Date: Tue, 3 Sep 2002 08:31:20 -0700
Reply-To: Mark Keller <kelphoto@HIGHSPEEDPLUS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@HIGHSPEEDPLUS.COM>
Subject: Turbo question Water Jacket Seal failure
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Hi Damon,
Welcome to the list. My name is Mark Keller. I've thought some about
the type of responses you might get from other listmember regarding your
question.. MY general feeling is that you'll be told to swap motors or
get a lot of flack for wanting to turbo the water boxer engine. Let me
share my views as well.
First I did an internet search on Google for the Subaru waterboxer that
is turbocharged. There is nothing wrong with the basic layout being
turbo charged. I could not find any issues with respect to the
compression seal issue with the VW block. It seems the real issue was
the exhaust pipe routing for proper pulse according to firing order of
the engine to achieve a efficient spool up design. In other words, a lot
of plumbing for the right setup. Drag engines I've seen, SPENCER's or
SMITH VW in Tampa, Fl , had a World Record 1/8 mile dragster, 600 hp or
so, that used twin turbos, but I believer the high rpm range overcame
the need for pulse effect. Also this not a VW cast block, but a custom
block and air-cooled, but it held together.
The other item was I saw an image from a listmember in Japan's website
of a turbocharger on a Vanagon engine at one of their camp outs. The
listmember goes by the name of "Yoshi". If you search the Vanagon list
archives for the years 1999-2001, under his name you should be able to
locate is website.
My general feeling of the effect on durability of the engine isn't
negative, but there is a design issue that the waterboxer differs in
than the Subaru. The VW cylinders are removable. This necessitates a
thick rubber gasket only around the cooling jacket s to compensate for
dissimilar metal expansion-- VW's use very long steel studs which clamp
the aluminum cylinders and head assembly to the block.
This thick rubber gasket is susceptible to hardening, much like rubber
tires that are overheated during racing conditions . I've read a blurb
on the Michelin site that excesive heat in the rubber causes a
molecular change which resulting in the desirable short molecule chain
being converted to longer molecule chains and hence a effect of making
the compound of a harder rubber. I forget if this was for street tires,
long term high milage tire compounds and stablile compostions or racing
conditions. Either way tire rubber componds are prone to harding.
Applying this molecular hardening to the rubber seal due to heat may
offer some explanation to the waterboxer's high failure rate of this
item. It would appear that high heat short term , overheating, or just
long term normal operating temperatures would affect adversely the
critical pliability of the cooling jacket seal . In my opinion other
driving behavior can exacerbate the failure of this seal . I believe
the VW brand coolant for this engine includes some time of additive to
keep attempt to keep the exposed edge of the seal pliable or swollen.
This is where coolant is forced beneath the seal and corrosion of the
heads surface begins. Obviously , I don't believe anything can
completely compensate for the natural hardening due to molecular change
of the compound, and thus the seal expansion would degrade.
Another possibility are engines which have had several bouts of
overheating for whatever reason. And possibly a general driver habit of
driving for the first few minutes each day . During Cold weather or
below water freezing first start and then operating the engine at 2000
RPM s or more before the temperature needle has as least begun to move
and thus subjecting the thick rubber seal to the high hydraulic pressure
generated by the cooling pump and a closed thermostat, and thus forcing
coolant beneath and otherwise intact seal.
Therefore I believe it best to give the cylinder liners a chance to
expand and have adequate clamping force on the rubber cooling jacket
seal, before higher than 2000 RPMs operating, after the Temp needle
moves. ON my van I wait until the needle has just begun to clear the
big white mark at the bottom of the temperature gauge. But I only do
this religiously on cold freezing days. Other times I just wait until
the needle moves.
Back now to you turbo-ing the motor. I'd consider the effects of higher
heat on the hardening of this cooling jacket seal. You could have a
shorter time before needing to replace the gasket, kind of like racing
tires, before it hardened up. For certain the issue is keeping your
heat transfer down, moderate boost, ceramic coatings etc.
Sincerely,
Mark Keller
91 Vanagon Carat
Cowichan Bay, BC
