Another chainsaw dyno...

[NightRogue]

Depends on the model more than the brand. The 394 needed a lot more pressure than the 064 and 660 in the video.

True, and chain setup as well. Cant dog much with 404

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[Duane(Pa)]

Been a long week Joe. @Red97 Thanks for your efforts! TGIF

 

[Nutball]

Depends on the model more than the brand. The 394 needed a lot more pressure than the 064 and 660 in the video.

I thought you set your chain according to the saw so you don't have to put pressure on it. Don't get my attitude wrong: see? but you've given me enough crap about my sawing technique.

 

[huskyboy]

Slowest saw is 7.1hp ~

Fastest saw is 38% quicker

38% more than 7.1 would be 2.69 ~

9.8 hp ~ roughly... if we think the correlation is 1:1

Hp gain vs cut speed gain.

I would be fascinated to know the correlation between dyno hp results and wood cut times. 1:1 would be nice and convenient to calculate lol. I’m sure it varies depending on a lot of variables though if I had to guess.

 

[Red97]

I would be fascinated to know the correlation between dyno hp results and wood cut times. 1:1 would be nice and convenient to calculate lol. I’m sure it varies depending on a lot of variables though if I had to guess.

Easy way to tell would be send the 394. If it is 9.8 hp 1:1 It is lol.

 

[wcorey]

I would be fascinated to know the correlation between dyno hp results and wood cut times. 1:1 would be nice and convenient to calculate lol. I’m sure it varies depending on a lot of variables though if I had to guess.

If it's anything at all like h/p vs speed in vehicles then there will be some diminishing returns.
And it's some sort of logarithmic thing, the percent in speed gain vs h/p goes down drastically as the speed increases.
I know the cause and effects of each are much different but...

 

[Terry Syd]

And it's some sort of logarithmic thing, the percent in speed gain vs h/p goes down drastically as the speed increases.

And a lot of that loss in speed gain is the increase in wind drag, which doesn't correlate with chain speed in the cut. If it did, we wouldn't see racers putting 10-11 pins on saws, they would be increasing the cutting angle (raker depth) to keep the chain speed down and taking a bigger bite.

The whole matching the chain to the powerhead and wood appears to be the big thing in chainsaw racing.

 

[Terry Syd]

New leader in the 60cc class....

Modified filter elbow really woke up the mofo 361.

Now you have my interest in modding a 361 again. I wonder what a big bore (64cc) jug could put out on the lightweight 361 chassis. It would probably create a flatter torque curve, which wouldn't be a bad thing on a work saw.

 

[Sawrain]

When I run saws I run them where they want to be in the wood. After you run enough saws over the years you can pick one up and tell how it wants to be ran in the cut. Maybe that’s wrong idk but it works for me lol. The chain, sprocket and wood species is also a variable. But really the dyno eliminates most of those variables. I was just stating that what I saw with the 361 when I had it here in the wood made sense with what Joe saw on the dyno. Which is nice to see.

I definitely agree with this method over allowing the saw to self feed, for comparing cut time and saws.

If you have the feel to operate the saw where it wants to be by varying cut pressure you are generally going to find yourself around peak HP.

If you allow it to self feed there is no mechanism I can see that will yield an optimal or super consistent cut time, but simply that rpm will stabilise at a point where chain power requirements meet saw output, chain too aggressive rpm will be too low, unlikely people here would have this situation though, chain not aggressive enough and rpm will again go past peak power where power drops off to match the chains needs, a situation not using all the saws power & torque.

Could possibly work with identical saws, but not if comparing different ones.

I think Redbull661 tested a ms661, with 7, 8 and 9 pin sprockets and 3/8 chain, 8 pin was fastest, 7 and 9 were very close though, how does 7 vs 9 go as far as needing cutting pressure? I’v never run a 3/8 9 tooth.

Not surprised the cut times were close.

 

[Nutball]

I definitely agree with this method over allowing the saw to self feed, for comparing cut time and saws.

If you have the feel to operate the saw where it wants to be by varying cut pressure you are generally going to find yourself around peak HP.

If you allow it to self feed there is no mechanism I can see that will yield an optimal or super consistent cut time, but simply that rpm will stabilise at a point where chain power requirements meet saw output, chain too aggressive rpm will be too low, unlikely people here would have this situation though, chain not aggressive enough and rpm will again go past peak power where power drops off to match the chains needs, a situation not using all the saws power & torque.

Could possibly work with identical saws, but not if comparing different ones.

I think Redbull661 tested a ms661, with 7, 8 and 9 pin sprockets and 3/8 chain, 8 pin was fastest, 7 and 9 were very close though, how does 7 vs 9 go as far as needing cutting pressure? I’v never run a 3/8 9 tooth.

Not surprised the cut times were close.

Good point, we want to test saws at their max power. My problem is I mostly have hard wood, and at max power rpm most saws just don't seem to cut as well as they could. That's where I used to try to go farther and run the saw in whatever way makes it cut faster, but then you get a 362 that wins the race self feeding over a 590 while the 590 wins the race when leaned on because of the torque difference, which comes back to the issue of gearing. I don't care how much power a saw makes as long as it cuts fast. Seems to me like a lot of saws up to 90cc could benefit from 6t sprockets.

 

[Sawrain]

Good point, we want to test saws at their max power. My problem is I mostly have hard wood, and at max power rpm most saws just don't seem to cut as well as they could. That's where I used to try to go farther and run the saw in whatever way makes it cut faster, but then you get a 362 that wins the race self feeding over a 590 while the 590 wins the race when leaned on because of the torque difference, which comes back to the issue of gearing. I don't care how much power a saw makes as long as it cuts fast. Seems to me like a lot of saws up to 90cc could benefit from 6t sprockets.

Agreed, is your hardwood also dry?

For sure it is possible that the optimum sprocket/chain combination does not exist for some saws in particular conditions.

 

[Nutball]

Not always, at least not bone dry. For a while I was using Ash, and even green it would cut faster almost until the clutch slipped. I have a fresh poplar pole in the backyard I'll cut soon for some 395 port test comparisons. I plan to adjust the chain to run an 8t such that it self feeds at roughly max power, then start comparison cuts.

 

[huskyboy]

Easy way to tell would be send the 394. If it is 9.8 hp 1:1 It is lol.

@Mattyo owns it

 

[Duane(Pa)]

The whole matching the chain to the powerhead and wood appears to be the big thing in chainsaw racing.

An art form unto itself without a doubt...

Now you have my interest in modding a 361 again. I wonder what a big bore (64cc) jug could put out on the lightweight 361 chassis. It would probably create a flatter torque curve, which wouldn't be a bad thing on a work saw.

Joe’s inspirational dyno shop

 

[Sawrain]

Thoughts on cut speed Vs power changes.

I think we are lucky that the relationship should be fairly equal and linear.

The issue a vehicles at speed faces is that it’s predominant force to overcome is moving through air, these aerodynamic drag/friction forces increases with the square of speed (^2) and even worse the power required to overcome aero friction increases at the cube (^3) of speed, the contact friction of rubber to road is relatively low and the power needed to overcome it rises linearly with speed (^1).

This is a problem we don’t have, our situation is reversed from the vehicle in that the chain has a low aero Friction force to overcome and high contact Friction (cut force) to overcome.

Even better we often don’t even end up running a great deal more chain speed when woods ported, so the power requirement of the chain that do increase with the cube of speed are small enough to mostly ignore anyway.

The overwhelming majority of work being done, the tooth slicing through wood and friction against the bar are luckily linearly Related to speed, no squared or cubed relationships to severely diminish performance increases.

Now as long as chip thickness and the force required to cut correlate near 1:1 I think it’s a plausible theory.

Normal every day cutting, normal chain, everything working as it should, cut speed should somewhat loosely correlate to power, kerf width and wood hardness.

Just theory, not claiming to have tested any of this.

 

[Definitive Dave]

How many cuts before the self feeding slows down?
Then file and start over? What if there are 5 saws to test. Chain is compromised after the first two saws. Hundredths lead to tenths, tenths lead to seconds.

and when you start fine tuning to chase after thousandths, you know you got that baby dialed in and you are out of excuses

 

[Red97]

and when you start fine tuning to chase after thousandths, you know you got that baby dialed in and you are out of excuses

How consistent can a saw be in an 8x8?

Just curious on your experience.

Can you expect
.1 seconds or .01 on a good cut?

That would help in figuring the ratio HP to speed in your saws alone.

If you know saw A is 1.2 sec per cut and saw B is 1.4. How much power is needed to droo the .2 seconds

 

[huskihl]

How consistent can a saw be in an 8x8?

Just curious on your experience.

Can you expect
.1 seconds or .01 on a good cut?

That would help in figuring the ratio HP to speed in your saws alone.

If you know saw A is 1.2 sec per cut and saw B is 1.4. How much power is needed to droo the .2 seconds

Depends entirely on how much sod he cut between saws 1 and 2

 

[dustinwilt68]

I just like the perty graphs....

 

[Mattyo]

@Mattyo owns it

I do? I don't remember which one that is hehe. I have a few