This week we examine the tech of the cars that competed in the inaugural Australian running of Formula SAE. Many of the teams took a similar approach in engine and chassis design, but the suspension and bodywork made each car strikingly different to look at.
We'll then see how the judges rated the cars in the static events before the cars headed to the track. Their performance where it counts will be detailed in next week's full race report.
The Cars
The rules allow for a four-stroke engine with a swept volume of up to 600cc. The engines may be turbocharged without a capacity penalty. As they found their feet in this first year of the competition, none of the Australian teams opted for the added complexity that forced induction would add. The teams invariably used engines from 600cc motorbikes, these units providing extremely high power-to-weight ratios while being compact and generally easy to fit to the small, custom-built chassis. The Honda CBR-600 powerplant was the choice of several teams although for sponsorship reasons, the UNSW ran the engine from the more exotic Yamaha R6.
As in many other categories of motorsport, Formula SAE requires that an inlet restrictor be used. In most other categories, the restrictor may be placed before the throttle body (ie somewhere near the air cleaner box) which makes it relatively easy to fit. Formula SAE is different in that the restrictor must be placed between the throttle body and the engine itself. This means that a custom inlet manifold needs to be fabricated to include the restrictor. Most teams took this opportunity to discard the multi-carburettor induction which comes standard on the bike engines and designed the manifolds to include bosses for port fuel injectors.
On the exhaust side, most teams stuck with the standard bike extractors, fabricating only the muffler and tailpipe assemblies themselves. The Swinburne car, however, sported an eye-catching "spaghetti" style extractor system which used much longer primary runners than a standard bike exhaust. This helped to move the peak torque lower in the rev range to make the high-revving bike engine more suited to its new home in a car.
As would be expected, the majority of the Australian teams ran locally made, name-brand management systems. Of the six teams, three fitted MoTeC, one Autronic, one Wolf and one team a management system designed and built by the students themselves. Of the American teams, North Carolina ran the Australian Haltech. The standard of wiring varied greatly between the teams. Some cars had very professional looking installations while others, well, they looked like the thing could catch fire at any time!
Fuel rail design was fairly standard across the board although each team had their own ideas about tank, pump and injector placement. Since the engines were four-cylinder, sequential injection was easy to set up although the benefits were probably not great considering how high the engines rev. Injectors were typically from four-cylinder passenger cars that have a peak power output (and so a fuel flow rate) similar to the restricted bike engines.
To capitalise on the advantages offered by fully programmable management, many teams also ditched the bike engine's standard CDI ignition in favour of a system which was fully mappable. Owing to the high-revving nature of the engines, CDI ignitions were still the way to go since the coils on most inductive ignitions will run out of dwell time at about 9,000 rpm. All the ignition systems, regardless of whether they were CDI or inductive, were controlled by the ECU as direct-fire (distributorless) systems. The CDI unit or ignitors fed primary voltage to a pair of coils, each providing for two of the four cylinders in a "wasted spark" setup.
All cars retained the standard bike gearboxes (obvious really, since they're part of the engine!) which also gave the added luxury of sequential shifting. Because of this, the shift linkage could be kept relatively simple. The most robust solution was a push-pull cable or solid linkage, although the Monash car ran a pneumatic shifter with "tiptronic" style buttons. The air cylinder needed to be recharged periodically since the car didn't run a compressor. The popular solution for transferring the engine power to the back of the car was to use a chain drive. In most cases, the bike's standard front sprocket was used with the size of the rear sprocket set to optimise gearing.
Each team took a different approach to constructing and supporting the diff housing. The rear sprocket was typically bolted directly to the diff carrier centre. Torsen centres were the favourite, owing to their ability to behave like a locker for those clutch-dumps off the starting line while retaining the smooth differential action required for the many tight corners that were experienced on the autocross track. Everyone's choice of independent rear suspension meant that driveshafts from front-wheel drive passenger cars were a convenient solution for transferring power from the diff to the rear wheels.
A standout feature was the method of clutch operation on the North Carolina car. A bike-style hand-operated lever was incorporated with the shifter. The left foot was then free to operate the brake pedal, eliminatimg the need to heel-and-toe into corners.
The chassis were mostly spaceframes made from hollow tube or rectangular hollow section. In this first year of competition, the local teams tended to use materials that were easy to work with - such as mild steel. In future we'd expect to see an increase in the use of chrome-moly and aluminium tubes, if not full fibreglass or carbon-fibre monocoques. For bodywork, most teams went for a simple fibreglass shell. Deakin constructed a large, one-piece "bathtub" that sat over the entire front and centre sections of the car.
The standout team in this department was Melbourne Uni whose car has a superbly hand-beaten aluminium shell with some sections polished and others finished in an iridescent green.
The American cars were typically smaller than their Australian counterparts, reflecting the years of refinement that their cars have undergone. Their size and weight has been gradually reduced as new technology is implemented and the performance requirements of the car are better understood after competition experience.
Suspension designs varied greatly between the teams. Some teams opted for heavy but strong systems which would have looked more at home under a sedan. The Deakin car is a case in point here with twin coil-overs on each rear wheel, reminiscent of a rear end from an Seventies Jaguar.
At the other end of the spectrum, some teams went for full Formula 1 style suspension. These cars typically ran double wishbones at each end, with coil-over shocks mounted under the bodywork and operated by push- or pull-rods via bellcranks. Monash and UNSW did well here. This style was prevalent on the American cars, indicating that it is the way of the future for the local teams. The small size of the cars necessitated custom steering racks. One of the most elegant of the locals was the UNSW team's titanium rack, made by team sponsor, Bishop Steering.
Wheel diameter ranged from ten to thirteen inches, with a width of about six inches. Most teams ran custom wheels to optimise their steering and suspension geometry. All the teams came with sticky, slick racing tyres. Front brakes were typically from a small road car or a motorbike. The rules allow for a single disc at the rear, so long as the diff is slip-resistant and both rear wheels are capable of being locked. UTA had their front bike-style discs laser-cut to both reduce their weight and improve the airflow around the disc. Regardless of how effective this was, it certainly made for a good conversation piece!
The Competition Begins: Static Events
With the exception of the "sales" presentations (which were held months previously), the static events and scrutineering were held on the Friday before the race weekend. The teams that got through scrutineering first-go then had Friday afternoon on the practice track to do some last (or in some cases first!) minute shaking down before the serious stuff began on Saturday morning.
Swinburne were the early favourites. Their car appeared on the cover of September's Australian "Auto Engineer" and had the other teams worried from the outset at how complete it looked at that early stage. Most of the cars were nowhere near finished at the time of the presentation event - these teams had to rely on a smooth sales pitch rather than glossy photos of their product. At that stage at least one team's car didn't even have an engine or suspension installed! At the completion of the presentations, Melbourne Uni had drawn first blood, with Swinburne a close second. Most who saw the cars lined up on the first morning of the competition would surely agree that Melbourne's bodywork alone would sell the car.
Melbourne took out the second static event, proving that the best looking cars were not necessarily the most expensive. Swinburne was second again with the other four teams trailing. Actual price figures were not made public although it is expected that the winning entries had an all-up vehicle cost of around A$30,000.
This was the event where the academic pride of each university was really on the line. Each team tried hard to convince the judges that they'd done a good job of using what they'd learnt at uni to put the car together. They were also kept busy trying to explain the reasons behind the shortcomings of their work!
This time Swinburne beat Melbourne to first place. Once the bodies were removed, the Swinburne car showed the signs of being a well-integrated package. A lot of work had been put into their powertrain which exhibited the tuned-length extractors and excellent injector positioning. The front suspension was neat and compact although the rear sported a curious single coil-over unit serving both wheels.
UNSW made something of a comeback with third place. A standout feature of their car was that its engine was used as a stressed member to support the rear box section in which the both the diff was housed and the rear suspension supported. Monash, with their pneumatic shifter, scored fourth. RMIT's solid but unremarkable car scored fifth with Deakin beginning to show some signs that they weren't as well prepared as the others.
So at the end of the static events, Swinburne and Melbourne were well placed on 301 and 280 points respectively. The Uni of NSW had made up a lot of ground in the design judging and were now holding down third place with 233 points from the possible 325. The runner-up teams were looking forward to the on-track events where they were pretty sure that their babies would be able to hold their own!
Next week, things hot up as the cars head to the track. Our correspondent was there and he reports what things were like in his role of Engine Management Engineer and Driver for the Uni of NSW team.
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