From: Jim Creer 
Subject: Bell Stage I Turbo (#5)

I installed the Stage I turbocharger on my Miata during the fall of
1994.  This is the kit without the intercooler.  My comments and
proceedures must be sorted by the reader to determine which problems
were caused by installer "Head-space".  The 89/90 Miata was purchased
from a private seller in 1992, and I was unaware there was any
aftermarket parts, clubs, or publications until 2 years later.  I
probably made 50 modifications to the car and will try to list only
those which may influence the performance and installation of the
unit.  For over 30 years I relied on my Chilton's manuals for repairs.
The general purpose Mazda manual is more than adequate for changing
items such as brakes, struts, springs and exhaust.  I encourage any
one desiring to install a blower unit or change a timing belt to
invest in a good Miata shop manual.  No recommendations on
publishers-- anything would be better| May even buy one myself|

I originally ordered the Sebring Supercharger. On one occasion, I
visited Jim Goodroe at Downing/Atlanta.  He was very helpful in
answering questions, and showing the unit.  I tried to influence the
waiting list with cash in hand but he wouldn't budge.  After waiting a
few months, PBC (Performance Buyers Club) advised that 3 Stage I
turbos were on hand waiting for buyers.  2 days later the turbo

Most of two evenings were spent laying the parts over the living room
floor attempting an inventory and figuring out what it should look
like assembled.  The only drawing I had was one of the fuel pressure
regulator.  With a couple dozen hand labled baggies full of parts,
some still unidentified, I guessed the kit was complete and it was
time to just install it and see what happened.  Installation time was
about 16 hours spread over a weeks time.  Part of this time was
locating and figuring out how and where to mount the cruise control,
whittling off a stubborn nut with my Dremel and as a probable unneeded
step-- polishing the inside of the new manifold.  Think I was short a
couple of hose clamps and had an extra hose connector.

Installation: Removal of the original parts was fairly easy and since
the car was 5 years old with 45 K miles, I sprayed the probable
difficult (manifold & exhaust) nuts & bolts with WD40 the previous
day.  During removal, probably 95% of the new installation kit became
obvious and an idea was formed on what it would look like and how it
worked.  A few additional comments are provided:

     1.  The instructions indicated using a thinwall wrench to install the
center exhaust manifold nut.  There must be thinner thinwalls than
mine.  I opted to use punch and hammer.
     2.  Steps #42 & #43 mentioned mounting the fuel pressure
regulator and bracket as shown.  Unfortunately, no "as shown" could be
located.  Fortunately, it wasn't to difficult to figure out.
     3.  One unidentified small valve remained.  I called Corky Bell
at Aerodyne, and he advised of placement and stated it was for
California users.
     4.  When installing the fuel pressure gauge, step #47 of the
instructions indicated the lower fuel line as the inlet line.  The
lines reverse position when they curve back toward the firewall.
Consequently, I attached the supplied gauge to the wrong line and
showed no fuel pressure at idle.  This situation wasted a few hours
until it was figured out while I amused myself by switching gauges and
testing them on another vehicle.
     5.  There were 3 conflicts on the amount of turbo oil to use and
two conflicts on the type of oil to use.  This was derived from the
installation instructions, a tag attached to the turbo, and the actual
vial of oil supplied.
     6.  Overall, the project was easier than anticipated when the
parts were spread out on the floor.  A few diagrams or pictures
probably would have shaved several hours from the installation time.
A short video would have worked as well.  The kit seemed well made.
My initial concerns were the durability of the silicone connecting
hoses and how to check and change the turbo oil.

Testing: Fuel pressure was roughly set by trips around the
neighborhood and fine tuned on Interstate 20, which took about 15
adjustments.  Timing set at the 6' recommended starting point produced
"ping" at about 6K RPM along with a "scrubbing" noise from the turbo
unit.  I borrowed a remote headset with 4 pickups which simplified
monitoring.  A little experimentation eliminated all undesirable noise
at a little less than 5' BTDC using 93 octane.

A few days later a MSD boost control was added, and timing was set to
10'BTDC with no adverse affect.  This seemed to eliminate the small
lag and surges.  A suitable location for the MSD was simple since I
installed a "Bug-Eye" kit and had two convenient cavities where the
stock headlamps and motors were origionally located.

The only noise under the hood was a series of faint multiple
overlapping whistles heard only when entering the garage or when
driving very slowly. I was also pleased to find the performance
exhaust system was now quiter than the stock system.

A few weeks later, the inlet casing detached itself from the throttle
body casing.  Grouping under the hood in the dark while being
stimulated by the cold rain and hot engine, I dropped the hose clamp
in the splash pan.  The clamp was soon accompanied by my screwdriver.
A few hours and 2 miles later nearing my drive way a thump sounded
from under the hood and the engine was running raggy.  Fortunately, it
was only a plug wire blown from the well probably caused by rainwater
leaking under the seal.  The lesson learned was to tighten all of the
clamps as hard as you dare.  The second time the hose came off, I
cleaned the oily surfaces with starter fluid, built the casing up
friction tape to make the connecting hose fit tighter, then used a
double hose clamp.  Since then it has never came off again.  Each time
the hood goes up, the connecting hoses and clamps are checked.

A few months later I noticed the boost gauge was bouncing between 19"
and 21" at idle.  The problem was traced (I guess) to the "O" rings
that attach the casing from the air box to the turbo.  The rings
turned into black sludge.  Don't know if this was from the heat,
vibration, or both.  Had to do this 4 or 5 times during the past 2

After about 6 months I noticed the compressor tube assembly was
rubbing against the power steering bracket.  This caused a substantial
gouge in the pipe but didn't appear to be worn completely through.  I
filed off the sharp points of the bracket and clamped the extra
silicone connecting hose over the worn spot.  As needed the silicone
hose could rotated or moved as needed.  Maybe that was why the extra
hose was supplied??

Nearing the 10K mile mark and time to check the turbo oil and "Fill as
needed" I couldn't figure any practical way to measure the existing
oil.  Got a quart of SHC 630 from a local Grainger dealer ($8).  I
attached a piece of small of 1/8" vacuum hose to my Mighty-Vac, slid a
piece of safety wire inside the the vacuum hose enabling the hose to
hold form in any desired shape, then sucked the old oil out of the
turbo reservoir.  Measured new oil in the Mighty-Vac cup and reversed
the process.  Whole process only took a few minutes and didn't spill a
drop of oil.

I noticed a piece of lid on the on the air filter box was broken and
laying on the filter.  This piece broke from the center of the air
inlet opening and extended to the right side of the opening.  It's
purpose appeared to be to secure the filter.  The broken piece was
about 3" long and the filter appeared leak proof and secure without
it.  Intended to braze the broken piece in later but still haven't got
to it.

On later maintenance day I knocked the hood support out with a drop
light cord.  The hood came to rest on my deepwell set residing on the
air filter box.  The damage to the hood was severe enough to warrent
replacement or repair and paint the entire hood.  I purchased a mini
air scoop from JC Whitney (about $12) and painted it with an air
brush.  I taped several pieces of yarn at locations on the front,
drove around to determine the best mounting location, with
considerations for covering the dents, airflow, and location of air
intake (the bug-eye headlights didn't help ).  A screen was cemented
in the air scoop intake, a hole cut in the hood and the scoop was
mounted.  Don't know if any ram air effect was produced, but was
looking for colder intake air.  Don't know if performance was enhanced
but it looks aggressive in the parking lot.

I was fortunate to test my non-intercooled turbo while sharing a
couple hundred miles of I-75 with a Sebring Supercharger unit.  I
literally walked away from the Supercharger at a variety of gears and
speeds.  At some tries the Supercharged unit took a momentary jump at
"go" (CB radio helped) but was soon viewed in my mirrors.  To be fair,
the Supercharger was using a stock exhaust and carrying a passenger.
If the driver of the red Sebring reads this and remembers the blue
bug-eye, say hello.

During Spring of 1996, the turbo unit started developing a whine and
the boost was periodically "spiking" at an excess of 15 lbs.  I
changed and checked every thing.  The turbo oil was about 20cc low
after 6K miles, was very dark and had a burnt smell.  Since
installation, the turbo had always registered a little over 6 lbs
boost.  While cruising at 3-4K RPM then punching the gas pedal, boost
would rise to 10 PSI then drift back to about 6 1/2.  Now the boost
would periodically stick to 15 PSI and not drift back.

For a long time I was trying to get information on the upgrade with
the fuel pump and intercooler.  After calling Corky Bell at Aerodyne
the need to return the turbo for examination and adjustment to 8 lbs
boost was established.  PBC advised the upgrade kit would be 6-8 weeks
wait.  The turbo would take 10-14 days.  At the end of May the upgrade
kit was ordered, and late June the turbo was pulled and sent to
Aerodyne. 7 1/2 weeks later and $249 lighter The turbo was returned
set to 8 Lbs boost.  On 18 Sept the intercooler arrived.  Had I known
my Miata would be inoperable for over 3 months, I would have
reinstalled the stock manifold.  When constantly told another another
10 days to two weeks it didn't seem practical since free time to work
on the car was limited.

After reinstalling the turbo, I ran a compression check.  Using my 30
year old and rarely used gauge, a variation between 191/195 lbs was
noted at 73K miles (appx 27K with turbo).  Don't know if this is good
or bad for the motor or the accuracy of the gauge, but saw no big
variations.  Intend to retest soon with a known good gauge and find
out what the compression should be.  During the wait I also changed
the timing belt and cam cover gaskets.  The old timing belt still
looked brand new, but the gasket resembled one of those plastic
airplane model kits where the parts are snapped from the mold.  Don't
know if this is normal, caused by the extra heat, or from the 10-40
synthetic oil.  The clutch still seems to be working fine with no
slippage.  After over 35 years of driving with several standard
transmissions, the only clutch replaced was on an 84 Colt at 40K miles
that was used to teach 2 teenagers how to drive.  "Popping" the clutch
(in my possible jaded thinking) causes insignificant wear and damage
compared to "riding" the clutch.

At this point the upgrade kit has been installed.  If an interest is
shown, I am willing to provide and update.  This was my first attempt
at working with or owning any type of blower.  I still have never seen
another turbo Miata and only a few with Sebrings.  They seem to have
their difficulties also.  If this gets printed, I am prepared to take
shots, but hopefully will get some constructive comments.  I feel all
alone here in the Augusta GA area without any advice or assistance.  I
would still do everything again except be more careful where the
deepwell sockets are placed.