Q & A with Toyotas technical chiefs 20 Jul 2005
After running their 2006-spec V8 engine on track for the first time last week, Toyotas two technical bosses spoke to the teams press department about the progress with the programme to date
Luca Marmorini, technical director (engine):
Q: How long have you been working on the new Toyota V8 engine?
LM: It took around eight months to have the first V8 prototype ready and the engine was first fired up on the test bench on March 21. I don't normally remember those things but it was the first day of Spring, and a new dawn for us as well!
Q: Is it difficult to run parallel V10 and V8 development programmes?
LM: We had no choice. The 2005 rules say that we have to run a V10 but from March 2006 we have to race with a 2.4-litre V8. Obviously the winter off-season does not give sufficient time to develop a new engine and so we have to do the two programmes in parallel. Fortunately the engine department has the resources to do that and it is interesting from an engineering viewpoint.
Q: Presumably you started work as soon as the V8 rules for '06 became firm?
LM: Exactly. But at the very beginning we also had to make some critical assumptions before the rules were confirmed and then adapt slightly. It took time before some of the stipulations were confirmed, for example the 96.5mm distance between cylinders and the minimum weight of 96kgs. When you look at the weight of typical V10s this year and then consider that you are building an engine that is 20% smaller, it would have been possible for the weight to be less than 85kgs, for example.
Q: Do you have specific targets to achieve for the start of next year, in terms of horsepower and revs?
LM: We would like the V8 to rev slightly higher than the best V10 figures seen this year. And in terms of power, the target is 80% of the best V10 power figures seen in 2005. Approximately, that means that we would like to see power figures between 730-760bhp by the start of the 2006 season.
Q: What are the major design issues with a V8?
LM: Normally the internals - pistons, connecting rods and bearings - will look similar, but the castings are different and the stresses from vibrations present quite a tough challenge.
Q: Why does a V8 engine vibrate more?
LM: A 12-cylinder engine is fully balanced and you can have some 10-cylinder engine configurations that are well balanced. For example, the current Toyota V10 has very few vibrations. But if you use a 90-degree block and a flat crank typical for a V8, it's impossible to balance the second order vibrations. With a road car engine you might do it with a counter-rotating shaft, but on a racing engine, you don't. That is one of the main reasons why we wanted to run the engine so early. It is not so much for direct engine purposes but to monitor the components around the engine and the effects of the extra vibration.
Q: How has the shakedown gone at Jerez?
LM: The first test in Jerez went very well. It has been interesting. On the final day of the test Olivier Panis did a 1m21.2s lap as against a typical same car-spec' V10 time of around 1m18s. That is already quite impressive when you consider that the engine is being run conservatively with something like 200bhp less, in an adapted chassis. I think Olivier's experience will be very useful. The first day was very good the engine ran well and we solved some ancillary problems. On the second day we had a failure, but that's part of development, and on the third day we worked on several longer runs.
Q: Is an eight-cylinder engine new territory for you personally?
LM: My previous work included experience with eight cylinder performance road car engines but not racing engines. So, yes, it's an exciting activity for me. It's very different with lots of new problems to overcome. Toyota, however, has experience in CART, although I would say that running a V8 engine at more than 19,000rpm is a different and unique challenge. An open book, shall we say!
Mike Gascoyne, technical director (chassis):
Q: Did you run the V8 in a specially adapted TF105 chassis in Jerez?
MG: Yes. We have put a spacer between the chassis and the engine and so have just permanently modified one chassis.
Q: From the overall design perspective, is it easier to work with a V8 because you have smaller dimensions?
MG: It is more compact and so that means you have a bit more freedom in terms of volume. You have to decide where you are going to put the engine from a weight distribution point of view, but it can give more space either in front of the gearbox or, for fuel volume, in the rear of the chassis.
Q: Fuel consumption will be less and so does that have implications for fuel tank size?
MG: Fuel consumption will go down and you've obviously got additional volume to put fuel in, but really it will depend on the qualifying regulations whether you have to qualify with fuel or without fuel. That significantly alters your strategy on things like tank size.
Q: Are there any downsides to a V8, vibration for instance?
MG: The vibration levels are significantly increased and it's been an issue on the test bench with some of the engine ancillaries. But we anticipated that we would have those problems and we don't foresee any long-term difficulties.
Q: What are the implications of a V8 for chassis stiffness?
MG: Obviously the shorter you make the engine the stiffer it gets. Basically, when you reduce the engine length and put the length on the chassis, the chassis at that point is actually very stiff and so it can aid overall stiffness. But I wouldn't say that it is a hugely significant factor.