Floors and Diffusers – The basics explained

An F1 car is a complex vehicle, a lot of emphasis is placed on the things we can see, the wings and bodywork. Sometimes we can talk about less visible items such as engine, gearboxes, suspension or even electronics. But perhaps the least visible and detailed part of the car is the underbody. The floor and diffuser, that together create nearly half the cars downforce, for almost no drag. Underbody aerodynamics have been the key to F1 car’s ever faster laptimes. All we ever see of the underbody is the exit of the diffuser and sometimes, if seen from a low angle, the step under the cars floor. To aid explanations in my other articles on underbodies, I have summarised and simplified what the underbody consists of.

Reference plane

Reference plane: Red

This is the datum for the cars dimensions and is effectively the lowest part of the cars floor. When the old flat bottom regulations, dating back to the banning of ground effects in 1983 were revised in the wake of Senna’s 1994 crash, the floor has had to have a step along its length. So we see the stepped shape of the car in frontal profile, with the reference plane sitting lowest in the middle of the car. This step cannot be wider than 50cm or narrower than 30cm, the reference plane must by flat and run continuously from behind the front wheels to the rear axle line. The Reference planes leading portion, also forms the splitter, also known as the T-Tray or Bib.

Step plane

Step Plane: Yellow

Above the reference plane is the step plane, this is effectively the underside of the sidepods. This must sit 5cm above the reference plane. Again the surface must be flat and run from the complex regulated bodywork zone around the front of the sidepods to the rear axle line. A large clearance is mandated around the rear wheel to prevent teams sealing off the floor against the rear tyres.

Step or Transition

Step: Orange

In between the reference plane and step plane, is the step itself or transition. Simplistically there must be a vertical surface in between these two planes. Any intersections of these surfaces are allowed to have a simple radius to be applied, with a 2.5cm radius on the step plane and a 5cm radius on the reference plane.

Plank

Plank: Brown

Not considered part of the floor for measurement purposes, the plank is a strip of wood placed under the car to enforce a minimum ride height. The FIA technical term for this part is the skid block, although this term is rarely applied. Holes in the plank allow the cars reference plane to sit directly on the FIA scrutineering jig, for legality checks over the course of a GP weekend. Titanium skid blocks are allowed to be fitted in certain places in the plank and their wear is measured to ensure a car is not grounding from excessively low ride heights.
The plank can be made in two parts to make removing the floor easier, bit the front section must be at least 1m long. This must be made of a material with a specific density, to prevent excessivley heavy or hard planks producing a performance benefit. Typically the plank is wood based, eiterh jabroc a laminate of beechwood, although more exotic blends of woods and resins not unlike MDF have been used. The plank is 30cm and 5mm thick, any holes made into it must conform to a FIA template.

Diffuser

Diffuser: Yellow

A purely flat floor would probably produce lift rather downforce, so the rules have allowed a diffuser to be fitted to the rear of the underbody since 1983. Before that date there were no rules demanding floor dimensions and diffusers were the full length ground effect tunnels that typified the wing cars of the late seventies and early eighties.
A diffuser creates downforce by creating a pressure differential, with low pressure beneath and higher pressure above. The larger a diffuser is, the more expansion ratio is has, thus more potential to create downforce. Diffusers were limited to a simple 100cm width, 35cm length and 17.5cm height from 2009. Then for this year the height further reduced to just 12.5cm. This massively reduces the potential of the diffuser to create downforce compared to the previous rules. Diffusers are allowed to have fences, but the fences and the diffuser itself must not form undercuts when viewed from below. Which is why we see the simple vertical fences and jelly mould curvature.

Other rules around floors
Overriding all of the above rules are broader regulations covering holes and flexibility. No unsprung part of the car can be visible from below the floor. Typically this means anything, but the suspension and additionally the wing mirrors. This means that no holes can be made into the floor to let flow in or out. The underbodies surfaces are termed bodywork within the rules, there is no term ‘diffuser’ or ‘wing’ mentioned in the rules. Just as with any bodywork in the rules, these parts are not allowed to move or flex. For the floor in comparison the wings, there are few deflection tests commonly carried out, the main one being the splitter deflection test.

Exploitation

Double Diffuser

Over the past two year these rules have been exploited by teams. Firstly the interpretation of holes in the floor and continuous surfaces. This lead to the openings that allowed double diffuser. Effectively the step formed two separate, but individually continuous surfaces, allowing airflow to pass up above the step plane into the upper deck of the diffuser. This rule has been clarified for this year and a single continuous surface must be formed under the floor.
Additionally the flexibility of the splitter has been brought into question, teams were believed to be flexing the splitter upwards, new more stringent tests were introduced in 2010 to stop this.



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Red Bull – Preseason front wing update

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In the last pre-season test at Barcelona, Red Bull introduced their updated front wing. Like the rest of the car, this is an evolution of what has gone before. Albeit based on the complex late-2010 set up, with 3-4 elements in differing areas across the wings span. It’s the endplate and cascade that have changed the most. While the flaps take some inspiration from Renaults early 2010 shape.

Firstly the shape of the main plane remains the largely the same, While the 2 flaps also retain their extra slot on the outermost span. This creates a four element wing nearest the endplate, this section gains a gurney to help keep flow attached. Meanwhile the inboard ends of the flaps follows Renaults idea from 2010, as they are feathered. This is visible by the space created in between the wing tips, Looking at the set up intuitively, the flaps remain loaded, but their tip vortex would be broken up into two smaller less powerful trails. Which still creates downforce, but may be less disruptive to the flow along the centre of the car.

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The cascade is slightly revised, again with the two conjoined winglets. Now the larger outboard winglet is curved near the join with the endplate, creating a deeper angle of attack and correspondingly a larger vortex spilling of the wingtip to direct airflow around the tyre.

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Mounting the new cascade is a revised endplate vane, Red Bull merge this organically into the rest of the outboard wing shape, but in principle this is the same as the vanedendplate-less set up of most other teams. The vane is slightly more outboard creating a wider cascade, probably for both more downforce potential and also to move the aforementioned vortex further outboard.



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McLaren preseason rear end update

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McLarens pre season has been thwarted by unreliability and apparently aerodynamic problems. The team have run a succession of exhaust designs (at least 4 so far) and time has been spent mapping the cars aerodynamics with sensor arraysflowviz. While the exhaust solution has yet to be finalised (I have a forthcoming post on this), The last days of the Barcelona test allowed the team to introduce some new parts around the back of the car and a new front wing.

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Their new rear wing sports vanes along its lower edge. These are legal as they sit in a small 5cm loophole zone in the bodywork regulations. This area has been exploited before by Red Bull on the RB5 and subsequently Toyota and Williams in 2009. Sauber also have much smaller solution on their current car. Having bodywork in this area effectively extends the diffuser sidewalls by some 30cm, which helps maximise the expansion ratio of the diffuser for more downforce. Such is the shape of the flow out of the diffuser, the bodywork needs to be vaned to allow the flow to expand. McLaren have formed four vanes into the allowable area. For the test, the rear-pointing exhausts were lined up with these vanes, thus the exhaust flow (red) will be routed by these vanes, accelerating flow inside the diffuser for even more downforce.

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McLarens problems also delayed the testing of their DRS (Drag Reduction System) adjustable rear wing. To feed the hydraulics to the actuator mounted inside the middle of the rear wing, the team have routed a non-structural pylon up from the gearbox to the wing. This houses the hydraulic cables & sensor wiring and does little to support the upper rear wing.

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With the weather warming a little during the relatively cold Spanish tests, the team were able to reduce the size of the engine hot air outlet for the last test. In the middle of this outlet is the oval gearbox oil hydraulic cooler outlet. Leaving the rest of the outlet for general sidepod cooling



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Ferrari F150 – final pre-season update analysis

For the final test at Barcelona, Ferrari brought the long awaited revisions to the F150 (although the cars name has frequently changed, I’ll continue to use this title). This consisted of a revised wings, new sidepods and new exhausts. It was Ferraris assertion at its launch that the car would have evolved aero and specifically different exhausts before the first race. So despite some people suggesting the changes are copying their rivals, it’s more likely that different teams have converged on the same ideas.

The front wing pylons have been lengthened to form turning vanes

At the front the main changes are to the front wing and its supporting pylons. These pylons have been extended in a similar manner to Renaults ideas from 2009-2010. Since 2009 the rules on vanes and bargeboards around the front of the car have been severely restricted. The rules mandate a limit on the cross sectional area for the front wing mounts, Ferrari have therefore extended their wing mounts, but also narrowed them. Thus meeting the rules and still providing the car with some aero advantage.

3.7.2 Any horizontal section taken through bodywork located forward of a point lying 450mm forward of the front wheel centre line, less than 250mm from the car centre line, and between 125mm and 200mm above the reference plane, may only contain two closed symmetrical sections with a maximum total area of 5000mm2. The thickness of each section may not exceed 25mm when measured perpendicular to the car centre line.

A shapelier endplate has been added to the cascade

Details of the front wing have also changed, in particular the endplates, these now feature a more sculpted vane on the footplate. As well as the endplate fro the main front wing, the inner endplate for the small cascade mounted to it is also now shapelier. The small endplate now having a distinctly flared shape, aimed at redirecting flow inside the front wing.

New sidepod inlets and a blown diffuser are the main changes to the F150

Along the middle section of car, Ferrari have produced a new sidepod, initially similar to the launch specification. But the main radiator inlet is now reshaped, being much more of a “U” shape and smaller with it. The sidepod inlet retains the distinctive protruding upper lip. I was told by Nick Tombasis that this was an aero feature and not a structural one (i.e. side impact crash protection). Curiously this lip features a removable panel to allow for cooling. Being so far forward of the radiators its hard to understand how heated radiator flow could be ducted into the small exit, or perhaps some electronics of KERS components are sited within this hollow section.

Further back along the sidepods, the new exhaust system is routed along the floor and into an open section of floor in the outboard 5cm section of diffuser. This is the same solution as Red Bull has come up with, as already explained this was an obvious area in the 2011 rules for exploitation, as I even proposed this location in my pre-season trends and solutions article. Ferrari route the flattened exhaust inside heat shielding along the floor. The blowing effect of the exhaust passes under the floor for a more effective method of blowing the diffuser. Ferrari wanted to produce the exhaust in glass ceramic composite (such as Pyrosic), but this request was denied by Charlie whiting who clarified the exhaust must be made of materials on the permitted materials list. Such composites, while allowed to be used in some exceptions, are not allowed to be the actual material of the exhaust pipe.

Also the middle of the car gained revised wing mirror pods.  these appear to be split into upper and lower mouldings. Presumably to allow sensors or electronics to be fitted inside the pods during testing or free practice.

Lastly the rear wing has also been modified with a smaller flap. Several teams have switched their rear wing to smaller flaps, at first this is counter intuitive to the exploitation of the Drag reduction system (DRS) also termed the adjustable rear wing. As one would initially deduce that adjusting a larger flap would reduce drag by a greater amount. However, shallower flaps effectively flatten out when the leading edge is moved 50mm from the trailing edge of the main plane (50mm is the maximum slot gap allowed for the DRS). Thus they produce very little load and therefore little drag.



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Mercedes W02 – New front wing analysis

After three tests Mercedes produced their updated front wing at Barcelona today.  Elements of this wing have been seen on the Launch specification wing, such as the extra slot made in the main plane.  The wing (main plain and flap) itself is largely similar to the launch spec wing, while the endplate and cascades have been changed.  Mercedes front wing design harks back to the Brawn BGP001 of 2009.  The BGP001 pioneered the idea of the endplate-less wing.  With the wider wings for that season sitting as far out as the width of the tyres, the contemporary endplates before that time, no longer worked to direct  flow inside the front wheel.  Brawns aerodynamicists reshaped the wing to best redirect flow around the front wheel and effectively removed the vertical endplate and replaced it with vanes. These vanes are there to both redirect airflow and to meet the minimum bodywork rules.  To aid downforce in the area inboard of the front tyres, Brawns designers added a free standing winglet, known as a cascade.  Through out 2009 and 2010 BrawnMercedes developed the wing, but retained the two element layout.  The new wing retains all of these features to some extent.

Mercedes W02 launch spec front wing

The free standing cascade has been retained, but this is now aided by a small additional winglet inboard of the main winglet.  The split between the two winglets is inline with the inner face of the front tyre. This is not coincidence, as the two winglets seek to create tip vortices trailing both inside and outside the front wheel to set up  the airflow structures dividing either side of the front wheel.

Detail changes to the endplate include a small cut out in the trailing edge and a complex leading edge.  The raised section of footplate (the horizontal outboard section of endplate) cleverly features a tiny vane inside.  this vane curves outwards and was a feature of Mercedes 2010 wing.

Mercedes have not gone as far as a full three element wing, across its full width.  Instead they have divided the wing into three sections across its width.  Near the endplate, the wings leading edge rises, this reduces the angle of attack and amount of load this area of the wing creates.  This is because the area in front of the tyre is not a good location for creating downforce, as the tyre sits directly downstream of the wing.  The inner span of the wing nearest the cars centreline is also much reduced in chord length and angle of attack, again downforce does not want to be created here, as the wake will upset airflow over the middle of the car.  Thus the middle of the wing span, which sits both away from the tyre and the centre of the car, is the area where most load is created on the wing.  We can see this section has both the greatest flap size and angle of attack.  To keep the airflow attached to the wing with its more aggressive geometry, Mercedes have moulded a slot into the main plane.  Higher pressure air above the wing enters the slots and helps keep the flow attached to the wings underside.  This section of wing is therefore a termed a three element (two slot) wing.  This creates downforce where its most efficient to do so, maximising downforce for the minimum drag and downstream disruption.



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Williams – Rear wing mount and reports of lateral movement

Williams have a unique rear end set up, with the rear wishbone and rear wing mounting to the same pylon. In early tests other drivers and media suggested the rear wing moving laterally and this was related to the lack of stiffness in this pylon. However Sam Michael has refuted these claims and looking at the rear wing set up, you can see where the movement came from.

Due to its low gearbox casing, the rear leg of the top rear wishbone mounts to a vertical metal extension of the gearbox. The structure then continues vertically in the form of a carbon fibre strut, which mounts the top rear wing. Normally teams will also support the beam wing with sizeable mount to the top of the rear impact structure. As part of Williams ‘waisted’ approach to structures at the back of the car, the beam wing ‘floats’ above the impact structure. Thus aero loads from this device pass upwards through the endplates into the top rear wing and consequently into the vertical pylon back to the chassis. In early tests the endplates were not able resist the lateral loads the beam wing exerted on the assembly and as a result the lower of the wing moved laterally. Williams had already accounted for this with a small metal stay (illustrated – yellow) between the vertical pylon and the beam wing. Such were the cornering loads around Valencia, this was unable to steady the wing. So Williams added links from the endplate to the diffuser. This greatly reduced the movement and no negative comments have merged about the structure around the back of the car since.

Renault R31 – Cooling solution and diffuser performance

Renault are not only unique in their exhaust location, but also their sidepod cooling set up. Its possible that the two solutions are related.

Teams have to find the most efficient way to vent hot air from within the sidepods. This air has to pass through the radiators and coolers, as it passes from the sidepod inlet to the tail of the coke-bottle shape. In order to keep the car as slim as possible for reduced and drag and better airflow to the diffuser and beam wing, teams adopt different cooling outlet solutions to work with the other aero flow structures around the car. In Renaults case the majority of the outlet area is in three places: a tall narrow outlet above the gearbox and two low and wide vents either side of the gearbox. We can see the gearbox oil cooler within the upper outlet, so some of its volume is used for venting this heat. Reducing its ability to vent air from the sidepods.

Renault appear to have chosen the two lowwide outlets in order to boost airflow to the beam wing. The compromise in doing this, is the airflow over the diffuser. Airflow over diffusers might be considered as unimportant, as its the flow underneath creates the low pressure and hence downforce. But with a restricted diffuser height , the use of directing high energy airflow over the top of the diffuser and its trailing edge gurneys, helps the airflow beneath. Effectively making the diffuser act like its larger than it is. With other teams, they use the exhaust gasses or very narrow sidepods to direct as much high energy flow as possible over the diffuser. In Renaults case, the airflow running along the floor does not flow directly over the top surface of the diffuser, as these wide vents are in the way. Some people have suggested the teams are directing the heated airflow from within the sidepods out of these vents and over the diffuser for greater aerodynamic effect. However the reality is different, the air coming out of these vents will be of low energy, having passed through the various cooler matrices. Thus its effect in aiding the diffuser is much reduced.

So why have Renault thrown away some aero gains in this area? Probably because of the exhaust solution, As the flow under the diffuser is accelerated by the exhaust gasses passing under the floor, the diffuser does not need the effect of airflow blowing over the top. Thus they moved to the sidepod outlets to this area and played better airflow over the beam wing.

So far no other team have gone for low wide cooling outlets, but equally contrary to the rumour mils no teams has adopted front exit exhausts either. It will be interesting if any team follows Renaults solution in either of these areas.

HRT F111 – Launch & Analysis

With just a day and half of pre season testing left to go, HRT finally unveiled their 2011 car, the F111. Possibly the team with the least budget and smallest technical resources, their efforts to find a chassis partner in the past year have failed to deliver. Thus its been left to the teams Technical Director Geoff Willis to build up a design team to rework the 2010 F110 chassis into a 2011 legal car. Willis worked with Paul White, a designer with long F1 experience in both teams such as Jordan and Honda, as well a stints as a freelancer at Super Aguri. Construction of the car has been sub contracted to the usual range of F1 industry specialists. Then the cars then assembled at Kolles workshops in Germany (Greding, near Ingolstadt).

I had already been told by Colin Kolles that the car is based on the 2010 car, with the only major structure carried over being the top half of the monocoque. But visually the the car is a mix of new details and shapes from the old car.

Certainly the nose appears different at first. But the strakes, camera pods and the revised wing mounting pylons do a lot to disguise the overall shape, but the nose cone shape itself seems to have been carried over. Beneath is a front wing that is all new, the main plane is larger and the flaps are simpler being a pair of elements stacked above each other. The cascades are also new, which along with the endplates appear to be inspired by the Brawn BGP001, Paul White being a long time Honda designer, perhaps brought these ideas to the team.

In general monocoque shape and with it the roll hoop and front suspension are visually inseparable from the 2010 cars design. Equally the front brake duct design appears to be carried over. Aside the tub, the bargeboards are new, being quite tall pointed designs taking over from the smaller serrated versions. Then the sidepods are largely new, albeit with inlets similar to the F110, possibly due to the crash structures being in largely the same places. But the sidepods undercut is far more pronounced and the coke bottle shape, now much lower and sporting a low exit for the exhaust pipe. HRT maintained their periscope top exit pipes through out last year and never developed a blown diffuser.

Allowing the sidepods to be slimmer is a Red Bull style bulged exit above the gearbox. This also highlights the vestigial shark fin on the top of the engine cover.

At the tail a new rear wing is complete with new endplates and a central mounting pylon. This in turn shows that the rear impact structure has been redesigned to both accommodate the Williams 2010 gearbox, the wing mounting pylon and also the differing needs of a single diffuser over the 2010 double diffuser. No detail of the diffuser is clear as yet, but as the exhaust appears to be simply a set up to blow over the diffuser, the floor is not expected to hold any surprises.

As the car sports Williams gearbox technology and the gear case from 2010, the car is duty bound to have similar inboard suspension geometry and pushrod springdamper actuation. In order to package the new gearbox, HRT will have had to alter the rear suspension linkages and possibly the uprights. Being a well developed and contemporary aluminium cased gearbox, the Williams rear is likely to be lighter than the outgoing Xtrac gearbox. Although HRT did not specifically suffer with hydraulics unreliability last year. The Williams set up is also likely to be far more reliable and well package compared to the 2010 set up. This weight and design resource saving fro the Williams rear end will no doubt aid HRT in designing the rest of the car and getting down to the right weight distribution and still have the small amount of ballast to play with.

As with the Virgin who also run the Cosworth engine, no KERS is to be installed in the car. Thus these two teams use a slightly different spec of engine to Williams, whose engine is reconfigured slightly for the KERS installation.

In summary the upgrade to the car appears to be a logical and quite far ranging upgrade, possibly no less different year to year than other budget limited teams. it’s a surprising fact that although teams make th ePR headline that the car is all new and only something mundane like the wheel nuts are carried over. Most teams do in fact re-use a lot of componentry from older cars. Looking at their parts list for the current car will see model numbers for some parts dating back ten years.
In 2010 the HRT car kept pace with Lotus and Virgin through out the year, albeit still slower but the gap never increased significantly. While their rivals had many updates through the year, with big steps at Silverstone, HRT were able to develop the set up of the car to maintain the gap. Notwithstanding the discontinuity of drivers. A big update from a pair of respected engineers should allow HRT to keep up to the tail of the pack. However, testing suggests Lotus have made a larger step up the grid in pace than Virgin. It may be that HRT only have one team to fight with this year.

McLaren MP4-26 exhaust – is the “U” bend a Front Exit?

 

MP4-26 - the "U" bend is visible between the diffuser and suspension

McLaren lead the way with innovations in 2010 with the F-duct, but they were late to debut their double diffuser and blown diffuser. In 2011 McLaren appear to be right on the tail of this year’s novelty the front exit exhaust.
So far in testing, the MP4-26 has been seen completing a diligent aero programme with the car appearing with two different format exhausts. One conventional set up which blows over the diffuser and another which appears to have a “U” bend in the system. This latter solution is believed to be a front exit exhaust as used by Renault (http://scarbsf1.wordpress.com/2011/02/01/renault-r31-front-exit-exhausts-fee-explained/).

But as yet there is no sighting of the actual exhaust outlet.

Last year teams started to blow the exhaust over or through the diffuser to produce more downforce. With the method of opening the front of the diffuser up and letting the fast moving exhaust blow inside the diffuser, being the most effective route for more aero grip. Rule changes for 2011 prevented teams opening the front of the diffuser up (aside from a 5cm outer section of floor). So teams are faced with either blowing less efficiently over the floor or finding a new way. Renault have exploited another way, by leading the exhaust forward and pointing it under the front of the floor. Blowing the exhaust at the leading edge of the floor effectively creates more flow under the floor, which in turn creates more downforce. This front exit is a good aero solution, but packaging the duct from the main exhaust to the front of the sidepod is difficult due to the space constraints within the sidepod and heat rejected from the exhaust duct itself.

MP4-26 the conventional exhaust exits at the rear and blows over the diffuser

With McLaren’s conventional exhaust the four pipes merge into the collector and the secondary exhaust pipe points backwards to blow flow over the ramped outer section of diffuser. This set up has been used on and off consistently through the test. It also appears to the baseline configuration. As a lot of the aero tests using pressure rakes, flow-viz and long runs, are being completed with the conventional exhaust.

MP4-26 with the conventional exhaust exposed, the "U"bends crease in the floor can be seen

However other tests have been completed where the sidepod is revised. The sidepod features a bulge at the rear of the coke bottle, the bulged section appearing to house a revised exhaust system. Looking from the rear where the normal exhaust outlet can be seen is instead a “U” bend of exhaust tubing. With this set up the exhaust exit cannot be seen. Although several photos of sensors and cabling around the sidepodsplitter have prompted some fans and media to propose they are exhausts. In my opinion no photo as yet exposed the real exhaust outlet. With both systems, the rear of the floor and diffuser are the same.

MP4-26: This is how the "U" bend exhaust might look

Knowing the “U” bend system exists, I’ve tried to find proof for a front exit. One bit of evidence is on the launch car, which was initially unveiled without bodywork. Clearly a lot on the car was missing, but the floor appears definitive enough and just below the normal exhaust collector was a crease in the floor. This niche moulded into the floor is in the same location as the bulge in the sidepod when the “U” bend is run. Looking at its shape, I’d suggest this is where the collector and secondary pipe sit when the “U” bend exhaust is fitted. We can roughly predict that the collector sits further outboard and a little lower. The secondary pipe then curves inboard and then forward under the branch of four primary pipes (see illustration). Of course from here we don’t know where the exhaust routes, so we can’t confirm if it does blow back under the floor.

MP4-26: this is the aero rake used to measure flow accross the floor

Amongst the various aero rake tests McLaren have run, some tests features a huge array of pressure sensors in a rig mounted behind the diffuser. A later test had a simpler rig, which passes the floor ahead of the rear wheels. Initially this system ran with a conventional exhaust, and then later the rake was run with the “U” bend. I believe the rake was used to look at the pressure distribution under the floor. The two runs were used to map the different between the conventional exhaust and the improved flow of the front exit. So this suggests they are running some form of front exit.

MP4-26: the aero rake and "U" bend being run simultaneously

So where is the exit? I’ve looked at every picture I can find of the MP4-26 and I have yet to see any evidence of the front exit. I do believe its there, hidden behind the bargeboards somewhere below the sidepod inlet, or routed inside the splitter and blowing backwards. Other journalists at the Jerez test have confirmed some form of exhaust exit appears to be in there, kept out of sight both by other bodywork and the huddle of mechanics around the front of the car with the portable blowers to keep things cool when it returns to the pits. Also I’ve heard that the switch for one system to another takes 2 hours, which has reduced the McLarens track time.

But until we see a photo of the exit we can only speculate.

Notes:

This is not an exhaust

 

This is not an exhaust

 

This is not an exhaust

Red Bull RB7 – Sidepods and Cooling

When the Red Bull RB7 was rolled out, it was clear the car was a neat development of the RB6, but was not an innovative car. As with well developed cars like this, its details are well thought through, a particular case is the sidepod design. If you look at the RB7s sidepods, from the radiators back they appear to slope away to nothing. This leaves the distinctive flat floor and open area ahead of the rear wheels. This creates an obvious aero gain, but how is cooling achieved with such a tight design?

Firstly the sidepod forms the main blockage to the rear wing and diffuser. We’ve seen several approaches this year to manage the airflow around the sidepods to the rear of the car. In each case the team are trying to get the best and most direct airflow to the top of the diffuser and beam wing. As the better flow these devices receive, the more downforce they produce and the less drag is required from a larger rear wing.

Since the 2009 aero rules sidepods are extremely limited in the openings they are allowed, so most of the flow has to exit between the rear wheels. Normally sidepods send the heated air from the radiators back through the tapered rear (known as the coke bottle, due to its shape). In a simple sidepod this means the coke bottle ends with an opening and the hot air passes out and over the diffuser. However this makes the tail of the coke bottle unduly wide, which creates a blockage between the rear wheels and blocks flow over the diffuser. Red Bull discovered with the RB5 that the radiator airflow can pass up towards the centre of the car and exit above the gearbox in a bulged opening. This keeps the tail of the coke bottle nice and narrow.

With the RB7 Red Bull have taken this a step further, there is no appreciable exits in the tail of the coke bottle, so nearly all the radiator airflow ends up passing through the bulged outlet. This means the coke bottle is the slimmest and simplest of all the cars on the grid. Clearly the huge floor area and exposed beam wing show how easily airflow can reach the rear of the car. The concession Red Bull has to make for this benefit is the increased blockage in front of the rear wing. But as they are aiming for downforce from the more efficient diffuser and beam wing, the rear wings effectiveness is not such a concern. Other teams have similar low swept coke bottle shapes, but each of them still exploits some cooling exit at the back of the sidepod. Given enough testing a fully enclosed sidepod with the central bulged outlet could be copied.