Home made in cylinder transducer

Weycraze wrote: Please keep me posted on your findings Noah.I'm now wondering that your mechanical gauge was just measuring those humps which would be amplified with RPM increase.

If the humps are caused by the exhaust valve closing early they wouldn't affect exhaust pressure. If they showed up anywhere, outside the cylinder, it'd probably be as pulses in the intake.

Noah wrote: I will let you know when we get a cat on it.

The anticipation is killing me. :woohoo:

Actually no, Matt T pointed that out, sometimes I get a little ahead of myself. A gauge in an O2 bung would not pick that up. Only an in-cylinder transducer would pick up the restriction when exhaust valves open. Thanks, Matt T!

Now I'll throw this in there if all the cylinders had the same waveform; that would point towards timing ie chain stretch. But if the hump is just this lone cylinder, by virtue of engine design, a lifter issue.

The reason I lean towards timing/chain stretch is the duration of that intake event which I approximated at ~240-50ish degrees which is a very plausible spec, without knowing the true spec.

It would be sweet of you to post the vsm files you have.

Paul

Weycraze wrote: Actually no, Matt T pointed that out, sometimes I get a little ahead of myself. A gauge in an O2 bung would not pick that up. Only an in-cylinder transducer would pick up the restriction when exhaust valves open. Thanks, Matt T!

If it makes you feel any better, I had the EXACT same reaction when I first saw the in-cylinder waveform. Noah will tell you - I said timing problem. :silly:

Your Awesome Tyler!!!! YES, that does make me feel better!

It will be very interesting to see the outcome here.

Tyler was the first person I showed the waveform to and that was his immediate response.
I see it.
But...
If I never put a transducer in it and only did a back pressure test, I would put a cat in it with 100% confidence.
Especially considering there's a sensor on each camshaft and that there are no codes.
I'm not saying the chain isn't stretched, the miles alone suggest it may be. But if I hadn't used a transducer, I'd have no reason to suspect it.

I will post the file when I'm back at work.

Weycraze wrote: Thanks, Matt T!l

You're welcome Paul. It seemed plausible at first glance. Took me "a minute" to catch that the exhaust valve would have to be closed for it to be causing the pressure hump.

The strange thing about this engine appearing to have a timing problem is that the exhaust looks advanced but the intake retarded which seems unlikely unless someone has been in there.........

I think, too damn much :lol: ,there are a couple things which might be making things look strange. First is this engine probably has VVT which might be altering the valve timing??

Second is RPM isn't going to be constant on a 4 banger with a dead hole. Speed will drop during the dead holes power stroke then build back up. So cursors equally dividing 720* between TDC compressions aren't going to line up perfectly with the other BDCs and TDC.

One other thought on the exhaust hump is it might be caused by exhaust vale overlap. The next cylinder opening its exhaust valve while the transducer cylinders exhaust valve is still open. That next cylinder could be causing a spike in exhaust backpressure which gets pushed into the transducer cylinder??

Cam timing looks just as screwed up at idle. But I've found something that could explain it.

2AR-FE motor gained the Dual VVT-i system (variable valve timing with intelligence), driving intake and exhaust camshafts within 50 and 40 degrees accordingly concerning crankshaft angle. What is more, valve overlap varied from 7 to 97 degrees while intake and exhaust duration was equal to 244 degrees.

I figured up the time for 2 x 244* - 7* overlap and set the cursors to it. It seems to fit the waveform pretty good.

Matt T, good thinking about the VVT. I do know that the in-cylinder waveform is unique to a cylinder, another cylinder's valve events won't affect that. Intake Pulls and Exhaust Pushes are affected by other valve events.

This is a non-turbo engine, so this hump is preventing 'scavenging' in the combustion chamber. This Rise in pressure at the end of the Exhaust stroke as the piston is approaching TDC can only be because of all Valves Closed.

Weycraze wrote: This Rise in pressure at the end of the Exhaust stroke as the piston is approaching TDC can only be because of all Valves Closed.

Recently I was reminded in another post that we have to be VERY careful with qualifiers like always, never, must be, can only....

There are other possibilities to cause such a rise in pressure, for example a blown head gasket on a neighboring cylinder being on compression stroke. This usually will show up as a rise in pressure in the last 20 to 30 degrees before TDC exhaust in the affected cylinder, depending on the severeness of the leak.
Sure, there would be other symptoms like low compression and it would affect both neighboring cylinders in a similar fashion..

Another variable is a stuck open EGR valve .....

Thank-you juergen.scholl. Those are wise words not to use 'never', 'only'. They usually bite you in the behind. lol

But, that is absolutely correct, based on the cylinder chart in the post if there was a head gasket leak between Cyls 1&2, and 2 was on the Exhaust stroke, 1's Power stroke would be evident exactly as you describe.

So there definitely are other variables.

Interestingly enough, the waveform sure matches this one; but that would really depend when EVO occurs.



Thanks,

Paul

The Camry had it's turn in the shop today.
This is the capture taken in cylinder after changing the cat:

You can see that through the over all range that exhaust pressure remained steady. A great improvement over the other cat.
Gauge pressure confirmed the restriction had been removed.


However, power was not restored. So, in the eyes of the boss-man and the other mechanics, I blew the call.
Whatever, the cat was clogged, it just wasn't the whole picture. The car is just a junk auction clam, so there's no pressure and no customer to answer to thankfully.
Then it gets extra stupid...:silly:
I installed a fuel pressure gauge to appease the boss. Fuel delivery isn't on my list of suspects based on my prior test drive data.

To T in, i removed the entire snorkel, MAF, filter, etc.
It didn't want to run, but i managed to give it the magic boot and noticed that after a bout of bucking and farting that it was free revving better than it ever had :S ...
I removed my pressure gauge, installed the air cleaner assembly and suddenly the car has 95% more power.
I don't know what changed.
I cleared the codes I had set thinking maybe it finally decided to ignore the MAF, but that was not the case.
This is not the gratifying outcome I was hoping for.

This the in cylinder idle waveform as it is now.

There's still the tail at the end of the exhaust plateau that suggests the exhaust valve is closing too early, but you can actually drive the car now, and I'm not sure why. :S

Noah wrote: To T in, i removed the entire snorkel, MAF, filter, etc.
It didn't want to run, but i managed to give it the magic boot and noticed that after a bout of bucking and farting that it was free revving better than it ever had :S ...
I removed my pressure gauge, installed the air cleaner assembly and suddenly the car has 95% more power.
I don't know what changed.

You may have fixed a restriction somewhere in the air intake. Do you have MAF and MAP PIDs in your pre-fix scan data?

Matt T wrote: You may have fixed a restriction somewhere in the air intake. Do you have MAF and MAP PIDs in your pre-fix scan data?

I wondered the same? :huh: But I looked back at the first in-cylinder capture. If 500mV is atmospheric for his sensor, and the lowest that the intake pull went to during the WOT snap was right at 500mV, then that would suggest the intake was truly at atmospheric pressure.

A restriction that was screwing with airflow across the MAF, maybe? But then why did the upstream A/F show rolling coal rich during the WOT test drive? :silly:

However, power was not restored. So, in the eyes of the boss-man and the other mechanics, I blew the call.

Haters gonna hate. Waiters gonna wait.

Atta boy Noah, awesome diag. Looks like you were up against a couple of issues and came out ahead. Tell your Boss to put the old Cat in and take her for a ride!! He'll come back and thank you!

Nice Work,

Paul

Is it possible that the air filter was/is coming apart and restricting the airflow?
I once experienced this on a Ford F150 where the plastic cone came off the filter. The car would bog down on heavy accelerating/WOT as the cone was sucked into and blocking off the air.

Could just be carbon buildup on the intake side of valves due to the backpressure pushing back into intake with the plugged cat. Time for some seafoam or pop intake off and clean intake runners and valve ports with some cleaner.

juergen.scholl wrote: Is it possible that the air filter was/is coming apart and restricting the airflow?
I once experienced this on a Ford F150 where the plastic cone came off the filter. The car would bog down on heavy accelerating/WOT as the cone was sucked into and blocking off the air.

The air filter looks to be brand new-ish.
There was this bit of under britches integrated into the lid of the filter housing assembly.


And there were some leaves in the bottom of the box, pre filter, but I don't think either one explains the change in symptoms.
It still barely ran with all of that off the car until I gave the throttle a right boot work out.

I returned said under britches to it's place in the filter box and it still runs just the same.

Weycraze wrote: Atta boy Noah, awesome diag. Looks like you were up against a couple of issues and came out ahead. Tell your Boss to put the old Cat in and take her for a ride!! He'll come back and thank you!

Nice Work,

Paul

Thank you Paul, it still doesn't feel like a win though.
Many unanswered questions...

As for the boss, I'm not interested in convincing anyone at the shop. I find that when I'm doubted, the universe has a way of eventually delivering my vindication.