Toro Rosso STR14: Technical analysis

Toro Rosso has relied more heavily on parent team Red Bull for its 2019 F1 car design. Will that, plus an improving Honda power unit, help them climb up from last year’s ninth in the constructors’ championship?

In his first article for RaceFans, F1 technical expert Craig Scarborough (@Scarbs) analyses the Toro Rosso STR14.

Toro Rosso have been noted for their innovation in car design and for running an autonomous design team separate from Red Bull for the past 14 years.

With the release of its new car for 2019, the STR14 shows a shift in the balance between its innovation and independence, as the team adopts more ideas and hardware from Red Bull. Its STR14 reverts to some older suspension ideas, rivals’ sidepods concepts and the entire Red Bull Honda rear end.

Is there enough new on the Toro Rosso to win in the battle of the midfield?

What’s new?

Having run the Honda power unit in 2018, the team acted as an incubator for its sister team Red Bull Racing. Honda’s performance has been improving under the co-operation of Red Bull Technologies (the overarching technical operation for both teams).

Now both teams will run the Japanese power plant and the RBT gearbox package with it. This will be the first time Toro Rosso has adopted the full RBT rear end, having only run the gear cluster before. It will now race with the RBT gear cluster, casing and rear suspension. This means that much of the engineering at the back of the car is completed outside of Faenza, leaving the smaller Italian design office to focus on the front half of the car.

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Front suspension

With the launch images being just digital representations of the new car, care needs to be taken with the aero add-ons, but the structural changes are safer to accept as accurate details. One of the key changes from 2018 to 2019 is the front suspension, which has reverted to a pre-2016 layout for the wishbones, where they are mounted lower down.

For the last two years STR ran high-mounted wishbones, raised to aid aerodynamics under the car. These required the top wishbone to be mounted to the wheel via a swan-neck camber plate. This emerged through the brake duct and pivoted high above the wheel rim. With the wider wheels and tyres introduced in 2017 this set-up could still produce good geometry, as demonstrated by Mercedes who also ran this layout.

Now the wishbones are still mounted relatively high at the chassis, but slope down and meet the upright inside the wheel, without the need for the exposed mounting. The switch back for 2018 is not driven by regulation, so the change will either be aero or tyre related.

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Sidepods

Being a more restricted in resources than the top teams, last year’s late addition of the Halo diverted resources from other aspects of chassis design and as a result the STR13 ran conventional sidepod inlets. It has been increasingly attractive to repackage this area to gain downforce from better airflow over the diffuser, a direction Ferrari led in 2017, which was followed by Haas, Williams and Red Bull last year.

This change in sidepod design – termed a high-top sidepod – repackages not just the sidepod, but the side impact spars within the sidepod front. The side-mounted crash tubes must be fitted within a small height window. The sidepod bodywork is also capped to a maximum height. Together, the sidepod inlet must dodge the side impact spar and still fit under the maximum bodywork height.

Ferrari found that by lowering the upper side impact spar and moving the inlet above it, filling the maximum allowable height, there is not only good airflow into the sidepod, but the undercut created below the inlet could be larger. This pushes airflow down around the sidepod, over the floor to the diffuser, creating more downforce.

Toro Rosso have now followed this high top sidepod concept, with a neat forward-facing inlet, which has extra vanes formed around it to direct airflow into and around the sidepod.

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Mirrors and vanes

Allied to the change in the sidepod packaging, new rules for mirrors and bargeboards have led to some new aero solutions for the sidepod area.

The rear-view mirrors now need to be mounted further from the cockpit, to give the driver a better rearward view, and are limited to two mountings. Each of the STR14’s mirrors are therefore in the new regulatory position, with the two mounts are manipulated to not just support the mirror pod, but to form aero surfaces. Particularly with the inner mount spanning across to the cockpit area, which is then used as an aero device to direct airflow over the sidepod top.

One feature on the mirrors missing from last year are the vented pods, which was another concept copied from Ferrari. Toro Rosso adopted these mid-season in 2018, as the air being ducted through the mirror housing was found to reduce drag and direct airflow downstream more accurately. These may be fitted to the car in testing, but it raises the question of whether this style of mirrors is still legal within the new rules.

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Also in this area, the array of vertical vanes mounted to the sidepod last year are restricted in height for 2019. Thus, the car was presented with a single vane mounted high enough rearwards to be at the full height. What’s unusual is that the single vane is mounted to the edge of the sidepod with a simple horizontal vane. This is a clean and neat solution, but as with the un-detailed floor-edge and bargeboards seen on the launch images, they are likely to become a lot more complex as the car gets to race. With the simplified front wings, it’s these areas that will be increasingly used to control the airflow along the car until they are likely to be banned for 2021.

Honda

From its disastrous re-entry to F1 four years ago, the manufacturer has come a long way with power, reliability and packaging. 2018 was still a public test programme, with the inevitable power unit failures, but when compared to Renault, the RA618H was a close match. Even from the start of testing on 2018 it was clear Honda with the Red Bull as partner was an improving offering.

Its fair to say that Toro Rosso won’t have a chassis and power unit to match Mercedes or Ferrari, but its battle is in the midfield with the Renault and customer Mercedes units. Even with its evolution, the Honda remains a tidy power unit package, with its split turbo and reasonable cooling demands. It’s more than possible that the Honda package has been tidied with the Red Bull design team changing layouts to suit chassis and aero requirements. These details and their effects that will be interesting, as McLaren’s ‘size zero’ demands hampered Honda’s original power unit concepts and Red Bull have been uncompromising with ERS packaging in the past.

Last year Toro Rosso kept the twin intercooler package raced since these new turbo engines came into F1 in 2014, so a revised cooling package inside the impressively small sidepods is likely this year, given the resources freed up by the Red Bull partnership.

Red Bull package

There’s two effects to the new Red Bull listed parts agreement, firstly being tied to aspects of the rear end design from the RB15, then the resources being freed up with the design office at Faenza to do other things.

The first could be seen as a positive or a negative, taking the entire Honda and Red Bull rear end, fixes Toro Rosso to a lot of predetermined factors, rear suspension geometry, wheelbase and even rear wing mount design. With good communication, cooperation and the success of the Red Bull Racing package, on balance this must seen as a good thing for the team.

This means a big chunk of the cars packaging is supplied by RBT, this means that from front to rear they will be supplied, the battery and control electronics package that sits in a recess under the fuel tank. Then the Honda engine itself, with any Red Bull-led packaging changes.

At the rear the Red Bull rear carbon fibre casing, which houses the gearbox and rear suspension. What constitutes the rear suspension isn’t clear at the stage, there’s the mounting points moulded into the casing, the wishbones and driveshafts, the outer upright and then the inner working of rockers/dampers/springs.

Where the demarcation between RBT and Toro Rosso lies will only be evident when the see the car stripped down in Melbourne. Beyond the gearbox case, the rear impact structure has to be an Toro Rosso design by regulation, while the rear wing mounting point is fixed into the gearbox design.

Video: Toro Rosso STR14 revealed

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