Motorcycles The Basics Of Power
DT Racing 2020 KTM 450 SX-F Factory Edition Review
DT Racing 2020 KTM 450 SX-F Factory Edition ReviewRelated: 2020 Off-Road Bikes—DT Racing’s KTM 450 SX-F Factory Edition
Cylinder displacement, stroke-averaged net combustion pressure, and rpm. These are the basic variables that create horsepower. Cylinder displacement is obvious, for it tells us something about the volume of fuel-air mixture an engine can pump into itself. In an un-supercharged engine each cubic inch of mixture (at atmospheric pressure) contains a definite amount of chemical energy. The bigger the cylinder, the greater the push we can expect it to give its piston.
Tested: 1986 Ford Taurus LX Shapes the Future of the Family Sedan
From the Archive: Ford hits a homerun with its radically styled and superb Taurus sedan. According to Webster, a milestone is "a significant point in development." The term applies perfectly to Ford's new Taurus and its sibling, the Mercury Sable. With their smooth, flowing lines and European-style road manners, the Taurus and the Sable chart a new direction for mainstream American sedans. But you undoubtedly know that by now. Ford has orchestrated an unusually long and intensive publicity program to prepare the public for these novel cars.
Although we intuitively expect to gain power in proportion to displacement when installing a big-bore kit on a classic engine such as a Kawasaki Z1, the result is less than we expect because the engine’s valves were sized for its original displacement. Our big-bore kit “sucks” harder but the valves are really a bit small for the larger 1,000 or 1,100cc engine we’ve built, so they restrict the flow somewhat. The result is a less-than-proportional gain in power.
As an example of a more balanced approach to a displacement increase,increased the diameter of its 790′s intake and exhaust valves by 1mm each when it recently enlarged that .
2020 Chrysler Pacifica Hybrid: What You Need to Know
The 2020 Chrysler Pacifica Hybrid ranks highly on the strength of a roomy, comfortable cabin and user-friendly features. It also has swift acceleration and poised handling. © Fiat Chrysler Automobiles 2020 Chrysler Pacifica Hybrid The 2020 Chrysler Pacifica Hybrid is ranked: #2 in Minivans Is the Chrysler Pacifica Hybrid a Good Minivan? Yes, the Chrysler Pacifica Hybrid is a good minivan. It has seven welcoming seats, an easy-to-use infotainment system, and plenty of cargo space. The added torque from the electric motors help this van move quickly off the line.
Stroke-averaged net combustion pressure is an abstraction—in reality, combustion pressure is constantly changing, beginning to rise shortly after the spark ignites the mixture, reaching a maximum at about 11 degrees after top dead center (ATDC), and then falling as the piston descends on its power stroke. That constantly changing combustion gas pressure can be measured by fast, accurate high-pressure microphones, but we make a useful abstraction of it to simplify our thinking.
Therefore stroke-averaged net combustion pressure is abbreviated to BMEP (brake mean effective pressure) which averages the complex, changing actual combustion pressure to a constant pressure which, if it acted over the entire piston stroke, would produce the same power at the crankshaft.
Notice especially the word “net.” It is there to tell us that this BMEP is what is left after normal engine losses—the viscous friction of bearings and sliding pistons, pumping loss, etc.—have been subtracted from the raw energy of combustion gas. That is normal in dynamometer testing—the power we get at the sprocket or shaft is what is left after losses are subtracted.
2016 Porsche Cayenne Hybrid: What You Need to Know
The 2016 Porsche Cayenne Hybrid has incredible acceleration, athletic handling, and a stately cabin, yet it sits in the lower half of our luxury midsize SUV rankings. It has high ownership costs, subpar fuel economy for a hybrid, and a small cargo space. The 2016 Porsche Cayenne Hybrid is ranked: #4 in 2016 Hybrid SUVs #10 in Used Hybrid SUVs $30K and up Is the 2016 Porsche Cayenne Hybrid a Good Used SUV? There's no denying the 2016 Cayenne Hybrid is an exceptional vehicle, boasting sporty performance and a posh interior. But it will cost you more to buy this Porsche than it will to purchase most other luxury midsize SUVs.
BMEP is the sum of many parts.
- How well does the engine fill its cylinders? The more completely the cylinders are filled, the greater the BMEP. Cylinder filling is measured as “volumetric efficiency”—which compares cylinder displacement to the volume of fuel-air mixture actually trapped in the cylinder after the intake valves close. One hundred-percent volumetric efficiency means that the cylinder is filled completely, but wave effects in the intake process can sometimes increase this to as much as 125 percent.
- How efficiently does it burn that charge? There is some flame quenching on metal surfaces, and some injected fuel droplets may be too big to burn completely, or may hit the cylinder wall and be lost into the crankcase—swept away by the piston rings.
- How much energy is consumed by friction, heat loss, and the forced rapid movement of air in the crankcase? (One Japanese maker gained 5 hp in an 1,100cc four by “streamlining” this movement.) Engineers seek to make combustion rapid, as the longer super-hot flaming combustion gas is held between piston and head, the more heat flows out of that gas and into the metal parts, from which it must then be removed by the engine’s cooling system. At low or cruising throttle more energy is consumed by pumping loss, which is associated with making the engine perform the work of pulling against low manifold pressure. Mainly because of this, engines deliver better gas mileage on the interstate at 75 mph than they do tootling along country roads at 40 mph.
In general, engine BMEP has increased steadily as manufacturers have sought to produce more power from the various classes of engines they produce. This effect is obvious in the, but also operates in the , where ever-heavier bikes need more oomph to keep up with speeding multilane traffic.
2020 Indian Springfield Dark Horse Long-Term Review
We put 7K miles of daily use on the tough-guy tourer.2019 saw the introduction of Indian’s redesigned Chieftain fairing, new seat, and new saddlebag shape, but the Springfield was a little late to the party. That tall-backed seat design and more squared-off bag shape didn’t hit the Springfield models until 2020, but while those do have a major visual impact, that’s not the biggest update here. The Thunder Stroke 116 powerplant steals the show, improving power while maintaining everything we liked about the 111.
The third major element in engine power is rpm—revolutions per minute, which is a measure of how often our engine can perform its energy-release cycle. There are limits to the benefit of using rpm to boost power, because as revs rise so does friction loss. The sports management organization Dorna, which administers, did not want its manufacturers going mad as F1 had done, pushing the peak revs of big V-10 engines to 20,000. Being interested in such technology, I had been delighted to see push its five-cylinder 125 GP bike engine to 21,000 back in the 1960s, but pouring money into technology that has no marketplace application is a poor investment. For that reason Dorna set a limit to how far MotoGP could go in raising rpm through use of bigger pistons and ever-shorter strokes. In F1 piston diameter grew to be 2.3 times the stroke length, slowing combustion and increasing heat loss. Dorna therefore set a limit at 81x48.5mm, or a bore/stroke ratio of 1.67.
The need to meet more stringent emissions levels has required some rethinking about BMEP. The hotter combustion is made (by higher volumetric efficiency, higher compression, and more accurate control of mixture), the more oxides of nitrogen are produced—combustion hot enough to actually burn atmospheric nitrogen. Dyno operators are familiar with the sharp tang of such oxides. Another ill effect of higher combustion temperature is losses from molecular dissociation and from energy in very hot combustion gas being less available for piston-pushing duty because it partly takes the form of molecular rotation and vibration. This is a major part of how operation on lean mixture reduces fuel consumption. Leaning the mixture reduces peak combustion temperature, lessening the losses from the just-described effects. What pushes pistons is the velocity of hot gas molecules, physically hitting the piston and giving it a shove. But energy in the form of molecular rotations and vibrations, which appear increasingly at higher temperature, doesn’t push pistons. That energy goes out the exhaust pipe.
2020 Nissan Rogue: What You Need to Know
The 2020 Nissan Rogue places in the top half of our compact SUV rankings. It boasts a good predicted reliability rating, a generous list of standard safety features, and plenty of space, but its underpowered engine keeps it from ranking higher. © Nissan North America, Inc. 2020 Nissan Rogue The 2020 Nissan Rogue is ranked: #8 in Compact SUVs #26 in Crossover SUVs #16 in SUVs with 2 Rows Is the Nissan Rogue a Good SUV? Should I Buy the Nissan Rogue? Although the 2020 Rogue doesn’t have the highest ranking, it's a good choice for some shoppers. It boasts a smooth ride, excellent fuel economy, and an abundance of features.
In supercharging engines we boost power by compressing the mixture, in effect forcing, say, 300cc of mixture into a 250cc cylinder. But because of the above effects we don’t get the full 20-percent power boost that dividing 250 into 300 says we should. The hotter we make combustion by conventional tuning techniques, the greater the loss from these effects.
Therefore manufacturers get busy with test engines on instrumented dynos, with hundreds of possible fueling and ignition maps, to find ways to get the power their intended market demands, in a form that meets US EPA or European Commission standards.
I believe we will be seeing some slow reduction in motorcycle engine BMEP as it becomes necessary to reduce peak combustion temperature by use of leaner mixtures. To deliver or exceed the power of last year’s model, while meeting relevant emissions limits, it may prove necessary to compensate for loss of some BMEP by increasing the other two major variables in engine power: displacement and rpm.
As a former chief engineer at Harley, Earl Werner, once said, “The job of engineering is not to seek abstract extremes but rather to deliver what people actually want.”
2016 Toyota Prius: What You Need to Know .
The 2016 Toyota Prius ranks at the top of its class, thanks to its refined ride and handling, handsome interior, generous cargo space, and excellent safety and reliability ratings. The 2016 Toyota Prius is ranked: #1 in Used Small Cars $14K and up #1 in 2016 Affordable Small Cars #1 in Used Hybrid Cars $20K and up #1 in 2016 Hybrid Cars Is the 2016 Toyota Prius a Good Used Car? Why You Can Trust Us We’ve researched 20 Toyota Prius reviews, as well as hard data points like reliability scores and cost of ownership estimates, to help you make the best car-buying decision possible. U.S.