This means that a passenger side bank cylinder fires and then the opposite cylinder on the drivers side bank fires working it's way from the rear of the engine block (#1 & #4) to the front (#3 & #6) in a left-right-left-right-left-right pattern (as seen from the front of the car).
This is based on the lobe positions of the camshafts where the intake and exhaust lobes are farthest away from the lifters. Each coil fires two cylinders at the same time with one wire going to the cylinder with both of the cam lobes away from the lifters (top of compression stroke) and the other coil wire going to the opposite bank to the cylindar where the cam lobes are both pressing the lifters (overlap). The spark in the cylinder during overlap does nothing since there is no fuel/air in the cylindar.
I used a strip of paper about the width of the ribbed belt to wrap around the crankshaft pulley and marked it so that I had the exact circumference. I then folded the strip into 3 separate sections and marked the two fold creases and then taped it to the pulley so that the seam was at the TDC mark for cylinders 1, 5 and the two marks at the paper folds were exactly at 1/3 around which is the TDC for cylinders 4, 3, and 2, 6.
The alignment brackets on the front of the cam sprockets can be installed on either cam and are designed so that #1 cylinder is always at TDC compression stroke when using the camshaft alignment tool. It is impossible for there to be any other configuration.
I have no idea what the numbering is on the label on the coil. It makes absolutely no sense at all. Only the first two numbers in what appears to be the firing order are correct. But the camshafts do not lie!
It took about 3 hours to pull the heads last night. The head gasket was leaking into the coolant at cylinders #2 and #3. I need to go buy a strait edge to check the heads for warping.
Just a tip on lighting: I used a single halogen work light (used for construction) that I picked up from Home Depot and tie-wrapped it to the center latch of the hood so that it illuminated the entire engine bay. If you are going to R&R a rack or do any major work in the engine area, I highly recommend using a halogen work light. I didn't even need to use a drop light except for when I removed the nuts from the exhaust flanges under the car.
With the camshaft tool installed, the passenger side rear cylinder is at TDC of the compression stroke and therefore must be #1.
The label on the coil that was in the image that you posted doesn't have the cylinder numbering because the drivers side bank is not in linear order but instead, shows what cylinders each wire goes to:
Then the firing order listed on the label would match: 1-4-3-6-2-5. However, using this numbering, #1 cylinder is NEVER at TDC when the mark on the crankshaft is aligned with the mark on the timing cover! Only the PS rear cylinder and the DS middle cylinder are at the top of the travel with the crankshaft mark lined up.
If you use cylinder numbering based on the crankshaft mark and camshaft positions:
Then this firing order is correct and cylinder #1 is at TDC with the crankshaft pulley mark lined up: 1-4-2-5-3-6.
Therefore, coil label with the firing order and cylinder numbering (partial) must be only to aid in identifying where the wires should go and have nothing to do with the TDC mark on the crankshaft. I have never seen or heard of any engine, whether it be for a car, boat or aircraft, made with anything other than the #1 cylinder at TDC when the flywheel mark is aligned. That is pretty universal.
This is a strange anomaly and is probably the reason that there is no mention of firing order or cylinder numbering in the Bently or ElsaWin manuals. The closest thing that I could find was in the engine block section that illustrated marking the pistons with I, II, and III and it appeared to be the PS bank but it wasn't very clear.
So, the correct cylinder numbering and firing order depend on whether or not you need for the crankshaft mark to align for the #1 cylinder.
Both of the following are correct:
Cylinder #1 is at TDC with the crankshaft pulley mark lined up:
--- FIREWALL ---
--- RADIATOR ---
Firing order: 1-4-2-5-3-6:
Cylinder #3 is at TDC with the crankshaft pulley mark lined up:
--- RADIATOR ---
Firing Order: 1-4-3-6-2-5 (as listed on the coil label)
Note that TDC with the crankshaft pulley mark lined up means that the passenger side rear cylinder is either in the compression stroke or overlap stroke. Using the camshaft alignment tool or making sure that the larger holes on the cam sprocket alignment brackets are between the camshaft bolts and the smaller holes are on the outside when the pulley mark is lined up will ensure that the passenger side rear cylindar is at TDC compression stroke. If you don't know where the camshafts are when the pulley mark is aligned, then the passenger side rear cylinder could be either in the compression (time to spark) or overlap stroke (between exhaust and intake).
curiously, though, Bentley doesn't appear to clearly define the cylinder locations. There's been lots of discussion about this over the years, and about which cylinder is at TDC when the engine is set to "TDC". It pretty much accepted that when the engine is set at TDC using the marks on the crank pulley #3 piston is at TDC. Here are a few threads discussing it:
Correct. Cylinder #1 is ALWAYS at the front of the engine. For the 12V V6, #1 is on the right...
side (passenger), with #2 and #3 following on the same side. Cylinder #4 is located at the front, on the left side (driver's side) of the engine, followed by #5 and #6. The firing order per the Bentley manual (and the label on the coil pack) is 1-4-3-6-2-5. TDC means #1 is at TDC. Since there are 6 cylinders, each piston is positioned at 60 degree intervals (360/6 = 60). So, the exhaust cam lobe for #1 should be approaching the exhaust valve lifter when #1 piston is at TDC.
Came up with this idea to verify the TDC mark on the vibration damper of a 2.7t V6 engine. You can buy a similar USB snake cam (aka endoscope or borescope) for about $20. The camera head of mine is slightly bigger than the Audi spark plug thread, which is perfect.
I used a 15 inch breaker bar and a 15/16" socket (my substitute for the 24mm socket) to move the crankshaft near the TDC marker. Then while watching the computer screen, crank back and forth the TDC marker.
Inserting the snake cam into the passenger side front cylinder (closest to the radiator) shows that the cylinder is at bottom dead center, further away from the spark plug.
As shown in the attached picture, inserting the snake cam into the passenger side back cylinder (closest to the firewall) shows the cylinder is at top dead center, closest to the spark plug.
How you name that cylinder is a matter of choice, but TDC for the entire engine refers to cylinder one at TDC. This means physically, David (DMW96A6) is correct about the location of cylinder one.
For a 4-stroke engine, there are 2 TDC per cylinder per firing cycle,
but most people refer to the ignition TDC instead of the exhaust TDC. That means ignition-wise, David's firing sequence is also correct.
Conclusion: the first post of this thread is correct.
but TDC for the entire engine refers to cylinder one at TDC.
That little assumption is not correct for this motor.
You could have accomplished the same thing with a 3-cent piece of wire or a free pair of chopsticks from your favorite Chinese restaurant by sticking either of them through the same hole you deployed your camera into.
Anyone still questioning this should see my earlier post with all the links.
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