Published on: Jan 20, 2016 @ 21:04 Originally Published in: 2015 (old website) (C) Jay Auger - website owner & author Notice: Any form of duplication methods (including but not limited to copy/paste of text and screen capture) of the website's content is strictly forbidden.
INTRODUCTION
Spanish car maker SEAT, which was freshly out of the Fiat group, wanted an opportunity to have a strong presence in the rallying craze fuelled by the lax Group B regulations and boost its sales. However, at the time, there was economic and political unrest in Spain which gave SEAT very little budget to develop a top class international rally car. Four-wheel drive transmissions, which had become the norm in rallying, were relatively new and expensive technologies to develop. Two Spanish brothers, the Serviàs, privately came up with a cheaper solution to giving SEAT’s rally car four-wheel drive: use two engines!
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HISTORY
The Serviàs’ “Bimotor” idea quickly took shape and was presented to SEAT Sport which gave the thumbs up to begin work on the prototype. Spain’s national rally circuit was a perfect venue to test and develop such cars since it allowed all kinds of prototypes lacking official homologation.
The normal SEAT Ibiza itself was a new front-wheel drive supermini introduced at the 1984 Paris Motor Show. One interesting feature is that the engine and drivetrain was designed in collaboration with Porsche which, after paying royalties, SEAT could market the car under the “System Porsche” moniker. Furthermore, the bodywork was signed by Italdesign and manufactured by German coach builder Karmann. All of which was to give the new car much credibility, publicity, and boost sales. It was thus logical to use this particular car in the Bimotor concept.
To simplify things, the brothers used an additional front section of the Ibiza and joined it together, hidden under the rear bodywork. The “twin” theme continued with the engine, transmission, and suspension – all being identical. The instrument cluster also contained two of every gauge. The engines were twin 1461 cc “System Porsche” units tuned to produce around 125 BHP each, making in theory a total of 250 BHP. Adding the two displacements netted a 2922 cc total figure which would put the car in a favourable engine class if regulations ever came into play. A later “evolution” of the setup was reportedly performed which boosted each engine’s power to 150 for a total of 300 BHP.
There was obviously some difficulties at synchronising both systems together. One of those was that the front engine would run 1500~2000 RPMs higher than the rear one due to inertia. The other main issue was to find a way for the front and rear transmission linkage to work perfectly in sync. Cooling of the rear engine was achieved by installing the radiator in front of the engine in between the bulkhead which was fed cool air by two ducts mounted in the side windows. This left the area behind the rear engine open for the fuel cell.
The bodywork itself was left relatively unchanged and remained steel for the most part. Only the hood/bonnet, rear hatch, and arch extensions were made out of lightweight fibreglass. This is a far cry from other Group B or S prototypes that used very expensive exotic materials and polymers all around. However, the Ibiza was a small and lightweight car to begin with and even if fitted with two engines the claimed weight was a respectable 1001 kg (2207 lbs). Two cars were ordered and built.
The SEAT Ibiza Bimotor was mainly tested by Josep María Servià from 1986 through 1988 in the Spanish Gravel Championship amongst banned Group B cars then competing as prototypes. Over the course of three years, Servià would clinch four class victories and seven other podiums, finishing runner-up in the Championship in 1986 and 1987. Fellow Spaniard Alex Brustenga would net top ten finishes in 1986. He was replaced for the following year by compatriot Antonio Rius, who scored three podiums in the season – giving the Bimotor a 1-2 finish in the 1987 Rally RACE Ávila alongside event winner, Servià.
While some claim that the Bimotor was originally aimed at Group B regulations, serious doubts can be put forward since a theoretical production of 200 twin-engine homologation cars would make absolutely no financial or common sense for SEAT to attempt selling them as ludicrously impractical road cars. As such it is agreed by rally insiders of the time that the Bimotor was in reality aimed at the Spanish Gravel Championship as a research and development stepping stone for SEAT, not to mention giving the brand a decent image boost without the high cost of homologation.
While the close timeline of Group B’s 1986 ban and the Bimotor’s appearance in the country’s rallies often fuels the confusion, the planned Group S replacement of 1987, which demanded only 10 examples to be built without need for homologation road cars, would make the Bimotor a suitable and proper candidate for the category. The category would have undoubtedly caught the attention of SEAT, hence it is commonly acceptable to qualify the Bimotor as a theoretical Group S prototype. However, the BPICA’s plan to revive Group S never materialised within the FISA.
After the 1988 season, the project ultimately ended with the Bimotor never competing outside of Spanish dirt. SEAT would focus its following rallying efforts with the front-wheel drive Marbella Proto and in Rally Raid endurance racing. A SEAT Ibiza Bimotor would not be seen again until one made an appearance at the 2011 Goodwood Festival of Speed hill climb.
It is note to mention that at about the same time the SEAT Ibiza Bimotor was conceived, other manufacturers such as Mini, Citroën, Volkswagen, and even Abarth dabbled in twin-engine designs as well. Of course, this concept is incompatible with a production road car since there is no trunk/cargo space left. In motorsport, the twin-engine design just isn’t reliable enough since you have double the chance of something breaking or going wrong. It is also a distraction for the driver that has to monitor two engines. Furthermore, unlike today’s advanced electronics, there was no way back then to alter front to rear power distribution other than tuning one engine differently or mixing gear ratios. However, the twin-engine idea is a feat of engineering that is valid in itself.
IBIZA MARATHON CONCEPT
At the end of the development of the Bimotor, SEAT wanted to shift its rallying ambitions to “Rally Raid” competitions such as the incredibly popular Paris-Dakar and came up with the Ibiza Marathon concept. It would feature space-frame tubular construction, lightweight composite bodywork, and use of a Audi-sourced 300 BHP V8 engine paired with four-wheel drive; these features are highly reminiscent of Group B designs of the previous years, making some people mistake the Ibiza Marathon as a being a Group S prototype. In any case, the car itself never materialised into reality but the concept served as the technical basis for the iconic 1992 Toledo Marathon, aptly driven by the Servià brothers – quite befittingly.
BIMOTOR SPECIFICATIONS
| Group/Class | S | PROTOTYPE | ||
| Conception/Production | 1985~1986 | # built: 2 | ||
| Engine | ||||
| Type | “System Porsche”, I-4, OHC 8v, gas (x2) | located front & rear transverse | ||
| Displacement | 1461 cc (x2) | WRC: 2922 cc | ||
| Compression ratio | 10.5:1 | |||
| Output power – torque |
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| Materials | block: cast iron | cylinder head: aluminum | ||
| Aspiration | Normal / Natural | |||
| Ignition | – | |||
| Cooling system | water-cooled | |||
| Lubrication system | – | |||
| Transmission | ||||
| Type | front & rear wheel drive | 5-speed manual (x2) | ||
| Gearbox ratios | 1st: – 2nd: – 3rd: – 4th: – 5th: – R: – |
1st: – 2nd: – 3rd: – 4th: – 5th: – R: – |
||
| Differential ratio | – | – | ||
| Clutch | – | |||
| Chassis-body | ||||
| Type | Twin Ibiza front sections joined with roll-cage. 3 door hatchback steel bodyshell. Fiberglass hood/bonnet, rear hatch, and arch extensions. | |||
| Front suspension | McPherson type struts, anti roll bar | |||
| Rear suspension | McPherson type struts, anti roll bar | |||
| Steering system | rack and pinion | |||
| Brakes |
|
– | ||
| Dimensions | ||||
| length: 3638 mm (143.2 in) | width: – | height: 1394 mm (54.9 in) | ||
| wheelbase: 2448 mm (96.4 in) | front track: – | rear track: – | ||
| Rims – tires | 14 inch rims | Michelin M4 – 185/60R14 | ||
| Dry/Unladen Weight | 1001 kg (2207 lbs) | |||
| Weight/power | 4.0 kg/HP (8.8 lb/HP) | |||
| Fuel tank | – | |||
| Drag coefficient | – | |||
VIDEOS
REFERENCES
(C) Article by Jay Auger – website owner, main author & chief editor
- Images & videos are the property of their original owners
- Eifel Rallye Festival pictures used under permission – McKlein Publishing
-
DISCLAIMER / LEGAL NOTICES
SPECIAL THANKS:
- Phillip Kruger (Ibiza Marathon info)
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