 Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 Changes of E-KERS Rules to Make F1 More Relevant to Road Cars Albert Boretti 1, 2,* 1 Department of Mechanical and Aerospace Engineering, Benja min M. Statler College of Engineering and Mineral Resources, West Virginia University, Morgantown, USA . 2 Military Technological College, Muscat 111, Oman . Received 27 Oct ober 2016; received in revised form 21 March 2017; accept ed 05 April 2017 Abstract Today’s F1 hybrid cars are based on very similar power units made up of about the same internal co mbustion engine (ICE) and energy recov ery system (ERS). Because of restrictive design rules permitting too much fuel per race, the internal co mbustion engine is not part icularly fuel e ffic ient. The methodology is based on lap time simu lations and telemetry data for a F1 H car covering one lap of the Monaco Grand Prix. The methodology is based on lap time simu lations and tele metry data for a F1 H car covering one lap of th e Monaco Grand Prix. The p resent limit o f 100 kg of fuel per race is e xcessive. The low power energy recovery system is used strategically rather than fuel savings recovering very little bra king energy. The 4 MJ of storable energy is used only when it is s trategically needed. The 2 MJ of recoverable energy a llo wed per lap a re a lmost never collected. To return to be technica lly attractive, F1 should permit much more freedom in the definit ion of the ICE and the ERS. As the goal of the ru les should be lowering the fuel consumption wh ile keeping technical and sporting interest high, the best solution is more freedom to achieve the fastest car within mo re stringent limits of fue l economy. A rea l limit to the total fuel consumption for a race track like Monte Carlo should be not mo re than 80 kg o f fuel. This would translate in more energy recovery to the ERS per lap and better fue l e fficiency of the ICE and will ce rtainly help mo re the design of passenger cars . Keywor ds : hybrid cars, kinetic energy recovery systems, motorsport, F1, Le Mans 1. Introduction Today F1 racing cars, similarly to other popular racing car series, are hybrid cars as the environmental concern must be at least apparently the driving force for every sport activity. The power unit now comprises an internal combustion engine and an energy recovery system. The energy recovery system in theory should recover the waste energy, mostly kinetic, to reduce the fuel energy supply to the internal co mbustion engine. Bac kground informat ion on kinetic en ergy recovery systems for rac ing cars can be found in [1], wh ile the specific internal co mbustion engines and kinetic energy recovery systems (KERS) fo r 201 4 F1 cars are discussed in [2-4]. The fuel saving goal is however practically eluded by the most part of the F1 tea ms. The kinetic energy recovery system is indeed mostly used strategically to boost the performance of a car, being , otherwise, the internal combustion engine not that powerful as it was in the recent past, by discharging the energy storage in selected lap and not certainly charging and discharging the energy storage every single lap . The lack of freedo m given to engineers to develop a technical solution delivering a target fuel economy is the reason why F1 is not technically challenging in a way that may be benefic ia l to road transport while being attractive to the motor enthusiasts. Purpose of the manuscript is to suggest changes of the technical regulations that could improve the energy * Corresponding author. E-mail address: a.a.boretti@gmail.com Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 27 Cop y right © TAETI recovery and the fuel conversion effic iency of the internal co mbustion engine for a better fue l economy while permitting top-class motorsport performances. It is shown how a mo re restrictive total fuel usage per race and mo re freedo m to develop the internal combustion engine and the energy recovery system may benefit the interest towards the racing event and the value of the technical development for production cars . 2. LMP1-H vs. F1 hybrid 2015 The latest 2015 Le Mans race was dominated by the Porsches and the Audis battling until the very end of the race, wi th four class 1 Le Mans Prototype hybrid (LMP1-H) car manufacturers, the two Ge rman plus the Japanese Toyota and Nissan, proposing for the event very d ifferent technical solutions for what concerns the internal co mbustion engine (ICE), Diesel or Gasoline, d ifferent displace ment, turbo or naturally aspirated, and the energy recovery system (ERS), e lectric or mechanic or electro-mechanic, o f different powers and different energy storage. The rules set different limitations to the fuel flo w rate per diffe rent ERS energy storage limits and fuel selection. These rules give the LM P1 -H engineers the freedo m to develop diffe rent ICEs and different ERSs. The developments of alternative solutions are ultimately what are needed to ma ke the race event attractive to the motor enthusiast and be relevant, in long term perspective, to the design of every day passenger cars. The same technical enthusiasm does not certainly apply to todays’ F1 hybrids. Ref. [4] provides an assessment of the differe nt KERS options available in class 1 Le Mans Proto-type hybrid (LMP1-H). Fig. 1 F1 KERS (ES+MGU-K) and E-BOOST/WHR (ES+MGU-H) from [5] Todays’ F1 hybrids have power units where simila rly to LMP1-H the ICE is one ele ment of the power unit that also includes an ERS. Table 1 reca lls the present specifications of the ICE and the ERS. The ERS inc ludes two motor generator units (MGU) linked to an energy store (ES) recharged by the braking work and eventually the waste heat. The four power unit components, plus the ICE and the turbocharger are the six separate e le ments making a power unit. Four of each e le ment are available to each driver per season without incurring in a grid penalty. During a race, drivers may use steering whee l controls to switch to different power unit settings, or to change the rate of ERS energy harvest. Fig. 1 (fro m [5]) presents the F1 KERS (ES+MGU-K) and E-BOOST/WHR (ES+MGU-H). The set-up of the power unit of a F1 hybrid is therefore in princ iple not that far fro m the one of the Porsche 919 H winner of the last Le Mans 2015 race. The d ifference is , however, substantial when the details are considered. F1 is much better fo r what concerns the turbocharger, as the MGU -H fitted to the turbocharger shaft and connected to the ES gives wider opportunities than having just a power turbine downstream of the traditional turbocharger turbine to recover a minimal a mount of waste heat at the expenses of increased back flow. However, F1 hybrids are less flexible under all the other aspects. In F1, the turbocharged 1.6-litre V6 engines are pretty much the same fo r every tea m. Not only sa me d isplacement and (about) same fuel, but also same number of cylinders, same 90-degree V angle, sa me rev limiter at 15,000 rp m, sa me four poppet valves per cylinder, same direct fuel in jection, same single fixed geometry turbocharged, same bore, same stroke, same crankcase height, almost everything the same to deliver about the same 600 HP or 447 kW of top bra ke powe r, with bra ke mean effective pressure and brake specific fuel consumption curves also expected to be very similar. Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 28 Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI The 600 HP or 447 kW are the values of peak powe r c laimed by the most part of the teams for the 2014 season. The fuel flow rate is limited to 100 kg/h, that considering a lowe r heating value for gasoline of 44.5 MJ/Kg translates in a ma ximu m f uel power of 1236 kW or 1658 HP, for a pea k powe r e ffic iency of the ICE o f 600/ 1658 = 36.2%. Per ru mors, a couple of tea ms outperforming the others this 2015 season could have moved around this limit pro mpting the federation to seek for re medy. If the fuel flow mete r is placed in a certain location of the fuel line, there is always the opportun ity to accumulate fuel downstream of the flow meter, and , therefore, en joy an instantaneous flow rate delivered by the high -pressure fuel injectors more than the instantaneous contemporary reading of the ambient pressure flow meter flow rate . Table 1 Data of power units of 2015 F1 hybrid cars Internal Combustion Engine Disp lacement 1.6 liters Rev limit 15,000 rp m Pressure charging Sin gle turbochar ger, unlimited boost p ressure (but maximum 3.5 bar due to fuel flow limit) Fuel flow limit 100 kg/h (but not at the injectors) Permitted Fuel quantity p er race 100 kg Configuration 90° V6 Number of cy linders 6 Bore 80 mm Stroke 53 mm Crank height 90 mm Number of valves 4 p er cy linder, 24 total Exhausts Single exhaust outlet, from turbine on car center line Fuel Direct fuel injection Number of Power Units p ermitted p er driver p er y ear 5 Energy Recovery Sy stems M GU-K rp m M ax 50,000 rp m M GU-K p ower M ax 120 kW Energy recovered by M GU-K M ax 2 M J/lap Energy released by M GU-K M ax 4 M J/lap M GU-H rp m unlimited Energy recovered by M GU-H unlimited Every percentage point incre ment o f the ICE fuel conversion efficiency everything but difficult to achieve would t ranslate in an increase of the peak power of 12 kW or 17 HP. Simila rly, any percentage in crease of the instantaneous flow rate to the injectors would translate in an incre ment of the instantaneous peak power of 4.5 kW or 6 HP. As an additional measure to temporarily increase the peak power, the M GU -H can drive the turbocharger compressor that, otherwise, only depends on the gas expansion through the turbine that is also translating in back pressure for the engine. This can make plausible the large r peak power outputs rumored for 2015. In addition to the ma ximu m fuel flow rate, belo w 10,500 rp m the fuel mass flow must not exceed Q = 0.009 N +5.5, with N the engine speed in rpm and Q in kg/h. In addition to the fuel flo w limiter placed along the fuel line, the 2014 and 2015 season have seen the introduction of a total fuel per race capped at 100 kg, or 4,450 MJ of fuel energy per race, that is certainly a driver for much better fuel economies, but not certainly that strong. This fuel limit properly redefined may be the driver for a better product. Fully integrated with the ICE is the ERS that increases the unit’s overall effic iency by recovering the waste energy fro m the brakes and the exhaust. The recovery of the e xhaust energy is , however, simply the turbocharger turbine that may de liver energy to the energy store that is not delivered to the turbocharger compressor. The ERS accounts for an additional 120 kW or 160 HP to de liver about the same powe r output of the past 2.4 liters V8 engines naturally aspirated. The ERS co mprises two motor generator units (M GU-K and M GU-H), plus the energy store. The motor generator units convert mechanical and heat energy to electrical energy and vice versa. The MGU -K converts the car kinetic energy generated under braking into electric ity while it acts as a motor under acceleration returning power to the drivetrain . The MGU-H converts the exhaust heat into Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 29 Cop y right © TAETI electric ity but only through the turbocharger, i.e. only recovers the very s mall a mount of energy in the turb ine that would b e otherwise waste-gated when more than the compressor demands. The stored energy can be used to power the MGU -K. The MGU-H controls the speed of the turbo and the power fro m to and fro m the turbocharger shaft. The M GU -H may supply the e xtra energy needed at the compressor when the turbine energy is not enough, as for e xa mp le in low speed oper ating points or during accelerations, in this case ad-dressing the turbolag issues. It may a lso recover the e xtra energy available at the turbine otherwise waste-gated. The M GU-H may increase the power o f the ICE at any speed by precise extra boost, opera ting in the best point of the map, with supply or withdraw of e xt ra energy. While the E -Boost technology is certainly not new [10-15], the precise boost of the F1 M GU-H linked to the ES of the KERS may ce rtainly improve the overall powe r and energy management of the vehicle. Apart fro m the same design of the M GU and ES pure ly e lectric , a re the energy and powe r limits of the ES and the M GU -K that makes a huge difference vs. the LMP1 -H ca rs. While LM P1-H cars have ma ximu m re leased energy of 2, 4, 6 or 8 MJ/ lap and unlimited re leased power, in F1 a ma ximu m of 4 MJ per lap can be transferred fro m the ES to the M GU -K and then the drivetrain, but only a ma ximu m of 2 MJ per lap can be transferred fro m the M GU-K to the ES. More than that, the ma ximu m power of the M GU-K is limited to only 120 kW or 160 HP, wh ile the LMP1 -H a ll have powers of the M GU -K more than 185 kW up to a ma ximu m of 550 kW considered for the Nissan GT -R LM NISMO. The low power in addition to the limited energy is what makes the fuel saving kinetic energy recovery very difficult. As braking of F1 cars usually occurs with powers large ly e xceeding the propulsive power, up to about 2,000 kW the lo w power M GU-K must be recharged carefu lly, as this recharge t ranslates in a lap time penalty. In F1, the M GU-K is limited to recover 2 MJ of energy per lap while the M GU -K may then supply a ma ximu m of 4 MJ per lap to the drivetrain but the ma ximu m power in and out is limited to 120 kW (160 HP). Th is means that the ERS is more strategic rather than energy sav ing, as it can be certainly used to save or gain positions or improve the time of an indiv idual lap, wh ile it is still not convenient and not encouraged to recover and reuse the braking energy at any lap as it would be the case if the fuel energy saving wo uld be the real issue. Table 2 Summary table of 2015 LMP1-H and F1-H power and energy rules (a) limited to <300 kW in 2016. (b) no driver. (c) with driver LM P1-H (Le M ans race track) F1-H No ERS ERS OPTIONS Released Energy M J/Lap 0 < 2 < 4 <6 < 8 <4 Recovered Energy M J/Lap 0 <2 Released Power kW 0 unlimited (a) unlimited (a) unlimited (a) unlimited (a) 120 kW Car M ass kg 850 (b) 870 (b) 870 (b) 870 (b) 870 (b) 702 (c) Petrol Energy M J/Lap 150.8 146.3 141.7 137.2 134.9 M ax Petrol Flow kg/h 95.6 93 90.5 87.9 87.3 100 Petrol cap acity carried on-board l 66.9 66.9 66.9 66.9 66.9 Fuel Technology Factor - 1.061 1.061 1.061 1.061 1.061 NA K Technology Factor - 1 0.983 0.983 0.983 1 Diesel Energy M J/Lap 142.1 140.2 135.9 131.6 127.1 M ax Diesel Flow kg/h 83.4 83.3 81 78.3 76.2 Diesel cap acity carried on-board l 54.8 54.8 54.8 54.8 54.8 Table 2 presents a summary of the 2015 LMP1-H and F1-H powe r and energy rules. In case of one lap of the Monaco Grand Prix, 3.337 km long, a F1 of curb weight 702 kg less the driver weight may use 1.28 kg or 57 MJ of fuel energy, i.e . 17 MJ/km. In case of one lap of the Le Mans race, the Circuit de la Sarthe is 13.629 km long; a LMP1-H of curb we ight 870 kg may only use 134.9 MJ of fuel energy, i.e. 9.9 MJ/km. Even if it is not desirable for energy saving to switch on the MGU-K at end of straight for a small-time interval before the driver hits the frict ion brakes, this is what presently makes the largest contribution to the amount of energy available to t he ES in F1. The overall lap t ime may also be faster with this strategic recharge because of the faster acceleration up to speed on the Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 30 Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI next straight may mo re than co mpensates for the lost time . This technique is not , however, in the direct ion of imp roving the fuel economy, as the direct path engine to wheels is much mo re effic ient than the path engine to MGU -K to ES to M GU-K to wheels. The M GU-H is in theory uncapped, and an unlimited a mount of energy can be t ransferred between the M GU-H and the ES and/or the MGU-K. The M GU-H technology is still far fro m being fu lly developed, but it is expected to help more in terms of ICE output by precise boost rather than recovery of waste heat. The use of MGU-H and M GU-K and ES may permit fu rther enhanced energy and power management. 3. Energy analysis of a F1 2015 lap of Monte Carlo To understand the present status of energy recovery and fuel economy, tele metry and lap time simulat ions may help. The selected race track is Monte Carlo. The Circuit de Monaco is a street circuit of length 3.34 km. The total dis tance is 78 laps or 260.52 km. If we do consider the last 5 years of the Monte Ca rlo co mpetit ion, 3 with the naturally aspirated 2.4 liters V8 and a very small M GU-K of 60 kW, and the latest 2 with the turbocharged 1.6 liters V6 with the la rger but still sma ll present MGU-K of 120 kW, clea rly the latest F1 are much slo wer than their predecessors no matter the c laim of preserving the ma ximu m power output to preserve performances. In 2011, with sunny, fine and dry conditions, the best qualifying time for pole position was 1:13.556 while the fastest lap during the race was 1:16.234. In 2012, with warm and sunny conditions, about same fine conditions except the threat of showers at the end of the race, the best qualifying time fo r pole position was 1:14.381 while the fastest lap during the race was 1:17.296. In 2013, with sunny and dry conditions, the best qualifying time fo r pole position was 1:13.876 while the fastest lap during the race was 1:16.577. During the first season wit h the new rules, in 2014 with sunny and dry conditions, the best qualifying time for pole position was 1:15.989 while the fastest lap during the race was 1:18.479, roughly 2 seconds slower. Finally, this year, 2015, with sunny and dry conditions, the best qualifying time fo r pole position was 1:15.098 wh ile the fastest lap during the race was 1:18.063. Therefore, the new ru les have certainly slowed down the cars . Some imp rovements have however been achieved in terms of fue l economy, even if the 100 kg of ma ximu m fuel pe r a race is not yet the driving force for the further development of the ICE and the ERS to drastically reduce the fuel consumption. Tele metry and lap time simu lations may be used to compute the like ly performances of F1cars during one lap. The dynamic of rac ing cars and the equations governing the motion of the car a re proposed in [6]. The specific software used in t his paper, [7], is very simple but reliable. Not having too much of supporting information as detailed dig itized tele met ry data and vehicle para meters, more co mplicated approaches as for e xa mple [8] only introduces additional difficulties to define the many other additional para meters involved in the simulat ion. The code [7] solves the Newton’s equations of motion in the three directions for a point moving along a curved path. The minimu m we ight of the car including the driver but not the fuel was 690 kg in 2014 and it is 705 kg in 2015. The weight of the car is , therefore , ta ken here equal to 720 kg. For what concerns the aerodyn amic d rag, we appro ximate the aerodynamic drag fo rce as ½∙ρ·v 2· CD·A, where ρ is the air density, CD is the drag coeffic ient and A is the frontal car area, and the lift force as ½∙ρ·v2· CL·A where CL is the lift coefficient. We take ρ=1.29 kg/ m3, CD=0.85 a nd CL=2.4 when A=1.5 m2 for the specific very low speed circu it. As the drag force dra mat ically impact on the energy requested by a F1 ca r to cover a lap, the above far from accurate values certainly impact on the accuracy of the energy computation. The simulat ions require definition of fe w additional para mete rs, as the tires radius, the lift (downforce) coeffic ient, the rolling resistance and the longitudinal and lateral friction of tires, the gear ratios of the sequential gearbox, the final d rive ratio, the drive efficiency and a grip ratio, in addition to the specification of the engine power curve and obviously of the race t rack. Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 31 Cop y right © TAETI While some of the latest lap time simu lation codes as [8] also account for lateral and longitudinal we ight transfer, real t ire effects as camber, slip rat io and slip angle, te mperature and pressures, vehicle yaw over-steering or under-steering and, finally banking and grade on the track, the code [7] does not. Today’s most sophisticated lap time simu lation tools are fully int egrated with the vehicle manage ment and data acquisition systems. While these tools are very accurate, they also rely on the in -deep knowledge of the detailed vehicle operation that is proprietary data of only the tea ms. Without this in -deep knowledge, they are only mo re co mp licate without being more accurate than [7]. Fig. 2 Lump mass model of a F1 car Fig. 2 presents the lump mass model of a F1 car. The three-dimensional computation of the car aerodynamic with moving wheels and ground is proposed in [9]. The ae rodynamic simu lations return drag and lift coeffic ients to be used in the model. The car is modelled as a pa rtic le moving a long a curved path subject to propulsive and braking forces. Th is simplified model permits a straightforward evaluation of the energy flow of the car covering one lap of a race track. The Ne wton’s equations of motion are solved for the longitudinal, lateral and vertical directions . (a) Velocity vs. distance of a F1 car (b) Longitudinal acceleration vs. distance of a F1 car Fig. 3 Velocity and longitudinal acceleration vs. distance of a F1 car covering one qualifying lap at Monte Carlo Fig. 3(a ) presents the velocity vs. distance from te le metry and fro m the simu lation, and Fig. 3(b) presents the longitudinal acceleration. The tele metry informat ion was digitized fro m an image, and , therefore, suffers of poor resolution. Lap time is 1:15:100. This optimum lap is covered by using the ICE and the electric energy The simulat ion produces one velocity value every half a meter o f the race trac k, but the diffe rences in between the two traces are not only due to the different resolution, but also to the model not fully tunable by lack of knowledge of the vehi cle parameters and limited by the simp lified mathemat ics. The lap time is 1:15:100. This optimu m lap is covered by using 13 MJ of ICE fuel energy delivered with up to a power of 450 kW depending on engine speed plus 4 MJ of electric energy delivered with up to a power of 120 kW . Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 32 Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI (a) Propulsive vs. distance of a F1 car (b) Bra king powers and propulsive, braking and recoverable energy vs. distance of a F1 car Fig. 4 Propulsive and bra king powers and propulsive, braking and recoverable energy vs. distance of a F1 car covering one qualifying lap at Monte Carlo Figs. 4(a ) and 4(b) p resent the propulsive and braking powers and propulsive, bra king and recoverable energy vs. distance of a F1 ca r covering one lap at Monte Carlo as detailed in Fig. 3. Lap time is 1:15:100. This optimu m lap is covered by using the ICE and the electric energy. The propulsive energy is 17.69 MJ; the braking energy is 9.20 MJ and the theoretically recoverable energy is 1.99 MJ. The graphical co mparison of tele metry and model results shows a good accuracy. This comparison is usually enough for this kind of simulat ions and perfectly aligned with the scope of the paper aimed to discuss changes of rules rather than the accuracy of lap time simulations . (a) Velocity vs. distance of a F1 car (b) Longitudinal acceleration vs. distance of a F1 car Fig. 5 Velocity and longitudinal acceleration vs. distance of a F1 car covering one standard race lap at Monte Carlo (a) Propulsive vs. distance of a F1 car (b) Bra king powers and propulsive, braking and recoverable energy vs. distance of a F1 car Fig. 6 Propulsive and braking powers and propulsive, bra king and recoverable energy vs. distance of a F1 car covering one standard race lap at Monte Carlo Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 33 Cop y right © TAETI Figs. 5 and 6 p resent same results of Fig. 3 and 4 with a diffe rent set up permitting 1.6 s slowe r lap t imes. In Fig. 5, lap time is 1:18:700. This lap is covered by using the ICE energy only. The grip is reduced 9% vs. the qualify ing conditions reflecting tire usage. In Fig. 6, lap t ime is 1:18:700. This lap is covered by using the ICE energy only. The grip is reduced 9% vs. the qualifying conditions reflecting t ire usage. The propulsive energy is 16.12 MJ; the bra king energy is 8.38 MJ and the theoretically recoverable energy is 2.00 MJ. 4. Discussion Traditional limit ing factors fo r the M GU -K bra king energy recovery a re the powe r o f the unit, the total energy storage, the balance in between the front and rear a xle b raking and the balance in between MGU -K and friction braking. Certain ly, energy storage at powers much higher than 120 kW also has some downfall for an F1 car. The aero drag is so huge that there is much less energy available at very high vehicle speeds. Furthermore, the very high energy numbers only las t for a fraction of second. However, the much higher power and energy storage limits permitted in the LMP1-H series certainly show the way to move. If the energy input fro m the M GU -K to the ES may not e xceed 2MJ in any one lap and energy re leased fro m the ES to the M GUK may not e xceed 4MJ in any one lap, this means that the continuous use of the KERS is eventually limited to just the 2MJ recovered and reused per lap, while in the strategic use of the KERS, the 4MJ could be made available in a lap providing in the previous lap there has been no discharge of the KERS. This does not help the fuel e conomy. Fro m a global fue l energy perspective, the total fuel available to cover the 78 laps or 260.52 km in Monte Carlo is 100 kg. This translates roughly in 1.28 Kg per every lap of 3.34 km. By assuming a lowe r heating va lue for gasoline of 44.5 MJ/Kg, this translates in a ma ximu m fue l energy supply of 57.0 MJ per lap. The power unit energy requested per lap is less than 16.1 MJ. This translates in an average fuel effic iency of only 28.2% requested to the engine without any working kinetic energy recovery. By recovering the 2 MJ per lap with the MGU-K, this effic iency could be further reduced to an even smaller 24.7%. These efficiencies are everything but great. While better estimations may certa inly follow the use of the tele metry data and the lap time simu lations tools the teams do have, when considering the 1.5 liters V6 turbo engines of the prev ious turbo era a lmost 30 years ago were a lready operating with effic iencies we ll above 30% in a range of operating points of interest, it does not seem that th e 100 kg per race is a rea lly an up-to date limit set to push forward the boundaries of energy efficiency, as the teams may easily ach ieve th e 28.2% efficiency and avoid recovering the braking energy in norma l laps, recharging the ES only strategically and using the MGU-K only when needed to gain/defend a position. The previous analyses are done without any inclusion of the Drag Reduction System (DRS). This overtaking a id permits a driver within one second of a rival car within designated DRS act ivation zo nes to alter the angle of the rear wing flap, reducing drag coefficient and thereby achieving a temporary speed advantage. The DRS has no relevant impact on the fuel economy. Regarding the energy flow through the MGU-H, any transformation of energy type, for e xa mp le mechanical to electrica l to chemical back to electrical and back to mechanical occurs with efficiency far from unity. How powerful is today’s power unit of hybrid F1 when compared with traditional powe rtrains of the past is a question difficult to answer. For ma rket ing purposes, it is co mmon to c laim that today’s power units have the peak power of the ICE, plus the peak power of the M GU-K, with the MGU-H possibly further increasing the power of the ICE by precise e xtra boost. The ICE delivers power to the whee ls as a function of the speed of the crankshaft. The 450 kW of peak power are obtained at high speeds approaching the speed limite r and certain ly not at low speeds. The M GU -K also delivers power to the whee l, but the 120 kW of peak power are now available at any speed of the crankshaft. Advances in Technology Innovation, vol. 3, no. 1, 2018, pp. 26 - 35 34 Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI Cop y right © TAETI The best use of the MGU-K is to produce a faster acceleration after a bend and not to increase the top speed on a straight. The MGU-H of untapped power does not deliver any power to the wheels. The MGU-H is only linked to the turbocharger, and may only help the ICE to delive r more power by spinning faster the turbine above the balance in between gas expansion in the turbine and air compression in the compressor. If the MGU-K power is supplied at low speed, then the equivalent torque of the engine drastically improves. Today’s power unit of hybrid F1 are by fa r less powerful of past traditional powert rains, but certain ly have much better torque. 5. Conclusions To return to be technically attractive, F1 should permit much more freedo m in the defin ition of the ICE and the ERS. As the goal of the rules should be the lowering the fuel consumption while keeping high the technical and sporting interest, the best solution is more freedo m to achieve the fastest car wit hin mo re stringent limits of fuel economy. This would benefit the racing and the everyday car. A real limit should be set to the ma ximu m a mount of fuel to be used for a fixed distance race, and the engineers should be , then, left free to develop the hybrid power unit with at the most a prescribed displace ment of the engine. The p resent limit of 100 kg of fuel per race does not force the teams to recover the 2 MJ of energy every lap, and does not force them to use the fuel much more efficiently within the internal combustion engine that what is common practice since decades. A real limit to the total fuel consumption for a race like Monte Ca rlo should be not more than 80 kg of fue l, that would require the recovery of the 2 MJ of energy every lap and an average fuel effic iency of the ICE of 30.9% , everything but impossible to reach with today’s technologies, but certainly much better than what is presently delivered by today’s F1 inter nal combustion engines. Alternatively, the teams could continue to use only strategically the M GU-K not as a fuel saving measure, but they should, then, improve their internal co mbustion engines to an average fuel e fficiency of 35.2%. These numbers will certainly need the development of novel strategies that may help the design o f passenger cars . References [1] A. Boretti, Kinetic energy recovery systems for racing cars, Pennsylvania: Society of Automotive Engineering (SAE) International, 2013. [2] A. Boretti, “KERS braking for 2014 F1 cars,” Society of Automotive Engineering (SAE) Technical Paper 2012-01-1802, September 17, 2012. [3] A. Boretti, “F1 2014: turbocharged and downsized ICE and KERS boost ,” World Journal of Modelling and Simulation, vol. 9, no. 2, pp. 150-160, 2013. [4] A. Boretti and I. Aris, “Regenerative braking of a 2015 LMP1-H racing car,” Society of Automotive Engineering (SAE) Technical Paper 2015-01-2659, September 27, 2015. [5] M. Petrány, “How formula one's amazing new hybrid turbo engine wo rks,” http://jalopnik.com/how-formula-ones -amazi ng-new-hybrid-turbo-engine-works -1506450399, January 22 2014. [6] W. F. Milliken and D. L. Milliken, Race car vehicle dynamics, Pennsylvania: Soc iety of Automotive Engineering (SA E) International, 1995. [7] “OptimumG-vehic le dynamics solutions,” http://www.optimumg.com, 2017. 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Definitions/Abbreviations a acceleration LMP1-H Le Mans Prototype 1 Hybrid E energy m mass E-KERS Electric KERS MGU motor-generator unit ERS energy recovery system MGU-K driveline MGU ES energy store MGU-H turbocharger MGU F force P power ICE internal combustion engine R force KERS Kinetic Energy Recovery Systems v velocity