Race Engine Technology - August 07

CONTENTS : AUGUST 2007

Features

Insight: FORMULA ONE 2007
Mid season state of the art in powertrain tech
Click here to read full article

Report: LE MANS
How the 24 hour race engines fared

Motorcycle: DESMODROMIC
Ducati’s unique valve return system

Supply Chain: VANCE & HINES
How the Harley-Davidson specialist works with its suppliers

Profile: AUDI V12 TURBO-DIESEL
Inside the pioneering double Le Mans winner

Focus: CON RODS
How the suppliers view current and future tech

Letter From: ENGINE EXPO
New and refreshed technology on show

Departments

Grid
The Race Engine Technology world

Expo
News from suppliers to race engine builders

IRED: LE MANS
The 24 Hour race engine builders

PS
F1 horsepower






















Ian Bamsey assesses the state of the grand Prix art in a season characterised by the introduction of not only a spec tyre but also a 19.000 rpm rev limit and a frozen engine specification.

SANTANDER BRITISH GRAND PRIX, SILVERSTONE, ENGLAND, JULY 6-8 2007:

This was round nine of the 17-race FIA World Championship, thus it was precisely the mid point of the season, one that found the title chase led by a rookie. In his first Formula One season Englishman Lewis Hamilton even started this race from pole. However, the McLaren-Mercedes home hero needed considerable racecraft to hold at bay Kimi Raikkonen’s menacing Ferrari through to the first of what transpired to be two rounds of pit stops for the leaders. Raikkonen had kicked up dirt at the final turn on his final lap of qualifying; it was almost certainly that error which had relegated him to second on the grid.

Having robustly countered Raikkonen’s advances prior to pitting, Hamilton slumped to third through the first round of stops. In contrast his teammate Fernando Alonso leapt from third to emerge the new leader. But Raikkonen had put more fuel on board. Initially the reigning champion’s McLaren-Mercedes edged away from the Ferrari but towards the middle of the stint lap times evened up, the Italian-made car matching the pace of the British-made car in spite of its heavier load.

Overall, this weekend it didn’t look as though either front running car had a clear advantage in terms of ultimate speed. However, it was evident that the Ferrari was making better use of its race tyres than the McLaren. Both Alonso and Raikkonen ran the middle stint on the softer ‘Option’ Bridgestone and it was later onset of tyre degradation that allowed the heavier Ferrari to keep the leading McLaren in check over the latter part of it. Its fuel load allowed Raikkonen to get the job done at the second round of pit stops.

With hindsight Hamilton suffered by running the harder ‘Prime’ tyre through his first two stints (by regulation each driver has to use both Option and Prime during the race). Silverstone is an abrasive circuit consequently the Prime offering was the very hardest tyre Bridgestone makes this year while the softer Option alternative was closer than usual to it in performance. On Saturday the Prime had looked to be perhaps a better bet for the race but that proved not to be the case.

Hamilton and his crew compounded this error of judgement with a wrong set up adjustment at his first stop. On top of this Hamilton made a false start from that stop – his first driving error ever in a Formula One race. That cost him less than a second but not only did he drop to third, he found himself off the pace he needed to better that position. In response McLaren ordered him to turn his engine down, to preserve it for the next race.

McLaren ordered Alonso to turn his engine down, too, albeit after the second stops when it was obvious that Raikkonen had the race sewn up. “Strategic racing,” McLaren boss Ron Dennis calls this situation in which engines have to run two consecutive events and duty cycles have become a key performance factor.

The two-race rule, the 19,000 rpm rev limit and the freeze on development from the internal specification homologated at the start of the season have contrived to cap Formula One horsepower. Each year at Silverstone we carry out a mid-season poll of top end outputs, collating expert opinions from engine and chassis technical directors across the teams. We draw up a chart indicating the peak power of each engine as hypothetically tested on the same dyno under the identical conditions. Time has shown an averaging of the opinions of those in the know to be as good a method as any to produce such a chart.

In 2006 the cut from 3.0 to 2.4 litres together with the mandating of a 90 degree V8 configuration with a maximum bore size of 98 mm and the two-race requirement initially pushed all the engines close together on top end power. Our investigation at Silverstone in 2006 left us unable to draw up a chart: the conclusion was that everybody was at 755 bhp plus or minus 10 bhp. As the season progressed some engines edged over 765 bhp but in doing so their peak power speed crept well over 19,000 rpm.

A generous amount of scope was provided to modify the engine for 2007 but not a generous amount of time. The base engine had to be retained and the 19,000 rpm cap cut the output of the strongest engines. Some experts do not accept that it is possible currently to attain 765 bhp given the new limitation. But the majority expert view is that again the ballpark is 745-765 bhp. Again there is insufficient spread to draw a meaningful chart.

At the same time the consensus is that engine characteristics have not significantly changed. In spite of the 19,000 rpm cap the substance of the 2007 power curve is little different to that of its predecessor and driveability is fundamentally unaltered. Scope for ongoing development outside of the seals that define the frozen engine configuration saw Ferrari introduce new intake and exhaust geometry at Magny Cours, the race before Silverstone. But the general feeling is that these days there isn’t great benefit to be gained from alteration to air box, trumpets, exhaust pipes, pumps and so forth.

So at Silverstone one year on engine performance remains pretty much the same but for many a powertrain gain has been the adoption of seamless shifting. This is worth something like a quarter to a third of a second per lap: not a lot but highly significant when the entire 2007 field can be within three seconds.

Honda has run seamless for a couple of years, apparently using the Weismann roller clutch principle. McLaren has toyed with a twin clutch and last year Williams went that route, too. But it was heavy (too much inertia), required a momentary ignition cut and in practice reliability became an issue. This year using the Toyota engine, Williams is partnering with Toyota in development of what has become the conventional seamless approach.

That approach relies upon ultra-precise control of a conventional gearbox, albeit one modified so that such precision can be accurately actuated at the teeth of the shaft-fixed dogs that still do the work of selection and de-selection. Simultaneous engagement and disengagement (without any ignition cut) can be attained if the clutch is slipped an almost imperceptible amount at precisely the right instant in terms of dog position.

Thus what has become conventional seamless shifting relies upon both hardware and software development. Of course, these days the Formula One car’s control software is highly sophisticated. For example, not only do the 2007 cars exploit traction control some of them also exploit what might be termed reverse traction control.

Aerodynamic forces increase as the square of road speed therefore under braking the loading from downforce reduces disproportionately to the reduction in speed. Given the forward weight transfer that occurs under braking this multiplying decay in downforce makes it challenging for the driver to avoid rear wheel lock up. In response the same sensors that identify the onset of rear wheel spin are employed to identify the onset of rear wheel lock and as necessary engine power is applied against the braking force to avoid it. This is why Formula One rear brakes sometimes run hotter than the fronts!

Aside from the success or otherwise of this strategy, which all 11 teams appear to employ, thanks to the current regulations there isn’t much to differentiate the braking performance of the various cars, aside from the influence of aero performance. Given the use of ‘control’ tyres from Bridgestone much of the less-than-three second difference between the front of the Silverstone grid (McLaren and: BRITISH GRAND PRIX Ferrari) and the back (Super Aguri and Spyker) was attributable to aero performance. That was the prime factor, with tyre usage the secondary influence, one critical, as we have noted, between McLaren and Ferrari (rather than between McLaren and Spyker).

This year’s control Bridgestone tyres lack grip compared to the rubber supplied by the manufacturer and its rival, Michelin, last year. Deliberately so, for in the absence of a tyre war Bridgestone was asked by the FIA, as the governing body, to go this route, to check cornering speeds. It did as it was asked but on-going aerodynamic development by the top teams has countered that loss of tyre performance. At Silverstone in 2006 the pole was claimed by Alonso’s Renault in 80.253 seconds; this year Hamilton lapped in 79.997 seconds.

In 2006 the top speed of qualifying was registered by Michael Schumacher’s Ferrari at 299.7 kph: this year’s fastest car was Alonso’s McLaren at 300.2 kph. Under normal circumstances the aerodynamicists reduce drag as well as increase downforce from one year to the next. But in developing the current cars they did not seek to reduce drag. Downforce was the over-riding consideration: above all the 2007 Bridgestone tyres respond to downforce. Consequently this year not only is engine power about the same so is the drag level: that mere 0.5 kph difference is more about wind speed and direction than anything.

Silverstone (a former airfield) is notoriously gusty. Last year Alonso took Copse absolutely flat in qualifying; this year with comparable grip (less from the tyres, more from downforce) Hamilton needed to feather the throttle. The wind was again to blame.

Then there is the question of balance. Over the first half of the season it became apparent that the 2007 cars need 44-47% of static weight on the front tyres to attain a workable handling balance. All of the cars on the grid carry sufficient ballast to attain anything in that range, so in each case there is a free choice.

Working at the lower end of the feasible front loading, with the appropriate aero split clearly puts the maximum downforce on the rear, which helps maximise rear grip. However, the characteristics of the 2007 tyres are such that the fronts will be generating even more grip leading to an oversteer tendency. This suits Hamilton, who famously thrives on oversteer whereas some other top drivers need a measure of understeer to be comfortable, particularly at a circuit with dauntingly fast corners such as Silverstone.

Accepting a measure of oversteer has two key advantages.

One, the current front tyres do not readily accept sharp directional changes. Drivers whose style depends upon such changes have been struggling this season; others who look to a more conventional smooth line have benefited. Those who drive in the textbook way and who can accept a measure of oversteer are in the best position for the oversteer can help the car turn in.

Two, to create a car acceptable to drivers who cannot cope with an oversteer tendency it is necessary either to increase grip at the rear or to reduce it at the front. Given the current aero regulations, it isn’t possible to find additional rear downforce without spoiling performance at the front and in any case the rear tyres wouldn’t happily accept more than 56% static weight to balance it. So the only possibility is to reduce grip at the front relative to the rear, which can be done by putting more static weight up there – this is where the 47% comes in. While reducing the performance of the front tyres in this manner creates the required handling balance at the same time clearly it reduces the overall level of grip.

Hamilton’s willingness to work with oversteer in part explains why he performed so well over the first half of the season, well enough to lead the World Championship going into Silverstone and emerging from it, third position notwithstanding. It seemingly took most of the mileage driven through to this mid point of the season for Alonso to get as comfortable with the characteristics of the 2007 Bridgestone tyres.

Likewise Raikkonen, who had often been in previous races shaded by teammate Filipe Massa. At Silverstone Massa started from the pitlane after stalling on the grid, victim of an electrical glitch. Nevertheless, he literally scythed through the field, eventually to finish fourth, splitting the BMW team that had regularly been this year’s third best outfit. It was a performance that suggested Massa would otherwise have been challenging his teammate for the win.

The Santander British Grand Prix was a Ferrari race but that was due to chassis characteristics, nothing to do with relative powertrain performance. A power game Grand Prix racing 2007 is not.