Polo 1,2 3-Cyl. - WPS 500 Pressure Question

Hi,

Looking at a 2006 1,2 L 3-Cyl. BMD-Engine in a Polo i did a Snap-Throttle Capture.
Car has a VERY long story to it,but that is maybe for a later Post.

What i can not get in sync in my Head is, why is there a second pressure after the
Compression when snapping it, while at idle the Pattern looks fine ??
And if the WPS is not lieing, it is over 1,5 BAR !!!

I thought maybe Exhaust pressure, but connection to the front O2, we
can not get the Gauge to get over 1,5 PSI (not BAR as in the Pico image) even
at reving it to the Limit ??

We did the same Test with the WPS500 with the front O2 removed complete,
but besides a heck of a sound in the garage, the pattern did not really change for this "bump".

The Engine has no Variable cams or anything fancy.

Maybe it is normal, i would love to compare a other car against it, but
can´t get a hold of one at the moment.Maybe next Week or so.

Maybe someone can explain , why it would be normal, because i
would think, there should not be this Pressure at that time.

Hi,

Could you specify what problems with the engine are currently.

Could you show the work of all the cylinders?

Thank you.

A long shot but what about "Valve Bounce"?

Hi,

@kona
You mean a relative Compression Test ?
Or WPS Readings of each Cylinder ?

The Car starts fine, idles fine, revs up fine, no error Codes set,
all Readiness Monitors run - Short Term is at around -10% - so far so good .)
But the Cat starts GLOWING red Hot after a short time driving, or even
when you perform the Readiness Tests in the Bay.

The Car was at at least 8 shops, they all looked, put parts on it,
but didn´t get ride of the GLOW CAT , and as well the exhaust Valves
burning off.If correct the Head was changed already once and had
Valve Jobs twice in the last Year - because of leaking Exhaust Valves.
*Looking at the Temps the Cat has, i am not suprised *

I think besides the ECU, the Car has all sensors/actors and stuff already new,
i would have to look at all the Paperwork in the Glovebox.

@Technician :
Valve Bounce ?

Hello again,

It's interesting to see WPS Readings of each Cylinder.
And further ...

It may be worthwhile to note the oil pressure at high engine speeds.
Too much oil pressure may not allow the valves to close.

You can suspect the weak valve springs (do not have time to close).

Good luck.

Hi,

Yes valve bounce is a long shot, but as Kona says you might have a valve not closing correctly, i.e. burned seat. The additional pressure in the exhaust system has to be generated from somewhere, and the cylinder pressures are the creation of it, however, another long shot, has it got a EGR valve fitted and would that being stuck open not allow additional pressure to increase into the exhaust system?

However, before all of the above, you advised;

The Car starts fine, idles fine, revs up fine, no error Codes set,
all Readiness Monitors run - Short Term is at around -10% - so far so good .)

Short term around - 10%, so far so good?

I'll take that to mean short term fuel trim [STFT] ?

If you confirm that I am correct here, this is your heat build up problem, the engine is over fueling, which if I am correct here this would be the first priority to look at!

terbo wrote:Hi,

Looking at a 2006 1,2 L 3-Cyl. BMD-Engine in a Polo i did a Snap-Throttle Capture.
Car has a VERY long story to it,but that is maybe for a later Post.

What i can not get in sync in my Head is, why is there a second pressure after the
Compression when snapping it, while at idle the Pattern looks fine ??
And if the WPS is not lieing, it is over 1,5 BAR !!!

I thought maybe Exhaust pressure, but connection to the front O2, we
can not get the Gauge to get over 1,5 PSI (not BAR as in the Pico image) even
at reving it to the Limit ??

We did the same Test with the WPS500 with the front O2 removed complete,
but besides a heck of a sound in the garage, the pattern did not really change for this "bump".

The Engine has no Variable cams or anything fancy.

Maybe it is normal, i would love to compare a other car against it, but
can´t get a hold of one at the moment.Maybe next Week or so.

Maybe someone can explain , why it would be normal, because i
would think, there should not be this Pressure at that time.

Looks to me that you have a compression leak.

See https://www.picoauto.com/library/case-s ... ault-codes

Read it all carefully and much will be revealed

The Case Study is nice.
I will read it complete later, i just had a quick look.
Biggest difference is that the Polo in the Case study is
a 12 Valve with 2 CAMs, ours is a 6 Valve with only one
CAM.

Onyl have Handy Access at the time....

Keep in mind that in cylinder compression tests provide no useful information at high engine speeds.