Chainsaw RPM's (Frankie gets the last word)

Nutball

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I've always wondered at what rpm chainsaws cut. I always assumed around 6000-8000rpm, not a bad guess. I watched some old videos I have of my saws cutting, and listened to them while trying to match the frequency with a saw tooth tone generator on my phone. Just for fun, here's what I found:

Echo 271t: Max power ~10,600, Optimal cut speed in 4-8" wood 9250, max torque (before loss of power and stalling) 8100-8300.

Chinese husqvarna 365's
newer, stronger, with new aggressive chain: Optimal cut speed 7000, max torque 6250. (This saw may have still been tuned too rich, I know one I had was)
older, weaker design with old chain: Max power 9250, optimal cut speed 8500, max torque 6800.

Husqvarna 390 with 20" bar, 19" cut depth in 10" and 25" logs: Max power 9750-10,650, optimal cut speed 8500-9500, max torque 7800-8300.

All saws tested in solid hickory or oak.
 
Interesting.

Keeping good/optimal rpms is something I think about on most every cut.
 
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Me too. I try to challenge myself with holding perfectly steady at the optimal rpms, no frequent repositioning 5 times a second.
 
A little off topic but a little on. I found an app called engine rpm at the app store if y’all are interested. Be good for tuning.
 
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It counts the number of pops the engine sounds in a second I assume. My saws were cutting at around 100-180Hz.
 
I used one of these apps in a chainsaw test. We then tested same saw in three phones and got very different results as microphones have different soundfrequence the take up just like ears. Mine less than most...
 
Accracy was very bad. You could tell rpm was high or low, I was more precise in my ears then app was.
Its no good to use if you wish to know in any accuracy under 5000rpm.
I bet most can hear rpm better than these apps.
 
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It depends on the frequency and amplitude measured. I would expect it from different apps more than different phones.
 
How accurate/safe is it tuning by tach vs tuning by ear? Let's say a saw is specced at 12.5k, if you adjust the high til it hits 12.5k, you're good regardless of sound?
 
With a carbureted saw (once warmed up properly) adjust the High idle such that a slight burble / 4 stroking sound is heard when lifting the saw out of the cut momentarily. She should clean up once the slight load of cutting is again applied. The mtronic/autotune will adjust the carb automatically. Better off on the rich side with an adj carb
 
Yea, that's what I do more or less. I don't completely trust my ear, so I leave it a little fat and I'll adjust it back over long periods of time. I'm probably leaving a little speed on the table, but I like the insurance. Spark plug looks good.

That was why I was asking. If a gauge is foolproof, I'd consider getting one for tuning, but if I'd have to use my ear anyway, I'll just keep doing what I do.
 
Fat is where it’s at as long as you tune when the engine reaches operating temp. If you watch enough saw vids you can hear some builders saw start to “go lean” and lose the tune after a few cuts-getting hot 🥵. My builds take a good couple of long cuts to reach operating temp and then stay there ... This Hotwoods 462c actually Gains speed as she warms up (2nd cut faster than first) - the competition? First cut fastest and downhill from there 😂... tape don’t lie ....
 
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the competition? First cut fastest and downhill from there 😂... tape don’t lie ....
As you were saying, it's about the tune, so these other builders must have their saw simply tuned too lean in the video. Easy to do whey they only make a couple cuts and never get it warmed up. As for the power decreasing when hot, that happens to any engine partly because the hot engine heats the air decreasing its density.

Yea, that's what I do more or less. I don't completely trust my ear, so I leave it a little fat and I'll adjust it back over long periods of time. I'm probably leaving a little speed on the table, but I like the insurance. Spark plug looks good.

That was why I was asking. If a gauge is foolproof, I'd consider getting one for tuning, but if I'd have to use my ear anyway, I'll just keep doing what I do.
It's easier to hear 4 stroking with a modified muffler. I once tried tuning a stock echo 490 by the recommended rpm, but the rev limiter happened to be set there or just a bit lower, or the carb jet or needle was such that noting would happen even with much adjusting, so I just did it by ear.
 
@Nutball Not tuned too lean , loosing power because of heat. Building saws and not knowing how to adj a carb 🤔 sounds fishy to me , besides, as any 2-stroke tuner knows ... IF the saw isn’t warmed up properly it should run RICH not lean, probably not a good idear to be putting the boots to it when not up to operating temp anyhoo ... Cranking up compression can do that because of increased heat. A guy can loose up to 20% power ... I see the same pattern over and over again so obviously it’s not a “tuning issue” but rather a heat issue, watch the videos - tape don’t lie son 😀 ... besides, high compression 2-stroke chainsaws are just a silly fad anyways ... Here’s a great video by Donny Walker that gives ya the straight goods ... He’s FAR more knowledgeable about chainsaws than 99% of the builders out there
 
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Tuning a saw is not just about rpm per say its about performance.
You can take 10 saws of same brand and model and they all perform differently if set after rpm's. I set them after best performance.
Doing that allow you to find the ones that is a tad better o worse and know what to do do if something is not right.
It's harder unless you have several saws to compare with so you know how it can perform at its best.
You also need to know the differences in the models lifespan so you know what to expect from it.

Same with chains. You can get a lot more out of a saw if you know what chain models it runs best with.
 
I disagree with that analysis, Frankie, the Husky 262xp is a prime example of what high compression can do for a saw, 60cc saw with 70cc power. To fight heat you add more fuel.
The two saws I have left, Husky 350 and Dolmar 5100s, are both running without base gaskets and .018" squish, that's as tight as I like it, but it's a big jump in compression, I run good fuel and better two stroke mix and run them a little fat. I can tune either to run stupid rpm's, but they wont cut anything but small limbs, they just bog down in wood. Fatten them up, they rip.
Raj, be careful with that tach, it may not be able to register the difference between a two and four stroke engine, I've been burnt by this one once.
 
High compression makes more powa no doubt , also puts more stress on the bottom end , also creates more heat (fuel cools , oil lubes: right-0) also enhances low-mid power at expense of top-end rev. Lotta ways to build a strong saw - high compression ain’t the only way , especially if a guy/gal wants the saw to last as long as a stocker. I’m from the school of “let them run” instead of “make them run” especially with these newer offerings. The golden era of chainsaws has came and went. I’ve got a Hotwoods ported 1990 064 that will whoop ass on these newer saws and it’s 31years old! Cannot compare pre epa saw today’s versions , apple and orange. I doubt folk in the future will be extolling the virtues of the 500i in 2052 😎
 
There are set limits, parameters that can't be changed when tuning saws. Physics is one of them.
If you put some work in the saw you can alter most mechanical stuff in it and affect pressures, flows and temps.

262 is a large branching saw, not so much torque as needed in a felling saw like 162 was.
There was EPA regulations then too, not as stupid as the ones today, but close.

EPA rules is an odd thing as the saws built to last have better environmental impact calculation than those today that don't.
Its more there to make sure saws are built in a way that many is sold than anything else.
 
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