GR Impreza Rallycross Build

[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.

[tbtstt]

Sorry folks, couldn't fit it all in the first post, so here's the rest...

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.







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:



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:









Not quite ready for these yet:



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!

[tbtstt]

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:



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.

[tbtstt]

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!

[AndyWRX]

Looks good mate good read

[STI 05]

Subscribed lets hope Kevin can have it ready for Lydden, be good to see how it compares against Steve Hill's Evo

PS thanks for sharing

[BIG"E"]

out of

What a good write up.

[tbtstt]

Originally Posted by Markie

Subscribed lets hope Kevin can have it ready for Lydden, be good to see how it compares against Steve Hill's Evo

PS thanks for sharing

You're welcome! Yeah, I hope so! There was an outside hope that the car would be finished before the end of 2011, but to complete the build just wasn't feasible in the time available. Just under three months until the 2012 season kicks off though so, all being well, the car should be ready for its competitive debut at Lydden. Based on what Kevin said last time I spoke to him, I'm hoping to get a call to come down there and see something close to a finished car early in the new year... fingers crossed!

Be great to see a GR Impreza and Evo X running head-to-head in the British Championship. Was hoping to see Hill start to squeeze more reliability out of the Evo X in the 2011 season, but the car still seems to be giving him a lot of grief. Hopefully 2012 will see some better results for him as well!

Originally Posted by BIG"E"

out of

What a good write up.

Cheers mate! Will endeavour to keep the thread going as I get more info!

[ajf]

Any ideas what's happening to the old shell


Adrian

[tbtstt]

Originally Posted by ajf

Any ideas what's happening to the old shell


Adrian

It was still up for sale last time I asked! Couple of folks on Scoobynet expressed an interest in some of the panels, but I believe he wants to sell it complete.

Can ask him what the situation is with it if you are interested?

[ajf]

Maybe interest all comes down to cost

Cheers

[tbtstt]

Originally Posted by ajf

Maybe interest all comes down to cost

Cheers

Will drop him a message and let you know.

[The Gimp]

Originally Posted by ajf

Maybe interest all comes down to cost

Cheers

Gayer!!!


lol


Steve

[tbtstt]

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:









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



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:



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



Underside view of the right side wishbone and chassis mount:



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.





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!

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:



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…



…then along the right side of transmission tunnel…



…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…





…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.



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:



Immediately in front of that is the fuel cell:



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





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







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:

[tbtstt]

And a bit more...

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



As well as the all-important roof vent:





Battery located just behind where the passenger seat would be:



Jacking points in place:



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:



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!

[STI 05]

Thanks for the update, will look forward to its debut in April

[Steve_PPP]

Great update mate, looks like it'll be a beast

[tbtstt]

Originally Posted by Markie

Thanks for the update, will look forward to its debut in April

Fingers crossed! As I say there is still a hell of a lot to do, so hopefully a month will be enough time to fit it all in.

Originally Posted by Steve_PPP

Great update mate, looks like it'll be a beast

Should be mate! There has been a huge amount of thought gone into it so it should be a very rapid car when its finished...

...it needs to be to be competitive in the British Championship though, especially as the calibre of cars continues to rise!

[tbtstt]

An update (of sorts) to the story so far. Kevin sold his old two door shell to Gary Pusey, who has subsequently transplanted the contents of his four door rallycross Scoob into it.



Great to see this shell staying in rallycross. I know Gary is down to run the BTRDA Championship in it and I'm hoping he'll show up to a British Championship round (or two) as well.

As for Kevin’s GR Impreza, it’s pretty much there, but Kev is now debating whether to use it for rallycross or hillclimbing. I seem to be struggling to clear a weekend to pop down and see him and the car, but I’m hoping to run into him at Blyton this weekend. Assuming I do I will get the full story then!

[tbtstt]

Another minor update. The GR made its public debut on the BTRDA rallycross stand at this years Rallyday. Although its cosmetically complete its not quite finished mechanically, so still not ready for competition.

The final round of the British Rallycross Championship is in mid-October which doesn't leave much time to finish the car, however the final round of the BTRDA Rallycross Championship is in mid-November which seems a feasible target.

Unfortunately I was unable to attend Rallyday so I haven't got any more photos to add to the thread. I hope to be at the final BTRDA round though, so I will be sure to get some pictures if its there!