Front Suspension

Front NA Koni race shocks with 750# 2.25" Hyperco springs on Koni threaded perches with NB top mounts.  No bump stops, front or rear.

Top mounts are stock NB pieces with a simple washer and centering collar located underneath, and a generic rubber bushing and washer on top.

Racing Beat hollow front sway bar measures 1 1/8" diameter, 3/16" wall thickness.  Mazda Competition supplied the end links which have also been shortened 1/2".

Got to do something about those stock 14" wheels...

/

Rear Suspension

  Rear NA Koni race shocks with 450#  2.5" Eibach springs on Ground Control threaded perches with NB top mounts.

 Modified rear upper control arms from AWR have an eccentric at the outer upright and allow simple and fast camber adjustments without affecting toe. I do not plan to use a rear sway bar.

Out with the old and in with the new.

Seems to have plenty of droop in the rear with the revised version of Koni's Race shock.

Initial ride height measured at the pinch weld is 4 5/8" rear, and 4 1/2" front.  Tires measure 22 3/4" tall.  Center of hub to fender measures 12 1/4" front, 12 3/4" rear.

Seat

   Just like on my 1995 STS Miata, I used the factory Mazda seat tracks and bolted them to the bottom of a Momo Start seat.  Some modification to the tracks is required to get the bolt spacing correct, but this leaves you with an adjustable seat a bit lower than stock.

The factory seat belts work well.

The seat is a tight fit in the NB chassis and just barely hits the door panel at the shoulder.  Minimal clearance at the bottom front also with 1" clearance at the transmission tunnel and only 1/8" clearance at the door panel pocket.

The OEM seat weighs about 31 pounds including the seat belt receiver and factory sliders.  I will need to ballast the Momo seat to weigh a minimum of 25 lbs including mounting hardware.

99 Miata driver side seat with tracks and seat belt receiver.

No ballast added yet.

Momo Start with 99 tracks and receiver.

Merry Christmas

A few gifts for the 99 STR Miata ...

Gauge faces from Adam at revlimiter.net. 

Amazon had a special on the Contour camera and I picked up a simple Panavise clamp too.

Console

   As mentioned previously, I installed an NB2 Miata (2001-2005) center console into my 1999 STR Miata because the factory NB1 console is poorly designed and breaks easily.  The newer console pictured at the bottom has better cup holders and a one-touch power window switch.

The newer console is a few ounces heavier.

1999-2000 Mazda Miata Console

2001-2005 Mazda Miata Console

Shift

   As described, the MiataRoadster short shifter kit includes everything you need for installation and good detailed instructions on the web site.

The old shifter boots were torn anyway so this is a good time for the kit.

Completed install has the same throw, but puts the shifter knob higher and closer to the steering wheel.

Club Sport

    The 2003 Club Sport is a great choice for a STR Miata, and probably a better choice than a 1999 Miata.  A few Club Sport Miatas appear for sale occasionally, and a great example is here.

 














This model was only available in 2003, and a limited number were sold and only available in red or white.  Soft top is deleted and air conditioning was an option.

Manual steering, no stereo, and no cruise control.  You would think this model should weigh less than a 99, especially without a top, but the 2001 and newer cars (NB2) have a few changes that make the car better and stiffer.  Extra under side chassis bracing and body reinforcements have been made and larger brakes and wheels are used.  Reports indicate that a race prepped Club Sport model still weighs a bit more than a comparable 99 Miata.

The 01+ Miata engine has a higher compression ratio and uses a different head that has VVT, or variable valve timing.  Tuning the VVT has proven to gain good midrange torque without sacrificing top end horsepower.  However, revving the engine much above its factory set 7200 rpm limit can be an issue as there have been reports of engine damage at higher rpm. I plan to run my 99 Miata past 7700 rpm which should keep me out of third gear and avoid 'riding the limiter' for most autox courses.

So why did I not buy a Club Sport or convert a standard 2003 Miata instead of buying a 99 ?

1. Cost.  It is about twice the price to buy into a similar condition 2003 Miata, and if doing a package conversion you will need a hardtop and manual rack and pinion, adding about $1500 to the cost.

2.  Rev limit.  The increased rev limit on the 99 may give me just enough room in second gear, especially on some of the faster courses we may see in the SoPac division.

3.  Weight.  The information I have gathered shows the Club Sport to be about 50-80 pounds heavier. I wish I could verify this data though, as my calculations say both cars should weigh the same with identical preparation.  I believe the Club Sport may have thicker gauge metal and more structural reinforcements built into the unibody to address torsional rigidity, especially from the transmission tunnel to the rear bulkhead.

4.  Daily driver.  This is my only car and daily driver.  It is bad enough not having AC and dealing with a racing seat and stiff suspension.  At least I have to keep the stereo in the 99.

AC/PS

  Removal of the air conditioning and power steering systems is not too difficult.

With the radiator and intake removed there is a lot of room to access everything. 

PS already gone.

And a shot from below showing the manual rack and missing AC.

More Parts

   I will be using the standard NA Koni "yellow" Race shocks for this STR suspension.  Some nice monotube AST or Pesnke shocks would be nice, but the Konis fit my budget much better and in my experience they have proven to be fast and reliable.  A combination of  Hyperco and Eibach springs on Koni and Ground Control perches will be used with stock and/or modified NB top mounts (the pimpy purple Flyin Miata tops will not fit the NB chassis).

  












Don't believe the hype.   If installed per OEM specifications, the NB tops do not give any more bump travel. 

  
   More frugal Ebay shopping and I got this intake kit delivered today. The instructions say it mounts to the power steering bracket.  Whoops.

Evaporator

First step in the air conditioning removal is to remove the evaporator assembly from under the dash and replace it with a simple tube supplied by Mazda.

Exhausting

  Ok,  so I saved a few dollars by purchasing an OBX 4-2-1 header from Ebay.  Overall quality, finish, and welds are very good, but it does take some effort to get it installed.  The header will not physically fit into position unless the steering shaft is moved or the engine is pushed to the right.  Fortunately, I was installing Mazda Competition motor mounts at the same time so all I had to do was jack the engine up a few extra inches and the header slipped right in.  Then I wasted time trying to get the EGR tube to fit because the angle of the fitting is off a few degrees. Also, a slight misalignment in the header causes it to rub against the flange between the engine and transmission.  A new midpipe from Good-Win-Racing includes a high flow catalytic converter and resonator and bolts nicely between the OBX header and existing Roadstersport muffler.

    






 

The car originally was equipped with California emissions which includes two cats; one in the header and another cat further downstream.  With the aftermarket header install, I am basically converting the car to 49-State, or Federal emissions which only includes one cat and also relocates the oxygen sensors.

   With the heavy, restrictive OEM header gone, the car now breathes better and revs much more freely above 4K rpm.

Battery

   I purchased an Odyssey PC545 back in 2007 for my STS car and the battery has proven to be reliable and has never failed me.  I recently installed this same battery into my 99 Miata and it still works well.  It does seem to crank a little slower, but some of that could be attributed to the crank trigger design and the higher compression engine relative to my early 1995 Miata.  Winter time is approaching too and the colder weather and heavy engine oil do not help matters.

  

 

Packaging

  A key part was delivered today that will help convert my PEP optioned car to a Base model.  The manual steering option was available on select Miatas for the 1999 and 2003 model years, and due to its limited availability and my desire to get going on the project, I ordered a brand new NB manual rack and pinion through Mazdaspeed Motorsports Development.

   
   Technically, I am converting the car to a Sport package model and using the comfort and convenience and other allowances to get the car equipped as I prefer.  The cruise control system and factory windblocker have been removed, but the power windows, power mirrors, and tweeter speakers will remain for now.  The power antenna has been replaced with the lighter manual unit.

Also included in the shipment is a box full of hoses, fuel filter, motor mounts, and stickers.
  

 
  
  
   For 1999, the Sport package Miata is equipped with a factory installed rear spoiler, front air dam, and front strut bar, all which can be removed (or added) under the STR rules.  Air conditioning and power steering are optional on the Sport package Miata for 1999. A Torsen LSD and Nardi 3 spoke leather steering wheel are standard on the Sport and both will be kept as part of this autox build. 

    Sharp observers will notice that the center console is from a 2001 and newer model Miata.  This is a common modification to the 99-2000 Miata because the newer NB2 console has a much better design and functions better.  Although technically not legal under the SCCA rules, comfort and convenience may allow this modification if it does not offer any performance benefit or weight savings.  I have yet to get a comparison weight on these two consoles.

Begin

   I purchased this 1999 Mazda Miata on October 10th, 2011 with 113,600 miles.  This Miata was originally equipped as a PEP, or Popular Equipment Package, and includes cruise control, windblocker, power antenna, power rack and pinion with Nardi leather-wrapped steering wheel, and air conditioning. Also included are goodies such as tweeter speakers, power windows, locks, and mirrors.  A 4.30:1 geared Torsen limited slip differential receives the factory advertised 140 horsepower through a five speed manual transmission.  

 













  I plan to build the car for solo, or autocross competition, in SCCA's Street Touring Roadster class, also referred to as STR.  The rules for the class intend to allow common aftermarket suspension and performance modifications while still racing on 140 tread wear street tires.  Complete rules for 2011 can be found here.
 
   Other popular cars in the STR class include the Honda S2000, Toyota MRS, Mazda MX5, Nissan 350Z, BMW Z4, Saturn Sky, and others. Size and weight are the enemy in autox, and this car will be one of the narrowest and lightest in class.  

  I previously campaigned a 1995 Mazda Miata in Street Touring Sport, or STS, so I have a feel for what this car's potential can be and what can make it fast.  We will see if the plan comes together.