Mazda RX7S – Group S Prototype

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Mazda RX7 Group S Prototype

In 1985, the FISA (former ruling committee of the FIA) announced a possible replacement class to Group B that was referred to as “Group S”. The new regulations would require only 10 cars for homologation and was essentially a “prototype” class for rallying. The class was originally scheduled to make its debut on January 1st 1988, then as a heavily revised replacement to Group B for 1987, but both were ultimately cancelled. To learn much more about the history of Group S, please CLICK HERE!

Very few people knew that Madza had actually toyed with the idea of joining Group S, especially since their rear wheel drive Group B RX7 never was very successful (less its 3rd place finish at the 1985 Acropolis Rally highlight), that is until the car was widely seen at the Nostalgic 2 Days Japanese auto show in 2014. Built by Mazda Rally Team Europe (MRTE) in Belgium somewhere in 1986, the prototype features a space-frame chassis with a body very loosely based on the new generation FC3S RX7 of the time period.

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Comparisons with the Ford RS200’s styling can be debated though the Group S RX7 does sport a very similar overall theme.

Powering this car is a 3-rotor 13G naturally aspirated rotary engine (precursor to the 20B) sourced from the Mazdaspeed 757 LeMans racer which produced around 450 HP. Since the engine was very compact it was able to be mounted in a front-midship position for better weight distribution.

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What may be considered as the biggest departure from the Group B car is that the Group S prototype features four wheel drive and most strikingly four wheel steering. Details about the 4WD system and differentials used are unknown. However, a small adjustment lever next to the shifter in the cabin seem to indicate it had locking and/or ratio altering capabilities. Suspension is handled by double wishbones and dual dampers at every corner.

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The wide body features lightweight composite construction with front and rear opening clamshells. Very subtle air scoops can be found on both sides of the pillars which seem to provide air to small twin coolers (transmission / differentials most likely). A roof scoop provides air to a rather large engine oil cooler. The radiator itself remains in the nose of the car with cooling aided by a bonnet/hood vent/extractor. A scoop provides fresh air to the intake. The car also features a mono (single) wiper setup that looks very similar to units used on the Mercedes W210 CLK a whole decade later. It is unknown if the wiper system is in fact original to the car or was later added to it.

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Notice the large fuel tank right behind the seats.

Two prototypes are rumored to have been built. It is unknown if they are identical or have different features. What is certain is that, if Group B & S wouldn’t have folded, this car would have provided the fans with a sight and sound spectacle like no other!

SPECIFICATIONS

Group/Class S PROTOTYPE
Production 1986 # built: 2 (rumored)
Engine
Type 13B G3, Wankel 3 rotors, peripheral ported, gas front mid-mounted
Displacement 1962cc
Compression ratio N/A
Output power – torque 450 HP @ 8500 rpm 289 lb-ft @ 8000 rpm
Materials block: N/A cylinder head: N/A
Aspiration naturally aspirated variable lenght intake
Ignition & Injection
  • Nippodenso Fuel Injection
Cooling system water-cooled
Lubrication system dry sump with rear mounted reservoir and roof mounted cooler
Transmission
Type four wheel drive 5-speed manual transmission (presumed)
Gearbox ratios
  • N/A
  • N/A
  • N/A
Diffrential ratios
  • N/A
driver controlled variable locking center differential ratios
Clutch N/A
Chassis-body
Type
  • FC3S based steel space-frame with integrated roll-cage
  • 2 door coupe widened lightweight bodyshell with front and rear clamshells
  • Composite windows
Front suspension Double wishbones, Dual shock absorbers, anti-roll bar
Rear suspension Double wishbones, Dual shock absorbers, anti-roll bar
Steering system rack and pinion four wheel steering system
Brakes
  • four-wheel vented disc brakes
  • handbrake
dual circuit with servo
Dimensions
length: N/A width: N/A height: N/A
wheelbase: N/A front track: N/A rear track: N/A
Rims – tires
  • N/A
  • N/A
Dry/Unladen Weight 950 kg (2100 lb) *estimated  Bias:N/A
Weight/power 2.1 Kg / HP (4.7 HP / lb)
Fuel tank N/A

VIDEOS


(C) Article by Jay Auger – website owner & author

  • Images & videos are the property of their original owners
  • Eifel Rallye Festival Pictures used under permission – McKlein Publishing
  • This website is not affiliated with any entity listed in this page

SOURCES:

SPECIAL THANKS TO:

  • Phillip Kruger
  • Leo Rossi

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