Seems that most TiiCo owners have found that the engine puts a
low frequency vibration/resonance into the body at about 4000
rpm. Having experienced this with many 4 cyl cars in the
past, I knew that with careful fiddling, it can be
tuned out. I had some ideas and decided to give it a
go. I made several changes at the same
time, so my experimental process stinks. I didn't
figure out which, if any created the biggest improvement.
Here's what I did: 1) replaced a rusted, thin 3
bolt exhaust flange on the muffler upstream side. 2) replaced all of
the nuts/bolts on these flanges with the largest stainless
replacements that would fit. If the exhaust is
contributing to the vibration, then it's got to be as rigid as
possible to resist. 3) I put rubber spacers (hacked from
old muffler hangers) between the arm that supports the muffler
and the muffler itself. The muffler now sits on
these rubber pieces in an attempt to dampen
it's vibrations. 4) Probably the most
effective change: The right motor mount on our Vanagon was
too close to the attachment plate on the engine carrier
arm. I could see by the shiny spots on the plate that the
mount had been "bottoming out" when the engine twisted under
hard acceleration. I supported the engine, removed the
mount and elongated the holes in the arm attached to the
engine. This allowed the mount to be pulled away from the
plate that it had been hitting. Interestingly, from the bottom
this arm seems to have been cast in a way that allows
elongation of the holes if needed. 5) Finally, while looking
things over, I pushed on the exhaust header to see how much
flexibility there was. None found in the header, but the
engine itself bounced on it's mounts for many cycles. Ah...
damping needed. This is wierd but bear with me.
From road racing experience I have learned that the closed
cell foam found in swimming pool float toys has miraculous
properties. My kids call these things "noodles". They
can be found at most large toy stores. These noodles are usually
about 3" in diameter, 4 ft. long, wild colors and really cheap (like
$2.00). I have used this stuff to make suspension bump-stops
for race cars and for our Vanagon. As long as the foam is
contained (as in the small voids in the TiiCo motor mounts) it has
amazing progressive damping characteristics. It's also
indestructible, it'll be bouncing long after we're gone. Use a razor
to cut pieces that are a snug fit in the motor mount openings and...
quiet! It's no Rolls, and no one will ever
think that you have a BMW six in there, but it's a huge
improvement.
Gary |