If I was going to run exhaust pipes under CV joints I'd sure have a heat
shield there.
I would think an exhaust pipe 2 or 3 feet from the exhaust manifold  under
hard running could get to 400 degrees F easily ..
so if only say 2 inches from a CV joint ...
not so good... it would shorten the life of the rubber boot, and make the CV
joint run hotter too.
I suspect inner CV joints might wear a little bit more than outer ones due
to running hotter , being by the trans.

I don't see an obvious elegant solution, unless they spend some time making
a very custom fitted tucked- in nicely system.
   I think I would almost make an exh. system that would come off the left
side, go aft, then across the rear of the engine ( like above , below, or
alongside a slender muffler ) then do a u-turn and come back through the
muffler with tailpipe on the left side .
 The basic idea of crossing from one side of the engine/trans to the other
..
unless you have lots of ground clearance ....doesn't seem that 'natural' to
me.

scott
www.turbovans.com
----- Original Message -----
From: "Don Hanson" <dhanson928@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, October 19, 2010 6:49 PM
Subject: Speaking of heat and rubber.. CV boots?

>  Anyone want to guess or actually divulge knowledge on how much heat the
> inner CV boot on a manual tranny van could take?
>
>  I am having some custom pipes bent for the exhaust on my "new" 2.0 liter
> Jetta motor in my 84 van.  The Inline Tuners tell me that about 30" is the
> correct length for the primary 'runners' on the dual downpipe manifold
> that
> is the best one for the ABA motor..30" and then you merge the two into one
> and on to the cat and muffler.  I am thinking in order to get that length
> in
> a Vanagon installation I shall turn the pipes forward...run them along the
> driver's side of the motor then cross  under the nose of the tranny and
> return along the passenger side..
>
>  In order to preserve full ground clearance, I am thinking I might go just
> below the CV joints...I shall probably have to make some type of heat
> shield
> to keep the boots from being too hot...especially when stopped with the
> motor going...Right?
>
>  My alternate plan is to simply make the downpipes as long as I can get to
> fit, configured like my current system....guessing I can put about 24-29"
> inchers in there,  doing it like my single down pipe current
> exhaust....But
> that will mean some power I don't get from having the  full optimum
> length.
>  It should still be a significantly better breathing system than the tiny
> single pipe that is sharply bent and crudely welded that I am running so
> far....
>
> The tuners (Techtonic Tuning in Or.) tell me they dyno  out ABA motors,
> with just this one exhaust change, and see them usually gaining
> 10-12hp..I'd
> like that, for just the cost of a nice fall drive to Bend to the exhaust
> shop and some fab time $ using all the parts I have and the manifold that
> came with my $300 motor...
>
>  Don Hanson