When VW designed the Waterboxer the went to great pains to make it NOx
compliant and -pre-ignition resistant. The is why the concave piston, low
compression, retarded ignition timing curve, etc. There are reasons they
simply didn't go with the in line engines even though the Diesel was already
fitted. In the Automotive world many car engines get de-tuned when placed in
truck or van applications. For example in 99 I bought a 34 ft. RV with the
Ford Triton V-10. It was rated 275 HP. The same engine in a regular van for
that year was 325 HP.  This is the reason that approved late model engine
upgrades need to consider matching the engine type with the type of vehicle
originally designed for.

One of the problems with pre-ignition, (ping) is that it begins to happen
long before you can hear it, especially in the Water Boxer. The future
problems will be burned valves and pistons and in real bad cases rod
bearings and bent rods.

Check the ignition timing, make sure it is set to factory specs, maybe even
retard a few more degrees.
What spark plugs are you using? The platinum types are bit more ping
resistant as they do not have the protruding metal center electrode.
Consider additional oil cooling. Keeping the pistons cooler may help.
Coolant? Some of the newer Diesel formulations or using "Water Wetter" may
help.
Of course use premium fuel.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Steve Williams
Sent: Sunday, March 17, 2013 11:32 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Calif. Smog Fail and Catalytic Converter

Thanks, very interesting.

At 11:18 PM 3/16/2013, Dennis Haynes wrote:
>... the Cat and O2 sensor failing together is usually due to a common
cause.

Just to clarify, I don't know whether mine failed together.  My O2 sensor
failed two years ago, right after passing smog.  It's possible the cat
failed then, or anytime since.

>There was a deflector shield that I bet is missing.

Is that something I can look for?  Photo?

>Since you have a modified engine there is probably increased
>compression and you may also have the ignition timing over advanced.

That could be.  I have noticed what I think is some pinging in high gear at
full throttle going up a modest hill.  That went away when Van Cafe tuned
the engine six months ago, but now it has returned, so I must reduce
throttle or gear down to prevent it.  I don't know what might change the
advance over time, but it may be time to adjust it again.