Nissan: “It went off like a bomb”

And there you sat, happy in the assumption that racing at an old French circuit is as simple as strapping a powerful engine into a carbon fibre tub, inserting a racing driver and crossing your fingers? Well, Nissan's LMP1 team can tell you that actually no, that's very much not the case.

You'll know all about the monster, 1250bhp front-wheel-drive hybrid Le Mans Prototype, and if not, you should. Having failed a crash test in March, Nissan's LMP1 campaign took a significant scheduling blow, which meant the GT-R LM couldn't make its planned racing debut at Silverstone earlier this month.

Even worse, the team wouldn't be heading to the pre Le Mans warm up at Spa on 2 May. This means the first time they'll been running competitively in anger is at the Big One at Le Mans in June. For 24 hours. Flat out. Against Audi (13 wins), Porsche (16 wins), and Toyota (winners of the 2014 WEC championship). No pressure, then.

So as the team prepares for the final push ahead of the 24hr race, we caught up with Ben Bowlby - the genius behind the radical, front-wheel-drive, 1250bhp LMP1 contender - to talk about some of the challenges involved in making a front-wheel-drive, 1250bhp Le Mans Prototype last an entire da at practically full throttle...

"I'm not sure anyone has ever passed all the elements of an FIA crash test the first time. Two areas gave us trouble," explains Nissan's Ben Bowlby, the genius behind the radical, front-wheel-drive, 1250bhp LMP1 contender set for this year's Le Mans 24hr race.

"The first was the front roll hoop test. If you imagine you've got a 40kg carbon fibre tub, and you have to squash the bridge-like structure across the top of the windscreen with nearly eight tonnes, it creaks and groans a bit.

"We passed the first private test and everything checked out except the roll hoop. We thought ‘we know how to fix that'. But we failed the test in front of the FIA, which was very surprising, and caused us a massive headache. Unfortunately when it happened, it destroyed the chassis.

"It was such a violent failure, it sort of went off like a bomb."

Yikes.

"The FIA have very wisely decided that the door should have an anti-burst load," explains Ben, "because if you have a side impact, the driver's head might make contact with the door padding. So they asked us to push these flimsy little doors with 750kg of force, and it was very difficult to pass that test.

"The first time we failed and cracked our door skin. We had to completely redesign the door structure. So we redid the tooling, and a few tens of thousands of dollars later, we had a new door. We tested that and it passed absolutely fine."

Phew.

"A completed chassis ready for a crash test is somewhere in the region of $170,000," says Ben. "So it's pretty upsetting when you lose one. But for us, getting it ready for an impact test is something like eight weeks. It's two months out of a very tight schedule.

"From the outside racing looks very calm and controlled, but we work so hard to get to this point. You can delay a rocket launch, but you cannot delay the start of the Le Mans 24hrs. You cannot afford to fail on this timeline. It's why we didn't do Silverstone or Spa - of course not at all what we wanted to do - but it was our only option."

"We have now actually completed a Le Mans distance," Ben says, before doing a mini whoop. "This isn't very cool in some respects because we should have completed four or five by now, but with the engine - producing around 550bhp, with a 6,500rpm limit - we've been able to do 30 hour Le Mans simulations with 23 hours at full throttle, running through duty cycles, stopping the engine for 45 seconds to simulate a pit stop, refiring it hot, and carrying on.

"We can replay that on a dyno, but it doesn't have the effect of suddenly hitting a kerb and the driver doing something different, it's not completely realistic, but it's a really good indicator that the engine is very, very strong and reliable. That's a good part."

Bodes well for the future of the GT-R road car, too

"One of the big parts of the car that gives us cause for excitement and anxiety is the ‘Energy Recovery System," says Ben, referring of course to the ‘hybrid' aspect of the LMP1 powertrain. It's a mechanical flywheel system that spins at over 52,000rpm.

"We specced out an extraordinarily powerful ERS, but it's given us plenty of trouble just because it's a hard thing to do. It's more expensive than an engine - it's basically a special engine done from scratch.

"On the dyno and on track, we have pushed out over 1000bhp on our ERS alone. Obviously we've got the big kick that ‘woah this is amazing', however, there are a lot of factors, and being reliable is very important. So we're probably going to have to be a little bit more... conservative. 24hrs is not a burn up the straight, it's a long job. We'll have to be very careful with our ERS.

"But by not going up to the full potential of our ERS... the brakes for example, we were going to be absorbing something like 80 per cent of our energy into the system from the front brakes, which meant our front brakes were hardly going to need any cooling. We save drag like crazy, we save weight, but then we have the situation where we had the ERS trip out because it's finding an error due to temperature or something, and suddenly the brakes are smoking hot and we have to stop. So we have to plan on being able to run at full speed with the brakes being able to take care of themselves. We've had to uprate the brakes, increase the cooling dramatically, it's caused us to spend a lot of time, so we can run at Le Mans come hell or high water.

"At one level it's a bad thing, because it's difficult for spectators and fans to get an understanding of what's been done to maximise the speed of the car, by looking at management of energy for the lap. We simulate so many different characteristics... do we lift and coast, do we power down by absorbing energy into the ERS when we've got too much power from the engine but we want to operating at maximum volumetric efficiency...?"

Ben's brain, if you haven't figured it out yet, is HUGE.

"The gearbox was a real problem child," says Ben. "The last couple of thousand km we had at our last test (at Bowling Green in Nashville), we took the gearbox apart and there wasn't anything wrong. We are quietly confident now having sorted out the oil system and materials on certain elements within the gear train.

"There was a time when we'd basically break the gearbox - we'd snap the main shaft or drop gear sets - every single time we ran. We were getting through them faster than they could make them. And it was just small things, and slowly with the engine mapping and ratios and gap between the ratios and oil system and having all the right parts and pieces, now we start to see everything coming together.

"We're in good shape with the gearbox. Gearboxes are always hard though. We are going to have to coach the drivers. They can have a whale of a time in the car, but they are going to have to drive in a very measured, smooth and consistent way to get the lap time without abusing it."

"Unfortunately," says Ben, "we'll have to keep it that way for Le Mans, because we couldn't get the ERS to deploy to the rear wheels reliably. We'll work on it for the future, but for now, and Le Mans, it's front-drive only."

Not that he thinks being solely FWD is a bad thing, mind. "The nice thing about front-wheel-drive is the tremendous stability you have. We were testing at Bowling Green which is perfect for us as it's modelled on elements of Le Mans. In the wet conditions, we had rivers across the circuit - all very useful of course - the drivers were going for it, and we're doing 309kmh on the straight in the soaking wet conditions. We're thinking ‘isn't that risky?' They're like ‘no this thing is nailed on'. We're looking at traction control strategies so the drivers can give it the beans in the wet and not break anything.

"In the wet we used to break the gearbox because it was too violent. Had it been rear-wheel-drive and they were bombing down the straight and aquaplaned, it would have spat the rear around.

"When the tail gets a bit happy, and you put the power on, it's like tightening a piece of string, it pulls itself straight. The stability of the situation is that you can use a thing like that."

"Michelin are coming up trumps for us," explains Ben. "One of the things we decided to do was unique tyre sizing. The rear tyre... everybody is jumpy about it. When we started it was narrower than what we've got on the car now, because theoretically that would have been adequate.

"We went wider and then the aero was affected negatively, so we've gone to this slightly bigger tyre - roughly an eight inch tyre - but Michelin have done such a good job of making this skinny little tyre have the capacity to handle Le Mans speed and performance. In fact, our simulated life on the rear tyre is north of nine stints at Le Mans! That's a really good thing.

"The compounds are conservative, and we haven't yet run in hot, rubbered-in track conditions, and it's only our first year, so we have to be a little bit cautious. Have we left performance on the table? Probably, yes. But do we have a risk of a blowout? No."

"Logistics is the big challenge now. We're in the final stages of freezing the design spec on what we're going to manufacture and go to Le Mans with. We've got two cars testing next Monday (4 May 2015), and we have to cycle nine drivers through those two cars.

"Meanwhile the last car is getting completed back at base, then we put our entire lives in packing cases, send them to Silverstone where all our trucks and cases are, and then head over to Le Mans for the test day. We stay in the garage all the way through until the 24hr race.

"After Le Mans, we'll give everybody a little break, we'll have given everything we've got. Then we get back and rebuild - the spec of the car will change however, for the races that come after Le Mans, because they're much more focused on maximum downforce; they're tighter, twistier tracks. Le Mans is the focus of what our car was aimed at, but we have to compete in these other races too.

"We've already started drawing the 2016 car, and there will be significant updates with what we've learned, all within the same concept. When we started we did it from a blank screen. This is about the most competitive era to enter as a manufacturer. But it makes it worth being there."

"It's tough out there, it always looks so controlled but every day is a 14-hour day, often it's nearer 20 hours," says Ben. "Our crew is tired, and it's like being in basic training or boot camp. You get beaten up and tired, and you all learn to work together, which is important when you get into the tough situation at the race of being up for 36 hours towards the end of the race. You can't afford to have a slip up. So there's a value to this ridiculously hard training.

"Quitters never win and winners never quit. We know what it feels like to win, and we know what it takes to win. All I want to do is come out at Le Mans knowing as a group we all did our absolute best. If we keep doing that we'll be successful. Our experience is much less than other people, and I'm sure we'll get there. We just want to do our best possible job."

Here's hoping so. Stay tuned to TopGear.com over the coming days to find out what this monster, 1250bhp hybrid feels like to drive: we have a chat with GT-R LM driver Jann Mardenborough...