Kinda a chainsaw 101 question, but I got ask. Assuming your saw is rated to comfortably push a 18" or 20" chain............will you notice a pretty significant power differnece if you go with the 18" bar/chain selection? Your driving less chain over a shorter distance, but wasn't sure if you'd notice it. Thoughts?
Bar length choice vs power
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Insignificant between those two choices. Really only matters if both bars are fully buried in the wood. A 16" bar and a 20" bar setup mounted on the same saw running the same chain, etc. should cut any log under 16" at near the same rate. If the bars were buried then obviously it takes more power to cut through a 20" tree in one pass than a 18" tree.
So...maybe that's my question. If your bar is buried in the wood....will you see a defference in a 18" vs a 20" setup?
Maybe a very slight difference, but I highly doubt it. Now go from an 18" bar to a 28" bar on a 60cc saw, and you'll notice a difference. 
Yes there is a difference. I use 16" bars because it is rare that I'm cutting more than 32" log. I also like my bars and chains to interchange. I have an 034 and you can't push it in hard enough into a white oak log to stop it from spinning. That being said I'd like a long bar chain saw but I haven't found the 066 that I'm looking for.
Assuming your bar isn't buried in wood, it will take some extra HP to rotate the mass of the chain about the bar...additional friction...all that stuff. I can't do the math/physics to tell you how much power that will take, but I'm guessing that 4" of chain (two on top and two on bottom) isn't going to make a perceptable difference.
Now, if your bar is buried in the wood, one would think you would need 11% (2/18) more power on your saw to get the same performance (2" more of bar in contact with wood with a baseline of 18") on when using a 20" bar over an 18". This would probably be noticeable, especially the if the HP required to run either bar is near the max HP of the saw (probably the case with a 45 - 60 CC saw) because you don't have any extra HP in reserve. If you are running a 460, the saw has some extra HP on reserve that it can't utilize (based on a limitation of how many RPMs it can generate), so you probably won't be able to tell a difference.
A good mechanical engineer or physicist (hell, probably even a bad one) can probably do a lot better and more accurate job explaining this. I'm just going by a public school education and common sense
Now, if your bar is buried in the wood, one would think you would need 11% (2/18) more power on your saw to get the same performance (2" more of bar in contact with wood with a baseline of 18") on when using a 20" bar over an 18". This would probably be noticeable, especially the if the HP required to run either bar is near the max HP of the saw (probably the case with a 45 - 60 CC saw) because you don't have any extra HP in reserve. If you are running a 460, the saw has some extra HP on reserve that it can't utilize (based on a limitation of how many RPMs it can generate), so you probably won't be able to tell a difference.
A good mechanical engineer or physicist (hell, probably even a bad one) can probably do a lot better and more accurate job explaining this. I'm just going by a public school education and common sense
You're*
Most yahoos on this board under-bar their saws and will answer in the affirmative. This yahoo says woodcutting isn't a race and having that extra bar when you need it is way more important than any perceived power gains one might achieve with a shorter bar.
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That would be the differance between soft pine vs hedge apple.......Your not going to pull a wild thing with a 24 inch bar through my hard woods. You west coaster's get ahold of one of these you would sing another Song!
Bars=weight. Regardless of what a particular saw can pull I wouldn't put a 28" bar on any saw that I didn't need it on. I rarely even have a 24" on a saw that could pull a 32" with ease. As to your original question I agree with other posters that a few inches here or there is negligible.
Exactly why I run the size bar listed for each saw in my signature.
The CS-520 50cc. It came with a 20" small radius bar, and a .325" low kickback chain.
I upgraded it to an 18" Oregon Pro-lite bar (larger radius), and a real chain. World of difference. I really like running this saw now. And with the bar buried in hardwood it pulls just fine. Could I have ran a 20" bar...probably. But as mentioned, buried in hardwood, even that was a little on the overly optimistic side.
The CS-400 40cc. (My first saw.) It came with an 18" small radius bar, and a 3/8" low-profile low kickback chain.
I upgraded it to a 14" Oregon Pro-91 bar (larger radius), and a real chain. Much better. This saw just did not have the balls to pull that 18" bar/chain combination buried in hardwood (soft maple was doable) in a reasonable amount of time or effort. Good limbing, cleanup, and small-stuff saw. A nice backup saw too.
The only way I figure, is that they are trying to sell the saw on bar length alone. In my case, the CS-400.
Just take a look at the big-box-store Poulans especially.
(PS. Porting is not something I want. I also very rarely need a bigger saw...so the 50cc/18" bar combo is enough for 95% of the time)
Cheers.
The CS-520 50cc. It came with a 20" small radius bar, and a .325" low kickback chain.
I upgraded it to an 18" Oregon Pro-lite bar (larger radius), and a real chain. World of difference. I really like running this saw now. And with the bar buried in hardwood it pulls just fine. Could I have ran a 20" bar...probably. But as mentioned, buried in hardwood, even that was a little on the overly optimistic side.
The CS-400 40cc. (My first saw.) It came with an 18" small radius bar, and a 3/8" low-profile low kickback chain.
I upgraded it to a 14" Oregon Pro-91 bar (larger radius), and a real chain. Much better. This saw just did not have the balls to pull that 18" bar/chain combination buried in hardwood (soft maple was doable) in a reasonable amount of time or effort. Good limbing, cleanup, and small-stuff saw. A nice backup saw too.
The only way I figure, is that they are trying to sell the saw on bar length alone. In my case, the CS-400.
Just take a look at the big-box-store Poulans especially.
(PS. Porting is not something I want. I also very rarely need a bigger saw...so the 50cc/18" bar combo is enough for 95% of the time)
Cheers.
The 20 inch on the 390 cuts most of the wood on our property, if I need a longer bar I'll go with 28 inch on th 660.
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That would be the differance between soft pine vs hedge apple.......Your not going to pull a wild thing with a 24 inch bar through my hard woods. You west coaster's get ahold of one of these you would sing another Song!
*yawn
Yeah. . . we have NO hardwoods
I took my echo from a 16" bar to a 14" bar and it made a world of difference . My 20" poulan pro has 2 bars one 20" stock and one 18 huskee bar . I use the huskee bar most of the time and the 20" only when I need the length to get through some larger rounds. The 18" makes a huge difference in how it cuts because it has a better tip sprocket as well as it is slightly thicker. As for speed yup they both haul way better when they are sunk into the wood.
Pete
Pete
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