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stevefh

S4 timing

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Hi all,thought I had set the timing correctly but she is running with the exhaust manifold and cat getting very hot.Done about 3 miles at 30 mph or less and didn’t notice any loss of power or popping out of the exhaust.

First q.   Are the red and blue timing marks as seen from the front of the engine repeated in exactly the same positions on the back of each pulley? If not there’s my problem as I did it from the rear

second q.I double checked the spot alignment at TDC with the cam belt fitted but not tensioned. I tensioned at 30 BTDC to 110hz a few times but can’t remember checking the spots and TDC were still correct.Could the tensioning have upset the timing to cause my problem.

Third q.Can you suggest another cause.

thanks for any help

 

 

 

 

 

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Thanks Andy,so if I use a mirror to look for the spots from the front with my current setting they won’t be there!From what you say I have set the cam pulleys 180 degrees out, how can it run?

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As Andy said. Better check you haven't damaged any valves as a result of this. I would recommend you don't run it again until you have set the cam timing correctly. Would also do a compression check once cam timing is correct and  aligned to get an indication.

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Yes, check them at the front but also check them by aligning the centres of the cams, not just the dots being together.

Our cars run wasted spark, so they fire on two cylinders at once, one being wasted by virtue of there being no compressed fuel & air mixture to ignite. So, with the engine one crank revolution out it still fires at the correct time. The fuel is fired based on a flywheel sensor, so each cylinder's delivery can only be based on crank/ piston position, not whether the exhaust valve is opening vs whether the inlet valve is, so again, it doesn't really matter. What does matter is that it's easy to get out by one tooth on a cam timing  if you approximate where the alignment should be, so either use a rule running through the mid points, or use two rules (one above the camshafts, one below) and measure to find the mid-point line.

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You need to look from the front.

double and triple check alignment cos one tooth out is all too common

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Andy are you saying that from the front ,  the inlet pulley  has a blue dot directly behind the front red dot and 180 degrees away vice versa?It is raining hard so I had a quick look using a mirror and exactly in front of the red dot on the inlet pulley (seen from the rear ) is a dot but I cannot make out its colour. This would be repeated on exhaust pulley ?

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What I'm saying is, if you have two identical pulleys, and line up the keyway, you'll see that the coloured dots are in the same place, now turn just one of the pulleys so that the "back" is facing you and align the keyways, compare the two pulleys again and you'll find that the dots still are aligned, the point being, they are not just a repetition of the dot the other side. So as @sailorbob states, using the dots on the back will throw the timing out (the exact amount depends on the engine configuration, so 10deg may well be right for an S4). 

 

If you get a piece of carboard, long enough to sit across both camshaft nuts, cut circular notches  of  10.0mm-10.5mm (I think they are 19mm nuts, so think that's the circle of a 19mm nut allowing for rounded corners) radius at the ends, that will sit on the nuts and give you your line between the camshafts, the line where you need the coloured dots to align with at TDC.  Then, the work with the mirror in the rain will be pretty easy.

 

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Just looked at a pulley. You cannot look at the dots on the rear. The way the pulleys are marked with the key ways and dots - one side is for exhaust cam the other for inlet cam.

you will need to set up the timing again from the front of the engine 

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