zeN's mussing on 2070 vehicle technology, How do they get those flat acceleration curves? Options

[InfinityzeN]

*EDIT: Cleaned up presentation and updated my mussing, along with including some more from comments*

This is part of my ongoing mussing into SR4 vehicles, creating new ones, and filling in the gaps within the vehicle rules. This part has no vehicles or rules in it however, since it is focused on the vehicle tech in 2070. It will eventually be tied into an idea I had for helping create a more living SR 2070 world with information on how the varies technology functions according to RAW.

First lets talk about torque, horsepower and some of the basics of the internal combustion engine...

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Torque is a measure of force, while horsepower is a measure of work. An internal combustion engine (ICE for short) is a very specialized vacuum designed to take the drawn in air, add fuel, and burn the mixture to create power. There are hard limits on the amount of air an engine can draw in, the amount of this maximum capacity used at any rpm and throttle position being expressed as an engines volumetric efficiency (VE for short). VE is the % of the total volume of the engine that is actually used per rpm. So a 5L engine running at 80% VE is flowing 4L an RPM. The best modern engines (read: race car engines) will produce something in the range of low 90s ft/lbs of torque a liter with a usable powerband, with a couple of special application engines (read: drag engines) producing just over 100 ft/lbs a liter, though their usability for anything other than their application is limited. Most modern engines produce something in the low 60s to low 70s range of ft/lbs a liter.

Past to present...

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If you look back 60 years or more ago, you would find that even the most efficient engines (including race engines) did not produce a whole lot of torque per liter (mostly in the 30s ft/lb range). Shortening that distance back to 40 years and you will begin to find several engines very close to modern range. In fact, in the mid/early 60s Ford sold cars with the 427 Cammer engine. It produced over 70 ft/lbs of torque a liter and is the most powerful production car engine ever sold by Ford at 657 horsepower.

Do any of you see the problem here? If we had engines since the mid 1960s in production cars producing as much torque per liter as modern cars do, how do we produce more powerful engines? Well, there are several ways. First, you keep pushing at getting an even higher VE. Tuning the intake manifold and runners allows for a higher VE, sometimes even managing over 100% through very limited rpm ranges (tuned vacuum effect, google if you want more info). Higher flowing and more efficient head and header design also contributes. This increases the amount of air/fuel processed. Or you can try to increase the amount of energy extracted from the air fuel mix. Increasing mechanical efficiency, higher compression, and optimizing fueling and ignition timing work along this route. All in all, the best production (ie. not racing!) engines of today only produce ~10 more ft/lbs a liter then the best of the 1960s, with most of those gains happening in the first 10 to 15 years. And every additional ft/lb is that much harder to gain.

So how do you get more horsepower then? (horsepower being actual work, is more important then torque) Simple, if you can't increase one of the variables that produce horsepower (torque), you increase the other one (rpm). With a high rpm cam, you push the torque curve up the rpm band, netting more horsepower. However, you can only go so far before the engine will begin to have problems operating at low rpms. To counter this, things like the original VTEC (multi stage cams) and VVT were invented, allowing engines that could rev to high rpms while still being smooth and usable at low rpms. They also had the added benefit of helping optimize fueling and ignition timing.


All of this leading us up to 2070, with my predictions below (some with additional details in spoilers).
1) Average production car engines will produce something between 70 and 80 ft/lbs a liter

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This 70 to 80 ft/lbs a liter is only for common production vehicles. Motorcycles and other highly tuned vehicles will be pushing something closer to 90 ft/lbs a liter at peak. Special application engines will be in 100 ft/lbs a liter with a still broadly usable power-band (race car engines), while engines only utilized for a very tightly controlled conditions will be making around 110 ft/lbs a liter (drag car engines).

2) Inline engines with 4 and 6 cylinders (I4 & I6) will be the most common, with 6 cylinders being preferred where possible for their inherent stability and smoothness.

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In performance vehicles, inline 6 and twin bank 6 cylinder engines will be the norm (I6 & V12). Most performance engines will be of the I6 type. Engines not utilizing one of these three standard formats will normally be because of a specific engine format being the held "standard" for a vehicle. The Corvette for instance will most likely never utilize anything but a V8, while a return to production of the Viper (ending production in 2010) will most likely not utilize anything but a V10.

3) RPM ranges will be one and a half to double what they are today (10k to 14k), with high performance engines reaching higher (14k to 16k) and sport bikes in the 16k to 20k range.
4) Engines will be built out of highly advanced aluminum alloys and ceramics.
5) Instead of cams, the valves will each be individually controlled by solenoids, allowing total control of valve lift, timing, and duration.

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This is currently being researched today, though only in the part prototype stage. This is a very important change in engine design, since it will save weight (both total and rotating) while allowing the vehicle to have a very flat torque curve. The reason for the flat torque curve is because the engine will always be able to adjust each individual valve to the position that will best support power production at a given point. As a side effect of this, the current hard limit of no performance gain after 4 valves will most likely raise to 5 (3 intake/2 exhaust) or 6 (3 intake & exhaust). This very fine control of the valves will also help reduce fuel use and greatly increase engine smoothness.

6) The above, combined with dynamically changing intake runners and active exhaust systems, will result in very flat VE (and thous, Torque) curves, often at or near 100% VE throughout the rpm range.

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Dynamic intake runners change the intake tube length and shape from after the throttle body to where it meets the intake valves. Longer intake runners are better for low rpm, steady growing shorter as the operating rpm increases. Active exhaust on the other hand, address another limitation of engines. What flows in, must flow out. Since a given size pipe can only flow so much, the more power an engine produces, the larger the exhaust required. However, too large an exhaust will actually inhibit flow at lower volume, cutting into low end power. Active exhaust address this by utilizing more then one exhaust pipe, with the ability to close them off or open them to match the engines flow requirements. This allows for smoother power, as well as letting the engine operate quieter at less than full load.

7) Most engines will run on a mixture of petro (derived from bio-oil producing bacteria) and ethanol (type of alcohol) with an octane rating in the 110~120 range.

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Bio-Oil producing bacteria are currently in the prototype testing stage today, with large scale production expected sometime in the next 10 to 15 years. They grow utilizing organic waste as a food source and are specifically engineered not to be able to survive in the wild. This second point is something that any Bio-Oil Corp will spend a great deal of effort to maintain, since the effects of the bacteria being able to survive and run rampant are pretty bad for the environment and humanity. The ethanol component will also be produced from organic waste, rather then the food crops as done today. Garbage which you can easily sell is far less valuable then food, especially with the steadily raising population.

8.) Transmissions will be continuously variable transmissions for most production vehicles, with sequential manual or semi-automatic for performance vehicles.

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CVT are large and bulky compared to other transmission technology, with lower power handling and very low surge handling capabilities. They are also the most difficult transmission type to add a reverse gear to. Since hybrid electric will be the standard, a way to get around this is to only use the electric engines for reverse in CVT equipped vehicles. Sequential manual transmissions are small, light, very good at handling power and surge, with the shortest by far off power time of any of the shifting transmissions (that is, everyone but the CVT which does not shift). These are the reasons they are used in F1 cars, motorcycles, and newer Ferraris.

9) The speed of the transmission combined with the direct neural interface will result in negligible time to shift gears (10ms or so) for non-CVT.
10) All vehicles that are not purely electric will be hybrid electric vehicles with advanced kinetic energy recapturing ability.
11) All vehicles will have some form of all wheel drive capability. At the very least, this will be electric motors powering the wheels not powered by its fuel engine.
12) Due to lighter/stronger materials, better design, and advances in friction reduction drive train losses will be half or better what modern vehicles exhibit (in the range of 5~10%).
13) Forced induction capabilities will be greatly improved by memory materials (allowing changes on the fly of compressor and turbine) and friction reduction.
14) This will allow a turbo to perform at the peak of fast spool-up and low end torque through high horsepower/flow for its given size, without surge.
15) Superchargers (positive displacement and centrifugal) will also gain most of these advantages, extending their power production and greatly reducing their drive power usage.
16) The easiest way to improve engine performance will become increasing displacement (longer stroke/larger bore) or rpm range.

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The reason that most ways to improve performance today will not work is they will almost all be done from the factory. Intake and exhaust will already be optimized, cams do not exist anymore and their effect is now totally controlled by the computer which is already targeting optimal power and fuel economy. This will lead to a couple of effects...
1) Engine Customization for Accel is achieved through ether increasing displacement, or increasing rpm range with a shorter final drive.
2) Engine Customization for Speed is achieved through ether increasing rpm range, or increasing displacement with a taller final drive.
3) Engine Customization for both Speed and Accel is achieved by increasing both displacement and rpm range.

17) Vehicles will weigh only about 75% as much as current cars of their size, while being stronger and stiffer.

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Cars today weigh more then they did only a few years ago. Dispite the rapid advances in material technology, there are steadly raising demands of more space/comfort, emmissions, and safety. Eventually we will hit the point where the weight savings finally outpace the increases required, but having cars the same size as today weighing half as much or less will most likely be far furter into the future then 2070.

18) Brakes, clutches, and other friction parts will use ceramics that have a high density, strength, heat capacity, and heat radiating capability.

Examples

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(All the below examples are naturally aspirated engines, no forced induction)

So a 2070's sports car with a 3L I6 would produce between 210 and 240 ft/lbs of torque through its whole rpm range, peaking at 600 (15k redline) horsepower at the crank.

Most commuter cars will have 0.5L to 1.5L engines (65 to 280 crank horsepower). Their electric engines will be able to produce something between 25~50% of the same power. A four door subcompact with the driver in it will weigh in at about 1 ton. With a 0.5L engine and electric engines capable of about 50% of the petro engines power, it will have nearly 120% the power to weight ratio of a modern four door subcompact with driver, while getting over three times the gas mileage.

1L sport bikes will produce between 275 and 340 crank horsepower (roughly 2~2.5 as much power as modern bikes), though they will not have nearly as advanced a hybrid electric system as a car due to serious space and weight limitations (used only for cruising, not additional power). They will also only get about 75~80% better gas mileage under cruising conditions.

The crazy super cars/exotics can be made into crazy monsters. A 6.3L V12 will peak at 500 ft/lbs of torque and over 1300 horsepower. This car would have to use very long gears and all wheel drive (otherwise it would just spin the tires) and its hybrid electric systems would function the same as sport bikes (only for cruising). Before you knock it, remember that it takes 8 times as much power for every time you double speed. An engine such as this would barely allow a 2070 Bugatti Veyron to crack 300mph. Its much lower torque would be partially offset by its lower weight, but it would still suffer in the acceleration department. Though it is beyond the talk here, I would expect turbos to up the torque, while having a lower redline.

A quick rundown of a 2070s vehicle then would be a hybrid electric/petro vehicle, making extensive use of synthetic materials in its construction. Its engine is roughlly half the size or less of modern day cars in its class, but able to rev far higher. It would provide power smoothly, while constantly adjusting to always use the least fuel and energy.