History: Periscope Exhausts

Following the meeting of the Technical Working Group, the FIA have agreed to mandate periscope style exhausts from 2012. This has been in an effort to rid the sport of exhaust blown diffusers, a trend that has dominated aero development in 2010 & 2011. While initially it was the FIA’s intention to move exhausts to the rear of the diffuser, the teams preferred to route the exhaust out of the top of the sidepods “periscope” style. This solution is far more aero neutral and prevents teams developing new complex exhaust routing to gain what little aero advantage there is from the rear exit. Also it benefits the engine suppliers who don’t have to retune their engines for long secondary exhaust pipe lengths.

It’s interesting to note the history of the periscope exhaust, as this was at first a retrograde step in aerodynamic development. Historically F1 cars ran their exhausts straight out of the back of the car. Only the introduction of ground affects and turbo engines forced a packaging rethink to exhausts routing through the top of the engine cover. When ground effects were banned and teams sought to find some aero gains at the rear, it was Jean Claude Migeot, who was then the head of aero at Renault, doing the exhaust blown diffuser solution in 1983. This trend continued through the late nineties, when F1 engines were normally aspirated and the V10 format became the trend, as were ever higher rev ceilings. Teams were finding the aerodynamics sensitive to throttle position and slowly they started to move the exhaust away from the diffuser kick line and towards the trailing edge to reduce this sensitivity. This necessitated quite long secondary exhaust pipe lengths (the single pipe section leading from the multipipe collector). This passed the exhaust in close proximity to the gearbox and hydraulics as well as the rear suspension, which at the time was starting to be made form carbon fibre. Back in ate nineties materials were not as advanced as they are now and heat resistant materials were not as effective.

In 1998 this forced Ferrari into a rethink of the exhaust solution. Head of Aero at Ferrari at the time was Willem Toet, he explained to ScarbsF1 how the periscope came to be. He starts with an honest explanation “I was sort of forced into the periscope exhausts at Ferrari”. At the time Ferrari were developing their 90-degree V10 engine, seeking to find higher revs to regain the power lost from the more powerful V12s. This engine developed was the catalyst for the move according to Toet “Long pipes didn’t suit the engine at all so we needed to go short”. Unable to create the long secondary pipes the traditional rear exits were unviable, however their first solution was not immediately the periscope, “We found the best solution, quite an aero gain at the time, was to exit the exhausts out of the sides of the bodywork beside and ahead of the rear tyres with an extra panel to protect the tyres from hot exhausts. That’s how the car was launched”. This solution met the initial aero and engine development targets, but was not without its problems, as Toet adds “The materials available at the time weren’t so advanced and we had mechanical grip and driver feel problems associated with the rear suspension, still steel on the Ferrari in those days, deforming under temperature. We were forced to abandon this due to the handling feel of the car”.
Again the workaround was not the periscopes “We went to a simple blown diffuser but the performance loss was “noticeable”. We then tried a short pipe leading into but not connected to a secondary pipe but had some fires due to exhaust flame outs off throttle that then caused problems”. With other solutions finally exhausted Toet shifted to an up and out exhaust solution, which we tend to call periscopes, but he terms snorkels. Toet concludes “And so the exhaust snorkels were born. Then with lots of optimisations we got them to work quite well (not as good a solution aerodynamically speaking as the side exits but not bad in the end). The solution then allowed for tighter rear bodywork which began to bring further benefits”. Looking at the rear of the 1998 Ferrari F300, the first design of periscope stood the test of time and in concept hasn’t changed much in the ten subsequent years. Ferrari of course had initial problems with the periscope design. Although the shorter exhaust bundle kept the radiated heat away from the side of the gearbox, where the suspension and hydraulics are packaged. But instead the hotter exhaust plume played over the rear bodywork of the car and critically over the suspension. Ferrari suffered suspension problems despite their early attempts at heat reflective materials being added to the upper wishbone. Detail development continued and by the end of the season Ferrari had proven the periscope was a workable solution.

F300 periscope exhaust, courtesy of Gurneyflap.com

It was a while before other teams followed the periscope solution. As their engine suppliers demanded shorter pipes, their carbon fibre suspension struggled with the heat and the throttle sensitivity upset the handling. So eventually every team switched to the up and out solution. By 2001 nearly all teams had gone this route. Leaving just Minardi and McLaren with blown diffusers. Minardi exiting their exhaust relatively high up over the trailing edge of the diffuser, at the time technical director Gabrielle Tredozi told me this was to reduce heat rejection and throttle sensitivity. However the team did trial some low exit exhausts, similar to McLarens at the high speed tracks of Indianapolis and Monza. But for 2002 the Asiatech V10 engine Minardi were to use demanded shorter exhausts and Minardi went for the periscope design with the Gabrielle Tredozi designed PS02.
Up to the 2001 MP4-16 Adrian Newey at McLaren directed his exhausts low down through the central boat tail of the diffuser. But in 2002 Newey was forced to go with periscopes, as he explained to me in my first ever interview with him in 2002 “The 2000-2001 cars had the same engine, we now have new engine, and different V angle that’s obviously changed, some of the packaging of the car the engine also has some different requirements, which is affecting us. Requests from the engine supplier Ilmor were different exhaust system requirements which meant we could no longer continue with putting the exhausts exits out through the floor so we had to go for top exits”. I pressed him if this was purely for engine demands, which he confirmed, but when asked if it was specifically for shorter pipe lengths he cautiously replied “I’d rather not go into details; we couldn’t accommodate what was wanted”.
So by 2002 every team had exploited the less sensitive, but aerodynamically inferior periscope design. It seems the effect of blowing the top rear wing or beam wing was of little advantage with the periscope design. However the trend in the 2000′s was for ever tighter sidepods, the periscope design enabled teams to go much further with the slimness of the coke bottle area as the pipes no longer needed to exit rearwards through the tail of the sidepod, they could be packaged further forwards in the sidepods. Slimmer and slimmer rear ends were developed, all to the benefit of the diffuser airflow, which in itself reaped aero gains. Initially the teams had the exhaust collector point upwards, with the short secondary pipe pointing up the turning 90 degrees to exit rearwards horizontally. As sidepod heights and widths reduced it became better to point the collector forwards and curl the secondary pipe in a “U” bend to point backwards. This placed the bulk of the exhaust system above the radiators and left very little volume to the side or behind the engine, to the benefit of the slim rear aerodynamics.
During the 2000s teams continuously varied the exit format of the exhaust. At some points during the decade an oval exit was used with a small horizontal stiffener added for strength. Also the exit varied between flush to the sidepod surface and protruding through the bodywork. Ferrari adopted a protruding exhaust, surrounded by a tall fairing that aided the extraction hot air from the sidepods. Some teams also exploited the hot exhaust for rear tyre temperature. Jordan exited their exhaust high and wide through the flip up ahead of the rear wheel. They had optional exhaust pipes that sent more of the exhaust plume over the rear tyres to increase their temperature. Renault also briefly tried a scoop that caught some of the exhaust plume and directed it over the rear wheel.
Then in 2010, it was Adrian Newey who returned the exhaust position to low down on the RB6, in order to exploit the fast moving exhausts gasses passing over and through the diffuser, the Exhaust Blown Diffuser was reborn. Several teams discarded periscopes during 2010 for low exhausts. But for the start of 2011 every team had gone for a low exit and the periscope disappeared. It appeared as though it was lost from F1. Now with its mandatory renaissance in 2012, it will be interesting to see if teams can further develop this simple concept further.

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