Opel Manta B 400 – 4WD Prototype

Published on: Feb 8, 2017 @ 01:53
(C) Jay Auger - website owner & author
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In 1982, the rear wheel drive Manta was already set to replace the Ascona for Group B competition later on in 1983, but by then the Audi quattro had started to run circles around the competition at the slippery events. As such, Opel team manager Tony Fall ordered a four wheel drive (4WD) prototype of the Manta B 400. Fall contacted FF Developments (FFD) for them to design a suitable system specifically for the Manta. The company was already offering 4WD conversions on customer cars and were providing 4WD for Opel Monza and Senator models and had engineered full time 4WD systems for production for the AMC Eagle and aftermarket upgrades on Triumph 2000s and Stags and for the Range Rover.

For this very special study project, Opel provided a basic, all white, “narrow body” road car which was reportedly driven straight from Rüsselsheim, Germany, to FFD in Coventry, England. It is said that it took the Ferguson team six months to produce a driveable prototype. For this, FFD raided their conversion parts bin and rigged up a system that used Triumph 1300 uprights and driveshafts for the front axle. A second Manta was reportedly converted to four wheel drive and updated to the rally “wide” specifications for comparison purposes. However, no official documents are available from Opel Motorsport (as it is expected of most prototypes) to confirm the actual number of prototypes built.

Bill Munro, author of the upcoming book “Traction For Sale” (FFD History), explains in detail the workings of the system:

“The heart of the Ferguson system is the Viscous Control torque splitting device. This consists of inter-meshed vanes running in a high viscosity silicone guild that transmits torque in varying degrees depending on its temperature, which is varied according to friction generated between the sets of vanes. This is dependent on the differential between the speeds of the front and rear driveshafts. When one axle starts to slip, torque is transferred to the other axle. It reacts almost instantaneously, maintaining traction and eliminating slippage.”

The particular system engineered for the Manta was set up to distribute torque Front 36% / Rear 64%, which is typical for a car of this layout. The extra mass of the entire system was said to increase the weight of the car to around 1200 kg (2690 lbs). Besides this, the engine of the road car prototype is said to have been a basic 144 HP “phase 1” unit from the B400 production model and was left untouched. For the rally version, the engine was upgraded to the “phase 2” setup as used in the Group B rally Ascona B 400 at the time. However, it was reportedly re-tuned which resulted in a tamer 240 HP to help favor better low end torque.

The rally version of the 4WD prototype was delivered to the test drivers with a brash statement: “With this car you can no longer spin-out!“. The tests were performed under the supervision of Opel Motorsport project head technician Erich Koch. The drivers quite enjoyed debunking Ferguson’s statement by spinning out the car multiple times thanks to harsh maneuvers. Koch quickly came to the defense of the 4WD system by citing improper time to correctly set-up the car beforehand.

This was followed by measured acceleration tests. The setup was said to be able to propel the car from 0 to 100 kph (62 mph) in 6.3s on the tarmac, while the same test on “wet grass” wielded a time of 8.5s. In comparison, a rear wheel drive rally Manta achieved the same “wet grass” test in 13.5s, taking five whole seconds more. This proved the potential of the Manta’s four wheel drive system for rallying.

Opel Manta B400 4WD Proto Article.jpg

The test drivers reported some driveability problems such as torque steer on the front axle, uneven performance while turning, and strong understeer but the latter could be compensated with proper driving techniques. The suspension had limited travel and was on the soft side which didn’t give the drivers a reassuring feeling. Furthermore, the extra weight of the four wheel drive system is said to be felt through the chassis which could have benefited from further strengthening to help dampen the vibrations it created. However, the ride was reported to be fairly smooth and enjoyable nonetheless.

Opel Manta B400 4WD System.jpg

A few months later, the same 4WD rally Manta prototype, sporting the license plate “GG-CM 537”, was officially shown as a publicity stunt before the 1983 Swedish rally to promote the company’s upcoming switch from the Ascona to the Manta in the WRC (the debut car sported the same plate but was not 4WD). Ari Vatanen, who was a driver with Opel at the time, tested the prototype on the Swedish snow and reportedly told the journalists that it was “better than an Audi quattro”. The car definitely sparked the curiosity from the people present as they noted other subtle visual cues differentiating it from the 2WD Manta.

opel-manta-b-400-4x4-prototype

In fact, apart from the rally “Rothmans” livery, visual inspection of the car shows that it is equipped with a roll cage and that it does sport the squared arch extensions from Irmscher (as is the rally version). It also features the tall roof antennae (as is the rally version). However, it is equipped with the normal production hood (bonnet). The front bumper cover is different from both the road and rally version, it seems to be closer to the road version but with the lower air duct enlarged. The auxiliary lamps are also placed differently than on the definitive rally version as well. The grille itself has only one row of horizontal slits instead of the two on the rally version. Many of these features would put the car as a modified “pre-facelift” early production version of the Manta B400 (which 23 were produced in 1981).

OMantaB4004WD.jpg

Since the prototype was still being reviewed by the GM/Opel board, there were no immediate plans to produce and homologate the 4WD Manta for Group B rally competition, so they went forward with the rear wheel drive version as planned. In the end, severe concerns were put forward that the 4WD Manta wouldn’t be competitive without a turbocharged engine, which was planned for 1984, especially if it had any hope of going head to head with the Audi quattro. Furthermore, the prototype Manta was said to be too heavy and unsophisticated, again when compared to the quattro which had a few years head start in its development. The whole project was thus abandoned due to high conversion costs (approx £5,500 GBP / $10,000 USD per car (200 would be needed), in 1982 money) and too much further investments needed to refine and improve the setup.

It is arguable if Opel made the right decision since in its inaugural 1983 WRC season the rear wheel drive Manta could only watch the fight between Audi and Lancia without being able to truly impose itself. As such, Tony Fall ordered another study based on the Manta: the Kadett D 400, but that also turned out to be a futile exercise. In 1984, overwhelmed by the fierce competition, the Manta fell further down the leader-boards and Opel’s international rally efforts were basically abandoned. In one last push, Fall convinced the GM board that the German team’s future in Group B rallying was indeed with four wheel drive, and started development of the more nimble Kadett E 4S prototype equipped with the Xtrac system.

SPECIFICATIONS

The following specs are for the 4WD rally prototype

Group/Class B/12 PROTOTYPE
Conception/Production 1982 # built: 2 (rumored, one road, one rally)
Engine
Type 4S “phase 2” with Cosworth “crossflow” cylinder head, I-4, DOHC 16v, gas located front longitudinal
Displacement 2410 cc WRC: 2410 cc
Compression ratio 11.2:1
Output power – torque 240 HP @ – rpm – (- Nm) @ – rpm
Materials block: cast iron cylinder head: aluminium
Aspiration
  • natural / normal
  • 2 x Weber carburetors
Ignition electronic, firing order 1-3-4-2
Cooling system water-cooled
Lubrication system dry sump
Transmission
Type four wheel drive 5 speed gearbox
Gearbox ratios N/A N/A
Differential ratio N/A Ferguson Formula (FFD) center differential with viscous coupling. Front differential integrated into sump guard.
Clutch N/A
Chassis-body
Type steel monocoque chassis. 2 door coupe with integral roll cage. Kevlar bonnet, boot lid, front and rear wings with wheel arch extensions, side skirts, doors and rear spoiler
Front suspension double unequal wishbones with coil springs, telescopic gas shock absorbers and anti-roll bar
Rear suspension live axle with 4 longitudinal links, panhard rod, coil springs and telescopic gas shock absorbers
Steering system rack and pinion 2.7 turns lock to lock
Brakes front and rear ventilated rotors, cable handbrake Dual circuit with servo, adjustable ratio split front to rear
Dimensions
length: 4475 mm (176.2 in) width: 1687 mm (66.4 in) height: 1320 mm (52.0 in)
wheelbase: 2518 mm (99.1 in) front track: 1384 mm (54.5 in) rear track: 1375 mm (54.1 in)
Rims – tires N/A N/A
Dry/Unladen Weight 1000 kg (2200 lb)
Weight/power 4.2 kg/HP (9.2 lb/HP)
Fuel tank 110 litres

ANECDOTE

The rally 4WD prototype is rumored to still exist with its Rothmans livery but has since been converted back to rear wheel drive after changing hands multiple times over its history. Also, there is some Opel Mantas & Asconas that were reportedly converted to 4WD by using leftover Astra / Kadett E 4S mechanicals after the official ban of Group B / S, circa 1986-87. These cars can be easily identified with their front wheels’ 4-bolt pattern versus the rears’ 5-bolt pattern, and are not to be confused with the original Ferguson prototypes.


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

  • PARTIAL SOURCE: (C) Auto Moto and Sport Magazine – January 1983 (translated, abridged, and much modified)
  • Images & videos are the property of their original owners
  • This website is not affiliated with any entity listed in this page

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