LNF Wiseco Pistons stock rods
09-15-2015, 06:32 PM
#26
V8's need balancing when weight changes, but inline 4's (and 6's, and boxers) do not. There is always another piston moving in the other direction that cancel out the primary forces and you can't balance your way out of the secondary.
Daniel
Daniel
Last edited by TurboWood; 09-15-2015 at 07:18 PM.
09-16-2015, 12:39 AM
#28
- The crankshaft is balanced by itself (rod & piston weight has no impact on the crank balance)
- The rods and pistons need to be the same mass
If you do those things then the assembly is balanced and those things are done already. What else could one do?
Daniel
09-16-2015, 03:27 PM
#30
Senior Member
What exactly needs to be balanced on a 4-cyl?
- The crankshaft is balanced by itself (rod & piston weight has no impact on the crank balance)
- The rods and pistons need to be the same mass
If you do those things then the assembly is balanced and those things are done already. What else could one do?
Daniel
- The crankshaft is balanced by itself (rod & piston weight has no impact on the crank balance)
- The rods and pistons need to be the same mass
If you do those things then the assembly is balanced and those things are done already. What else could one do?
Daniel
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TurboWood (09-17-2015)
09-17-2015, 04:37 PM
#32
http://www.enginebuildermag.com/2014...alancing-work/
At the end of the day, go ahead, skip out on balancing - people do it in all sorts of engines, and swear by it;
My link is no more legitimate than Kevin's, but both need to be taken with a grain of salt;
Is it possible that a perfectly balanced engine may last longer, or make more power than one which isn't properly balanced?
The same arguments can be used for and against replacing the balancer at the front of our engine with an over-glorified pulley - some do it, some opt to steer clear...
Considering the negligable cost at the time of doing a full on build, I will always opt to:
-align hone (when possible; requires a deck plate)
-balance
Again, I will repeat myself;
IMHO to suggest that balancing isn't needed is redonkulous.
... but that's just my opinion.
With a horizontally opposed four-cylinder engine, two pistons are always moving in when two pistons are moving out.
Consequently, the forces, equal and opposite, are essentially balanced provided the weights of each piston and rod assembly is equal. Balancing these types of engines is fairly simple because all you have to do is equalize the weights of the piston and rod assemblies.
With an inline four-cylinder engine, two pistons are moving up while two pistons are moving down. The motions of the pistons offset each other, but because they are not horizontally opposed the crankshaft needs counterweights to offset the reciprocating forces.
Consequently, the forces, equal and opposite, are essentially balanced provided the weights of each piston and rod assembly is equal. Balancing these types of engines is fairly simple because all you have to do is equalize the weights of the piston and rod assemblies.
With an inline four-cylinder engine, two pistons are moving up while two pistons are moving down. The motions of the pistons offset each other, but because they are not horizontally opposed the crankshaft needs counterweights to offset the reciprocating forces.
My link is no more legitimate than Kevin's, but both need to be taken with a grain of salt;
Is it possible that a perfectly balanced engine may last longer, or make more power than one which isn't properly balanced?
The same arguments can be used for and against replacing the balancer at the front of our engine with an over-glorified pulley - some do it, some opt to steer clear...
Considering the negligable cost at the time of doing a full on build, I will always opt to:
-align hone (when possible; requires a deck plate)
-balance
Again, I will repeat myself;
IMHO to suggest that balancing isn't needed is redonkulous.
... but that's just my opinion.
09-17-2015, 05:43 PM
#33
Senior Member
I was just posting something i found with the google becauae i have never heard that before
09-17-2015, 07:46 PM
#36
Senior Member
09-17-2015, 09:09 PM
#37
Yes. There is a big difference between a V and an inline engine. I'm not at all talking about V engines when I'm suggesting that the ecotec doesn't need to be balanced.
All engines have primary and secondary forces. In the case of the inline 4 all primary forces are naturally balanced by the fact that there are pistons moving up at the same time that others are moving down.
The only major forces left unchecked are secondary and these occur at twice crank speed so they absolutely cannot be offset by anything you do with the crank, rods, or pistons. The only way to counter this is with balance shafts.
Soundjunky,
I'm sorry, but I do not understand what you want to balance. Are you suggesting that we need to add bob-weights to the crank during balancing? What are these bob weights going to offset? You will be adding the exact same weight 180 degrees apart. What good will that do?
*edit*
To comment on your link. I think enginebuildermag just had one incorrect word in their article. The boxer 4 does not require counterweights on the crank because the opposing rod journal is the counterweight. By comparison an inline 4 does have counterweights, but these are only used to offset the mass of the crankshaft (rod journals). enginebuildermag should have said that the inline 4 needs counterweights for the rotating mass (not reciprocating).
I would also suggest giving a look at Honda crankshafts. To the best of my knowledge the S2k crankshaft is balanced by itself w/o any bob-weights. When I looked at various honda forums you can find people suggesting a full rotating group balance (clutch, flywheel, and crank pulley), but hopefully you agree this is only a racecar option. For us mortals we don't want to rebalance the system when the clutch wears out.
Daniel
All engines have primary and secondary forces. In the case of the inline 4 all primary forces are naturally balanced by the fact that there are pistons moving up at the same time that others are moving down.
The only major forces left unchecked are secondary and these occur at twice crank speed so they absolutely cannot be offset by anything you do with the crank, rods, or pistons. The only way to counter this is with balance shafts.
Soundjunky,
I'm sorry, but I do not understand what you want to balance. Are you suggesting that we need to add bob-weights to the crank during balancing? What are these bob weights going to offset? You will be adding the exact same weight 180 degrees apart. What good will that do?
*edit*
To comment on your link. I think enginebuildermag just had one incorrect word in their article. The boxer 4 does not require counterweights on the crank because the opposing rod journal is the counterweight. By comparison an inline 4 does have counterweights, but these are only used to offset the mass of the crankshaft (rod journals). enginebuildermag should have said that the inline 4 needs counterweights for the rotating mass (not reciprocating).
I would also suggest giving a look at Honda crankshafts. To the best of my knowledge the S2k crankshaft is balanced by itself w/o any bob-weights. When I looked at various honda forums you can find people suggesting a full rotating group balance (clutch, flywheel, and crank pulley), but hopefully you agree this is only a racecar option. For us mortals we don't want to rebalance the system when the clutch wears out.
Daniel
Last edited by TurboWood; 09-18-2015 at 03:27 AM.
06-03-2016, 01:52 PM
#40
Finally answering my own question...the stock piston with rings are 390gm. The stock replacement wiseco pistons are 360gm.
I think it's reasonable to say the wiseco pistons aren't putting more load on the rods than a stock piston. That is unless the ring pack is more than 30gm.
Daniel
I think it's reasonable to say the wiseco pistons aren't putting more load on the rods than a stock piston. That is unless the ring pack is more than 30gm.
Daniel
06-03-2016, 03:06 PM
#41
This is slightly off-topic, but I thought I'd throw this in. I was talking to a shop at SEMA that forged rods and theirs were H-beams. I asked why they did it, and his answer was basically that rod failures are usually due to tensile stress from slowing the piston down at the top of the stroke so it doesn't really matter (translated in my head to "looks cool"). Since an I-beam is more resistant to bending in the way that I've seen rods fail than an H-beam, personally I'd go with the I-beam for rods if I were to change.
06-03-2016, 03:40 PM
#42
Senior Member
On the ZZP site it says u have to use aftermarket rods with aftermarket pistons
06-03-2016, 10:03 PM
#44
This is slightly off-topic, but I thought I'd throw this in. I was talking to a shop at SEMA that forged rods and theirs were H-beams. I asked why they did it, and his answer was basically that rod failures are usually due to tensile stress from slowing the piston down at the top of the stroke so it doesn't really matter (translated in my head to "looks cool"). Since an I-beam is more resistant to bending in the way that I've seen rods fail than an H-beam, personally I'd go with the I-beam for rods if I were to change.
Correct me if I'm wrong, but both refer to the cross section looking like either an upper case 'H' or "I" depending on the angle it's looked at.
I also believe that the the term "H beam" is more commonly used for aftermarked rods which have more pronounced ends;
I believe the term "I beam" is more commonly used in construction with steel beams;
A similar term "I joist" is used for manufactured floor joists.
06-03-2016, 10:08 PM
#45
I'm pretty sure "H beam" & "I beam" are referring to the same thing. Correct me if I'm wrong, but both refer to the cross section looking like either an upper case 'H' or "I" depending on the angle it's looked at. I also believe that the the term "H beam" is more commonly used for aftermarked rods which have more pronounced ends; I believe the term "I beam" is more commonly used in construction with steel beams; A similar term "I joist" is used for manufactured floor joists.
06-03-2016, 10:36 PM
#46
If the I beam is less durable it has nothing to do with the shape. For the same cross sectional area, the I beam will resist bending better than the h beam (higher moment of inertia). The only reason I can think of for doing an h beam is that it looks cooler.
06-04-2016, 11:56 AM
#48
I looked it up, you're right - sorry guys! Video Link: https://youtu.be/fszNIRbS8yw
06-04-2016, 01:26 PM
#49
06-04-2016, 01:27 PM
#50
The "all other things being equal" statement in the video is a little confusing. Seems to me the things that are equal would be material and bending stiffness. That's the only way the I-beam would be lighter but the H-beam would be "stiffer." That particular stiffer would be axial stiffness. For axial stiffness, cross-sectional area is the only factor. If you keep the weight the same, the I-beam will be just as stiff axially and stiffer in bending. Therefore, there really is no reason for an H-beam rod.