VW Lupo Valveproblems

If you are not a PicoScope user and want advice with a diagnostic problem then post here. Forum members may be able to help.
terbo
TwoWaves
TwoWaves
Posts: 69
Joined: Sun Jul 06, 2014 2:40 pm

VW Lupo Valveproblems

Post by terbo »

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 817 times

User avatar
Robski
Advanced User
Advanced User
Posts: 598
Joined: Tue Sep 14, 2010 6:36 pm
Location: Yorkshire

Re: VW Lupo Valveproblems

Post by Robski »

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.

Chris C Stahl
OneWave
OneWave
Posts: 20
Joined: Mon Jun 09, 2014 2:22 am

Re: VW Lupo Valveproblems

Post by Chris C Stahl »

Have you got a waveform running it apears as cam timming is of a little to close to tell on a cranking waveform

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1581
Joined: Sun Aug 25, 2013 7:22 am

Re: VW Lupo Valveproblems

Post by Steve Smith »

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

Chris C Stahl
OneWave
OneWave
Posts: 20
Joined: Mon Jun 09, 2014 2:22 am

Re: VW Lupo Valveproblems

Post by Chris C Stahl »

Exhaust valve opening should be 30 to 60 degrees before BBDC this is more like 5 degrees

terbo
TwoWaves
TwoWaves
Posts: 69
Joined: Sun Jul 06, 2014 2:40 pm

Re: VW Lupo Valveproblems

Post by terbo »

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

Chris C Stahl
OneWave
OneWave
Posts: 20
Joined: Mon Jun 09, 2014 2:22 am

Re: VW Lupo Valveproblems

Post by Chris C Stahl »

Put the pressure transducer in each spark plug hole and check the pressures

terbo
TwoWaves
TwoWaves
Posts: 69
Joined: Sun Jul 06, 2014 2:40 pm

Re: VW Lupo Valveproblems

Post by terbo »

As you asked...
Attachments
arosa-z4.psdata
Cyl.4
(588.58 KiB) Downloaded 647 times
arosa-z3-2.psdata
Cyl.3
(587.26 KiB) Downloaded 736 times
arosa-z2-2.psdata
Cyl.2
(588.26 KiB) Downloaded 636 times
arosaz1-1.psdata
Cyl.1
(568.6 KiB) Downloaded 772 times

Chris C Stahl
OneWave
OneWave
Posts: 20
Joined: Mon Jun 09, 2014 2:22 am

Re: VW Lupo Valveproblems

Post by Chris C Stahl »

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.

terbo
TwoWaves
TwoWaves
Posts: 69
Joined: Sun Jul 06, 2014 2:40 pm

Re: VW Lupo Valveproblems

Post by terbo »

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.

Post Reply