In this video I cover using a vacuum gauge and scoping a MAP sensor to ID a valve problem. Here is Part 1 of this series http://youtu.be/tZWsOupUzhY Visit my…
In this video I cover using a vacuum gauge and scoping a MAP sensor to ID a valve problem. Here is Part 1 of this series http://youtu.be/tZWsOupUzhY Visit my…
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Also, the overlap of the cam might be seen in the intake waveform. Maybe
that is why we see two distinct humps at the top of the waveform. When you
don’t see 2 clear humps, maybe that is due to poor intake valve sealing.
Also, isn’t it possible we have an exhaust valve leaking, and the shut
intake valve is blocking us from seeing much of that exhaust pulse? We need
to add a channel that measures exhaust pulses.
Is it possible to use a gm fuel tank pressure sensor or a pico wps 500 at
higher resolution to see more exact detail than a zoomed in map sensor?
Slower engine speed should provide more time for a pressure leak to occur
and increase visibility by the scope.
OH man!!!! I cant wait to join the class. i want to pursue full course in
RTI. (the bad part is i am in india)
damn good co learning experience.
Hmm just wondering why not change the trigger to a injector. From my
understanding a injector firing should be paired whit a intake valve
opening. Correct me if i am wrong.
Can you share your capture I have a pico scope also
Paul starting at the 6 min mark you made two different comment as to the
cylinder #1 sinc. at first you said you were using the coil turn on and
after you said you were using the #1 injector turn on. Looks like a coil
voltage spike . I do find this fascinating , hope to see more. For me
I’m completely lost as to seeing a difference.
Here’s how 50:14 should have happened:
Kap: What the f*ck’s an anomaly?
Scanner Danner: Uh, it’s a fifty-something year old instructor not knowing
what the word anomaly means.
I thinks this is one of the most interesting case study so far, Wouldn’t
the leakage past the valve be canceled out from the next intake valve
opening? That is why you didn’t see any gauge fluttering
I would love to see more pico vids
it would be nice if you could split the screen to see you talking and the
smart board at the same time
Thanks
Dang I was looking forward to some pictures
take a temperature on the intake runner(warmer) and exhaust
manifold(colder) of the bad intake valve? and i am thinking that the intake
manifold is balanced/even with airflow enough that the vacuum from the the
good valves and the pressure, if any at all from the one bad valve is
cancelling itself out? yeah if it is just a valve seat problem, most likely
wouldnt show what you want to see on the vaccum gauge or scope. if it was a
bent valve it better show intake manifold + psi. a MAF sensor might be too
far away to try this.
This is Part 2 of a 3-4 part series on troubleshooting a valve problem on a
2008 Hummer H3. The main purpose of the rest of this series is not to
determine whether or not we have a valve problem but to identify which
testing methods will show it. (a leak down test confirmed a valve issue in
Part 1) click here to watch Part 1
http://youtu.be/tZWsOupUzhY
loved the debate !!!!
Given that in a 5-cylinder engine so many things overlap, it’s probably
more useful to focus on specific key points rather than the general shape
of the trace.
Take a look at http://i.imgur.com/lkfUlqT.png for some points I’ve picked
out.
1) Valve opening: the size of the dip when the valve opens gives an
indication as to the pressure differential between cylinder and manifold
immediately prior to opening. As can be seen at #4 opening there is hardly
a dip, so the cylinder was probably much closer to manifold pressure than
#5, indicating that manifold pressure had been leaking into the cylinder
immediately before opening.
2) Valve closing: there is a little spike in manifold pressure when #5’s
valves close, but no such peak in #4. I’m not sure what the physical cause
of this is, but this spike seems to be a good thing. (Maybe to do with the
valve
3) Min manifold pressure: minimum manifold pressure is lowest after #5’s
power stroke, and highest after #4’s power stroke. This indicates that #4
is leaking pressure from the cylinder to the manifold during the power
stroke (when in-cylinder pressure is highest).
4) Max manifold pressure: maximum manifold pressure is in the middle of
#4’s power stroke, again indicating that #4 is leaking pressure from the
cylinder to the manifold during the power stroke.
Based on 1) I’d rank the cylinders 5, 3, 1, 2, 4 in terms of health.
Based on 2) : 5, 3, 2, 1, 4.
Based on 3) : 5, 3, 1, 2, 4.
Based on 4) : 5, 2, 1, 3, 4.
So some conflicting results, with the overall ranking (best to worst): 5,
3, 1, 2, 4.
With a 4 cylinder engine, as there’s much less overlap between power/intake
strokes, you can probably get more detail from the trace itself.
Ford toreass defeated me. Tried everything. EVERYTHING. I will never know
what the hell it was. Ended up swapping motor with a kick back car. That
fixed her.. :(
Paul look at john thorton book that u have learned todo incylinder pressue
testing, intake , exhuast of multiple cylinder overlaps…during the 720
rotation and the waveform is the event of reaction from multiple
cylinders.. 180 degree split u did is good only for single cylinder
pressure test not for all 5 cylinder. in my view u need 5 * 20 partition
within 720 degree..
your vacuum gauge never dipped when you snap throttle it should go down to
zero. but some times there are little one way check valves and those can
mess your readings bad. how about relative compression form with your gm
tank pressure sensor during cranking and control air intake. just a crazy
idea.
Paul I was reading some info and find out that a five-cylinder engine gets
a power stroke every 144 degrees (720° ÷ 5 = 144°).
My thoughts:
Voltage drop = increased vacuum, intake valve opens just before TDC? with
some overlap with exhaust?
MAP is not right at cylinder, there will be a pressure(Vacuum being
negative pressure) wave starting when the valve opens – when the voltage is
highest.
At TDC is when piston is moving slowest. first drop is when exhaust is
still open, flow out exhaust valve causes vacuum in cylinder, exhaust valve
then closes causing buildup of pressure in cylinder due to inrush of air
not instantly stopping – second peak?
I’m thinking the vavlve opens just before the first peak on the blue trace,
closes around the lowest point.
I think you have the cylinder positions in the right place.
(I could be completely wrong, just what I think I’m seeing…)
In part 1 we could see lower compression in the relative compression test
when comparing the humps. Perhaps the reason for not finding anything in
the in cylinder pressure test and the MAP test is because it is such a
small leak that the air needs time to escape from the cylinder. It is not
that it is a massive leak. At cranking speed there is enough time for air
to escape but when the engine is running at idle it is much less
significant and when revving it even higher the compression loss is
probably next to nothing. If it is that a small leak then you would not see
any pressure rises in the intake because there is not enough volume of air
leaking out the cylinder to create a pressure increase in the intake at
all.
nice work sir,i am learning lots things from u.
I think the big thing that’s working against you on using MAP sensor
voltage test to find a valve problem aside from the lack of practice using
that particular test is the fact that most likely multiple intake valve
seats are wearing on this motor. I’ve found that when a worn valve seat
occurs on this motor that’s bad enough to cause a misfire, usually there’s
more of them starting to wear, which would hide a bad waveform among ones
that are borderline. May wanna try this on a different kind of motor that’s
running like it’s supposed to to get a feel for what the waveform is
supposed to look like.
i haven’t watch all of this video yet but until 31:40 you can clearly see
that the manifold pressure spikes are significantly higher when number 4
cylinder is in it’s compression and power stroke especially at the point of
ignition.
G”day Paul, using the 720 degree rotation it is still possible to sync the
five cylinder intake valve opening events, as long as we know the firing
order, and have an understanding of the four stroke cycle. If number 1
cylinder is on the power stroke then the cylinder in the 5 cylinder series
on the intake stroke must be 2 cycles backwards, as the next cylinder to
fire in the four-stroke cycle is always one cycle behind. Example: Firing
order, 1,5,4,3,2. IF number one cylinder is on the power stroke, number 5
cylinder is on the compression stroke, number 4 cylinder is on the intake
stroke, and number three cylinder is on the exhaust stroke. Using this
method you can have the 720 degree cursors on the pico and also insert five
divisions that relate to each of the five cylinders 144 degree rotation.
Still using the ignition to sync you now know that when number one is
firing then the valve opening event aligned with that must be 2 cylinders
down the firing order, 1,5,4,3,2. Hope this helps. Keep up this fantastic
work, love it!!! Great learning resource, mate.
If you remove a spark plug, the corresponding cylinder will not produce a
vacuum in the intake. So you will be able to see where it is in the
waveform.
be nice to see this wave form with the new head
Paul, love your videos. Plus you have some super smart people that comment
on your videos as an added bonus.
That part, where you were confused which valve is which, why didn’t you try
a pressure transducer to work out a problem one
If the low point of the blue line means more vacuum, then the opening of
the intake valve is at the high point.
Fantastic, cant wait for the next part.
shows us the intake vacuum pulses using a low pressure transducer or picos
first look. Sync it with a injector.
the little humps are blowby, going through the pcv back into the intake
Paul to identify which waveform is the number 4 remove valve cover and
stick a thin feeler gauge between the number 4 valve stem and rocker arm to
slightly hang the valve open then run engine and record waveform
Hi Paul, very interesting case study! A few comments on the MAP waveforms:
1) for a 4-stroke engine, if you have more than 4 cylinders, there is going
to be “overlap” in the strokes from different cylinders. Here, for a
5-cyl, there is (180-720/5)=36deg overlap in the intake strokes. Still, you
can pick out the “dominating” event, as you did with the #4 intake stroke.
For a V8, you would have 90 deg overlap, so picking out a specific cylinder
event would not be possible.
2) You are 100% correct that we have to focus on the #4 compression/power
strokes, as the leak is only in effect when the intake valve is closed and
pressure is building.
3) With such a small leak however, you are right that picking it out on a
MAP waveform, especially with stroke overlap, is very difficult indeed.
Looking forward to part 3!!
Danner i think each drop on the sensor Map is intake of each cylinder, that
means before the spark is the cylinder 1 intake, the next drop, cylinder 3
(don’t remember the fire order), this is my teory, since the sensor map
measures the intake pressure of all cylinders, Im not an expert, hope it
helps 🙂
Sry about my english
I can’t believe how much I’ve learned by watching your videos. As soon as I
can devote my time well, I’ll subscribe to your premium channel. Have a
good one.
Take another sample of the in cylinder pressure and compare the amount of
time required for that cylinder to peak psi compared to the others. example
initial compression hum time . Would it be slower to build to max psi cause
of the pressure loss as the valve leaks almost like how we would measure o2
sender switch time