Valve position at TDC

[RDA990]

When the engine is at TDC with the camshaft marks facing up are cylinder 1 or cylinder 4 valves fully closed on the compression stroke?

[Smac770]

https://www.ebay.com/itm/133383137942
can also check the product on ECS, though I was curious why the print on the VVT on the ECS pic looked so "cheap".
But they all seem to show the same thing, timing mark up, cyl 1 lobes down, cyl 4 lobes coming up.

[Theiceman]

It wouldn't make sense that both are on compression. I would imagine cyl one compression cyl 4 exhaust.
1342 is the firing order

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[mc_hotmail]

There are 2 TDC in each cylinder's 4-stroke cycle: compression TDC (right before ignition) and exhaust TDC. At compression TDC, both intake and exhaust valves are closed (they have been fully closed since compression bottom death center BDC). At exhaust TDC, the exhaust valves are open (they have been opened since exhaust BDC), but the intake valves are closed.

The B8 engine cam shafts next to cylinder 1 valves also have a cut-out. At compression TDC, the cut-out of the exhaust cam and the intake cam should be facing each other with a slight angle, similar to the cam sprocket marks. That cut-out also fits a 16mm wrench used to press the valve spring a little when fitting the timing chain.

[RPMtech147]

Firing order 1-3-4-2, like just about every I4 I've seen.

The maths are beyond me. I've never checked. When I bolt down heads, I back the crank off a few degrees so I know all the pistons are "down enough" and it doesn't matter where the cams are. What do you need the info for? I always have at least 1 2.0t apart, I'd be happy to check for you tomorrow, but I feel like it couldn't be relative to any situation.

1 and 4 run together (and 2-3) as far as physical piston height is concerned.

[Smac770]

Pics pretty much spell it out.

CAE exhaust cam order.jpgCAE intake cam order.jpg

So we see on the intake side that cyl 2 just closed and cyl 1 is about to open.
On the exhaust side we see that cyl 1 just closed and cyl 3 is about to open.

Cyl 1 TDC happens twice per cam revolution, but the marks up cyl1 TDC appears to be:

just finished:
cyl 1 exhaust
cyl 3 power
cyl 4 compress
cyl 2 intake

about to start:
cyl 1 intake
cyl 3 exhaust
cyl 4 power
cyl 2 compress

[Smac770]

Jeez, the attachment image presentation sucks so bad here. Well, click on the pics to view the markers. Remember, the cams turn same as the engine, clockwise.

[RDA990]

https://www.ebay.com/itm/133383137942
can also check the product on ECS, though I was curious why the print on the VVT on the ECS pic looked so "cheap".
But they all seem to show the same thing, timing mark up, cyl 1 lobes down, cyl 4 lobes coming up.

I didn't think of looking at the camshaft lobes to figure it out. I assumed that at TDC cylinder 1 would be on compression with all valves fully closed since the firing order is 1-3-4-2.

It wouldn't make sense that both are on compression. I would imagine cyl one compression cyl 4 exhaust.
1342 is the firing order

Sent from my SM-G973W using Audizine Forum mobile app

You're right, I should have asked which cylinder is on the compression stroke at TDC.

What do you need the info for?

Performing a leak down test. I thought I had bad cylinder 1 exhaust valves this whole time at TDC but it turns out cylinder 4 has all the valves closed instead.