MADRX2 - Simon's 1974 Mazda RX-2 Sedan

 

Story: Ben Winstone

Photos: Ben Winstone, Simon Kingswell, Kathy Smith, Robin Pearce and Keith Dickson.

 

It could be said that the RX-2 model is sometimes overlooked in the popularity stakes in terms of being modified, often being overshadowed by its more popular RX-3 and R100 siblings. However once in a while a neat example comes along which makes you wonder why more people don't attempt to 'do one up'.

 

Simon Kingswell's 1974 RX-2 Series II sedan is one such car. The exterior is subtle yet effective, the interior is purposeful and neat and under the bonnet, well you better be wearing your sunglasses, oh and not to mention that nice big turbo residing in there...

The car is a classic example of a choosing a few select modifications to create a very impressive package that kicks some serious ass whilst looking very... well... normal (in the nicest possible way). A case of how appearances can be deceiving...

 

No prizes for guessing which engine powers MADRX-2. That's right, the ever popular 13B makes a shiny appearance in the engine bay, and is certainly a long way from the 120hp 12A carby mill which was housed in it when the car rolled off the Toyo Kogyo production line back in 1974.

 

Simon explains that the car went through a number of engine buildups before landing on its current setup. "Originally the car was purchased in 1998 with a Bridgeported 13B using a modified Niki carby. Using a locked 4.1:1 diff, the car made around 120kw (161hp) at the wheels and ran a 14.2 @ 93.3mph at Calder Park" Simon says before going on to add that "by then the drag racing bug had bitten, and I began the familiar search for more horsepower."

 

The car was then taken to Maztech of Melbourne where a electronic fuel injection setup was grafted onto the motor and included hardware such as a Webber manifold and twin down-draft throttle bodies, custom-made surge tank and EFI pump in the boot and a crank angle distributor for direct fire ignition. A Microtech MTX-8 computer was put in charge of running the show. This setup was then good enough for an approximate 20kw increase at the wheels. Simon points out "that there was a very substantial increase in torque and driveability after the fitting of the injection system." A few more trips to Calder in mid-1999 using this setup resulted in a best time of 13.39 @ 98.5mph.

Fast forward to around a year later and the car was sitting in the workshop of Promaz Automotive in Thomastown and the usual 'minor freshen up' had turned into a full driveline replacement. The bug must have bitten pretty hard as the 'Bridgey' and the rest of the drive train were removed in favor of a 13B turbo motor equipped with a Turbonetics T-60 turbo, Series 4 RX-7 5-speed and a heavy-duty 9-inch diff.

The car was then taken to the Summernats event in Canberra at the end of that year (2000) where Simon was happy that "it qualified for both the 'Horsepower Hero’s' (turbo rotary class) and 'Go to Whoa' events before unfortunately picking up a dodgy batch of fuel, which blocked up the filters, injectors and created all kinds of havoc."

The bad luck didn't end there however, as after having the filters replaced, injectors cleaned and the car re-tuned, MADRX-2 made the trip to the 2001 Easternats at Sandown Raceway in Victoria where the motor expired just two laps into cruising on the first day of the event.

A few months later another import motor was sourced and fitted with the idea to lower the boost and just enjoy driving the car for a while, however Simon goes on to say that "the motor let go in a big way with just 400km under its belt during its first dyno tuning run."

Which brings us to the cars current mechanical setup. Simon switched workshops again and ended up at Dyson Rotary in Geelong, where he has since been a satisfied customer. Impressed with their speed and service, Simon stated that "Craig could not have been more helpful, and the job was done in a timeframe that I thought was close to impossible for such a job, as I was in the car again only two weeks later."

 

Based on a Series 4 13B turbo motor, the guys at Dyson Rotary stripped it back to its bare basics and proceeded to prepare it for the power it was expected to make. This included dowelling the block for increased strength and rigidity as well as performing a 'turbo-extend' port to the plates to increase the airflow into the combustion chamber.

A number of parts were retained from the original turbo setup including the twin down-draft throttle bodies, polished aluminium radiator and custom-made front-mounted intercooler and the intercooler piping.

The turbo was rebuilt and a HKS 66-mm front wheel replaced the original 60-mm one, and is mounted on a custom-made stainless steel manifold, sucking in air through a K&N air filter. Excess exhaust gas is shown the door via a 42mm Turbonetics external wastegate, which limits boost to 14psi for the street and 18psi for the track. A 3-inch stainless steel exhaust from the turbo back helps to make the radio obsolete, exiting via a MagnaFlow muffler. The popular Turbosmart Type 3 blow-off valve is also fitted to vent excess boost between up-shifts but is also useful for scaring unsuspecting pedestrians amongst other things.

 

Looking at the fuel system, the car runs two 12A Turbo (880cc) injectors as primaries in conjunction with two 1000cc Rochestor injectors as secondaries. The car also has a methanol injection system setup but this hasn't been used, with two 13B Turbo (550cc) injectors installed for this. Two lift fuel pumps feed three polished aluminium surge tanks (including one for methanol injection) and three line pumps (including one for methanol injection once again) proceed to send the juice to the motor. A Malpassi rising rate fuel regulator is also used to keep pressures high. As mentioned previously, a Microtech MTX-8 ECU is used to control fuelling and ignition needs with a Microtech MT-2 Fuel-only computer used for the methanol injection.

 

The driveline remained the same, utilising a Series 4 RX-7 Turbo gearbox coupled with a 9-inch lightened flywheel and Centreforce clutch before sending the power down through a custom 3-inch tail shaft to the Ford 9-inch 4.56:1 differential (with mini spool and 31-spline axles).


Once the new combo was run in, Simon returned to Dyson Rotary where the car was tuned for street driving with boost set at 14psi and Optimax fuel used. The car then reeled off an impressive 281kw (379hp) at the wheels. Further tuning using Avgas and winding the boost up to 18psi resulted in 298kw (399hp) at the wheels being achieved, just shy of the 300kw mark. Simon also comments that "the motor makes good power all the way to about 9000rpm with the rev limiter set slightly higher than that."

After making the Top 8 in the drag racing event at the 2002 Easternats, Simon was extremely keen to test out the car on the strip and so headed to Heathcote Park in northern Victoria where the car ran a 12.7 @ 120mph on street tyres before slicks were bolted on and a best time for the day of 11.1 @ 126mph was attained.

 

In August 2002, Simon attended a Calder Park off-street meeting and proceeded to run the cars current best ET of 10.75 @ 128mph, even more impressive is that this figure was obtained using the 'street' setting of 14psi and Optimax.

He is also keen to point out that the car also took out the 2002 Springnats Dyno Challenge (Rotary class naturally) using 18psi and Avgas with 298kw (399hp) at the tyres and says that "the disappointment was missing out on overall winner by just 8hp."

 

When asked whether he has hit the track with this setup, Simon explains that "the car has been raced at Calder with the 18psi tune, however the power seems to be too much for the clutch and causes it to slip" and he describes what it's like to drive at the track as "with the 4.56:1 diff gears it really jumps off the line, with the slicks on it feels like its going to throw you into the back seat when it launches." The car also 'just' lifts the left front tyre clear of the track as it takes off from the start line.
 

On the road however, Simon is extremely pleased with the general nature of the car and describes driving it as "very drivable down low and user friendly when driving in moderate traffic." He continues by saying that the car "drives smoothly through the gears and is not 'too' loud, a lot of people have been very surprised at how well behaved it is."

In fact the car is so easy to drive that he says his fiancée Kathy "drives it almost as much as me, plus she has also raced it at Heathcote."

 

With regards to the way the turbo comes on boost Simon explains that "once you load it up, the turbo starts to really come on at around 4000rpm and is making full boost usually by about 5500 to 6000rpm. The boost comes on quite forcefully but progressively throughout that rev range and on the street starts frying the tyres at about 5800rpm in 2nd and 3rd, leaving two black lines the whole way!" Not that we condone that sort of behavior here at mazdarotary.net :)


The car not only has the goods under the bonnet, the exterior also looks the part with the bright orange paint being applied before Simon purchased the car. Apart from that there are just the usual assortment of badges and mouldings on the exterior.

 

Inside it is a different story with the most obvious addition being the polished alloy bolt-in roll cage, an important safety necessity when you consider the speeds that the car is capable of. Helping to hold Simon and a passenger in place are Saas Interceptor (no they aren't out of a BT-1 Commodore) race buckets, and as per VicRoads requirements, the rear seats have been removed in order for Simon to use Sabelt racing harnesses.

An Autotechnica sports steering wheel takes control of the turning duties, while the obligatory Monster Tacho and a trio of Autometer gauges (boost, water temperature and oil pressure) allow Simon to keep a check on the vital signs of the motor. The gauges are housed in an otherwise standard dash.

As for a stereo, well the only music you need (or want) to hear is coming from under the bonnet isn't it?

 

The car rolls on 16x7-inch ROH wheels with 205/45 tyres on the front with 225/50s on the back attempting to put the cars substantial power to the ground, although often failing at times and turning into white smoke.

Helping to bring the car back to 'socially responsible' speeds are 10-inch ventilated discs up front being squeezed by Commodore calipers with Bendix Ultimate brake pads. Up the back, the 9-inch diff has had RX-4 drums added to help the cause.

 

Lately however, the car sees little street use and is mainly taken out to participate in events held by the Eastside Cruisers Car Club, of which Simon is heavily involved with. "The club holds a number of cruises each month, as well as participating in events like the Easter and Springnats and holding dyno and drag days" he details.

 

Subsequently, the car has since been sold, and the new owner plans to do some serious drag racing with it and realise the cars true potential, taking over the reigns of one MAD-RX2...

 

Contact:

Dyson Rotary - 71-75 Douro St, North Geelong 3215, (03) 52722366. www.dysonrotary.com.au

 

Model: 1974 Mazda RX-2 Sedan

Engine: 13B Twin Rotor Turbocharged

Engine Modifications: Fully prepared Series 4 13BT motor (including extend porting and dowelling), twin 50mm down draft throttle bodies, Turbonetics T-60 turbo (with HKS 66mm compressor wheel), custom aluminium radiator and intercooler (polished 2½-inch Stainless-Steel intercooler plumbing), Turbonetics 42mm external wastegate, custom Stainless-Steel exhaust manifold, 3-inch Stainless-Steel exhaust from the turbo back, two 12A Turbo injectors (primary) with two 1000cc Rochestor injectors (secondary), two 13B Turbo injectors (for methanol injection), two lift fuel pumps, three line pumps (including one for methanol injection), Malpassi rising rate fuel regulator, three polished aluminium surge tanks (including one for methanol injection), Turbosmart Type 3 blow-off valve, K & N air filter, Microtech MTX-8 Fuel and Ignition Computer with Microtech MT-2 Fuel only Computer (for methanol injection).
Driveline: 9-inch lightened flywheel and Centreforce clutch, Series 4 RX7 Turbo 5-Speed gearbox, custom 3-inch tail shaft, Ford 9-inch 4.56:1 differential (with mini spool and 31-spline axles).

Suspension & Brakes: Standard coils (front and rear), 10-inch ventilated discs with Commodore calipers (front) and RX-4 drums (rear).
Performance: 298kw (399hp) @ wheels (18psi and Avgas), 281kw (379hp) @ wheels (street trim using 14psi and Optimax), 10.75 @ 128mph.

Wheels & Tyres: 16x7-inch ROH with 205/45 (f), 225/50 (r), 24x8.5-inch slicks on a 13-inch wheel for the strip.