Impreza P1 by Prodrive

Development History

The project was instigated a year before the first announcement of the car, at the end of 1998 after the success and rush for the official import of the 22B-UK and the similarly badged official grey competitor, the Mitsubishi EVO6. Both of these cars were brought into the UK under the Single Vehicle Approval (SVA) route which side stepped the full European Whole Vehicle Type Approval (ETA). This brought about some criticism as it was by this very same route that the much maligned, and criticised grey STi were being imported into the UK. The 22B-UK fell foul of this approval method when it was discovered that the limited quantities allowed had already been reached by the grey importers and a delay into early 1999 was required. Meanwhile prospective owners of "official" Mitsubishi EVO6 vehicles have a trip out to Holland to first drive their cars outside of the UK to circumnavigate the quota ruling.

On the horizon though was a relaxing of quotas of both officially imported and SVA imported cars, but also a tightening of what would and would not pass the SVA test. To currently pass the SVA an STi only requires the speedo to be converted to mph, the fuel filler to be restricted only to accept an unleaded nozzle, and a rear fog light to be fitted. With the new SVA Mitsubishi have said it is unsure whether the EVO6 will pass the new noise emissions test and it is unknown whether the STi will pass. Even so with the threat of many more grey 276bhp Imprezas on their way an official import was on.

Subaru UK and Prodrive set out to convince the Japanese that a fully homologated European 2 door Impreza was a possibility and after a meeting between David Richards and the Subaru Japan President Tanaka development work on the P1 started in earnest. To be able to compete with the grey imports, the engine must be at least as powerful at 276bhp, whilst here was also an ideal opportunity to tune the car, in particular the suspension, to European tastes.

As mentioned above, to gain credibility for the project full European homologation, rather than SVA was the way to go and was no small feat as the two door Impreza is not sold in Europe and thus did not have any European type approval to start with. Structural integrity of the two door shell is better than the 4 or 5 door models and so was not difficult to homologate, but still expensive! Everything upon the car must carry an EU/CE mark to say that it complies with the correct regulations which includes glass, lights, seats etc.

Engine/exhaust emissions were thought to be too technically difficult to pass by the Japanese parent company especially if the 276bhp target was to be kept. Most lacking just recently on the STi5 is an ECU which can adjust to UK/European specification fuel as it is intended to be used on Japanese 100RON. The use of UK Super Unleaded at 98RON was a must, but this has now been reduced to 97RON and the use of 95RON premium was a definite recipe for disaster. Even on 98RON fuel, careful monitoring of the engine under hard acceleration and load shows that the Japanese specification does knock/ping/pink in a large number of cases. Subaru Technica International (STi) rewrote the ECU code to Prodrives specifications and modified the exhaust to incorporate one large catalyst instead of the much smaller single unit in the current STi (or the twin unit used in the lower powered UK spec.). Up until 1998 the STi models have had two catalysts, as do the current European specification Imprezas but recently they have changed to a single unit in the down pipe. The one fitted to the P1 is externally identical but internally has a much greater surface area of catalyst exposed to the passing gases and is thus more efficient. It is also rumoured that there is a Broquet catalyst in the fuel system to raise octane rating of fuel.

Keith Hadley the Group Homologation Manager at International Motors spent nearly 6 months in total obtaining the necessary certification for both the 276bhp engine and the different body. The car is homologated under the "Supercar" rules which allowed one extra decibel on the noise tests, but to qualify the car has to be able to accelerate in third gear between two fixed points within a specified time. The P1 qualified, and can now officially be classed as a "Supercar".

The Type R upon which the car is based was thought to be too raw and unrefined so Prodrive set about developing a chassis more suited to European tastes. Quite a few owners of STi greys upgrade their cars with after market units from the likes of Leda. On the 22B (and 22B-UK) an owner has said that the springs are too soft and the dampers too hard. This results in a very stiff ride but on long sweeping bends you find the car progressively leans more and more. Another effect is over heating of the damper oil on a twisty country route leading to a spongy ride.

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A wide range of different wheel and tyre size, spring, damper and anti roll bar rates were then evaluated from the complete Impreza/STi range. Benchmarking the handling of the car was then done against its main competitors such as the STi5, 22B, EVO6, BMW M3, and Porsche 911. The final set up for the P1 arrived at 17in wheels sporting 205/45 Pirelli P Zeros (as seen on the much acclaimed RB5), dampers from the STi range but bespoke springs from Prodrive/Eibach that lower the ride height by approximately 20mm compared to the STi5. Completing the overall handling package a quicker steering rack (13:1 instead of the standard cars 15:1) was planned to be added but this proved in testing to be a mistake with the car being extremely nervous. Unfortunately the Press and ultimately the public picked up on this fact and were looking forward to a feature that would not apear :-( One interesting fact not realised is that the white car driven by the Press did not have the rack fitted and it was only towards the end of the development cycle in November did it actually get one.

Two things which have fallen foul of the rules and regulations are the much loved climate control and the electric folding wing mirrors as found on the grey imports. The switch gear of the climate control protrudes outside of the facia area and thus fails an impact safety standard. It will be interesting to see if the same switch gear on grey imported STi fall foul of the new stricter SVA which has mention of a sphere to test the impact areas and protrusions... Likewise the wing mirrors are not approved on any European model and thus would have to be recertified for crash worthiness. One other, more likely reason is that the European dashboard has no place for the required switchgear and no associated wiring on the European wiring loom.

Unusually for an importer, the European Whole Vehicle Type Approval for this car is exclusively held by Subaru (UK) Limited and not the manufacturer and the manufacturers plate on the suspension strut is a Subaru UK item not the normal Fuji Heavy Industries.

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Page last updated 25th June 2000
Copyright © 1999/2000 Steve Breen
All photographs unless specified otherwise on this page copyright © Steve Breen and may NOT be reproduced anywhere without permission.