Honda has revealed intimate details of its RA806E 2.4 litre V8 F1 engine to a group of publications including Racecar Engineering. The engine you see pictured here is V023 which finished 3rd in the 2008 British Grand Prix. Honda continued to develop the engine in 2009 and 2010
For Honda work towards the 2006 season started in 2004 when it became clear that Formula 1 was to switch from 3.0-litre V10 engines to smaller, less powerful 2.4-litre V8s. Honda already had some experience of building racing V8s for the IRL but those units would be little help in developing a 20,000rpm Formula 1 screamer.
The first prototype engine was run in the back of a development car at Mugello in September 2004, so the team could gather data on performance and the effects of the increased vibrations caused by a V8 on the surrounding systems. The engine development project team was run under Kazuo Sakurahara, who revealed to RE: ‘The most worrying problem would be a level of engine vibration which the design team had never experienced before.’
The vibration issue could potentially have lead to a range of problems that would keep both the engine and chassis design teams busy. Design of the RA806E, the eventual full race engine, started in January 2005 and it first ran in July of the same year. ‘The initial concept of the engine was to create a package with greatly improved body joint rigidity, which would surpass the V10 in terms of power-per-litre running at full revs in the opening race of the season. Then the focus of the development stage was to try and solve the vibration issues inherent in a V8 engine,’ explains Sukurahara. The new engine regulations would limit the freedom of Sukurahara’s team on overall architecture of the engine, and also the materials they could use. It had to be a V8 engine of no more than 2400cc, with a V angle of 90 degrees. Only two inlet valves and the same number of exhaust valves would be permissible. The regulations were tight and very restrictive, even the cylinder spacing was fixed at 106.5mm (+/- 0.2mm).
A really difficult part of the regulations for the designers, however, were those regarding the engines centre of gravity, as laid down in article 5.5: 5.5 Weight and centre of gravity: 5.5.1 The overall weight of the engine must be a minimum of 95kg. 5.5.2 The centre of gravity of the engine may not lie less than 165mm above the reference plane. 5.5.3 The longitudinal and lateral position of the centre of gravity of the engine must fall within a region that is the geometric centre of the engine, +/- 50mm. The geometric centre of the engine in a lateral sense will be considered to lie on the centre of the crankshaft and at the mid point between the centres of the forward and rear most cylinder bores longitudinally.
These regulations meant that the Honda team would have to check the materials, positions and details very carefully at the design stage. There were also some other issues for the engine team, as well as the V8-related problems already mentioned, to overcome as senior technical director, Shuhei Nakamoto, explains: ‘In the early stages of development it was hard for us to produce torque efficiently because of the ban on variable trumpets. The torque curve is not smooth on a V8 and that created challenges from the point of traction control. It took us a while to flatten the curve out.’
The engines development continued into 2006 with track testing, and then on into the racing season itself, as Sakurahara expands: ‘During the early part of the season we focussed on reliability, using slightly reduced revs without sacrificing too much in terms of power. Other teams seemed to be pushing hard the rev limit to ascertain engine loads during the early stage of each race. The engine was capable of running at 20,000rpm momentarily, but to run it consistently at that speed throughout a long race seemed impossible.’
Going on to explain one of the reasons the Honda V8 did not rev as high as some of the other engines, such as the Cosworth V8, Sakurahara continues: ‘It is as we have a relatively small bore and a long stroke, but we think we produced about the same amount of horsepower.’ Despite this, the early races were not to be good ones for Honda’s engine team, and this was highlighted by the ‘afterburner moment’ suffered by Jenson Button at the final corner of the Australian Grand Prix. And other similar problems dogged the team for some time afterwards.
‘We encountered seven engine failures in the course of 18 grand prix weekends, all of which were reciprocation-related problems. Many of them were caused by the uneven quality of the parts affected by vibration in the crankshaft area. This had never been a problem with the V10. As a result we had to improve the quality control process,’ explains Nakamoto. ‘The long stroke increases piston speed and that makes durability harder to achieve. Our early season reliability problems may also be related to this.’ Even the victory in Hungary was overshadowed by an engine problem, as Sakuhara admits: ‘The Victory in Hungary was strange for us, as on qualifying day we had an engine failure which initially was a mystery as the part that failed had never done so before. But the cause was found to be a higher than normal oil temperature at the previous race in Germany. This forced us to investigate the relationship between higher oil temperatures and higher engine revs.’
The ongoing development was halted at the end of the season by an engine technology freeze that is to last throughout the next two years at least. But, prior to that, the RA809E had received a number of updates, including a new induction system and a new injector in the early part of the year while, during the mid season, the engine team found a way to modify the structure of the pneumatic valves and reduce friction.
Towards the end of the season the engine received a new fuel system and the injector design was modified, and the final update before engine homologation kicked in was a new cylinder head. In addition to increasing peak power the new head improved low and mid range torque. Reliability was improved in the second half of the season too, and the team managed to increase the rev limit and get the engine to run in reliably at a higher oil/water temperature which, in turn, meant the engine team had done its bit to help overall car aerodynamic efficiency by allowing the car to run smaller radiators.
Honda continued in F1 with the RA806E used by it works team up until early 2009 when it suddenly quit Formula 1, the team morphed into Brawn GP and won the 2009 World Championship with Mercedes power. The RA806E was also fitted to the Super Aguri customer chassis between 2006 and 2008. Honda is set to return to F1 in 2015 as an engine supplier.
2008 Technical spec
Capacity: 2395.5cc
Bore: 97mm
Stroke: 40.52mm
Compression ratio: 13.0
Weight: 95kg (Regulations)
Max power: 747bhp
Max rpm: 19,000rpm (regulation)
Engine life: 1350km
Honda will return to F1 in 2015 with an all new V6 engine in the back of the McLaren team cars. The engine will be built in Japan and run from a new factory in Milton Keynes
Lots more pictures at the source--> Racecar Engineering
