IndyCar Series drivers didn't only come out of the recent
Daytona Open Test pleased by what they found running on 100 per cent fuel grade ethanol for the first time, but also raved about the work done by engine supplier Honda during the off-season.
Two major changes were made to the Honda HI7R Indy V8 engine for the 2007 season, with the shift to ethanol accompanied by an increase in displacement to 3.5 litres. The results from Daytona showed improved reliability and suggested that the level of competition would rise in the coming campaign, leaving Honda Performance Development technical leader Roger Griffiths happy to discuss the changes and their effect on the engine programme.
Q:
Why the increase to a 3.5-litre engine, and how did you make the change?
Roger Griffiths:
With the addition of more road course events on the IndyCar Series calendar, we felt it was important to improve the torque response of the Honda Indy V-8, and increase the width of the usable power band. This makes the engine less 'peaky' and better suited to road racing. It also means the engine will be less stressed, which is good for reliability and helps us reduce costs to the teams as well. Increasing the displacement to 3.5 litres was relatively simple to accomplish by changing the crankshaft and connecting rods. All other major components are the same as in the previous three-litre engine. There also are some minor revisions to the intake system to achieve the targeted performance levels, reduce costs, and simplify the engine building process. The last two are key components in the plan to once again reduce the overall programme costs to the teams.
Q:
What additional changes were needed to accept 100 per cent fuel-grade ethanol?
RG:
The most important aspect to the fuel change is making sure that all components in the engine that come into contact with the fuel are 'ethanol compatible'. This includes the fuel injectors, fuel lines and seals. The ECU settings have also been adjusted to meet the 'burn' requirements of ethanol. Fuel mileage has improved, to the point that the 2007 fuel cells have been reduced in size to 22 gallons.
Q:
Based on the mix of street/road course and various-sized ovals, what are your thoughts and projections for '07 regarding a less-costly engine programme for teams but one they can have confidence in?
RG:
With the increased engine life, teams may well get an additional event out of an engine build, and that helps further reduce costs. Engines that ran two races between rebuilds should now last for at least three events. Despite the fact that our cost targets are significantly lower for 2007, we've been able to maintain Honda's high quality assurance procedures. We have very thorough mileage tracking and development testing procedures that will remain for 2007 and beyond. In fact, in durability testing of the engine, we regularly run far in excess of the track mileage limit and under tougher running conditions, so that we go into the races with a high degree of confidence about the reliability and performance of the Honda Indy V8. We're looking forward to another great season this year.
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