Date:         Sat, 27 Apr 2002 19:29:28 -0400
Reply-To:     SpaceKommander <jboldway@BEE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         SpaceKommander <jboldway@BEE.NET>
Subject:      1.9L exhaust system comments
Content-Type: text/plain; charset="us-ascii"

Hello, I just got a new exhaust system for my 85 Westy - the exhaust was
made by JP group in Denmark - I guess it's OEM stuff. Very heavy duty pipe
gauge, massive connecting flanges. However, there are two problem areas I
see. first is a large amount of welding "scale" - little balls of weld that
attach themselves loosely to the interior of the exhaust pipes. When the
exhaust gets hot the little steel balls will fall off (I was able to knock
most off with a screwdriver) and can get sucked inside the engine. Little
pieces of steel inside the engine aren't so good . . . .

Second - the "U" pipe that the O2 sensor attaches to has a fairly large
restriction in it. The area where the two pipes merge in to the large pipe
just before the O2 sensor area has the pipes folded in - it looks fine from
the exterior but if you look inside you see the cross-sectional area of the
round pipe now is a "D" section with the flat side of the "D" almost in the
middle of the pipe - about a 1/3 reduction in cross-sectional area. Pretty
massive restriction in my book. I plan on removing this restriction and
having a weld bead placed on the exterior of the pipes.
I've posted pictures on my website.
ftp://ftp.cottagesoft.com/users/jboldway/vw1.jpg and vw2.jpg - first is a
shot of the restriction (note backwards facing "D" in left hand exhaust
port), second is an exterior shot showing where weld bead will go. The
restriction is in a very bad spot - where essentially two venturis exit in
to the same area - pipe going from large- small - large is a venturi - how
a carburetor works. It's a high pressure/low velocity in large area going
to a high velocity low pressure area in the narrow range, then back to a
high pressure area low velocity after the restriction - but two venturis
exiting in to an area smaller than the combined two inlets results in a
pressure gradient extending up in to the venturis - essentially a
roadblock. This leads to a whole host of problems - exhaust back pressure
causes restricted breathing, poor flow "tuning," increased exhaust valve
temperatures, etc.
Ok, while on technical subjects - onward to the wizardry of VW water cooled
boxer engines. I'm on a roll now . . . heregoes . . . You have an aluminum
alloy block with water jackets which go up to the head on the outer
periphery of the head. Inside you have two steel cylinder barrels that mate
up with the middle areas of the heads. Eight LONG bolts attach the head to
the crankcase. This is truly evil. Steel and aluminum expand at different
rates - so in the heating/cooling thermal pattern of engine operation the
head gaskets see non-uniform pressures on them - essentially the head
gaskets are forced to expand and contract. This should not be happening.
So, my two cents says that head bolt torque is vitally important to engine
head gasket life.

Anyway. What's this talk of inferior and weak & flexy crankshafts? Due to
many reasons - flow restrictions and ECU cutoff - the engine won't rev past
5,500 RPM anyway - and I've never heard watercooled VW engines having a
common failure of throwing a rod or breaking a crankshaft or wearing out
the main bearings due to "crankshaft flex." I think the lower end is almost
bulletproof. I have over 200,000 miles on my 1.9L and usually rev it up
near 5,000 RPM before each shift - and the previous owner did same and
cruised the highways of Kansas for hours at 4,500 RPM. Kansas isn't a small
state. 4 hours each weekend at 4,500 RPM should rule out any "crank flex"
problems. OK, if you are some yahoo with Dellorto 42 IDAs and open headers
trying to turn 7,500 RPM then maybe you have a valid point.

Comments? Boston Bob? Ken? How many wasserleakers are replaced due to
broken cranks or connecting rods? I'm sure there are some, just don't think
it's the primary reason for engine replacement. I think if VW had done a
proper job with the heads (sleeved steel inserts in an alloy block) the
engines would routinely turn a quarter of a million miles with no problems.