Page 20 - PCA Metro NY Region POST | 2019-August-eMag
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(Track Ramblings, Continued from page 16)
heavy, adding about 200 pounds to their weight when compared to a gas-filled car. The tech- nology is evolving very rapidly, so that these disadvantages are likely to reduce over time. There is a Chinese car company whose solu- tion to the charging-time problem is an auto- mated system which replaces your run-down battery with a charged-up one in less than 4 minutes.
One of the wonderful features of the EV is the high low-end torque which is produced by the electric motor. In last month’s column, I dis- played a typical torque-power curve for an in- ternal combustion engine. It showed that torque is very low at low engine revs, which is part of the reason that such cars have multi-speed gearboxes in order to get the benefit of torque- multiplication. By contrast, an electric motor makes it greatest torque at low revs.
Long ago I added a turbo to my 1973 Dat-
sun 510. The stock 100hp increased to about 130hp. Of course, this was a very primitive device compared to today’s cars. All turbo engines of the era, including the 1976 Porsche 930, suffered from turbo-lag due to the lack of appreciable boost effect at low revs and poor low-rev torque since their compression ratios had to be lowered from normal levels to avoid hi-rev detonation (‘knocking’) which is very damaging to the engine.
Today’s turbo engines are greatly advanced over those from decades ago. The ability to modify the behavior of the turbo as the revs change, wastegates, speed and load-sensitive turbo vane configuration, knock sensing, vari- able valve timing, and computer-controlled di- rect fuel injection all contribute to this progress, allowing them to deliver considerable power and low turbo-lag throughout the rev band. There is also exciting progress on the super- charging front. Recall that the main drawback of superchargers is that they consume a great deal of power themselves from the engine in order to drive the impeller. Audi has devel- oped a system which powers the supercharger electrically, thus eliminating the power draw of mechanically driven systems. The 2020 Audi SQ7 has a turbocharged diesel engine which is supplemented at low revs by a 48 volt electri- cally powered supercharger to remove turbo lag. The system engages only momentarily at throttle tip-in. Consequently, it doesn’t over- whelm that battery’s capacity, and since the supercharger is electrically driven, rather than mechanically by a connection to the engine’s speed, it can be operating at full speed even when the engine revs are low. There is a fasci- nating video explaining the system at https:// www.youtube.com/watch?v=k8-_UrfbRBA.
Electric Vehicles
Much of the automobile innovation today is around electric vehicles (EVs). This is largely happening for ecological reasons, such as reduction of pollution and efficiency concerns. At the present time the big drawback of EVs is their limited range - typically around 200 miles, the length of time needed to replenish their batteries – varying from 1⁄2 hour to more than a full day(!!) depending upon the type of charging system used, and limited availability of charg-
Top speed for a vehicle is mostly influenced by
air resistance drag, meaning that a lot of power
is required to make a car go, say, 150mph. Air resistance is not a factor a low speed since it varies with the square of the speed, meaning that it is 25 times as low at 25mph as at 100mph, for example. Consequently, an inherent feature of EVs is that they are very strong at low-speed acceleration. I recently drove a Tesla. It accelerates from a stop incredibly well. You actually have to try hard to perform a smooth, pleasant take-off. And EVs generally have no transmission since their rev range (often up to 20,000 rpm) is so large that there is no need for any gearing, not even for reverse, since electric motors can happily run backwards.
I’ll see you at the track.
Feel free to contact me at [email protected]
 ing stations. The batteries are also quite
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METRO NY REGION PCA * PORSCHE POST AUGUST 2019



















































































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