Toyota’s Ideal Successor Programme: IS-1 & IS-2

 There’s no better way of conveying just how seriously Japanese car makers took rallying at the dawn of the nineties than by looking at Toyota’s Ideal Successor programme, a poorly recalled attempt to divine how best to approach WRC competition for the decade to come. The programme spawned the IS-1 and IS-2, the former nominally based upon the then newly released ST185 Celica GT-4, the latter clothed to resemble the then current  ‘sporting’ Corolla, the AE92 GTI-16.

First, some history. The Ideal Successor project began to take shape in earnest at the dawn of 1991, a significant year in that it marked the final season of outright Italian Delta dominance. Toyota, long the spearhead for Japanese interest in rallying, had tasted WRC success with its ST165 Celica by this point, but it was clear to the company’s sporting arm, Toyota Team Europe, that to truly make the championship its own would require them to engineer a more complete, more capable (better cooled), and better balanced contender. 

Toyota's plans were lent further impetus by the knowledge that the new decade would invariably bring with it a crop of even more technically polished rivals, all backed by hefty budgets and all now compelled to tackle the season in full. Nissan's Sunny GTI-R was already nearing completion, while Mazda had its stalwart 323, still underpowered thanks to a sub-2.0l engine, but fully developed and campaigned by a team seemingly in it for the long term. 

Had they deigned to peer even further into the future, then Toyota's sages would have been able to discern the outlines of even more advanced competition in the shape of Prodrive-fettled Legacies and Imprezas, a slew of Ralliart-developed Lancers, and of course Ford, at this point preparing to commence work on what would become the Escort Cosworth.

In short, rallying's premier class was set to become a whole lot more competitive and cut-throat as the decade unfolded, and while no one at TTE could've predicated how it would play out, all concerned with the programme knew that resting upon the ST165's hefty laurels would be akin to a dereliction of duty. 

Enter stage left, the Ideal Successor programme, an undertaking overseen by Group A legend and all-round TGC hero, Dieter Bulling (he of Catalunya '95 infamy). Never intended for homologation and thus WRC competition, IS-1 and IS-2 are nevertheless linked to TTE’s rally endeavours by their mechanicals, and, more pertinently, what they represented, namely Toyota’s steadfast refusal to be anything but the dominant force in World Rallying. 

Based upon the immensely successful Toyota Celica ST185, the IS-1 was primarily a study in weight distribution, hence why TTE went to great effort to re-mount its 3SGTE in a longitudinal configuration. It also boasted a trans-axle, with both the Xtrac gearbox and differential located at the rear of the car in order to strike a better overall weight distribution. 

The project took shape over the course of 1991 and therefore pre-dated the debut of the 'proper,’ homologated ST185 rally car by a good few months, and ultimately sported a spec analogous to that of the final, full-fat ST165 (aside from the rotated drivetrain, of course). While never intended to be a rally car, the IS-1 did form the basis of a feasibility study for a stillborn rallycross campaign, and subsequent testing for this aborted endeavour showed the car to make an easy 600 bhp with its FIA-mandated restrictor removed. 

The IS-2 was an even more ambitious undertaking because of its groundbreaking specification, and the fact that packaging so much hardware into the confines of the AE92 shape Corolla was always going to pose a greater challenge than that of the Celica.

The 3SGTE's 300 bhp was routed rearwards to a seven-speed transaxle, via an Xtrac hydraulic centre differential, the same as used in the ST165 rally car. TTE also invested considerable resources into the IS-2's suspension arrangement, which is why it wound up with a beautifully engineered multi-link push rod setup not too dissimilar from those found on contemporary F1 cars. You need look no further to glean just how much money was invested in the IS programme than this suspension setup. 

Neither car has spent much time in the public eye since the early '90s. IS-1 was tested at the Valkenswaard rallycross track during the final phase of its development (giving rise to the rumour that it was intended as the basis for an official Toyota RX entry), while IS-2 was driven around Spa-Francorchamps by Marc Duez. 

I’m sure you will all agree that both IS-1 and IS-2 are fascinating cars, with the latter being of particular interest. You really don’t need too fanciful an imagination to envision an alternate reality, one where Toyota developed and campaigned a Corolla-based rally car years before the debut of the World Rally Car we all know and love in 1997. 

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