Miata Mailing List: April 1993, Message #34
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   From: (none)
Subject: Re: Misc. questions
   Date: (none)

James Adams writes:

I just joined the list and understand that there has been some
discussion of turbocharger/supercharger installations.  If anyone has a
summary of commercial sources with brief descriptions/prices, please
email me a copy.

	Can't help you there, but I'm sure someone else can.

I also had a few other questions:

Has anyone dyno tested or flow-tested the stock exhaust system back of
the converter vs. aftermarket systems?  If so, how restrictive is the
stock muffler and tailpipe setup?  If it's worth changing, any
recommendations on sources/prices?

	Miata Magazine did some testing which revealed some
	improvement with a freed-up exhaust system.  I run
	an HKS system on mine and am quite satisfied.  Borla
	has just introduced a Miata system, and their stuff
	is generally very good (but pricey).  One low-cost
	option you might want to consider is just replacing
	the stock muffler with a Walker DynoMax.  That ought
	to be good for a couple of HP all by itself.

	In general, however, there are no major gains to be
	had by playing with the exhaust system unless you go
	with a header as well.

Does the ignition/ECS have a knock sensor? (i.e., will there be any
significant variation in output from the stock engine with increased
fuel octane above 97 r+m/2?)  (Haven't got the shop manual yet...)

	Don't know about the knock sensor, but there is good
	reason to believe that higher octane fuel is wasted
	on the Miata (and may even cause problems).  I have
	experimented with various grades and have found that
	anything over about 89 octane tends to produce hard
	starting (especially on cold days) and a mid-range
	stumble, probably from fouled plugs.  Stick with any
	reputable unleaded regular, and you'll be fine.

Has anybody seen a nice leather-covered gearshift knob that matches the
leather-wrapped steering wheel?

	There's a very nice-looking one among the stuff that 
	the MCA sent along with their latest newsletter.  I
	can't remember which outfit had it, but I do recall
	thinking that it looked quite nice indeed.  However,
	I'd be wary of changing the shift knob for a couple
	of different reasons.  You may pick up nasty buzzing
	vibrations in your shift lever, and worse yet, I've
	had aftermarket knobs come right off in my hand when
	the knob and the threaded sleeve part company during
	enthusiastic autocross shifting.  Not a comfortable
	experience at all, so I'll stick with the stock one-
	piece knob.

	- Steve Bruun

	P.S. Has anyone found a source for Talbot-style rear
	view mirrors to fit the Miata?  (Classic sports car
	mirrors, bullet-shaped with a swiveling/locking lens
	bezel, usually chrome-plated.)  I think they'd look
	wonderful on my car what with the retro Cobra stripe
	job I've put on it, but I can't find good ones any-
	where.  Millen is thinking about introducing a model
	specially tailored for the Miata, but hasn't done it
	yet, and I'm an impatient guy.  Thanks...