PRO DRIVE’ S NEW WEAPON
David evans gets under the skin of a revolutionary rally cross beast
What did you get for question six? Remember those inevitable post-exam debriefs? And that slightly uneasy feeling when your answer didn’t tally with those around you. That was Silverstone last month when the GCK Megane R.S. RX car rolled out of its garage towards the Stowe circuit for the first time.
There had been plenty of chatter about the potential revolution this car was going to provide, but rarely does the reality live up to the rumour. It did this time. And it did thanks to Prodrive. Anybody pulling a late one past junction 11 of the M40 recently will have noticed the lights have been on longer, later than usual. The reason is Guerlain Chicherit and his desire to do something different in rallycross.
As an extreme skier, Chicherit is more than used to taking an alternative route to the masses, but no couloir or cliff jump in his previous life is as radical as what he and Prodrive have come up with to challenge the established order of the World Rallycross Championship.
“When I started my own RX team, I wanted to make a car from scratch,” says the Frenchman. “There are cars coming to RX from other sports, but nobody built one completely new. I knew my team couldn’t do this, but there was a team I had been dreaming about since I was young. This was the same team my hero drove for, my hero was Colin [Mcrae]. And the team is Prodrive. It’s incredible for me to come to the place where Colin was and it’s even more incredible for me to see what Prodrive has created for me. I have to thank those guys: they’ve made my dream real.”
And, on paper (or more likely a computational fluid design [CFD] page), it looks like Prodrive might have created every other team’s nightmare.
The Banbury firm’s pedigree in world rallying and endurance racing is beyond question, but its brief flirtation with rallycross didn’t deliver. In between fixing up Sir Ben Ainslie’s America’s Cup challenger and making the world’s lightest folding bicycle, there was an idea to revisit RX.
Prodrive technical gurus David Lapworth and Paul Doe sat down with a copy of the World RX technical regulations. Already acquainted with them from the time they converted the Mini John Cooper WRC into an RX racer, they were ready to crunch the numbers on a whole different project.
Zero carryover (actually, that’s not true – the wheelnuts share the same part number); empty screen; free your mind.
Doe explains: “We wanted to avoid the limitations which comes with [converting a] rally car. On the chassis side [in a rally car], the engine position has to be kept within 25mm of the production engine, which allbut forces you down the transverse [layout] route. The suspension is going to be Macpherson struts, which come with massive limitations and the sub-frame has to be interchangeable with a road car – again this creates problems.”
The solution was a simple one: tear it up. Forget convention.
The real benefit for Prodrive mid-way through 2016 was that the car wouldn’t be breaking cover until last month and that gave them plenty of thinking time.
Lapworth smiles the smile of an engineering genius emerging from 18 months of playtime in a series with significant regulatory scope.
“The last time I did something like this was back in the 1980s,” he says, “when we worked on an off-road project…”
That off-road project? Porsche’s 959, the one that finished 1-2 on the 1986 Paris-dakar.
He continues: “In the beginning, Paul and I started looking at priorities, themes and what we could do and where we could do it with the car. We did that for six months before we started committing the resource to it. It’s rare that you get that time, but it’s so, so valuable. Commercially you’re almost always backed into a corner in terms of development, then you’re up against it and trying to cut corners to get the car ready in time. This wasn’t like that.”
And then, just like Prodrive had with its Mini World Rally Car, the whole thing was designed and built virtually.
“This [approach to design] is something that’s been coming more and more for the last 10 years,” says Lapworth. “It’s a cliche, but, who was it? [Abraham] Lincoln, I think, said: ‘If you’ve got a day to chop down a tree then spend the morning sharpening the axe.’ That’s what we’ve done. Time is more valuable than money when it comes to developing a car. Honestly, to be given twice the amount of time rather than twice the budget is preferable.”
And that clean sheet of paper meant nothing would be compromised. The engine mounts would be perfect for a Prodrive-designed motor to slot into a Prodrive-designed chassis.
“Prodrive is a very data driven company,” says Doe. “We have a huge amount of experience to call on, but we do like to do it with the numbers. We’ve had a lot of fun in the last 12 months.”
Ground-up revolution
The most talked about part of what will be the fastest-ever accelerating Renault Megane is the absence of brakes in the wheels. All four discs are inboard, which means the fronts are located inside the engine bay.
“We came close to doing this with the rear brakes on the Mini WRC,” says Lapworth, “but in the end it was too much of a risk when you have events like Mexico which can be really hard on brake temperature.”
With four-minute races, rapidly rising brake temperatures won’t be a problem. And the pay-off is potentially huge in terms of improved unsprung mass and the ability to contain tyre temperatures and pressures – via tailored aircraft-style O.Z. Racing wheels.
“So far, it’s worked pretty well,” says Doe, deadpan, not giving anything away. “We should be fine providing World RX doesn’t introduce half-hour races.”
The absence of brake mountings on the hub means a very minimalist upright and this leads the eye nicely into suspension.
“The suspension is a good step,” confirms Lapworth. “It’s not all win, but on balance we think it’s the right way to go. The Mini, with some development, would have been a very good rallycross car without throwing everything away that we’d done for rallying. But with a clean sheet of paper it wasn’t difficult for us to say that we would discount the Macpherson strut straight away.”
In its place is a double wishbone set-up which offers wider camber options and much improved grip as the car loads up in a long corner.
“The car’s ready to turn more and more in the long corners,” says Doe, “in these places, with the limitations of the Macpherson, you would have started to lose to the tyre. The double wishbone takes away friction issues and gives us so much more freedom around the geometry.”
All of which should result in improved grip and balance from the car. And it’s the grip where Lappy reckons the big win could come.
“The limitation on grip is probably why this sport’s not F1-expensive,” he says. “I don’t know exactly but I’d say 60 or 70 per cent of the lap is probably grip limited, so you don’t need to chase 1000bhp – you’re not going to need it and it’s not really an aero formula. Of course you need to optimise what you’ve got [in terms of aero], but Adrian Newey wouldn’t get very excited about rallycross because you’re not chasing after 1000s of Newtons, you’re chasing a few hundreds of Newtons and the difference between one car and another car could be measured in 10s of Newtons. Like I said, I think we’ve made a good step with the suspension.”
Damping comes courtesy of bespoke Ohlins.
New engine is crucial
To make the inboard brakes work, any plans for a transverse engine were binned. Which was just as well because – for issues of centre of
“Prodrive is a datadriven firm” Paul Doe
gravity and mass distribution – Doe and Lapworth favoured longitudinal anyway.
Doe explains: “The engine is as low as it can go. We’re limited by the flywheel regulation [sized at] 240mm. We can’t go smaller than that, so we have crankshaft, [the] 120mm flywheel radius, a very small gap, floor and road. It doesn’t go lower than that. Look at other longitudinal cars and normally the engine is sat on top of the transmission with driveshafts going under the engine, in this case we’ve really sat everything on the floor.”
Once the layout of the engine was decided, the research and design was handed over to Arthur Shaw, Prodrive’s chief engine engineer.
“We’d done an in-depth study into all engine options and it became clear that designing our own bespoke engine was the way forward,” says Shaw. “We have experience of this with the endurance programme, which has given us real insight into both power and durability. The power was the key attribute.
“Once we knew the parameters, namely the two-litre [capacity] and 45mm restrictor, we then worked backwards and sketched the geometry. It’s a fairly high output from a two-litre engine, so we worked hard within the restraints of maximum bore and valve size, the minimum crank height. We wanted a low-friction engine, there’s no point making all that power only to throw it away with friction and heat.”
Another key area was the engineside airflow as well as the water system. “This is like nothing we’ve really seen before,” says Shaw. “We’re really proud of the water system, we’ve put a lot of effort into it. [On] a lot of previous projects, we’ve inherited water jackets, but we’ve been able to cure a lot of those ills with this engine. In a nutshell, we did a lot of CFD work around the waterjacket: the water goes in in the inlet side, goes around the block and through the head and comes together to exit out of the exhaust side of the head. This means the heat generated on the hot side of the head never goes into the head it just gets pushed straight out.”
After hours and hours of fatigue analysis on the equipment, virtual valve-train work and the consideration of acceptable levels of torsional vibration, the plans were handed over to the purchasing department which went out and sourced the required parts.
“We have an extensive analysis process,” admits Shaw. “This is key to leading the design, and it means no surprises at the end. We front-loaded the project with design and analysis, so when you get the product, you can be pretty sure it’s going to work. It’s much harder to come back from a problem than it is taking the time and getting it right in the first place.”
Once the bits were bolted together, it was time to fire it up on the bench. Shaw adds: “We did a full engine calibration and system optimisation to make sure it worked out of the box. Then we handed it over to the chassis group to go and drive it.”
Which they did.
Transmitting the power
The gearbox casing and transmission architecture is tailored to the Megane, it had to be to make it work with the engine position and inboard brakes. The internals, the differentials, gear cluster, the rear ’diff disconnect, they were all off the shelf having been used in an American racing series where plenty of power and truck-loads of torque are high on the agenda.
What about the skin?
While Renault had nothing to do with the project, the area where it was keen to be looped-in was in how the thing would look when it took to the grid for the first time.
Doe says: “You can sometimes find when designers like myself have a go at styling work, the cars can come out looking a bit ugly: that can be seen in the RX paddock. Renault hasn’t been tremendously involved in the engineering side, but they did give us some help on the styling work.”
But the styling’s not all about the look, it’s about the feel from the aero as well. While RX cars rocket off the line, they’re not known for towering apex speed – but when they spend so much time sideways, they’ll take all the help they can get in keeping the car on track.
“We see some crazy, crazy slip angles in this series,” says Doe.
“So we’ve run different analysis for yaw to create the right angle for the rear wing. That combined with the suspension means this thing just hangs on in the corners.”
Immediately, the Megane R.S. RX signalled its intentions with Chicherit’s team-mate Jerome Grosset-janin blitzing the timesheets to go fastest around a sunny Stowe RX track during the official test.
That was the clincher. That was the point when everybody in the paddock started questioning their own answer to question six.
But this week comes the real answer. There’s more to a team than just the car; Prodrive’s still short on RX experience, track time and real-world data and Grosset-janin and Chicherit will face the full force of the WRX pack when they drop the clutch and aim their revolution at the apex in Turn 1.
Only then will we know if this Chicherit-prodrive alliance has graduated to become WRX masters. ■
“We have had time to perfect this car” David Lapworth