[s-cars] S6 pinging woes - the continuation

[joe.pizzimenti at gmail.com]

Compression tests take about 10 minutes to do, though.


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-----Original Message-----
From: "pmische" <pmische at comcast.net>

Date: Wed, 29 Jul 2009 09:39:46 
To: 'Bares, Vittorio'<Vittorio.Bares at nuance.com>; <djdawson2 at aol.com>; <t44tqtro at gmail.com>; <s-car-list at audifans.com>
Subject: Re: [s-cars] S6 pinging woes - the continuation


During the leakdown, vent the cooling system and the cam cover for insight
into where that air's ending up - you'll see bubbles and/or hear it.  You
can also hear leaky valves by listening at the tailpipe or inlet tract.

Compression tests, which I believe are next to useless, do not necessarily
correlate to leakdown tests.  Leakdown tests are much more telling.

PJM

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of Bares, Vittorio
Sent: Wednesday, July 29, 2009 9:11 AM
To: djdawson2 at aol.com; t44tqtro at gmail.com; s-car-list at audifans.com
Subject: Re: [s-cars] S6 pinging woes - the continuation

A friend of mine is coming by tonight w/a leakdown test device - not
nearly as quick and simple as a compression test - but I would assume
that if there is an HG failure between cylinders, where the adjacent
cylinder has open valves relative to the test cylinder at TDC - the
leakdown percentage should be very high for both those cylinders. 

I would assume that a compression test would show low compression in
those two cylinders also.

Vittorio -
-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of djdawson2 at aol.com
Sent: Tuesday, July 28, 2009 1:00 PM
To: t44tqtro at gmail.com; s-car-list at audifans.com
Subject: Re: [s-cars] S6 pinging woes - the continuation


 I believe that 30 minutes with a cheapo compression gauge is going to
give the answer... call it pre-ignition or detonation.

There are many documented cases of headgasket failure between 2 adjacent
cylinders.? The headgasket fails, then it burns a little groove in the
cylinder head between those 2 cylinders... allowing flame travel...
BTDT.

The one I experienced was between 4 and 5.? 5 was being pre-ignited.?
The result was an engine that sounded like it was "pinging" under any
and all conditions, even idle.

Letting this go for too long will result in total failure of a piston.

I would urge you to do a compression test before doing anything else.

Dave


 


 

-----Original Message-----
From: Taka Mizutani <t44tqtro at gmail.com>
To: s-car-list at audifans.com
Sent: Tue, Jul 28, 2009 10:50 am
Subject: Re: [s-cars] S6 pinging woes - the continuation










You've just contradicted yourself, Brett- if the fuel/air charge ignites
prematurely, you get a large increase in cylinder pressure, which causes
all
sorts of bad things to happen to the engine.

You've stated this below as well as stating that it doesn't.

Anyway, the bottom line is that it's bad, the OP may have damaged
his/her
engine and it should be checked out. Having that happen with all of the
high
boost mods taken out is a bad sign.

I'd also check the fuel system to make sure that you're getting the
proper
amount of fuel actually delivered- if the pump or FPR or injectors are
not
doing their jobs, the computer might think it's sending enough fuel when
it's not.

Taka


On Tue, Jul 28, 2009 at 11:48 AM, Brett Dikeman
<brett.dikeman at gmail.com>wrote:

>
> Pre-ignition does not increase cylinder pressures and temperatures
> much beyond normal values (I think).  Pre-ignition is bad because it
> puts more force on the engine internals, and in ways it wasn't
> designed...for example, if power is developed at exactly TDC, all the
> force goes against the rod, crank, bearings, and head gasket/bolts,
> instead of applying torque on the crank.  Detonation does increase
> pressure and temperature, massively- it melts and bends things.
>
> Cody's recommendation to drain/filter the oil and check the engine oil
> filter are sound.
>
> Brett
>
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