N62 compression test question
 

Hello, I want to do a compression test on my car but Ive heard stuff about Valvetronic varying the result on the actual psi reading, can someone tell me if this is true and how this happens?

Valvetronic limits the amount of air that can get into the cylinder, the same way as a throttle body being closed. Pressing the accelerator pedal will not force Valvetronic to increase lift.

The numbers may seem lower than other engines with the same compression ratio, but ultimately the more important thing here is the variance between cylinders. Compression test all cylinders and if one is drastically lower than the rest, it signifies a problem.

your valvetronic actuators will set to the same position when cranking over the car so it's not going to implement any real variance.

all you need to do is warm up the car, remove all spark plugs, release both bank fuel injector connectors (1 each side located on top valve cover cable tray). and crank each cylinder until the compression gauge stops (usually 5 compression strokes)

that makes so much sense thank you :thumbup:

sounds pretty simple, thank you

Well sorry to revive and old thread but what results did you get?
I took my engine (N62B48) apart and did a bunch of things, replaced everything I could, did valve stem seals, timing chain, guides etc. Now can't seem to start my engine. Checked a couple of cylinders for compression, they're both at 100psi. So I'm not sure if something is messed up or if that's normal due to valvetronics?

Hello, if im not mistaken im pretty sure I got like 120psi, you should look out for variance instead mentioned by some of the people under this thread. My problem was that one of the valves in cylinder two wasn't sealing properly. What do you mean you can't start your engine? Does it just crank away?

Is stock compression more than 10:1?

Yeah the engine cranks.

I'm not sure what's going on. I timed it well, but something is wrong...

1-8 are cylinder numbers

With valvetronic motors installed:
1. 20 psi
2. 85 psi
3. 20 psi
4. 85 psi
5. 100 psi
6. 95 psi
7. 90 psi
8. 105 psi

With valvetronic motors removed:

1. 30 psi
2. 85 psi
3. 25 psi
4. 95 psi
5. 120 psi
6. 155 psi
7. 145 psi
8. 90 psi

oof, those psi values vary a lot. Have you done a leak down test to find out where it's leaking from?

I have no doubt the leak is from the valves.
I'm trying to understand the valvetronic system but cannot find information.

It's possible I didn't time the engine properly. Because I tried doing a leak down test on it when it was out and I was timing it. But then I had leaks on all cylinders.

My friend told me it's normal, because valvetronic system was not installed.
I'm now thinking he had no clue what he was talking about.

I was extremely sure I timed everything correctly.

What I'm trying to understand right now is how this valvetronic shaft actually works. I can't find anyone talking about this one specific aspect of it.

With the valvetronic motors removed, can the valvetronic shaft be exerting pressure on the camshafts still, through the intermediate lever, keeping the valves open? Is for, how can I make sure that the valvetronic is in a position where it doesn't exert any pressure on the camshaft?

What I'm trying to dissect is if it's possible that the valvetronic shaft is causing my valves to stay open, or if something happened to camshaft timings.

That's why ideally I would love to see people's values of valvetronic systems and camshaft positions on INPA to compare it to mine.

But it doesn't seem I'll be able to get the information I need. So I'll take things apart again and try to retime it. But what if I take it apart, and find everything properly timed? What if the valvetronic is somehow interfering with camshaft timing? I don't know what to do then. TIS procedures don't mention anything about valvetronics when timing the engine..


I've also been looking at TIS and some things are confused.
I don't understand what camshaft adjuster they're talking about

11 31 071Check the timing for the camshafts on the right (N62/N62TU)

Attention!
When the engine is stopped, the intake and exhaust camshaft adjusters are normally locked in their initial setting.

The situation may arise in some individual cases where this initial setting is not reached and the camshaft can continue to be rotated in the adjustment range of the camshaft adjuster.

In order to avoid incorrect timing adjustment, it is essential to check the locking of the camshaft adjuster and if necessary perform locking by rotating the camshafts.

Checking locking of intake adjuster in initial setting:

Position at the hexagon head of intake camshaft and try to carefully turn the intake camshaft against the direction of rotation.

If there is no fixed connection between intake camshaft and intake camshaft adjuster, rotate intake camshaft against direction of rotation until limit position.

The intake adjuster is locked in the initial setting when the intake camshaft is non-positively connected to the intake adjuster.

Checking locking of exhaust camshaft adjuster in initial setting:

Align at the hexagon head of the exhaust camshaft and carefully attempt to rotate the exhaust camshaft in the direction of rotation.

If there is no fixed connection between exhaust camshaft and exhaust camshaft adjuster, rotate exhaust camshaft in direction of rotation until limit position.

The exhaust camshaft adjuster is locked in the initial setting when the exhaust camshaft is non-positively connected to the exhaust camshaft adjuster.

Attention!
If the intake or exhaust camshaft adjusters of the camshafts ”cannot” be locked as described, the adjuster is faulty and must be replaced.

I have no experience with n62 but I did tear a b58 valvetronic head apart completely (and put it back together). You should be able to turn the motor with a 4 mil hex key back to the limit position so the shaft is all the way disengaged. It should be fairly hard to turn counterclockwise as it's pushing the lever down, and then a little easier to turn clockwise and then at the very end it should spin clockwise really easily as it all lets go. There's also a service function to teach in the limit positions.

Interestingly I could only get 90 PSI on the compression check with the b58 that was hurt. I borrowed my neighbor's gauge and same thing. The factory manual says to put the accelerator pedal to the floor, but it didn't make any difference. I could never figure that out.

I think you might be out of time. When I did the timing on m52 I followed the directions but it didn't sit flush on the intake side. Repeat everything the same way and then it sat flush, don't know.. I also screwed the timing up on my Honda d16, it ran poorly and smoked bad, off a tooth.

What was the compression before you did all the work that you talk about in your thread?

Unfortunately N62s don't have the hex screw adjusters at the back of the valvetronic motors.
But I guess once they're removed, there's no more pressure on the camshafts from the eccentric shaft.

To answer the question about the compression before I did the work, i didn't check it. But the engine ran no problem.

I took off the valve cover off bank 1 yesterday, with crank locked at TDC, and my bank 1 camshafts, both intake and exhaust, were like 180 degrees off.
How that's possible I don't understand. I would've locked the crankshaft with the damper pin when I timed the engine the first time, and the camshafts have very obvious marks.
I had even made a video of how those camshafts are supposed to be pointing.

https://youtu.be/Y7kALRAkBwE?si=XbnLxS_ZypxnjSDp

So I really don't understand how I could've had them installed completely wrong
I retimed bank 1 and did a leak down test, and all cylinders are showing 100% leakage. So I don't know if I bent my valves or what.
If I bent the valves, I don't understand how, given that I had turned the engine by hand after timing it the first time (which seems like was done incorrectly).
I ordered an inspection camera to look at the valves, as I'm kinda at a loss with all this, which seems led so straightforward before

With one cam the crank doesn't care which stroke is exhaust or compression but when there are multiple cams they have to be timed together with the crank for compression or exhaust.