Usually if you have 2 engines of the same displacement the one with less cyliders will have more vibration in most cases. One reason is the fact to achieve the same displacement the pistons, or stroke, or both need to be larger. That extra mass being thrown around can shake things up. Short stroke, high number of cylinder engines will have the least amount of vibration due to the smallest amount of mass going up and down, and around.
My impression of the Foton FT 404
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greg_g
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Patently false. Well, in the context of utility tractor engines anyway. Besides, you're not going to find any comparatively short stroke engines - diesel or otherwise - on farm tractors. The longer the stroke, the higher the torque - and tractor work is for the most part about torque.schmalts said:
The vibrations that I'm describing are a function of how many times how many cylinders go up and down in relation to how many times the crankshaft goes around. Harmonics. I can think of no other reason that they would call the device that compensates for this - the harmonic balance shaft.
All else being equal, a 1.5 liter three banger should require less harmonic balance than a 1.5 liter four banger. Balanced properly, there should be little or no difference in the vibration factor between the two. If the four is running smoother than the three, then there's simply something wrong with the 3 cylinder that needs fixing.
//greg//
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tat2z1969
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Some Mitzubitchy and Iszuzu engines used in tractors a time back where 4 banger short stroke engines, also High rpm.
There should be hardly a detectable difference between odd numbered and even numbered cylinder engines IF balanced properly. I read the link greg posted that pretains to gas 4 bangers that are smaller than 2.2 liter, but that does not apply to diesels used in these tractors.
Any engine of size uses a harmonic balancer to balance the harmonics created by the piston, rod and crank hitting the bottom of the stroke, this helps to dampen flex in the crankshaft hence being able to produce engines with cast cranks that will resist breakage in lew of more costly forged cranks.In racing engines harmonic balancers are fluid.
Vibration is a result of the balance, weather internal balanced (more vibration) and the degree of manufacture duplicating each part to the exact weight,or external balanced (less vibration)
Some 3 cylinders will vibrate more or less than a 4 and vise versa, depending on the balance system used in manufacture.
Internal balance depends on all the parts matching ie all pistons same weight, all rods same weight and so on and the remaining balance is casted in the crankshaft on the throws of the crank to counter weight for the thrust and weight being spun, the critical balance is in the crankshaft if all else is manufactured true.
External balance used in many production engines and for a reason, it does not depend as much on the weight of internal componants, the crank is casted as average to spec., the correction is made for this imbalance in the flywheel and they run the engine on a machine that sort of prints the balance like getting your tires spun balanced and they weight the flywheel at that point for correct balance.(add weight or drill flywheel for desired balance.
Some might remember the Chrysler gas 318 and 360 the torque converter could be used on either engine if the BALANCE weight was knocked off the converter for the other engine to use it. one engine internal the other external. Same with some big truck diesels I won't even get into.
So if a weight comes off a external balance engines flywheel or someone in chop stickland or Detroit puts the flywheel on one bolt hole off we have a sight to moderate vibration.
On a internal balanced engine if the parts are not the same weight or if a part breaks while the engine is being built and another is put in its place without checking( matching) the weight we have vibration.
so I doubt if Chinese factories weigh parts or uses a balance spectrum analyzer that works sort of like the tach pickup does on Jinma and other tractors Spectrum Analyzer - MadTracker Wiki. this is just a idea how the analyzer works it has to be adapted to engine applications.
more here on the spectrum analyzer http://cp.literature.agilent.com/litweb/pdf/5952-0292.pdf
can be adapted to anything of frequency and or vibration and sound, by many different pickup devices.
just a little info for those who care to understand engines.
There should be hardly a detectable difference between odd numbered and even numbered cylinder engines IF balanced properly. I read the link greg posted that pretains to gas 4 bangers that are smaller than 2.2 liter, but that does not apply to diesels used in these tractors.
Any engine of size uses a harmonic balancer to balance the harmonics created by the piston, rod and crank hitting the bottom of the stroke, this helps to dampen flex in the crankshaft hence being able to produce engines with cast cranks that will resist breakage in lew of more costly forged cranks.In racing engines harmonic balancers are fluid.
Vibration is a result of the balance, weather internal balanced (more vibration) and the degree of manufacture duplicating each part to the exact weight,or external balanced (less vibration)
Some 3 cylinders will vibrate more or less than a 4 and vise versa, depending on the balance system used in manufacture.
Internal balance depends on all the parts matching ie all pistons same weight, all rods same weight and so on and the remaining balance is casted in the crankshaft on the throws of the crank to counter weight for the thrust and weight being spun, the critical balance is in the crankshaft if all else is manufactured true.
External balance used in many production engines and for a reason, it does not depend as much on the weight of internal componants, the crank is casted as average to spec., the correction is made for this imbalance in the flywheel and they run the engine on a machine that sort of prints the balance like getting your tires spun balanced and they weight the flywheel at that point for correct balance.(add weight or drill flywheel for desired balance.
Some might remember the Chrysler gas 318 and 360 the torque converter could be used on either engine if the BALANCE weight was knocked off the converter for the other engine to use it. one engine internal the other external. Same with some big truck diesels I won't even get into.
So if a weight comes off a external balance engines flywheel or someone in chop stickland or Detroit puts the flywheel on one bolt hole off we have a sight to moderate vibration.
On a internal balanced engine if the parts are not the same weight or if a part breaks while the engine is being built and another is put in its place without checking( matching) the weight we have vibration.
so I doubt if Chinese factories weigh parts or uses a balance spectrum analyzer that works sort of like the tach pickup does on Jinma and other tractors Spectrum Analyzer - MadTracker Wiki. this is just a idea how the analyzer works it has to be adapted to engine applications.
more here on the spectrum analyzer http://cp.literature.agilent.com/litweb/pdf/5952-0292.pdf
can be adapted to anything of frequency and or vibration and sound, by many different pickup devices.
just a little info for those who care to understand engines.
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greg_g
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Thanks Jim, that's the underlying premise of my statement - which unfortunately devolved into that 3 vs 4 bickering. The OP said the 3 ran rougher than the 4 in the same tractor. My contention is that - since they both should be reasonably balanced - odds are there was something on the 3 banger that needed the attention of a mechanic.tat2z1969 said:
//greg//
the reason i said what i did is the fact that i have a hard time believing the Chinese do a Balance job on thier engines. When out of balance my statment will be dead on. But your all correct in one way or another. When i listen to the Engineers at work talk about balancing theory, and do the math needed to figure what degree of engines do what, it makes my head hurt. there is so much math involved to actually calculate a design change its over my head. I took a balance thoery class and i was out-mathed about 3/4 the way through.
I am not talking about what is needed to do a balance job on an engine, but what is needed to calculate what will happen with different bank angles and cylinder numbers.. Holy crap that is something to figure
I am not talking about what is needed to do a balance job on an engine, but what is needed to calculate what will happen with different bank angles and cylinder numbers.. Holy crap that is something to figure
tat2z1969
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schmalts said:
Welcome Greg:
I never got into the math of cylinder angles and cam disposition thrust figures,never designed a engine from scratch, but I can balance a engine. when we build a new engine for the NASCAR all balance weights are by grain not gram and 1 grain is 1/7000th of a pound and we balance to 0.3 grain on each mulitiple part.
Enough of that, anyway this is how I see it, Chinese copied some Perkins and Buda diesel designs some are even Iszusu made, but the former are copies, the only thing I think the Chinese balance is their intake of rice and rice hooch and by some of the tractors I have seen they lean toward the hooch, (just kidding)
One of my sons bought a 354 with a bad engine and we built it into a pulling tractor for ha ha's. When we started checking weights, pistions were 1 to 1/12 oz difference between the 3, rods about 1/2 oz. I had to have a friend who runs Manley shop in Jersey make new pistons and we got a set of Perkins rods to work after we welded up the crank throws and cut it for the Perkins big ends. Chinese make things just a little different so you can't just swap parts.
MrFixit
Silver Member
A 4 cyl of the same displacement as a 3 cyl has Smaller pistons and most likely valves. The additional weight of the 3 cyl parts "may" add to the feeling of additional vibration.
Tim
Tim
Brad_Blazer
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greg_g
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Whoever wrote/edited that Wikipedia opinion (yes Wiki is as much opinion as it is fact) obviously didn't drive my 5 cylinder 1985 Mercedes turbo diesel. It was demonstrably smoother running than the inline 6 cylinder diesel that replaced it in '86. That's an opinion that can be supported by checking old auto review archives.Brad_Blazer said:
And I'll give you the benefit of the doubt, assuming you missed the part in Straight-5 - Wikipedia, the free encyclopedia that mentions "A 5-cylinder engine also gains smoothness over a 4-cylinder engine..." and "A 5-cylinder engine is longer and more expensive to manufacture than a comparable 4-cylinder engine, but some manufacturers feel these costs are outweighed by its greater smoothness."
But the odd/even thing is anecdotal. The root contention is that the FT404 3 cylinder design has inherently less harmonic vibration than the FT404 4 cylinder version. But once balanced, there should be little difference between the two. The fact that the poster complained the the cylinder vibrated more than the four strongly suggests that there was something else mechanically wrong with that specific 3 cylinder machine.
//greg//
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billbill1
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Greg, I've always heard the same thing that you're stating, but don't have any proof if it's true or not, I know the Chevy has started putting an in-line 5 cylinder in it's Colorado pickup and they used a 3 cylinder in the Metro. I haven't actually been around either one though. Dad had an old straight 8 in a Buick that was one of the smoothest running engines I've ever been around but it might have been an exception.
