Been yearning for the return of the 911 in international rallying? Well yearn no more. Tuthill Porsche has taken matters into its own hands and homologated a 997 GT3
Words: Martin Sharp Photography: McKlein
Thirty-nine year-old driver's self-developed-and-built 'prototype' GT-based rally car gets its first-blooding in competition on a World Championship rally. Brave, some might posit.
Yet the facts are worth a ponder. The car started 99th out of 127 (actually as Car 132 because of a 31-car gap in the entry list to cater for no-shows and the vagaries of the WRC rules). Despite running on Tarmac made dirty by the front-running four wheel-drive competitors cutting corners and pulling dirt and stones onto the roads, Richard Tuthill's new Porsche 997 R-GT jumped a massive 72 places to finish 27th overall after 326.02 stage kilometres and a total distance of 1305.79km on this year's Rally Germany.
It was the first time a Porsche 911 has finished a WRC event since 1986: 28 years since Saeed Al Hajri came fourth in the Acropolis in his 911SC RS.
'Prototype' is a misnomer; for sure the car is Tuthill Porsche's first example of its R-GT category rally car and as such is very much a development vehicle. It is, however, a fully FIA-approved rally car which has been 'homologated' using the FIA's latest 'Technical Passport' rules for GT cars for rallying.
The Technical Passport regulations appeared first this year and enable a car which is not homologated into rallying by its manufacturer to contest FIA-sanctioned events up to world level. The passport must be sanctioned by the owner's, or preparer's, ASN [national motor sport authority]; which in the case of the UK is the Motorsports Association [MSA]. The passport is applied to each individual car, by VIN, costs just shy of €8,000 and is valid for two years, with extension options.
Tuthill Porsche went to Rally Germany full of positive expectations. The laborious Technical Passport procedure (a 50-page documentation and photography effort akin to a full manufacturer competition homologation process) had been through the required processes.
Experienced MSA technical people had inspected the car's mechanicals, its unique roll cage; everything including the agreement that a 65mm diameter inlet restrictor would mean the car exceeded the minimum 3.4kg/bhp weight-to-power ratio demanded by the R-GT rules.
Initially, no restrictor 'plate', or venturi size confirmation was forthcoming from the FIA.
Then, while the car was on the trailer en route to Rally Germany host city Trier an FIA email announced on the Friday before the event started on the following Thursday, simply; 'Your restrictor is 36mm diameter'.
Tuthill Porsche's highly experienced rally engineer Graham Moore, formerly with Prodrive, faced a situation in which his project car would be lacking some 100bhp, and 1500rpm fewer, than planned -approximately 325bhp instead of the expected 425bhp. And the car was on the road to Trier. He found himself in a Trier machine shop, lathe at the ready, to fashion a 36mm restrictor. Dutifully the 36mm restrictor was installed in the car for the German rally. How it might have fared with a further 100-odd bhp is pure conjecture, but as this event was effectively a development test the results are - to say the least - encouraging.
Tuthill Porsche is a cohesive team; renowned for Historic 911 victories - and a bountiful sense of joi de vivre, much of which rubs off from its now-Principal, Richard, and his dad Francis, who started the company and still keeps his hand in with engines, gearboxes and event support. It seems nothing fazes this team: even the fact that a press presentation of the new car had to take place without the car in situ in the rally service park as Rally Germany's scrutineering schedule became delayed... and that the Technical Passport decal (effectively, approval to run) for the 997 R-GT was applied to its roll cage well into dinner time on the eve of the first day of the event.
At least the team's resourceful PR Anthony Peacock had ensured sufficient supplies of Hook Norton ale to keep the banter flowing...
The R-GT regulations cater for road-legal series production GT cars with two doors, two, or two-plus-two seats, and one or more luggage compartments which are available for sale through a manufacturer dealer network. Four-wheel drive GT cars can be used as the basis but a kit must be available to make them two-wheel drive to comply with the R-GT category.
At least 200 identical examples must have been produced in 12 consecutive months, but cars derived from a production model which are built specifically for a Manufacturer's Cup are allowed, so long as at least 30 of such cars have been produced.
The latter option was chosen by Tuthill Porsche for its first R-GT. Based on a Generation Two 2012 Carrera Cup racer this 997 is the best the team could get. As a Cup car it was, of course, equipped with many desirable competition components for R-GT use. Tuthill engineer Graham Moore has extensive experience of dealing with the FIA on homologation matters and saw the individual homologation of the car via Technical Passport through to its final approval on the eve of Rally Germany:
"Once we got the all-clear for homologating or using a Cup car we used that as our base because you get a lot of really good bits with it - engine, gearbox, brakes; all the sort-of nice stuff you want - carbon doors, all the lightweight stuff; all the air intake system for the engine, so it's a good base for the car. You could do one from a standard road car and come at it from a different direction, but we thought at the time the Cup car gave us the best option for performance and good components. Obviously we weren't expecting such a drastic restrictor size, so we need to review that and it may be that a standard engine with that restrictor might be reliable."
With their competition conrods and pistons, Carrera Cup engines are renowned for their reliability. Available in 3.6-litre and 3.8-litre capacities the general feeling among Cup preparation specialists is the 3.8-litre engine is a good step forwards and, as Moore points out, seems to provide the best characteristics, particularly when restricted by 36mm (911s running to national rally rules, such as those in France, Belgium and Spain generally tend to be fitted with 75mm diameter inlet restrictors).
The team ran Carrera Cup gear ratios and final drive on Rally Germany. Moore: "They actually weren't too bad. Obviously we didn't use sixth gear but the engine did have a reasonable amount of torque. We looked at ratios but we didn't bother to make new ones because we thought if the restrictor's going to change or whatever we'll end up having a load of ratios that don't match the engine power.
"It's good to get some data: we've never had any data on the correct sized tyres, because the Michelin tyres are 650mm diameter so the stuff we've been running for testing wasn't the
Above and below: The 997 GT3 in rally trim has no problem getting airborne, although we should point out that the below pic was taken on the Trackrod Rally in the UK, where Tuthill Porsche were running as course car in a pre German Rally shakedown
right diameter tyres anyway, so now we've got a good base set of data we can go back and look at it and just get the absolute optimum ratios."
Although based closely on the road versions, 997 GT3 Cup cars are, of course, built and designed for circuit racing. They don't have to be road legal. And, of course, an R-GT 'derivative' designed for use in rallies must comply with the road legislation in the areas where it competes. Unlike its racing cousin two people must fit in it, and it has to carry spare tyre[s].
Accommodating just the driver, Cup cars have asymmetric roll cages so the need to fit a co-driver in a Cup-derived R-GT car makes the Cup cage ineligible. Tuthill's Graham Moore has therefore designed a roll cage to the existing world rallying regulations which, together with the inclusion of other safety requirements, complies fully with the admirable side impact provisions laid down by the FIA, as he explains:
"There was a problem with Porsches in the old days when you had the door bars right next to where the driver's sitting; there was going to be intrusion into the driver's pelvic area if you have any [side impact] accident. But with this you've got 200mm between the seat and door bars and you've got all the [mandatory door-filling] foam so it's inherently a lot safer. Effectively it's the same as a World Rally Car in that respect."
R-GT rules mandate the fitment of one spare wheel as described and illustrated in the Technical Passport, two spares are also allowed (on gravel rallies, for example) and Tuthill Porsche modifications to its Historic 911s for the East African Classic Safari Rally enable two spares to nestle by the front-mounted fuel tank. However, with a different fuel tank, this is not possible in a contemporary 911.
Even so, when derived from a -non-spare-equipped - Carrera Cup car some chopping of the surrounding architecture is necessary to engineer a spare wheel and tyre into the front of the R-GT derivative: "You are allowed modifications to fit a spare wheel, and that's it; just for fitting a spare wheel, not for; 'Oh it would be nice if we could move X, Y and Z'. It's in the Technical Passport and the photos are in there to show that it's just for spare wheel fitment and not to get a bit of clearance here, or strengthening or whatever, so that's quite clear."
The Tuthill R-GT has nine-inch-wide front wheels with 11in-wide at the rear. A nine-inch rim with inflated tyre will just fit into Tuthill's homologated spare wheel space. Fitting an 11in-wide rear wheel in the front wheel space would require not only a punctured tyre, but one which had been reduced to significantly lesser volume. Then, that is just about possible. Moore: "We're looking at it - you're allowed to have a removable rear window, so we can just chuck it [a rear] in the back if we have a puncture. Just so you can carry it."
The team has already tested running a nine-inches-wide wheel at the rear: "Yeah it'll run, we tested it," confirms Moore. "For gravel you would probably want to run two spares, just because of tyre wear because we've seen that it [the car] does have an appetite for rear tyres - funnily enough!"
The Cup 997 has MacPherson struts up front and multi-link rear suspension; effectively an upper and lower wishbone, Moore: "It does all sorts of crazy things at full droop; it changes the toe and, so we've had to look at all of that and have messed around with all of that for here [Rally Germany]. So, we have different rear toe-steer characteristics for
race to rally; and front as well, because the racers' requirements are different over the suspension travel they use to what we need."
The team did "quite a bit" of work before Rally Germany to get the suspension to work with the wheel displacement: "It wasn't just a case of bolting on a set of dampers and crossing our fingers, so we have looked at it sensibly: if you're going through a bumpy Tarmac stage it needs not to be rear-wheel steering and all the rest of it, so yeah we've had a look at it."
Moore has long been an advocate of XTC dampers; those fitted to the R-GT he describes as; "Quite trick". Wheel travel for the Tarmac specification rally car is about 180mm all round ("about the limit you can get with the suspension links and stuff"), much more than a racer; and damper travel has been extended accordingly. Triple-rate progressive coil springs surround each damper, with rates selected to cater for end-travel protection when landing from jumps; and provide ride quality on bumpy surfaces. Typically, spring rates are half of what is run on a race car and similar front and rear. With a spare wheel and tyre in the front, and underbody protection at the front the front rates cannot be too soft.
The team submitted a dossier to the FIA on May 1st detailing a gravel suspension option which has already been passed by the homologation committee; although more bureaucracy is to
follow. Tuthill Porsche is renowned for the quality - and successes - of its Historic rallying 911s and already has a gravel damper, developed with XTC, which can be used straight away. But the suspension of the contemporary car complicates matters, as Moore explains: "The issue really is the travel and inherently with a GT car you don't have the travel there anyway. So with the regulations at the moment, which are Group N, you're not really allowed to move anything to get the extra travel."
With their swinging arms and torsion bars the team's gravel rally specification Historic 911s run with about 250mm of suspension displacement.
"You can raise the [R-GT] car up but that doesn't really give you enough packaging room, so we have asked, or seeked permission and suggested what could be done with a best-cost solution; because it's all about keeping the costs down: you don't want to be modifying the bodyshell and lifting spring mounts and all that stuff.
"You could probably get 20omm/22omm of travel, which obviously isn't to the scale of modern rally cars but would be safe enough. I'd be happy with 210mm/220mm of travel. We've got a solution; absolutely no sheet metal work involved; just modifications to the components around the damper we are seeking permission from the FIA to create."
Kevlar guards are fitted for underfloor protection, connected via metal mounting points to the existing plastic floor, with which the team identifies potential durability issues; hence an investigation into this is in progress: "Guards are free; you are obviously allowed to protect the underside of the car, so we'll be looking at what else we can do to improve the fixings, because the difficulty of the fixings on the standard stuffis that there are a lot of screws; which in a service park in 30 minutes you don't want to be taking 20 torque screws out of the bottom of it, so we're looking at things like that," explains the Tuthill Porsche engineer. All work in progress, but what progress.
Words: Martin Sharp Photography: McKlein
Thirty-nine year-old driver's self-developed-and-built 'prototype' GT-based rally car gets its first-blooding in competition on a World Championship rally. Brave, some might posit.
Yet the facts are worth a ponder. The car started 99th out of 127 (actually as Car 132 because of a 31-car gap in the entry list to cater for no-shows and the vagaries of the WRC rules). Despite running on Tarmac made dirty by the front-running four wheel-drive competitors cutting corners and pulling dirt and stones onto the roads, Richard Tuthill's new Porsche 997 R-GT jumped a massive 72 places to finish 27th overall after 326.02 stage kilometres and a total distance of 1305.79km on this year's Rally Germany.
It was the first time a Porsche 911 has finished a WRC event since 1986: 28 years since Saeed Al Hajri came fourth in the Acropolis in his 911SC RS.
'Prototype' is a misnomer; for sure the car is Tuthill Porsche's first example of its R-GT category rally car and as such is very much a development vehicle. It is, however, a fully FIA-approved rally car which has been 'homologated' using the FIA's latest 'Technical Passport' rules for GT cars for rallying.
The Technical Passport regulations appeared first this year and enable a car which is not homologated into rallying by its manufacturer to contest FIA-sanctioned events up to world level. The passport must be sanctioned by the owner's, or preparer's, ASN [national motor sport authority]; which in the case of the UK is the Motorsports Association [MSA]. The passport is applied to each individual car, by VIN, costs just shy of €8,000 and is valid for two years, with extension options.
Tuthill Porsche went to Rally Germany full of positive expectations. The laborious Technical Passport procedure (a 50-page documentation and photography effort akin to a full manufacturer competition homologation process) had been through the required processes.
Experienced MSA technical people had inspected the car's mechanicals, its unique roll cage; everything including the agreement that a 65mm diameter inlet restrictor would mean the car exceeded the minimum 3.4kg/bhp weight-to-power ratio demanded by the R-GT rules.
Initially, no restrictor 'plate', or venturi size confirmation was forthcoming from the FIA.
Then, while the car was on the trailer en route to Rally Germany host city Trier an FIA email announced on the Friday before the event started on the following Thursday, simply; 'Your restrictor is 36mm diameter'.
Tuthill Porsche's highly experienced rally engineer Graham Moore, formerly with Prodrive, faced a situation in which his project car would be lacking some 100bhp, and 1500rpm fewer, than planned -approximately 325bhp instead of the expected 425bhp. And the car was on the road to Trier. He found himself in a Trier machine shop, lathe at the ready, to fashion a 36mm restrictor. Dutifully the 36mm restrictor was installed in the car for the German rally. How it might have fared with a further 100-odd bhp is pure conjecture, but as this event was effectively a development test the results are - to say the least - encouraging.
Tuthill Porsche is a cohesive team; renowned for Historic 911 victories - and a bountiful sense of joi de vivre, much of which rubs off from its now-Principal, Richard, and his dad Francis, who started the company and still keeps his hand in with engines, gearboxes and event support. It seems nothing fazes this team: even the fact that a press presentation of the new car had to take place without the car in situ in the rally service park as Rally Germany's scrutineering schedule became delayed... and that the Technical Passport decal (effectively, approval to run) for the 997 R-GT was applied to its roll cage well into dinner time on the eve of the first day of the event.
At least the team's resourceful PR Anthony Peacock had ensured sufficient supplies of Hook Norton ale to keep the banter flowing...
The R-GT regulations cater for road-legal series production GT cars with two doors, two, or two-plus-two seats, and one or more luggage compartments which are available for sale through a manufacturer dealer network. Four-wheel drive GT cars can be used as the basis but a kit must be available to make them two-wheel drive to comply with the R-GT category.
At least 200 identical examples must have been produced in 12 consecutive months, but cars derived from a production model which are built specifically for a Manufacturer's Cup are allowed, so long as at least 30 of such cars have been produced.
The latter option was chosen by Tuthill Porsche for its first R-GT. Based on a Generation Two 2012 Carrera Cup racer this 997 is the best the team could get. As a Cup car it was, of course, equipped with many desirable competition components for R-GT use. Tuthill engineer Graham Moore has extensive experience of dealing with the FIA on homologation matters and saw the individual homologation of the car via Technical Passport through to its final approval on the eve of Rally Germany:
"Once we got the all-clear for homologating or using a Cup car we used that as our base because you get a lot of really good bits with it - engine, gearbox, brakes; all the sort-of nice stuff you want - carbon doors, all the lightweight stuff; all the air intake system for the engine, so it's a good base for the car. You could do one from a standard road car and come at it from a different direction, but we thought at the time the Cup car gave us the best option for performance and good components. Obviously we weren't expecting such a drastic restrictor size, so we need to review that and it may be that a standard engine with that restrictor might be reliable."
With their competition conrods and pistons, Carrera Cup engines are renowned for their reliability. Available in 3.6-litre and 3.8-litre capacities the general feeling among Cup preparation specialists is the 3.8-litre engine is a good step forwards and, as Moore points out, seems to provide the best characteristics, particularly when restricted by 36mm (911s running to national rally rules, such as those in France, Belgium and Spain generally tend to be fitted with 75mm diameter inlet restrictors).
The team ran Carrera Cup gear ratios and final drive on Rally Germany. Moore: "They actually weren't too bad. Obviously we didn't use sixth gear but the engine did have a reasonable amount of torque. We looked at ratios but we didn't bother to make new ones because we thought if the restrictor's going to change or whatever we'll end up having a load of ratios that don't match the engine power.
"It's good to get some data: we've never had any data on the correct sized tyres, because the Michelin tyres are 650mm diameter so the stuff we've been running for testing wasn't the
right diameter tyres anyway, so now we've got a good base set of data we can go back and look at it and just get the absolute optimum ratios."
Although based closely on the road versions, 997 GT3 Cup cars are, of course, built and designed for circuit racing. They don't have to be road legal. And, of course, an R-GT 'derivative' designed for use in rallies must comply with the road legislation in the areas where it competes. Unlike its racing cousin two people must fit in it, and it has to carry spare tyre[s].
Accommodating just the driver, Cup cars have asymmetric roll cages so the need to fit a co-driver in a Cup-derived R-GT car makes the Cup cage ineligible. Tuthill's Graham Moore has therefore designed a roll cage to the existing world rallying regulations which, together with the inclusion of other safety requirements, complies fully with the admirable side impact provisions laid down by the FIA, as he explains:
"There was a problem with Porsches in the old days when you had the door bars right next to where the driver's sitting; there was going to be intrusion into the driver's pelvic area if you have any [side impact] accident. But with this you've got 200mm between the seat and door bars and you've got all the [mandatory door-filling] foam so it's inherently a lot safer. Effectively it's the same as a World Rally Car in that respect."
R-GT rules mandate the fitment of one spare wheel as described and illustrated in the Technical Passport, two spares are also allowed (on gravel rallies, for example) and Tuthill Porsche modifications to its Historic 911s for the East African Classic Safari Rally enable two spares to nestle by the front-mounted fuel tank. However, with a different fuel tank, this is not possible in a contemporary 911.
Even so, when derived from a -non-spare-equipped - Carrera Cup car some chopping of the surrounding architecture is necessary to engineer a spare wheel and tyre into the front of the R-GT derivative: "You are allowed modifications to fit a spare wheel, and that's it; just for fitting a spare wheel, not for; 'Oh it would be nice if we could move X, Y and Z'. It's in the Technical Passport and the photos are in there to show that it's just for spare wheel fitment and not to get a bit of clearance here, or strengthening or whatever, so that's quite clear."
The Tuthill R-GT has nine-inch-wide front wheels with 11in-wide at the rear. A nine-inch rim with inflated tyre will just fit into Tuthill's homologated spare wheel space. Fitting an 11in-wide rear wheel in the front wheel space would require not only a punctured tyre, but one which had been reduced to significantly lesser volume. Then, that is just about possible. Moore: "We're looking at it - you're allowed to have a removable rear window, so we can just chuck it [a rear] in the back if we have a puncture. Just so you can carry it."
The team has already tested running a nine-inches-wide wheel at the rear: "Yeah it'll run, we tested it," confirms Moore. "For gravel you would probably want to run two spares, just because of tyre wear because we've seen that it [the car] does have an appetite for rear tyres - funnily enough!"
The Cup 997 has MacPherson struts up front and multi-link rear suspension; effectively an upper and lower wishbone, Moore: "It does all sorts of crazy things at full droop; it changes the toe and, so we've had to look at all of that and have messed around with all of that for here [Rally Germany]. So, we have different rear toe-steer characteristics for
race to rally; and front as well, because the racers' requirements are different over the suspension travel they use to what we need."
The team did "quite a bit" of work before Rally Germany to get the suspension to work with the wheel displacement: "It wasn't just a case of bolting on a set of dampers and crossing our fingers, so we have looked at it sensibly: if you're going through a bumpy Tarmac stage it needs not to be rear-wheel steering and all the rest of it, so yeah we've had a look at it."
Moore has long been an advocate of XTC dampers; those fitted to the R-GT he describes as; "Quite trick". Wheel travel for the Tarmac specification rally car is about 180mm all round ("about the limit you can get with the suspension links and stuff"), much more than a racer; and damper travel has been extended accordingly. Triple-rate progressive coil springs surround each damper, with rates selected to cater for end-travel protection when landing from jumps; and provide ride quality on bumpy surfaces. Typically, spring rates are half of what is run on a race car and similar front and rear. With a spare wheel and tyre in the front, and underbody protection at the front the front rates cannot be too soft.
The team submitted a dossier to the FIA on May 1st detailing a gravel suspension option which has already been passed by the homologation committee; although more bureaucracy is to
follow. Tuthill Porsche is renowned for the quality - and successes - of its Historic rallying 911s and already has a gravel damper, developed with XTC, which can be used straight away. But the suspension of the contemporary car complicates matters, as Moore explains: "The issue really is the travel and inherently with a GT car you don't have the travel there anyway. So with the regulations at the moment, which are Group N, you're not really allowed to move anything to get the extra travel."
With their swinging arms and torsion bars the team's gravel rally specification Historic 911s run with about 250mm of suspension displacement.
"You can raise the [R-GT] car up but that doesn't really give you enough packaging room, so we have asked, or seeked permission and suggested what could be done with a best-cost solution; because it's all about keeping the costs down: you don't want to be modifying the bodyshell and lifting spring mounts and all that stuff.
"You could probably get 20omm/22omm of travel, which obviously isn't to the scale of modern rally cars but would be safe enough. I'd be happy with 210mm/220mm of travel. We've got a solution; absolutely no sheet metal work involved; just modifications to the components around the damper we are seeking permission from the FIA to create."
Kevlar guards are fitted for underfloor protection, connected via metal mounting points to the existing plastic floor, with which the team identifies potential durability issues; hence an investigation into this is in progress: "Guards are free; you are obviously allowed to protect the underside of the car, so we'll be looking at what else we can do to improve the fixings, because the difficulty of the fixings on the standard stuffis that there are a lot of screws; which in a service park in 30 minutes you don't want to be taking 20 torque screws out of the bottom of it, so we're looking at things like that," explains the Tuthill Porsche engineer. All work in progress, but what progress.
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