VW Lupo Valveproblems

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VW Lupo Valveproblems

Postby terbo » Sun Jul 06, 2014 2:51 pm

Hi,

The 2000 VW Lupo 1,0 (ALL) of a friend ripped the timingbelt while driving.
Now he took it apart, and put on a new belt.But its running bad and
its making some noise.
I was there on my way by (only had 15 Min) and just took a few compression Waveforms.

Can anyone see something in there ?
Thinking Exaust-Valves hit because of the pressure between the real compression strokes.

Thx Chris
Attachments
arosa-z2-2.psdata
Arosa Cyl.2 cranking compression
(588.26 KiB) Downloaded 192 times
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Re: VW Lupo Valveproblems

Postby Robski » Sun Jul 06, 2014 6:52 pm

Can anyone see something in there ?
Thinking Exhaust-Valves hit because of the pressure between the real compression strokes.


Yes........ I can see that the tops of the compression towers are chopped off as you haven't got the vertical scale set correctly !

I would suggest taking a cranking waveform from the inlet manifold & exhaust tail pipe.

Is this 'friend' to be trusted with the timing ?
Until you capture a compression tower 'in full' it's a guess where the centre/amplitude of it/them are.
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Re: VW Lupo Valveproblems

Postby Chris C Stahl » Mon Jul 07, 2014 5:05 am

Have you got a waveform running it apears as cam timming is of a little to close to tell on a cranking waveform
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Re: VW Lupo Valveproblems

Postby Steve Smith » Mon Jul 07, 2014 11:54 am

Thank you for the posts guys. Looking at the compression waveform, the presence of a good vacuum pocket and peak compression suggest the valves of the cylinder you were testing are intact.

I have attached an image of my thoughts regarding the odd peak between exhaust and intake stroke.

I suspect an intake valve is deformed on another cylinder, resulting in this positive pressure peak at the point of intake valve open.

During the intake stroke, the waveform should start to fall negative at this point (under the odd peak). I suspect the intake valve opens as normal, but there is a positive pressure present inside the intake manifold due to a deformed valve on an another cylinder so allowing compression or exhaust gas to enter the intake manifold.

DEFORMED INTAKE VALVE 2014-07-07_12-38-49.jpg



Do you have any conclusions yet?

Take care.....Steve
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Re: VW Lupo Valveproblems

Postby Chris C Stahl » Mon Jul 07, 2014 2:21 pm

Exhaust valve opening should be 30 to 60 degrees before BBDC this is more like 5 degrees
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Re: VW Lupo Valveproblems

Postby terbo » Mon Jul 07, 2014 4:28 pm

Thanks, that was what i was suspecting.
Because of the odd pressure rise where i never seen one before.

As posted, the Timing Belt broke while the enige was running,
and because of the noise i expected that a valve got a hit.
I was just wondering if it is possible to see witch one "would" be bent.

So the head must come off, or the engine swapped, i think
the last option will be the one that will be taken, because a used
engine costs the same as ripping the Head off and repairing the "Damage".

The Timing is o.k, so far as the Marks go.The belt is set correctly.

Thx Chris
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Re: VW Lupo Valveproblems

Postby Chris C Stahl » Mon Jul 07, 2014 7:59 pm

Put the pressure transducer in each spark plug hole and check the pressures
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Re: VW Lupo Valveproblems

Postby terbo » Mon Jul 07, 2014 8:26 pm

As you asked...
Attachments
arosa-z4.psdata
Cyl.4
(588.58 KiB) Downloaded 140 times
arosa-z3-2.psdata
Cyl.3
(587.26 KiB) Downloaded 135 times
arosa-z2-2.psdata
Cyl.2
(588.26 KiB) Downloaded 130 times
arosaz1-1.psdata
Cyl.1
(568.6 KiB) Downloaded 139 times
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Re: VW Lupo Valveproblems

Postby Chris C Stahl » Mon Jul 07, 2014 11:52 pm

I am just commenting. it is very important that you see the top of each pressure spike to see that if they are even
or all over the place. I don,t know if i am the problem or the screen shots but they look all chopped of to me.

For comparsion on cranking compression waveforms go to atsnm.com then training and events then pressure transducer then screenshots taken with pressure transducers.
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Re: VW Lupo Valveproblems

Postby terbo » Tue Jul 08, 2014 6:29 am

Yes, the cutten tops are not good....

In the little time i was there i didn´t see that the curves were cut off
on the Laptop Display, and i didn´t really expect that that old engine
even reaches the compression max ;)

I will see if i get the chance of doing them again with
the next bigger scale, just for the intresst and saving purpuse.
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