Technical analysis: McLaren MP4-31

McLaren and Honda's reunion last year was a far cry from the success they enjoyed together a generation ago, as problems with both the chassis and power unit led to a horrific season, with neither pace nor reliability.

Amid the poor on track performances the pairing worked diligently behind the scenes to makes strides on both fronts. Launched on Sunday morning, the MP4-31 holds no surprises as the aero concept was tested throughout 2015, with more and more rake.

While the power unit was limited by the token system, the winter spend of up to 32 tokens would allow Honda to resize its turbo and MGU-H. It looks like the basics that were so wrong last year, within the unit pictured below, are now right.

Honda's power unit continues to be developed in its Sakura R&D base with little reference to outside knowledge. This classic Honda approach didn't pay off last year.

However, lessons were learnt and motorsport boss Yasuhisa Arai is already discussing a new turbo, and outlined that testing will be aimed at ERS development, both weaknesses last year.

This reinforces the belief last year that the Honda V6 engine was powerful enough, just not backed up by the electrical energy from the hybrid systems attached to it. This is phase one of the company's longer term plan to bring the power unit into full competitiveness.

What at first seemed like a clever idea to package a small turbo compressor inside the 'V' of the engine resulted in an overstressed turbo and MGU-H. It is understood the turbo remains in the same cramped position, but somehow scaled up in size.

This will change for 2017, but for this year the plenum and mechanicals on the front of the engine must have been revised to make more space. Honda will be hoping these changes will not affect reliability and can still deliver the missing performance.

On the chassis front, last year's car was a crossover between the new 'size zero' concept and the 2014 chassis, with its odd rear-suspension fairings. This year's car is planned by the three technical leads, and the influence of Peter Prodromou in particular on the aerodyamics and layout shows.

Notably the car is running much more rake - higher rear ride-height and lower front rideheight - creating a tail-up/nose-down attitude. This makes use of more underbody downforce and also improves the front-wing efficiency.

This isn't a case of just jacking up the suspension, the whole car needs to be designed around this concept. It affects gearbox design and splitter design, as well as suspension and aero.

McLaren's race weekend development has paid off as the car sits noticeably higher than in 2015.

At the MP4-31's front end, the nose is a tidied up version of the short version introduced midway through last season. Interestingly, the front wing mounting pylons feature a vertical slot, a feature not seen on other cars before.

As the wing mounts are a key part of the front end turning vane set-up, having a slot means McLaren is working this area quite hard and needs to ensure the airflow remains attached to the inner surfaces of the vanes.

This area is still subject to the same single-closed-section rule as the nose, so the overlap must be aligned to meet this regulation. Also it may be mistaken that the rules ask for single closed sections for each of the wing mounts, but this only applies to the very bottom section of the pylon.

Also included in the short nose is an S-duct, which was another mid-season introduction on the MP4-30. The whole set-up appears to be better integrated and more aggressive.

The sidepods remain part of the 'size zero' concept, but now that other teams have noticeably trimmed their bodywork the McLaren no longer looks so radical. These small sidepods are partly enabled as the rollhoop feeds the coolers behind the engine. The split inside the rollhoop inlet suggests that, again, there are coolers above the engine.

One key change from the MP4-30 is reverting to conventional rear suspension. The unique placement of the wishbones and track rod last year were a hangover from the butterfly fairings fitted to the MP4-29.

Having never raced with the fairing in 2015, the wishbones will be more effective in terms of aerodynamics and structurally more efficient in their new locations.

Above the gearbox are the new exhausts, with the turbo and wastegate each gaining their own tailpipe, creating a clover-leaf design - one high central tailpipe flanked below by the smaller wastegate pipes. This is due to regulation changes this year and the exhaust should end up being louder.

It's not clear from the launch photos but the team's launch video shows a vertical split in the central tailpipe, McLaren may have followed Toro Rosso's idea and passed the rear wing pillar through the exhaust. This keeps the rear end tidy rather than having a horseshoe-shaped pylon.

It's also likely that a lot of the bodywork, such as the wings and sidepods, will see development through testing, with wings typically hidden before the car hits the track and with cautious cooling for the early running.

Overall, McLaren has done the key structural work to make the power unit and the chassis work better. These changes alone should push the car up the grid, but it will be the unseen parts that will really prove just how competitive the MP4-31 will be as the season progresses.

It's been some time since McLaren had a top-level chassis and it needs to prove to the world it is capable of it. Honda needs to prove it can make an effective ERS and a reliable package, and without this any progress on the chassis will be for nothing.

For now, the jury's out on how far the team has come over the winter - last year's bold statements proved how unwise predictions can be.