Cam Timing - Optimum Setting for S4
12-12-2007, 12:23 PM
#31
Rennlist Member
That was some good info.
so, it seems the bottom line is the cams dont need to have 2mm variance. (about 2-5 crank degrees). Great ideal with the timing light. can you do this with the timing belt peak hole and look for the notch line up? (with some better colored paint?) this means if the cams are off .5 or 1 crank degree, they are off .25 to .5 cam degrees. that wouldnt equate to the .2mm the manual specs out. probably more like .1 degree or half the spec difference. (thats a guess).
what i do know is when i moved the cam to be equal to the driver side setting, i moved it about 2mm at the securing screw on the cam pulley.
when i did my compression test, i did have some variance, but i forget which way. I think the driver side was higher by about 5psi before the change.
Now, is pretty even all the way around! (190psi +/- 1-2psi)
mk
so, it seems the bottom line is the cams dont need to have 2mm variance. (about 2-5 crank degrees). Great ideal with the timing light. can you do this with the timing belt peak hole and look for the notch line up? (with some better colored paint?) this means if the cams are off .5 or 1 crank degree, they are off .25 to .5 cam degrees. that wouldnt equate to the .2mm the manual specs out. probably more like .1 degree or half the spec difference. (thats a guess).
what i do know is when i moved the cam to be equal to the driver side setting, i moved it about 2mm at the securing screw on the cam pulley.
when i did my compression test, i did have some variance, but i forget which way. I think the driver side was higher by about 5psi before the change.
Now, is pretty even all the way around! (190psi +/- 1-2psi)
mk
I suppose there are different methods to "sync" the cams, and everyone has their favorite. I've used a timing light to measure the cam timing difference between a cold and a hot engine and come up with numbers that show that the left side (drivers) cam advances about 2 crankshaft degrees when it gets hot and the right (pass) side advances about 3 crank degrees. It's kinda hard to tell the difference between 1 crank degree (0.5 cam degrees) so you can take those numbers as one step better than an educated guess. Since the cam timing is most important when the engine is at operating temp, I do my sync testing when it's up to temp. I measure compression on each side as soon as possible after it's been shut down. That way you don't need to take time to disassemble anything other than remove the plugs. Remember to open the throttle and let the engine turn through the same number of compression strokes (5 or 6) for each cylinder. Average the compression readings on the 4 cylinders on each side. The side that is retarded will have lower compression in relation to the other side. Then you decide whether you want to advance one side or retard the other side to get each side the same. Whether you advance one side or retard the other side depends on what engine characteristics you want. Use Ken's tool to make the adjustment on the side you want to change. One or two degrees is noticeable on compression. Put the rotor back on, run the engine up to temp again and take another compression reading. When each side is equal, or as equal as you want to take the time to work with, measure the cam timing on each side with Ken's tool. Write it down where it won't get lost and that's your reference for cam timing and cam sync. Better yet, take a picture of the Porken tool in place so there is no doubt later as to how they were set. If you have to get in to change sprockets or for some reason disturb cam timing, you can always get back to your reference. If you want to change cam timing on both sides for a performance check, you can change both sides from the reference with Ken's tool.
If you are putting on a new cam belt and/or sprockets, don't spend a lot of time getting real close reference right then. Wait until you have several thousand miles on the belt & sprockets before you tension them and take your reference. The timing will change a little between new belt and used belt.
If you are putting on a new cam belt and/or sprockets, don't spend a lot of time getting real close reference right then. Wait until you have several thousand miles on the belt & sprockets before you tension them and take your reference. The timing will change a little between new belt and used belt.
12-12-2007, 01:46 PM
#32
Three Wheelin'
That was some good info.
so, it seems the bottom line is the cams dont need to have 2mm variance. (about 2-5 crank degrees). Great ideal with the timing light. can you do this with the timing belt peak hole and look for the notch line up? (with some better colored paint?) this means if the cams are off .5 or 1 crank degree, they are off .25 to .5 cam degrees. that wouldnt equate to the .2mm the manual specs out. probably more like .1 degree or half the spec difference. (thats a guess).
what i do know is when i moved the cam to be equal to the driver side setting, i moved it about 2mm at the securing screw on the cam pulley.
when i did my compression test, i did have some variance, but i forget which way. I think the driver side was higher by about 5psi before the change.
Now, is pretty even all the way around! (190psi +/- 1-2psi)
mk
so, it seems the bottom line is the cams dont need to have 2mm variance. (about 2-5 crank degrees). Great ideal with the timing light. can you do this with the timing belt peak hole and look for the notch line up? (with some better colored paint?) this means if the cams are off .5 or 1 crank degree, they are off .25 to .5 cam degrees. that wouldnt equate to the .2mm the manual specs out. probably more like .1 degree or half the spec difference. (thats a guess).
what i do know is when i moved the cam to be equal to the driver side setting, i moved it about 2mm at the securing screw on the cam pulley.
when i did my compression test, i did have some variance, but i forget which way. I think the driver side was higher by about 5psi before the change.
Now, is pretty even all the way around! (190psi +/- 1-2psi)
mk
Yes, you can check with a timing light using the vent hole on top of the cam belt cover. The normal markings on the cam sprocket aren't very good for this. Next time the cam belt covers are off, set the engine to TDC and make a narrow mark on the back side of the cam sprocket that lines up with the little V notch on the plate behind the sprocket. When the engine is cold, use a timing light with an adjustable delay (one with a degree ****) and take a reference at 0 deg (TDC) on the crank. Then point the light through the hole in one of the cam belt covers and move the timing light dial until the mark you put on the sprocket lines up with the notch in the plate behind it. Check the timing light dial for a reference on that side. Do the same for the other side. Go back and re-check TDC reference number on the crank to be sure it hasn't changed. Ignition timing will change as the engine warms up. Do this all over again when the engine is hot and you can see the cam timing change. One some engines I didn't see any cam timing difference cold to hot between sides and on others I saw around 1 crank degree +/-. It's hard to see small differences like that. Like you found, I think the cam timing difference between sides the WSM procedure recommends is too much. Maybe half of that would be ok. Follow up with a hot compression check to see where you really are.
Knowing what the cam timing difference is between a cold or hot engine doesn't have a lot of relevance when you are using the WSM procedure for cam timing. If you are using the Porken tool, or trying to set cam timing with some unknown cams such as the Phil Threshie, or Devek B1, then you do need to know what timing change will happen when the engine is hot because you are setting the initial timing when it's cold.
