Amen Pat.
Gallons per hour....
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Amen Pat.
Redneck in training
Elite Member
Here is the most efficient piston engine in the world.
The Most Powerful Diesel Engine in the World
It has everything to do with the size. Surface area increases with square of dimension while volume increases with cube of dimension. The larger the engine the less friction/volume there is. Large engines have a fraction of friction/volume than small engines. There are other factors such as lower heat dissipation etc that increase efficiency even further. All engines are mechanical compromise. If this engine could be built as single cylinder its efficiency will be even higher. This engine is about 60% more efficient than small tractor engine.
Notice that it is turbocharged. The turbine recovers energy of escaping exhaust gases and returns it to the engine in form of higher pressure in the intake. If you measure pressure, temperature and especially velocity of the gas upstream of the turbine and compare it with pressure, temperature and velocity downstream of the turbine you would see that all three values are significantly lower. The difference is recovered energy. Since the exhaust gases enter and exit muffler with less energy turbocharged engines are also quieter.
Here are efficiencies of selected combustion engines.
Brake specific fuel consumption - Wikipedia, the free encyclopedia
The Most Powerful Diesel Engine in the World
It has everything to do with the size. Surface area increases with square of dimension while volume increases with cube of dimension. The larger the engine the less friction/volume there is. Large engines have a fraction of friction/volume than small engines. There are other factors such as lower heat dissipation etc that increase efficiency even further. All engines are mechanical compromise. If this engine could be built as single cylinder its efficiency will be even higher. This engine is about 60% more efficient than small tractor engine.
Notice that it is turbocharged. The turbine recovers energy of escaping exhaust gases and returns it to the engine in form of higher pressure in the intake. If you measure pressure, temperature and especially velocity of the gas upstream of the turbine and compare it with pressure, temperature and velocity downstream of the turbine you would see that all three values are significantly lower. The difference is recovered energy. Since the exhaust gases enter and exit muffler with less energy turbocharged engines are also quieter.
Here are efficiencies of selected combustion engines.
Brake specific fuel consumption - Wikipedia, the free encyclopedia
SPYDERLK
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An upfront HTD belt gear reduction of around 4:1 should enable use of the standard tranny. What to do about the wrong sound and durability???....Pat, I understand the equation perfectly and you are 100% correct. But, just try mounting a 50 horsepower 250cc 2 stroke motocross engine in your tractor and just see how much "work" it gets done. I guess if you had enough gears to let it wind up.....
larry
patrick_g
Elite Member
I basically agree with your post but... My NA Kubota only smokes when I start it up, especially cold, which makes a quite noticeable large puff of smoke or if I ram the throttle from idle to max which generates a moderate puff of smoke. I can work it in low range with full throttle loading it to the point of stalling the HST and it doesn't visibly smoke. Say for example a full load of dirt in my large HD box blade with hydraulic scarifiers down and digging while going up a grade. Depending on traction this will either spin some wheels (4WD) or bog the engine down to lower RPM but likely a combination of both. I don't think there is anything special about my Grand L-4610HSTC so it is likely a family trait.
Not complaining, mind you, I'm OK with not billowing smoke and looking macho (however macho you can look in a 39HP cab tractor.)
Pat
patrick_g
Elite Member
Larry, I don't think Ring ding ding ding Ring ding ding would go over too good with the fellas on down to the Cattleman's Association. They'd likely laugh me out of the county.
HP is HP is HP however developed (at least steady state like plowing or brush hogging) but... torque curves, their peak and slope have a very material effect on getting 'er done with a tractor. An attribute called STIFFNESS is important to a tractor. Working the tractor above the torque peak, especially one with a relatively steep slope demonstrates great stiffness. As the engine is loaded heavier and RPM drops you go up on the torque curve which resists further RPM drop. It is like a variable rate spring. The more you compress it the harder it is to compress but the rate of change is non-linear and much greater than a standard spring. On the other hand, if you let the RPM drop below the torque peak then the more you load the engine the slower it goes and the easier it is to make it go even slower.
I'm not entirely sure but I suspect the dirt bike/motocross engine would not have an appropriate torque curve for tractoring, irrespective of the tranny. used. Still, it would be good for some laughs (if the operator had good ear protection.) Rrring ding ding ding rrring ding ding.
Pat
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ruralruss
Silver Member
The amount of fuel is determined by the fuel control (incorrectly called the throttle) not the amount of air. Regardless of the position there should be little or no smoke unless you are lugging it down too much and need a lower gear. More fuel equals more more rpm and more pumping losses. The turbo lessens the pumping losses and thus increases the power available for external work.
Russ
SPYDERLK
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Im pretty sure the maximum torque and power achievable in any given diesel will be where you start seeing significant smoke. You waste a little fuel so that the absolute max that can burn during the power stroke is there when you need it. Both my L Kubotas smoke under heavy load before they begin to bog. This is optimum for power. OTOH, my Mahindra will not smoke until it bogs badly ... and it bogs easier [less stiff as Pat coined--less torque rise]. As far as Im concerned its upper limit of fuel injection is set too low.--the fuel curve needs a quicker ramp up in response to the governor.
larry
patrick_g
Elite Member
Larry, the limiting factor of my '97 Dodge/Cumins TD is heat. I have an aftermarket higher pressure than stock injector pump and injectors with smaller holes. The result is about the same fuel quantity is injected but in a finer plume that burns more completely. I get more HP and more Torque while simultaneously getting a little better fuel economy (MPG) through greater combustion efficiency. When I really get on it I have to watch the pyro measuring the EGT to avoid overheating the combustion chamber and melting the top of a piston. I can safely sustain higher torque and HP output without exceeding the temperature red line but at maximum it will overheat if you stay on it long enough. I can put out a puff of smoke at throttle up from a dead stop with a normal take off from a dead stop. If I take off like a drag race I put out serious smoke until the turbo spins up and then I develop MONSTER POWER without significant smoke!
Yes you can turn up the fueling till it smokes at any reasonably high engine output but... why? I can't use all the CLEAN power I can produce without overheating the combustion chamber. Maybe extra wasted fuel carries off significant heat and helps keep the engine cool? I think not.
What you report may very well be the case with other configurations that are different from mine.
Pat
SPYDERLK
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However, I can use all the clean power my tractor can produce. Your fuel system is modified yet the way I interpret it it still smokes a little on full boost. That seems about right to me. My tractor smokes none when on boost. I cant imagine the engine is in a high enuf tune to melt itself. To my knowledge the Cummins is boosted high enuf to need an intercooler. That gives a super rich /dense air charge. Easy to imagine you could feed enuf coal to melt it. Quite unsimilar to the tractor.
Ever notice the diesels at tractor pulls... They use more than all the clean power they can get.
larry
patrick_g
Elite Member
However, I can use all the clean power my tractor can produce. Your fuel system is modified yet the way I interpret it it still smokes a little on full boost. That seems about right to me. My tractor smokes none when on boost. I cant imagine the engine is in a high enuf tune to melt itself. To my knowledge the Cummins is boosted high enuf to need an intercooler. That gives a super rich /dense air charge. Easy to imagine you could feed enuf coal to melt it. Quite unsimilar to the tractor.
Ever notice the diesels at tractor pulls... They use more than all the clean power they can get.
larry
Larry, I should have said without noticeable smoke once the turbo spools up. According to my wife (who has followed me on the highway) at each shift of the automatic there is at least a small puff of smoke and likewise if I punch the accelerator pedal. From a standing start to avoid making a cloud of smoke you just don't make a jackrabbit start. For a really low smoke getaway you have to advance the accelerator fairly slowly and not let fueling outrun the turbo very much.
I see a lot of diesel pickups that produce way more smoke than mine under similar load circumstances and I assume they tuned for power not efficiency. I tried to get a good compromise and I think I just about nailed my target. The truck was originally sold in California and had an EGR system feeding exhaust into the intake manifold. Their design for that introduced irregularities into the distribution and flow of air in the manifold. I changed out the manifold to a non-EGR type and got more even distribution of flow to the cylinders.
I'm pretty sure my tractor, short of some kind of massive malfunction, will never overheat itself in the combustion chamber. I'm pleased that it doesn't smoke much except for a fair cloud when it starts and a just noticeable one with serious throttle up or if you bog the engine by working it really hard you can see a little color in the exhaust but not very much.
Pat
