GMI Concept of the Month: Holden Torana TT36
By Australian GMI Member BBDOS CV8
6 May 2007
What it isn't
Firstly, to hose down some unrealistic expectations: the Torana TT36 showcar is not anywhere near production ready, and many of the decisions about what would be in it, under it and would constitute its’ design are still to be made, if indeed it is to progress past concept. The show car was cobbled together from a variety of suspension and chassis components. This article is purely speculation on my part and I don’t know how similar it would be to any ultimate production version, but I think it is possible to extrapolate where Alpha could go. I don’t believe anyone at Holden or GM is any more certain at present, either.
Why did Holden do it?
The TT36 Torana served a purpose beyond show concept: Growing in confidence with increased recognition within international car circles and most importantly within GM, the Torana is designed to showcase Holden’s ability to engineer not only rear-drive cars but modern contemporary designs with advanced features. It also had a cheekier, hidden intent.
Confident they had the shape of the first 100% Holden designed Commodore right, but apprehensive about a styling debacle like Ford suffered with the ‘98 AU Falcon, they used Torana to float the VE shape in front of the public. Almost nobody twigged they were seeing the new car in a scale model, and the car like the Monaro developed not only national interest, but sent the internet alive internationally with conjecture about European, Asian and North American derivatives of a sporty sedan, hatch, coupe. Since release this testing has proven to be accurate – the VE is a style winner in the intended market and has made everything else look dated. GM then had to respond at a global level to the unanticipated accolades – sort of like Holden with the VT Coupe concept car back in ’97 which developed a life of its’ own as Monaro. With highly-placed supporters like Bob Lutz Holden would appear to be placed to advance the design of a midsize-compact vehicle.
What do we make of what has been said?
So – if it is a blank canvas, what will fill it?
Firstly, it is important to define what it will not, and must not be. Much has been made about the VE Commodore’s size and weight. That is a fullsize car designed not only to carry five fullsize adults and their luggage, but also engineered for over 500hp and to be the basis of light-commercial vehicles capable of carrying half their own weight and towing all of it. So there is a fair amount of overbuild in VE , plus the components can be used in the stretched WM without modification. It is designed to be operated in any and all climates from Alpine to desert and over extreme ‘roads’ which are car-killers. It has the potential for long-travel suspension in a SUV role and almost certainly AWD.
That means a cut-down Zeta would not cut it in a Vectra or Aura sized car. If small enough to fit under a mid-size sedan or able to be shortened for a 2+2 coupe, would still be likely too heavy a structure with outsize components , even if re-dimensioned. In the midsize class, packaging is everything. A midsize RWD is going to be relatively expensive compared to the FWD drones made as bread and butter transport, and a premium product, and can’t afford to be compromised in function by trying to make it a jack-of-all-trades. It certainly could be engineered AWD although it is questionable it needs to be, as the major competition in this category is not. With a 50/50 weight distribution and with modern traction, stability and antilock brakes it is likely to be manageable in most conditions up to extreme, and not likely to be chosen for those conditions even if AWD. AWD costs in weight, cost to build and operating efficiency and is not necessarily a plus for normal road operations for dynamic reasons. If best good-road performance is desirable, the market tends to vote for RWD overwhelmingly. Audis have it because they're really a FWD architechture. Volvos too.
A Sigma or Kappa-like structure with double wishbone fronts is not likely, either. Cost and space considerations in the engine bay and underguards would seem to preclude it. A coil-over spring coupled with a 4-link strut should provide the necessary travel with desirable geometry yet with size and weight advantages over Zetas’ articulated McPherson. If the front guards are to be of a weight-saving material plastic or alloy they could not be expected to be load-bearing so it would have to eschew the McPherson top mount for an extended top shock mount off the crossmember. This would trade travel, but also reduce the hardpoints, providing versatility in styling capabilities, if the guard only has to support its’ own weight and not the front corner of the car. Similarly the rear would be a 4-link design somewhat similar to Zeta and Sigma with a caged mount and bushings to isolate it from the body.
Powertrains
With the dual demand to cut emissions and improve economy, plus the need to provide a balanced vehicle for ride, handling and roadholding/dynamics, you will not see a V8 or over 4-litre motor in this car. While many people believe ‘nothing exceeds like excess’ every 50lbs you add in powerplant adds probably double that in component size. Brakes have to be bigger, transmission has to have higher torque rating, suspension firmer with bigger dampers, extra nose weight makes it harder to balance the car, larger cooling capacity, bigger starter, alternator and battery, it needs bigger wheels/tyres to put the power down, the increase in unsprung weight degrades compliance etc etc etc. The larger motor needs a larger engine bay, which cuts into your greenhouse space, and moves the CofG higher and further forward. More easily hidden in a larger vehicle, you end up with a lead-tipped arrow fast in a medium car which is meant to be poised and balanced.
Torana - lessons from the past
The second generation Torana in Australia fell into this trap: designed to accept the 253 and 308 V8s used in the fullsize Holdens, you ended up with a car which cost nearly as much to buy and run as a fullsize Holden but had much less utility, and couldn’t be sold for near as much, but cost very nearly as much to build so tended to be poorly equipped and so was worth less on resale and was a bit cheap. As a four it was overweight and underpowered, as a V8 it was borderline psychotic.
Instead Alpha should be engineered for 4 to 6 cylinder powerplants in a range from 1.8 up to around 3.5 litres. The old Torana formula was a big motor in a small body: It is more relevant today than ever. A 300hp V6 would provide stellar performance in a mid-size body with a kerb weight of 3300-3400 lbs. Plus, the small frontal area, low weight of the HFV6 and it’s compact design would increase ‘flickability’ compared to larger vehicles.
Within that range is the potential for diesel, petrol and even hybrid drives if that is still in vogue around the end of this decade - diesel is by far more important to have for Europe and potentially elsewhere.
With its’ DI variable-timing Ecotec alloy fours and the High Feature V6 range, GM has a compact range of motors which naturally-aspirated would provide spirited performance and, with a light enough car, a 25+ US mpg overall performance from fours and not much less from a six. With six-speed transmissions the performance and fuel economy with either four or sixes should easily be over 30 US mpg freeway.
How big will it be.
The front of the car if similarly dimensioned to the TT36 Torana would feature a similar dash height to the current Vectra, with similar accommodation inside but some inches shorter from a slightly longer wheelbase, due to the engine being positioned within the axles.
With these considerations and all things being equal Alpha should end up as very class-competitive. A kerb weight of 3200-3400lbs in a compact coupe-sedan, with around 110” wheelbase and 170-180” long.
Details, details
What would be good is for Holden and GM to stretch the boundaries on this one. In the VE there is a competent, conservative sedan which is up to the minute but breaks no moulds in materials. With Alpha there is room to go for broke with some cutting-edge features: alloy in the subframes, body panels and other weightsaving measures, plastic panels and perhaps even composite panels in upper-spec models. If the Alpha is to go head to head with the Euros and topline Japanese it can’t just be a slightly conservative, competent car but has to have market-equaling features. I can imagine a slightly shorter 3200lb coupe, about MX5 size, with a tuned 3.6 litre turbo V6, which would genuinely challenge the M3. Imagine some lighweight components with a big brake/wheel package. If Holden can get the VE handling-competitive with class-leading smaller cars, there is no reason it can’t do it with Alpha.
Alpha should continue to have good ergonomics and passenger friendliness and have short overhangs for the wheel-in-each-corner stance, and short engine bay for a maximized passenger and load capability (another reason to restrain engine size – the Ecotec and HFV6 are shorter engines lengthwise and heightwise than even the Gen IV V8). Fuel cell would be under the rear passenger seat and load section very versatile. Holden has the design of the SS-X, which is a hatch like the Mazda 6 with a coupe-sedan look. If side-impact safety can be retained with careful design (other makers have done this) this car could be built in both formats for different markets with the same side-panels.
Holden also has alloy-suspension experience with the all-paw Coupe4. .There is the potential for forged alloy suspension members for upspec versions to reduce unsprung weight and improve compliance. Perhaps even the front crossmember.and rear suspension cage.
For a smaller Cadillac or Pontiac, perhaps features like HUD and power adjustable controls, or as China has done each market could design/develop their own interior and exterior trim and equipment. Holden already has experience with premium sound system tuning on its’ larger cars – with a rigid tuned structure with ultrasonic fundamental like the VE, Alpha could bring good levels of quietness to the medium-compact class.