Miata Mailing List: July 1993, Message #55
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   From: Al Jenab 
Subject: RE>Re:  RE>Re: Buying used (headrest speaker install)
   Date: Wed, 7 Jul 1993 15:19:53 -0400


Mike Rother writes:

"Ahh, a Borla owner.  I've been thinking of adding the Borla exhaust
to my 1991 base model.  Couple of questions:

- Is the Borla system louder than the stock exhaust?  How would you
describe the sound in comparison with the stock exhaust buzz?"

It's pretty loud, lots louder than stock.  It starts off all smooth and burbly
like one third of a V-12 Ferrari, then after about fifteen minutes, it warms
up and starts to really snarl.  This may not be representative, though.  There
seems to be a small, but persistent leak which causes it to buzz from time to
time.  I need to get under the car and mess with it a bit.  This may cure the
excessive volume, also.  I don't see why the decibel level should change that
much over time & temp.  I don't know whether I've got a mutant version or not.
The other folks I've spoken with who have the Borla seem to think theirs aren'
t that loud.

"- Did you honestly notice any performance change?  In what way?"

Sure did.  A little more low-end torque and somewhat crisper high-end power.
When I go to my local race track, I pass through a mountain (well, a hill in
Virginia) pass with some pretty steep grades.  I used to have to shift out of
fifth and down to forth to make it to the crest.  I cranked all the way up it
in fifth last weekend, no sweat.  I should mention that my previous muffler
was a Walker Dyno-Max.  Didn't like it much.  On track there was a noticeable (
though not massive) increase in grunt from 5000-7000 rpm.  This is an
incremental, certainly not massive improvement.

"- How did you avoid shearing off the catalytic-convertor bolts in
installing the new exhaust?"

I didn't (he admitted, sheepishly).  This was one EXPENSIVE muffler switch.  I
got them off OK when I installed the Walker by just warming up the car and
carefully removing the nuts.  This must have fatigued the studs as even with
the warm-up, they sheared off almost instantaneously this time.  New converter
was (ouch) $350 with MCA discount!  Yes, I am a real dumbsh*t sometimes.  I
used ordinary (non-factory) metric nuts and lock washers to secure the
converter.  When you look at the factory nuts, the holes are actually oval-
shaped, and seem to be impossible to fit over the stud.  I don't see the
purpose for this, other than to keep folks like us from putting on different
mufflers or to sell more converters.  I have a Millen header on order and if I
break another one installing it, my dear wife will dispose of me.

"- Why does it backfire?"

Maybe backfire isn't the right word.  It "burbles" harmoniously in a vaguely
Italian/British way which suggests old, non-turbo F-1 cars (at least to me).

-Al