so wipe the others off.
If you have no marks at all you'll need to make a reference mark on the timing cover when you make the first mark.
I have actuall gone a step furthur than this on my current engine, and drilled a hole in the flyyheel case so I can see the ring gear, I have one tooth painted white, and a white mark on the casing, as the flywheel is a larger diameter its a more accurate mark.
 
 
Timing lights...... you will need an adjustable one, as the ecu will be giving an amount of ignition advance (say 15 at idle) so you set the gun for 15 degrees shine it at the marks and they should line up... if not adjust the gun so they do and this will tell you what the ecu is actually setting the timing to (ie how far the crank trigger is out which can normally be trimmed in the ECU software). You also need to be aware that with wasted spark ignitions electronic timing lights often get confused and read double. On mine with 15 degrees advance on the engine I need to set the light to 30 degrees to get the timing lights to line up. this is due to there being twice the amount of sparks on a wasted spark system, so it thinks the engine is turning at double the speed, so it throws the calculation out.

Im using a wasted spark system. I understand how to get the number 1 piston to tdc. What i dont get is the part where you say 'wind it back until it locks'? Do you mean i need to rotate the pulley in the opposite direction and mark it when this hits tdc as well? Surely marking in between the two exsisting marks will not be tdc? I believe the timing light im borrowing is adjustable. So i need to adjust my timing light reading until the tdc marks line up? Correct? Then i can input this into my ecu software. Bearing in mind i need to half the timing light reading? Thanks for the help. Ive never really got involved with ignition stuff!!

[mini13]

if you mark it when it touches the stop each way you will have a mark  a few degree's either side of TDC, half way between these is TDC.

[GreenMini17]

if you mark it when it touches the stop each way you will have a mark  a few degree's either side of TDC, half way between these is TDC.

Im still not sure i completely understand but i will give it a try and im sure it will make sense then! Also, piston number 1 is closest to the rad yes? And the mark i make on the pulley is inline with the largest spike on the timing case with '0' on it, yes?

[mini13]

Yes to both.