GR Impreza Rallycross Supercar Build
 

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 – I know some of you guys were interested in Simon Hortons rallycross supercar build, so I thought it would be rude not to share this 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:

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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:

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(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!).

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Reiger rear right shock, hub and brakes in place:

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

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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…

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…its not all bad news though as a replacement engine has just been finished! :thumb: 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 (as are the power limitations) 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:

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(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:

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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:

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Front left wing awaiting trial fitment:

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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:

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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.

Given the potential for serious impact in rallycross – as well as the sort of forces the car will endure during racing – a solid rollcage is vital. Custom Cages provided the cage for the previous rallycross car so Kevin contacted them again to provide the cage for the hatch.

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Looking in the back of the car you can clearly see how much the rear suspension mounting points have been built up. The opening on the car floor on the right is for exhaust routing purposes, though the exact route and exit point for the exhaust has yet to be decided.

Peeping out of the box it recently arrived in, one new slatted WRC style rear spoiler:

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I was treated to a brief glipmse of this, however the excessive amount of carbon was too much for me, so the spoiler was immediately reboxed before I became over-excited. Needless to say it should look the dogs danglies when its fitted. There is also a carbon fibre bonnet on the cards so the front end will be matching!

Finally, the car in its entirity:

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Not quite ready for these yet:

http://i6.photobucket.com/albums/y21.../KMCGRRX28.jpg

But its getting there!

As with so many motorsport projects budget and time are major issues. Although the bulk of the parts have been acquired and there has already been a significant amount of work done on the new car, there is still a long way to go. The plan is to have the car running this year though and I’ve been told that I’m welcome back when the car is nearer completion, so hopefully I’ll be able to see it sitting on its own wheels soon! :thumb:

awesome work bud love the thread keep posting :thumb:

amazing work mate keep it up :thumb:

Brilliant, followed Si's car with interest, keep the updates coming :thumb:

Looks great, the only thing IMHO that lets it down are the square suspension turrets, they look aweful in such an awesome car. Hope it goes as well as it looks.

Excellent ,cant wait to see this develop

Great job, looks like a big undertaking, but will be the dogs when it's finished:thumb:

Personnally i can't wait to see this motor on the grid, both me and kev have gone down totally different idea's for our respective rallycross scoobies so it will be facinating to see how they compaire on track. I had the option to go down the hatch route, but for me I like the more predicatable nature of a long wheelbase on the loose. I think that it will be very much horses for courses, with the shorter wheel base better in some situations and the longer one in other.

Do you know what he's doing ref cooling as i can't see any signs of rear rad fabrication yet if he's going down that route?

Also Kev needs a a turn around in luck as he's had nothing but bad luck for a few seasons now, i've felt really sorry for him with the troubles he's had. We both help each other out a lot and the last thing either of us want to see is the other stuck in the pits with a failure, so hopefully the new car with a back to basics rethink will help him. Also i think he's had some bad advise in the past and so people have taken advantage of Kev's good nature, i'm pleased to see Kev doing his own work and i'm sure he will make a very good car, he certainly has plenty of seasons experience in the supercar class and he's got some very good team members that help him out.

Keep us updated with any updates you get from Kev.

As long as I'm allowed in the garage you can count on it! :thumb:

Its not my handiwork, but I'll be sure to pass that on! :)

You can say that again! Rallycross supercars are serious bits of kits and running one has long been a motoring dream of mine. Until I win the lottery though being able to watch this car come together will have to satisfy me! :lol1:

Yeah, it'll certainly be interesting to see how the two Scoobs compare. Plus seeing one of each will make the grid more interesting to look at!

Watching the X-Games Super Rally last year and the Global Rallycross Championship this year both the Hawkeye and Hatchback have proven to be competitive rallycross cars, I hope you and Kevin can repeat that over here. :)

When I arrived at the garage on Saturday there were a couple of bits of large diameter Scat hose arranged in the rear of the car: I think that was as far as the rear radiator installation has got so far! :lol1:

Yeah, from what Kevin was telling me (and what I've seen at the British Rallycross Championship rounds I've spectated at) he certainly seems to have had his share of bad luck. The development of the original car seems to have been a very hit and miss process; he's hoping that he can take all the positives from the old car though and get it right first time with the hatchback. :thumb:

I've wanted to see being the scenes of a supercar for a long time, so I'll be lurking around the build (asking many questions!) as much as possible!

No updates as such at the moment as the build hasn't moved on much from when I saw it, but I did manage to get hold of some more specific details of the engine. I'll be collating as much information as I can thoughout the build so there is a complete specification list when the car is finished. :)

Engine:

Impreza WRC block.
Impreza WRC cams.
Arrow crank.
Arrow rods.
Omega pistons (running at 10.1 compression).
Dry sumped.
Garrett GT35R V-band turbocharger (with FiA mandated 45mm restrictor).
Modified Impreza S9 WRC inconel exhaust.
548 BHP and 554 Ft. Lbs. in the 5000 - 6500 RPM range.

Transmission:

Tilton Impreza WRC pattern one piece Billet steel flywheel.
Twin plate cerametallic clutch.
Hewland Impreza WRC six speed manual gearbox.
Impreza S5 WRC rear differential.

I also asked Kevin about the radiator setup as I noticed that the US rallycross Impreza's use a (rather cool looking) ducting setup running from the rear quarter glass:

https://farm7.static.flickr.com/6131...57c71b18_b.jpg

Sadly it seems that such a design would fail to comply with FiA build regulations though, so the intakes for the rear radiators will be located in the rear doors themselves.

Just spoken with Kevin and got a little update on the car, so I thought I'd add it to the thread, just to keep things up to date! ;)

The suspension is back at Reiger and there are a few uprated gearbox components in the works so, although progress has been slow the last few months, the car is gradually getting there. Looks like there will be a bit more time available over the next fortnight, so fingers crossed a bit more progress will be made.

Hopefully more updates to follow shortly! :thumb:

We have moulds for bonnet , tailgate and doors atm if your friend is interested

a great job guys, the old toyota corolla wrc front and rear suspension set up looks very similar. similar packaging to and drivers say it is one of the sweetest wrc chassis around. keep us up dated it inspires me on to bigger and better things. :notworthy

Will pass that one when I speak to him next! :thumb:

Will do! Hopefully my next post will have a bit more progress in it.

Time for a proper update! It’s been several months since I’ve last saw the build so, with a Saturday spare and the commencement of the 2012 British Rallycross Championship looming, I took a little drive to check the car out. Having seen the latest situation with the build I’m happy to report lots of good news but, sadly, a bit of bad news too.

Starting with the good stuff, the build has really moved on since the last time I was there. Although at first glance it still seems just a shell, many of the items that were previously sitting on the shelf awaiting a location in the new car have now been positioned and all the provisions for attachment made. Prior to my arrival pretty much everything was out of the car, so Kevin (rather kindly) placed the major items back in to give an idea of the configuration for the finished product. Hence if you look carefully in the pictures you’ll see some things aren’t sitting square and look rather vaguely fitted in place: that’s not sloppy workmanship, just where the parts are resting for the photos!

Beginning at the front – and with probably the most significant of all components – is the newly built engine, sitting in situ and ready to go. Nothing too radical with regards to the layout when compared to a conventional road car:

http://i6.photobucket.com/albums/y21.../KMCGRRX29.jpg

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The gearbox is currently on the bench, awaiting its final tweaks:

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Given the differing location of the driver and the gearbox between the old GC8 and the new GR, the shift lever needed considerable extension. Gartrac took up the challenge and have manufactured a very smart looking extension lever. Due to shifting the driving position to the left of the car, some final tweaks are still needed to this, hence why not all the mechanism is not currently in place.

The underside of the car at present, clearly showing the complete S5 front end fully transplanted onto the new car:

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Self explanatory really, but some mighty AP’s now fitted:

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Underside view of the right side wishbone and chassis mount:

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As with a lot of items on the car the finish on these parts is rough at present. Throughout the build components are constantly being modified though so, logically, it’s only when everything is in place and finalized that the whole lot will be taken off and painted. Conveniently there are actually two ovens within a stone’s throw of the garage so, when the time comes, it’s a case of wheeling the car next door for painting.

Just in case you are wondering what the protrusion below the engine is, it isn’t a Scalectrix inspired modification, but is part of an additional engine mount fabricated for working on the car with the gearbox out: basically with the gearbox removed the whole engine wants to rotate forward on its mountings, so this frame supports the weight across the front side allowing work to continue under the car without fear of the engine making a bid for freedom.

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The vertical protrusion on the frame is scheduled to be chopped off once the frame is no longer needed and can be removed from the car, but of course this can’t happen until the gearbox is ready to go back in: hence an emergency stop gap modification of white tape to its lowest point after someone walked into it! :lol:

The engine brace is one of loads of little things that have been done to make the car as modular as possible, thus individual areas of the car can be easily worked on without having to take half of it to bits. This extends from major component to little details, such as using bolts where you might normally use rivets, purely for the ease of quickly removing and refitting parts to and from the car.

The GC8, robbed of its innards, sitting on the ramp awaiting a new home:

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The exhaust system, which was originally planned to be 4” in diameter, has been dropped to 3”. This system has been largely fabricated from scratch and is now ready for fitment, though it’s not in place at the moment due to the ongoing work on the underside and engine bay. You can trace the exhausts path though, starting from the back of the turbo and dropping into the transmission tunnel…

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…then along the right side of transmission tunnel…

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…turning upwards and running into a void fabricated in the rear floor of the car, thus allowing the exhaust to run over the back axle…

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…before dropping back down and ending with a silencer which will runs across the width of the car and exits on the right side of the rear bumper.

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If you look carefully at the shot showing the length of the transmission tunnel, you can just make out several attachment points on either side of the tunnel. These are for braces running across the width of the car which, other than providing the obvious benefit of additional underfloor bracing, have hoops mounted on them which go around the prop shaft. The idea being that if the prop shaft does let go, the hoops will act as a containment ring of sorts and prevent the flailing shaft from causing any further damage. It’s a very minor element in the design, but one of many influenced by hard lessons from the past and geared towards keeping the car as reliable as possible: and ensuring that any failure that does occur has the minimum knock on effect on the rest of the car.

Moving back on top and it’s in the boot where the most visual progress has occurred. Last time I was there the layout of the radiator, fuel cell and associated ducting was just an idea in Kevin’s mind. Now everything has a firm location and attachment points have been prepared across the rear floor area. Looking from the boot inwards you have the radiator sitting right at the back of the car:

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Immediately in front of that is the fuel cell:

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Looking from the front of the car you can see the frame work for the radiator ducting:

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With the main box structure for the ducting intakes done in carbon fiber:

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As mentioned above these items were dropped in situ purely for photography purposes, so obviously the air box won’t have finger sized gaps at the joints when it’s properly fitted! With these bits sitting in place though, you can start to make sense of the internal design of the rear, where cool air will be drawn in though vents in the rear doors, pass through the radiator and exit via venting in the tailgate. I was shown the intakes for the cooling ducting which will be independently supported and sleeved, so the rear doors can still be opened and closed to allow quick accessibility to the back of the without having to dismantle the cooling system ducting.

You can also see inside the rear wings when looking in the boot, where very little now remains of the original structure. The second photo below also shows a little glimpse of the top side of the arch liner which is currently being manufactured from scratch:

http://i6.photobucket.com/albums/y21.../KMCGRRX52.jpg

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Staying inside the car and looking forward, the driver area is starting to take shape, with the pedal box and power steering in place:

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As well as the all-important roof vent:

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Battery located just behind where the passenger seat would be:

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Jacking points in place:

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With the front bumper pinned in place and the car lowered on the ramp again, you can really get a feel for how the car is going to look:

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Cosmetically the car doesn’t look that different from my last visit, but in terms of structure and configuration there is a world of change. The next major hurdle is the wiring loom. The original plan was to call someone in to sort this but, as things have turned out, the chap who was originally selected to do the wiring has ended up working for Kevin on a long term basis: so the electrical expert is now a permanent addition to the team! I ended up having a very lengthy conversation with this chap as his previous experience has been running and rebuilding Group A, WRC and Group N rally cars. His knowledge of Scoobs seemed vast and he’s already had considerable input into a lot of design aspects of this car.

So with all the progress what’s the bad news then? Well, as I mentioned at the start of the thread, the British Rallycross Championship kicks off in less than a fortnight now but, short of a miracle, the car isn’t going to be sitting on the grid for the first round. :( The goal was to have the car ready well in advance but the demands of work have deemed otherwise. Obviously Kevin would have preferred to have worked on his own car, but it’s a very brave (or very foolish!) man who turns down work, especially in the current economic climate.

The European Rallycross Championship hits Lydden in a month’s time though and, at present, that is the new target for the competitive debut of the car. It’s certainly an ambitious goal, as bringing the car out for its first outing against the best of the National drivers will be quite a test: doing the same against an International field is raising the bar even higher.

Even aiming for the European event, there is still a lot to do in a month: fingers crossed the car will be sorted in time! :thumb:

excellent post and update.

Personally I haven't spoken to kev since before christmas, so i'm really pleased to see the progress and that there is 100% light at the end of the tunnel now. It looks like a well thought out package and fingers crossed it should be very competative. Looking forward to seeing kev and the car back on the grid along side me at some point this year :)

awesome build, shame it wont be ready!

Should be a good year for Scoobies in the British Rallycross Championship this year: your GD, Gary Pusey in his GC8 and Kev in his GR.

Despite the deparature of a few drivers for the GRC, its still looking to be a superb year in the BRC in terms of cars and drivers. Can't wait for Round 1 to kick off!
Hopefully it won't be too long into the year before its ready to race! :thumb:

Cool build... Any updates?

I haven't seen the car since I last posted these pictures. I briefly spoke with Kevin last week and, although some progress has been made, he isn't aiming to have it ready for Round 3 (Mallory Park) which is towards the end of next month.

So, fingers crossed, the car will make its debut at Round 4 of the Championship, which will be at Lydden Hill on 26th/27th August. In a selfish way I'm rather glad, as I'll be at Lydden to see it! :thumb:

Hopefully I'll get to see the car before then though, if it does I'll be sure to post some more pictures up.

Ohhh, I hope you do.. can you maybe get me a picture of the rear diff setup and mounting points on the car?
regards Claus

Great write up mate.

holly fuk !

Superbly documented build. Thanks for sharing :)

+1

I shall try and remember! If I see the car in the workshop again it should still be on the ramp, so I can have a proper nose underneath: otherwise I've got to try and roll under it for a decent photo!

Cheers mate! Get your finger out and you can come and see the car in action! ;)

I hoping thats a good reaction! :lol1:

No worries, cheers for reading! I'm hoping that the next time I get to see the car it'll be moving under its own power. :thumb:

Thanks mate... wish i could come and see it live in action...

Hey, any updates? And is the car ready for Lydden Hill?

The car isn't ready yet. Spoke to Kevin a week or so ago and the plan is still to have it ready in time for Lydden; so a month to get it finished! :thumb:

Just spoke with Kevin. Both time and money have conspired against him, thus the car won't be making its debut at Lydden this weekend... :(


(...glory for the Impreza rests in your hands Simon! ;))