Tech Analysis: Engines

What’s your poison? A large capacity, powerful and torquey diesel engine, or a lightweight petrol engine? We take a look at what option is best for Powerboat P1

When it comes to engines in Powerboat P1, there’s no clear answer as to whether bigger is better. Since Powerboat P1’s inception, big, powerful diesel engines have been the de rigeur choice, powering the Italian teams to glory, particularly in the production-based SuperSport class. But the last two years have seen engine selection turned on its head. Right now, the advantages and disadvantages of nippy petrol engines and big diesel engines are just a hair’s breadth apart.

Some background. For 2008, both diesel and petrol engines are allowed in Powerboat P1’s Evolution and SuperSport classes, but there are strict engine capacity limitations to ensure close racing.

Evolution class

SuperSport class

Teams also have to factor in how engine choice and size will affect the weight and size of the boat. Powerboat P1 operates a power-to-weight ratio to ensure parity between entrants. More powerful, bigger-engined boats need to be heavier, which adversely affects accelerating and handling, unless the seas are rough. Less-powerful, smaller-engined boats can be lighter, making them faster in smooth waters. The difference can be as much as 1.5 metric tonnes – the equivalent of a medium-sized car or 20 extra people on board. So, engine size and hull size go hand in hand.

In the Evolution class, diesel engines (and the Italian teams) tended to dominate in recent years. But the emergence of the Ilmor petrol-engined #99 King Of Shaves Fountain boat in 2007 and the arrival of numerous US and British teams (many powered by Mercury Racing petrol engines) for 2008 seem to have turned the balance of power. One theory is that the tighter, twistier, closer-to-shore courses would reward the quicker acceleration of a petrol engine and a lighter boat, while the diesel-engined boats would only have a slight advantage on the shorter straights.

“To get the power out of diesels, you need a big engine,” says #99 Fountain Worldwide 1st4boats.com boss Craig Wilson. “They can be less reliable and, because they’re bigger and thirstier, they use the same amount of fuel as petrol engines, so there’s no weight saving from fuel economy. You also have to keep diesel engines spooled to higher revs – if it drops off, you lose a lot of momentum, and that means the acceleration and balance of the boat suffers.

“We run petrol-fuelled Ilmor engines, because they’re light – sometimes a third the weight of bigger diesel engines – they have great acceleration even from low revs and good top-end speed. Because they’re lighter, if you can get the power and top speed out of a lightweight engine, you’ll have a big advantage in the corners. They also sound fantastic!”

But, thanks to some cleverly-written rules, diesel engines – although not that popular, with only two Italian teams using them – are far from outclassed. In fact, the #60 GFN Gibellato boat of Marco Pennesi has proved to be a dark horse, often emerging fastest in the PowerPole session and scoring regular podiums.

The #60 GFN Gibellato boat’s only disadvantage has been sluggish race starts, which left the boat trailing the pack and having to fight its way back through the field. But the pace at which it can stage its recoveries - especially in the rough and unpredictable waters that have been a factor at many of this year’s races – has left crews reeling. “We had really horrible waters in Tunisia,” #69 Honeyparty.com crew member Mark Pascoe said. “It was always going to be the case that the #60 GFN Gibellato boat would come through the field. Once that boat burns off its fuel, it’s almost unstoppable.”

Certainly, Pennesi is content that diesel is still the best choice for the Evolution class. “During the winter, I was curious to know how the American hulls would perform,” he said. “But [at mid-season] I’ve won three PowerPoles and I’m happy to have demonstrated our strength. If we respect the power-to-weight ratio, then there is no difference, but diesel has three times the torque of a petrol engine. Last winter, when [Powerboat P1 CEO] Jim O’Toole came to me, a special premium for diesel engines was among his ideas. I said that there was no need. I knew that I would be strong just the same.”

In SuperSport, there has been a similar about-turn in philosophy. For years, the production-based class tended to mirror consumer-based choice of diesel engines, but the championship has been dominated for the last 12 months by the Mercury Racing-powered #44 Conam Yachts entry of Angelo Tedeschi. As he explains, there’s not a huge amount of difference between petrol and diesel.

“I don’t think there’s an advantage or a disadvantage between petrol and diesel,” he says. “In the Evolution class, the #60 GFN Gibellato team are proving that diesel still works. It’s how the boat is packaged that makes the difference. The last SuperSport championship won with a diesel engine was in 2005. But I’ve been saying many times for the last five years why I race with petrol – it has music like no other engine.”

And sometimes the choice can be as simple as that…