Is this normal?
In the spirit of keeping the in cylinder pressure transducer theme going, I am looking for opinions if this waveform is normal for the above vehicle.
I must preface this by telling you, this vehicle is fixed. The shop that had this vehicle, put a motor, injectors, spark plugs, crank and cam sensors, ignition coils, and had a PCM on the way. Still had the original complaint of cel on, with above codes.
The capture was taken from cylinder one, pardon the wrong 0 and 360 degrees label. It is obviously 720 degrees of rotation. Also I know the top of it is cut off, the compression and PSI was not the problem.
My concern is the vacuum pocket at the end of the exhaust valve event and the beginning of the intake valve event.
Hey Dean , is that deep intake pocket formed from stuck piston rings ?
Joe, no it is not. It is mind boggling what fixed this car. I am really baffled by that pocket!
The piston is traveling downwards at that point, so to make that vacuum pocket would mean that all the valves are closed and the piston is drawing a vacuum as it goes down. Then the vacuum pocket is suddenly relieved, so likely a valve(s) opened. This points to late intake valve timing. That's my thoughts anyways 🤔
By the way, you mentioned "above codes", but I don't see any codes in your post.
That vacuum pocket looks like trouble, I agree. Does this engine have a variable intake manifold that it maybe pulling on a broken or loose runner?
Matt it does have the variable valve lift on the intake side.
It appears to have leaning towers which would indicate a compression loss. Like everyone else I'm having trouble figuring out what's causing that odd vacuum pocket. I'm curious to hear what the fix was.
Bob, believe it or not the compression was fantastic.
Yes sir. And I see you are into hockey? Nice pic!
Yep, I play some old slow beer league hockey. emphasis on the beer.
Ha that's funny. My son plays and loves it. Tough sport, And if it makes you feel any better, the pic makes you look badass.
The exhaust valve it opening at the "wrong" spot. The intake seems to be opening and violently closing. There is no sustained vacuum pocket. Need more info on when this capture was taken. was VVT woking here? Was it stuck? At first glance, seems like a cam timing issue
Just some thoughts, Obviously without being able to measure anything these are just guesses. But with this being a cranking waveform it appears that you have about 1-2 psi exhaust plateau. I think this is making the exhaust pocket look more dramatic than it is but as far as I can tell the valve timing itself does not look unreasonable. And to be honest the intake timing doesn't look way off
Ok this had me curious enough to look up description and operation, not a lot of info but it does say the front oil control solenoid controls cylinders 1,2 and 4 ...interesting... Cant wait until you let us know what fixed it!
If this had VVL, this might make sense. I agree
That would be why it looks like a BMW on the exhaust side.
Ok, believe it or not, the fix for this car was the #1 and #2 ignition coil connectors were reversed. Plugged the connectors into their respective ignition coils cleared the codes and the car ran like a top. The above compression waveform was captured after the PCM shut down the number 1 and number 2 injectors and the vvl which is on the intake side.
Interesting. With all the new valvetrain designs that are out there, it becomes difficult to have any rules of thumb when interpreting in-cylinder pressure waveforms. You really have to collect known good waveforms on any of these new engines if you want to have a chance at finding what's good or bad. I took a snip of your photo above and added some mark-up to it. Keep in mind this mark-up is
Steven, I thought for sure when I saw this, it was indicative of a valve timing issue. It was not.