[tbtstt]

First up I have to start by saying that, sadly, this isn't my project. However I happened to stumble on the fact that a local rallycross driver was building himself a new GR Impreza rallycross car and, after a small amount of pestering (and a promise not to inappropriately touch anything with STi or Prodrive markings on it), the owner of the car invited me down to have a look and take some pictures – so I thought it would be rude not to share them with the rest of you!

The owner and driver of the car is Kevin McCann who previously ran this Impreza in the British Rallycross Championship:



This car started life as a road car but was built up to the equivalent of S5 World Rally Car car specification. Over its years of use in the British Rallycross Championship the car has undergone a significant amount of modifications and changes (some more successful than others!) to reach the configuration you see above. However the time has come for a change and thus the project you see here was born...

…as with the previous car, the base was a road going car again – in this case a hatch Impreza written off due to front end damage. There is no sponsorship or external funding for this project (or the running of the car) so, in order to reduce costs as much as possible, the decision was made to transplant as many parts as possible from the old car to the new. As you might guess classic Impreza World Rally Car parts don’t just slip into a road going hatchback Impreza, so there has been a signficant amount of modification required to get everything shoe horned in there. This is probably most evident when you look in the back of the car as the normal boot mounted rear suspension mounting points of the GR Impreza have been completely chopped out and a whole new box section assembled:


(The Roses tin isn’t structural!)

The same has happened at the front of the car as well – though slightly less custom fabrication has been required here – in order to successfully transplant the front suspension. You can see the suspension is mounted further inboard then you’d normally find it on the GR (nice bit of engine bay bling as well!).



Reiger rear right shock, hub and brakes in place:



And on the left, with the structure of the car exposed:







The plan is to take as much excess material out of the rear structure as possible so, in the event of impact, this area will collapse and absorb the damage (or at least take some of the energy) rather than it all acting on the suspension region. Plus, perhaps most obviously, less excess material equals less weight!

Sadly the old engine won’t be coming from the old car to the new car; its currently sitting on a bench displaying the wounds it acquired on its last outing…







…its not all bad news though as a replacement engine has just been finished! The new engine has been built by ex-Prodrive engineer Graham Sweet, who is responsible for building the engines for the Subaru USA rallycross cars. The needs of a rallycross engine are fairly specific and, on the dyno, this new engine is producing 548 BHP and 554 Ft. Lbs. in the 5000 - 6500 RPM range. As you’d expect the new engine is significantly beefed up from standard; I’ll try and get the exact details though I’m not sure how forthcoming information is on race engines.

Transplanted ancillaries installed upfront:




(The engine in situ is not the new engine, its actually an old RB5 engine just in place for measurement purposes at the moment)

The rest of the engine cooling will be located in the rear of the car, with the ducting running in from the rear doors. The relocation of the bulk of the cooling to the rear of the car is a fairly common design trait on rallycross cars, with the move helping to even out the weight distribution of the car and removing some of the components from the front where impact can (and often does) occur.

The old car, sitting on the ramp having been robbed of bits:



Obviously there is a lot of work still to be done, but even at this stage you can see the lines of the car coming through:









Front left wing awaiting trial fitment:



All these panels are metal at present; composite panels would be preferred but they come at a price, so these are in use for now with the composite panels to follow when budget allows in future.

One rather large transmission tunnel:





The transmission itself is a “H” pattern type gearbox. Although a sequential gearbox would be preferred, a sequential gearbox capable of taking the power and abuse required for rallycross is a lot of money, so that’s been relagated to the future shopping list for now. The large void to the left is waiting to be filled by a bespoke 4” exhaust system. The original route of the Impreza exhaust runs too low at the rear for rallycross use, so the plan is to re-route the exhaust upwards before the rear diff.