Thanks very much M Travler
One of the fascinating things about the history of automotive design is that just about anything you can think of has been thought of and probably tried. Ferdinand Porsche designed and built a petroleum electric hybrid in 1901. The idea for four stroke engine was conceived in the mid 1800’s. Up until the early 1900’s electric, steam and the ICE were all competing to be the power source for the horseless carriage. In 1920 when it was discovered that tetrahedral lead added to gasoline could vastly increase the compression ratio and power output of the ICE steam and electric lost the battle. Almost all of the improvements in the ICE since have come as a result of advances in materials and manufacturing. A hundred years later we are in much the same place. The market is ready for some “new” breakthrough. Vastly improved batteries could bring about the dominance of electricity for powering cars, but there are still a lot of improvements possible for the ICE and other technologies.
Good post, MT.
I would add another reason that other power sources (electric, and steam) lost out to the ICE was that Henry Ford decided on the gas-powered ICE for his mass produced Model Ts. Once those flooded the market, the choice was set.
Nothing new under the sun etc,it really amazes me the refinement and sophistication of the reciporcating engine,who would have thought chunks of metal reversing direction several times a second could be so effective at converting chemical energy into kinetic energy.Good posts MT and TSM-Kevin
Kmccune,
You asked about whether the fuel required to produce a given HP is a constant. What you’re talking about is “specific fuel consumption” and is effectively the effeciency of the engine.
Realistically, for a gasoline engine, you’re doing well if you can produce 20hp, for an hour straight, from 1 gallon of gas.
Kmccune,
You asked about whether the fuel required to produce a given HP is a constant. What you’re talking about is “specific fuel consumption” and is effectively the effeciency of the engine.
Realistically, for a gasoline engine, you’re doing well if you can produce 20hp, for an hour straight, from 1 gallon of gas.
Thanks MJ75,so we can sort of in a round about way calculate a vehicles fuel consumption,figuring in drag,weight etc and part throttle fuel flow at a given rpm?(a simplified view I’m sure given all the other factors)?-Kevin
Yes, you could possibly determine a rough idea of fuel burn if you had a vehicle’s CdA (frontal area X drag coefficient), it’s curb weight and rolling resistance.
I actually “reverse-engineer” this to see what BHP is needed…a car that gets 40 MPG at a steady 60 MPH is burning 1.5 GPH (and thus requires around 30BHP).
I noticed this from flight planning: at 75% cruise, an aircraft engine burns 1/20th of Max HP. Modern cars are somewhat more efficient, and it seems they can get 1/20th of the actual HP being put out.
meanjoe75fan, is your result of 30BHP at the flywheel or at the wheels? And what car was the subject of that “reverse-engineering?”
Thanks MJ75, what effiecency are we talking about? In other words a hybrid is a good deal-Kevin
Incidentally, this is how F1 engines work. They’re really small, and have ridiculously short piston travel, but they have a lot of cylinders spinning the engine at nearly 20,000 RPM, so they’re able to turn the wheels very fast. Their 0-60 isn’t nearly as good as if their engines were larger, but in that application it doesn’t matter, because about the only time you’re anywhere near as slow as 60 in an F1 car is when you’re pulling in to the pits for gas (and it’s still pretty impressive because an F1 car is so light).
So THAT’S why the pitcrew always pushes the car. It’s not to shave a second or two, but b/c the engine is so low torque / high horsepower that it’s not easy for it to start from 0mph, at the low end of RPMs
Good info never thought of it that way-Kevin
Unfortunately, all of these improvements had to wait for profitability to catch up. As long as lesser technology is more profitable to use, you won’t see it. Fuel injection, long held to be more efficient and reliable then carbs, had to wait for cheaper electronics to be include in all cars…same with just about every other development. When electrics are more profitable, you see more of them too.
Formula one and the battle field ,brought a lot new stuff and oddities out some advances and some stuff that while well thought out,ended up as one offs and curoisities-From the 16 cylinder,1600 cc Honda engine,to Smokey Yunicks 208 cid Chevy small block Indy motor,not to mention a tank powered by 5 -6cyl Chrysler flathead engines(worked out pretty well)-Kevin
James:
I have read about HP vs torque so often, and I still really don’t get it. It makes me feel very dumb.
If torque is the pull from the line…but why does my fathers TDI engine with greater torque than my V6 accord accellerate so much slower? If it has greater torque shouldn’t it be faster off the line?
But if HP equals work over time, then wouldn’t HP lead to better 0-60 time? Because the engine is able to move more weight in less time.
I feel like all I do is put myself into an infinite loop when I think about this. It really makes me feel like a moron.
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UsedEconobox2UsedBMW:
I know exactly what you mean…
I have no clue either.
Neither do most car buyers.
In the extreme example of torque,
massive piston only spins the driveshaft once per cycle,
you have a very strong “twisting” motion (like a tank that can go up a steep hill) ?
If you have tiny pistons, the driveshaft rotates many more times, for higher speed?
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James:
Wouldn’t torque refer more to how much work that the engine can do with each rotation, and horsepower indicates how many rotations the engine can make. So when combined you get a fast moving engine pushing with a lot of work done in each rotation?
Good Lord, how did things get so off track.
Torque refers to twisting force. It’s measured in foot-pounds (or in-pounds, or whatever). 100 ft-lbs of torue equals the twisting force that would be applied to a shaft if you applied 100 pounds of pressure one foot from the rotating axis. 200 ft-lbs of torque equals 200 pounds of pressure applied one foot from the rotating axis (or 100 pounds 2 feet frome the axis).
Horsepower is the amount of work that can be performed over time. 100 horsepower means you could lift 100 pounds one foot off the ground in one minute.
The question of smaller pistons and shorter strokes as they relate to higher engine RPMs is only related indirectly. Smaller pistons and shorter strokes reduce the amount of inertial energy developed by the reciprocating mass, reducing stresses and allowing the engine to operate at higher RPMs (all other things being equal). Higher RMPs allow greater amounts of inertial energy to be stored in the flywheel and rotating components, that stored energy being useful for acceleration at high speeds. Race engines are designed to operate at these speeds, to breath well there, to allow sufficient flow into and out of the cylinders, to provide sufficent fuel for the massive amounts of air being gulped, etc. Also, smaller engines weigh less, and that lower weight improves acceleration and handling.
Large cylinders and pistons create a great amount of initial force because they allow a huge explosion, pushing the piston with all its force much of the way down the stroke. But they also lose energy at the bottom of the stroke, because it then takes energy to stop the parts and change their direction at the bottom of the stroke. And it takes so much energy to keep stopping and changing the direction of those heavy parts (pistons and connecting rods) that they can’t rev very fast without becoming ooverstressed.
In short, torque and horsepower are two different measurements. Related, but different.
And small bores/short stroke do not by themselves manifest as more or less power, but they do allow the engine to have differenet performance characteristics for a different application.
A practical example of the differences between power and torque can be illustrated if you think about a multi-speed bicycle.
Imagine two identical bicycles travelling at 15 MPH. They both would require the same power output to travel that speed (in theory, keeping things identical.)
You can make the needed power by either stomping in the pedals slowly, in a “tall” gear (high torque, low rpm)…or by spinning the pedals faster in a lower gear (low torque, high rpm).
Good example “meanjoe75fan”… As the human being is incapable of developing much torque, a high cadence and frequent gear shifting to deliverer what hp they are capable to the road. This is much like tractors whose motors are actually better measured in horse power. Gear chaninging is essential to deliver appropriate power where motors are often much smaller then one would expect. In a tractor, the transmission is actually the center piece of performance, not the motor…where diesel is king, not just for torque but for hp with efficiency. This is a world where 2k is considered high rpm.
Higher torque is now developed by higher compression and better engine breathing through tubo charging and variable valve timing and not cubic inches alone. Look at the torque numbers for low displacement tubo charged Subarus and multivalve gas motors…pretty impressive !
Two strokes have surprisingly high torque for their displacement and why, even with emission standards, they are popular today in outboards that must pull water skiers out of the hole. Small light and powerful is a tough combination to beat… True in a lawn mower you have to push up or control on down hills and whose orientation might be tough on weighty, oil starved, low torque 4 strokes. Contrary to what many think, two stokes are actually lower rpm with more torque per cubic inch then gas motors…they just sound “fast” revving with their ignition occurring at twice the rate. Smoky two strokes are stil hard to beat for lots of applications.
Good illustration, Joe. I tip my hat to you.
It seems to me that the manufacturers are marketing horsepower numbers that are only momentarily produced.
Electric motors often have a duty cycle rating.
Designing something like a starter motor to run briefly then rest reduces its size and weight.
Same concept applies to IC engines.