McLaren Elva | First (brief, windy) ride

Where better to experience a car with a virtual windscreen than Snetterton in November?

McLaren's PR department had barely pressed "send" on the email containing the first images of the forthcoming Elva when PH received a short-notice invite to go to Snetterton for a passenger ride. Short notice as in the following morning.

While the opposite seat experience is now an established part of the new car launch process - and a frequently overplayed one - this wasn't going to be that. Before setting off for Norfolk I'd been warned that this wasn't going to be hard laps to show what the 815hp speedster will be capable of, rather a couple of runs down the main straight at no more than 70mph. Which seemed like a long way to go for not much, right?

The draw, and the reason I opted to wind 380 miles onto my Cayman's odometer, was the chance to experience one of the cleverest parts of the car for the first time. The Elva's ultra-light mission means it is going to be sold without a windscreen in most places, with McLaren very keen to demonstrate the abilities of the Active Air Management System to cut down on buffeting at lower speeds, despite the lack of any glass. The weather forecast is for a bracing 7 degrees, but at least it's not going to rain.

Before the full hair-dryer experience there's a chance for a talk around the car, and a look at the (very early) prototype wearing full dazzle camouflage. McLaren wouldn't let us take any pictures, and hasn't released any beyond the very limited set you see here, so you'll have to take my word for some of it, including the fact both sills and the vestigial doors incorporate ducting to help manage air flow down the side of the car.

At the back the prototype has four exhaust tailpipes, two top exit similar to those of the 600LT which are intended to project noise upwards for occupants of the car, and two lower in the rear grille to bounce noise off the road surface. These were in a different layout to those of the rendered images of the official release, which are closer to production reality, but the idea is the same. As Dan Parry-Williams, McLaren's Director of Engineering Design puts it: "the reason we designed it this way it just to be loud and have fun."

But most of the reason I'm here is to learn more about the AAMS. (The lack of a pithy name seems down to the fact Ferrari nabbed "virtual windshield" first for the SP1 and SP2 specials.) The first mild surprise is to learn that what I assumed to be the system's intake half way up the front clamshell is actually its outlet, despite being a long way below where you'd expect a windscreen to be. (The much less powerful "aeroscreen" that was offered as a little-chosen option on the Renault Sport Spider, was mounted where the base of the conventional screen would sit.)

On the Elva the outlet looks like that of a big hand dryer, with vanes carefully angled to create a plume of air that is aimed slightly forwards - 40 degrees past perpendicular. Air is collected from the centre of the front intake, with the decreasing size of the channel that carries it speeding it up by around 5 percent according to Andrew Kay, the Elva's chief engineer.

There is no fan, but the production version will get a motorized Gurney flap that rises in front of the outlet to create a low-pressure area for it to work in, and which can also vary the size of the plume. McLaren is still working on that at the moment, so the prototype - which is the first "aero-thermal mule" - has two different units that can be fitted into the space, one with the outlet blanked off and the other with the vent in place and the Gurney in its fully upright position. (The production car's vent won't close, but flaps inside the inlet will seal when it is not in use.)

McLaren stresses that we're experiencing the Elva well ahead of the point it would normally let outsiders sit in the car. The mule doesn't have a production interior and I notice that the digital instrument pack's start-up screen is still from the 720S it was presumably nabbed from. It also doesn't have the special low-level air vents that the finished car will have to help warm the cabin. My driver is going to be Fred Martin-Dye, Ultimate Series Project Leader but also a part-time GT4 racer. Not that today's gentle drive requires much of his on-the-edge skills.

The first run is without the system. I've been in cars without screens before, but the Elva's lack of glass still feels odd looking forwards and over the humps of the front arches. We head down Snetterton's pitlane the wrong way - McLaren has paid for an exclusive - and then do a U-turn before heading along the pit straight at graduated speeds: 30mph, 50mph and then 70mph. At the far end we stop and wrong-slot into the pit lane from the other direction.

It feels as cold and windy as you'd expect in something without a windscreen and not wearing a helmet, and although there is a promising rasp from the exhaust Martin-Dye is short-shifting well before it has the chance to sound properly interesting. After two of these mini-laps we return to the pits, and I'm feeling pretty happy not to be experiencing the Elva at higher speeds or longer distances without a screen.

Next follows 20 minutes of tea and biscuits while McLaren's technicians remove the blanking plate in the bonnet and install the prototype AAMS. Even under the camouflage it doesn't look like the most glamorous system, with the Gurney flap obvious in my eye-line looking forwards; apparently the production system will motor downwards at very low speeds to improve frontal visibility and when the system doesn't do anything. Then it's exactly the same drill again - out, U-turn and along the pit straight.

It works much better than I'm expecting it to. My instinct was that AAMS would reduce airflow from the front, but with 30mph showing on the speedometer it pretty much removes it entirely. I'm experiencing windscreen-appropriate levels of insulation without a windscreen. Martin-Dye accelerates to 50mph and there's now some buffeting, but the cockpit is still calm enough for us to converse in normal tones. By 70mph it's getting breezy, although much less than it was without protection, and I find I can reach upwards and feel the boundary between the calm air and the full slipstream - just as you could putting your hand above the windscreen rail in a conventional roadster.

Back at the pits Andrew Kay explains that the plume of air created by AAMS is always the same shape, as the air feeding the system is the same speed as the oncoming air. As speed increases, the occupants will feel an increase in turbulence, linear with vehicle speed. McLaren is aiming for occupants to be comfortable at around 70mph - but inevitably the buffeting will become more intense at greater speeds. "If you're going to travel faster than that - or use the car on a track - then we think you're going to be wearing a helmet," Kay says. If drivers do opt for a lid, they will be able to manually disable AAMS via a button in the cabin. Otherwise the system remains active at high speeds, and - much like the roof controls on a convertible - once rolling there will be an upper limit beyond which the switch will not function so as to protect the mechanism.

But first impressions are that within those limitations it works impressively well. It's hard to think of a better commitment to reducing weight than a windscreen made of air. I'm still very glad the Cayman has one made out of glass for my three hour journey home.

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