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| 08-31-2013, 06:54 PM | #441 | |
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Yeah, I know... it's hard to qualify the Alfa Romeo 4C.  Actually, it doesn't have any direct competition from a single brand in that you always have to mention both Porsche or Lotus but neither in isolation to find something with a slight resemblance. Let's us say that it represents the best of both Porsche and Lotus worlds. It's that good!  And, you definitely will find a better replacement for your sold 335xi with the Alfa 4C than with any Lotus in terms of some everyday practicality without losing any of the Lotus best dynamic attributes - non power assisted steering included. |
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| 09-02-2013, 04:29 AM | #442 | ||||||
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As we could see from the fuel-efficiency formula, the 'magical' formula, something is missing on the above M4 specs and I think this time we won't need SCOTT's help to figure out what it is...
It's obvious that the tiny turbos from the N54T engine mounted in the 1M (picture below) are not able to run enough boost to sustain 422 PS (416 hp) flat from 5400 to 7000 rpm, thus a much BIGGER turbo becomes a necessity:  However, as you all know with big turbochargers comes big turbo-lag. So, the new S55 engine will be the first ever series production engine to be equpiped with an electric actuated turbocharger in a biturbo arrangement where the electrically driven compressor is placed after the main 'BIG' conventional turbocharger and intercooler in the charge air path. The biturbo arrangement uses both a turbine wheel driven by the exhaust gas stream, and an electrically driven turbine that accelerates to very high speeds in an extremely short time. The so arranged new electrically-powered turbocharger would create power more efficiently and also have less turbo lag. When the main turbocharger’s energy output is low, the air is directed into the electric compressor and is compressed there a second time thus boosting the power at low revs. Then, that in combination with BMW's VALVETRONIC technology (absent in the 1M engine) means increased performance and fuel efficiency: Quote:
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| 09-02-2013, 04:30 AM | #443 | ||||
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The S55 engine's 2-stage variable biturbo employs different size twin-scroll turbos - a small ELECTRIC one (see above pictures) for quicker spool up at low rpm and a large turbo to take care of higher rev. They are connected in series so that the boost pressure from one turbo is further multiplied by another turbo. The distribution of exhaust gas is continuously variable, so the transition from small turbo to big turbo can be made seamless. The complete biturbo arrangement with a 4-cylinder engine example is as follows:
LOW RPM RANGE Quote:
 MEDIUM RPM RANGE Quote:
 HIGH RPM RANGE Quote:
 TWIN-SCROLL TURBO Quote:
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| 09-02-2013, 04:32 AM | #444 |
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What I'm seeing as a viable option for the new M3/M4 is the fusion of the following two arrangements from BorgWarner (see pics below) using BMW's patented electrically assisted turbocharger in place of the electrically driven compressor, the so called eBooster. With such arrangement the electrically assisted exhaust turbocharger would be equipped with as small a turbine as possible so that the rotating blades have a small mass moment of inertia in order to guarantee favorable response and to keep the acceleration performance requirements placed on the electric motor as low as possible. On the other hand, since in the BMW's patented electrically assisted turbocharger the compressor can be uncoupled from the turbine axle via a clutch then if the system is equipped with the corresponding electronics, a load can be placed on the electrically driven exhaust turbocharger by the electric motor when there is an oversupply of exhaust gas. The electrically driven exhaust turbocharger would then operate as a generator in a controlled manner, i.e. braked, so that a predefined rotating blade speed, meaning a suitable electrical charging, is attained. The braking energy is then released as electrical power into the electrical system of the vehicle in accordance with the efficiency chain. This way it renders a wastegate (and the check valve) needless because above the speed of the electrically driven exhaust turbocharger at which the BIG (twin-scroll) turbocharger in the system "passes" the small electrically driven exhaust turbocharger, i.e. when the BIG turbocharger provide the degree of charging required without support from the small electrically assisted one, the small electrically driven exhaust turbocharger, now decoupled from the compressor via a clutch, can be allowed to spin down naturally or can be regulated down in a controlled manner for the sake of energy regeneration and, hence, efficiency. The distribution of exhaust gas is continuously variable, so the transition from small turbo to big turbo can be made seamless. Depending on load, the exhaust flap opens increasingly and feeds exhaust gas to both turbos (see pics above). The benefits that can be gained using this system in terms of the transient response are determined solely by the capacity of the vehicle electrical system. The potential for improvement in the transient operating characteristics depends primarily on the amount of electrical power available and the electrical infrastructure of the vehicle. The main advantage of two-stage systems over single-stage units is that two different sized compressors can be connected in series so that an optimized map is available for each air flow rate range. When the two maps are combined, the resulting map has a power curve with a significantly expanded useful map width. At operating points where there is little exhaust gas available, the two-stage compression reaches a higher overall charging pressure level earlier. The charging system allows, as a two-stage compression variant, an increase in the intermediate pressure curve regardless of how much exhaust gas is available, thus is used to improve the transient performance as well as to increase the steady-state characteristics. The potential is only limited by the electrical system of the vehicle.
  Last edited by GoingTooFast; 09-02-2013 at 09:33 AM.. |
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| 09-02-2013, 04:40 AM | #449 | ||
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Quote:
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| 09-02-2013, 04:44 AM | #451 | |
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Alfa 4C full specs: Quote:
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| 09-02-2013, 04:47 AM | #453 | ||
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At 1195 kg (1120 kg + 75 kg) and doing 4.0 sec from 0 to 62 mph, to equal the fuel-efficiency rate of the Alfa 4C it had to have a fuel consumption of: [51.0 - (2.0 x 1195/100)] / 4.0 = 6.8 l/100 km which is exactly the same quoted fuel consumption figure for the Alfa 4C, however with 335 hp (more 95 hp than the 4C) this racing version of the Toyobaru can't possibly match the lighter Alfa 4C quoted fuel consumption figure  , therefore the Toyobaru even in this racing version still has a worse fuel-efficiency rate than the Alfa 4C, which is almost impossible to beat without diesel : |
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| 09-02-2013, 04:50 AM | #456 | |
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Some Alfa history:
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