Q&A: Mazda chief engineer details switch from diesel to petrol engine

What led to the decision to switch from a diesel to petrol engine? I'm sure the rule changes played a role in it.

Marcus Shen: A couple things ... First and foremost, the rules package. Diesel at Le Mans in the LMP2 category is probably never going to happen, especially with the new regulations for 2017. And the same thing with IMSA following a similar suit so there's really nowhere for it to play anymore. It kind of started with the GX car and then that went away. Then we put it in a prototype and now that is kind of going away too.

It's kind of written itself out in a sense. The other thing is the sheer amount of resources to continue development on that. It is a stock block engine based on a production motor. So we far exceeded the factory output by quite a bit. And to keep building on that, your steps aren't linear. It gets harder and harder the more you try to go farther than what it was designed to do. Your development cost increase, your time dedicated increases and it went beyond what an LMP2 category should be. We're talking an LMP1-type technical development on an LMP2 program.

How has the new engine package helped in terms of power, drivability and so-on?

Marcus: There's more top-end power and that's been a huge improvement. What's helped also is some of the drivability everywhere else on the track. Power is very linear for this package, similar to a diesel package actually. But the drivability is good for the drivers as for how they can get on the power and when they get on the power, when they can make passes at will. It's really been a transformation on the chassis as a whole. As you start going quicker, the aerodynamics work differently and the vehicle dynamic changes.

A lot of things changed there. Power delivery and the top-end has changed how we drive the car and how we engineer it. It's further evolutions on where we were last year, taking a step further. We didn't have to take a step back with this. We're just continuing where we were with the diesel and taking it to the next level.

So would you say you have a better overall package for this year, compared to your 2015 car?

Marcus: From a performance development, the higher top-end is huge for a track like Daytona with two massive straightaways. In some regards, where we've had to make up time to go faster, we've kind of hurt compared to the car last year. Last year we didn't have the top-end so we focused on downforce and maximizing the infield. Now we're trying to maximize the straight line so you take the downforce off and you can't corner as quick as we did last year. It's a sliding scale. As a whole, our package is stronger here now. 

How are you feeling about the reliability and making it the full 24 hours?

Marcus: The Lola chassis has been around for a quite a while now so it's a proven platform in the endurance races, including Le Mans. It's been around and has its pedigree. We have a pretty developed package, but when the two halves come together, it's a new thing. Each bit on its own has done the distance, so to say. So reliability wise, we should be good. 

What were some of your takeaways from the test in regards to how you compared to other prototypes?

Marcus: Everyone looks at lap times and sectors but I think our performance is pretty matched. Where we make up lap time is different than some of the others, but every car is going to have its strengths and weaknesses. I think we stack up pretty close to the front five of the prototype grid. All our drivers have been very consistent, which is key at this race. 

Is a podium result a realistic objective?

Marcus: I think that's a modest goal. Everyone wants to win and some race their whole lives and never get the chance to win. We've been fortunate enough to when this thing twice with the RX-8s back in the GT days. We understand what it takes, but just because you've been there, we know how how hard it is to get back there. So being realistic about it, a podium is a tangible goal.