Another chainsaw dyno...

[Red97]

Lots of wood variable there, I've gotten as much as 50% better cut times in a certain piece of wood, and there's no way power was increased by that much. Still would be interesting to see what you come up with.

That was why I really wanted to go the dyno route. I don't feel like learning how to do chain too. Leave that to the owners.

No clear winner as I see when it come to in the cut power rpm.

Going to be fun to see how many models have graphs like this. Then it I truly just a brand bias thing.

Are the little waves in the curve from you applying load?

The far right spike is from clean up, every one I have run has a dip/spike like that.

The others could be load, frequency the actual power output etc.

I try and do as smooth and quick of a run as I can to report the data to every 100 rpm. Too slow it gives multiple readings for the same rpm.

It is already collecting 200 samplesper second and avg them per every 100 rpm thst is the reason the graphs are as smooth as they are.

That’s about as close as it gets there. What saws?

73cc hybrid with mod carb vs 79cc hybrid.

Looks pretty even, going to guess the yellow curve is a larger saw, probably pick the lightest of the two as the winner! LOL

Yellow saw is 73cc same weight on the saws.

 

[cuinrearview]

I wasn't nitpicking. Just brainstorming. What if you had a little servo on the knob? I have no idea if it would even work or how hard the knob turns. Just thinking about consistency.

 

[Red97]

I wasn't nitpicking. Just brainstorming. What if you had a little servo on the knob? I have no idea if it would even work or how hard the knob turns. Just thinking about consistency.

Auto load valve, most agree they are a major hassle with 2 stroke. And almost impossible to dial in with a little low hp 2 stroke.

The max numbers have been very consistent between 3 runs. The way it spits out is not ideal. But still works well.

Even a major spike on the valve only shows a spike of .2-.3hp but then it drops so fast the data won't record, will drop from 9k to 7600 on the read out. I know it is a bad run.

 

[Red97]

I did try seeing what kind of rpm the clutch was full lock. And it is upwards of 5500 rpm from a bottom up pull under load. It will move the chain, but has a good bit of slip at that rpm.

So I'm thinking power much under 6k on a modern saw is a moot point.

Now the old reed valve monsters that only spin 9k those might grab a bit lower.

 

[Deets066]

I did try seeing what kind of rpm the clutch was full lock. And it is upwards of 5500 rpm from a bottom up pull under load. It will move the chain, but has a good bit of slip at that rpm.

So I'm thinking power much under 6k on a modern saw is a moot point.

Now the old reed valve monsters that only spin 9k those might grab a bit lower.

Get you some worn out clutch springs.

 

[Terry Syd]

Just a personal preference, I like a saw that pulls strongly off the bottom. A good test is to keep loading the saw on the spikes, if the torque stays strong until the clutch starts slipping, that's what I want. I don't like a saw that 'bogs' as the revs drop.

I don't cut at those low revs, but when I want to start a saw in the cut, I can just pull the trigger and it takes right off.

 

[Bigmac]

I did try seeing what kind of rpm the clutch was full lock. And it is upwards of 5500 rpm from a bottom up pull under load. It will move the chain, but has a good bit of slip at that rpm.

So I'm thinking power much under 6k on a modern saw is a moot point.

Now the old reed valve monsters that only spin 9k those might grab a bit lower.

They don’t “all” only spin 9k.

 

[Red97]

Get you some worn out clutch springs.

I think it may have something to do with the actual weight on the clutch shoes with these hybrids. Was only made for a 5.5hp 60cc...

Just a personal preference, I like a saw that pulls strongly off the bottom. A good test is to keep loading the saw on the spikes, if the torque stays strong until the clutch starts slipping, that's what I want. I don't like a saw that 'bogs' as the revs drop.

I don't cut at those low revs, but when I want to start a saw in the cut, I can just pull the trigger and it takes right off.

I think from highbrow pulled down the clutch holds better than low rpm up.

At least with these small clutches. Lots of load starting from a stop gains rpm and smoke. Lol

 

[Red97]

They don’t “all” only spin 9k.

Lol, I know had my share of old homelites.

 

[MustangMike]

Thoughts?

Any clear winner?

No clear winner, a statistical tie, but approx. 9 Hp in a broad cut range … in a light weight saw … both are winners, would take either one in a heartbeat!

 

[Bigmac]

What dose the stock saw echo look like on the dyno?
And was dose a 1/8 turn, 1/4 turn and a half turn more on the h screw look like on the dyno from optimum? Been kind curious on that

 

[Terry Syd]

An interesting test would be a saw with different carburetors to see how the powerband is affected. If someone had a Dolmar 7900 with a stock carb, a Poleman Twin Jet Zama and perhaps a HD-12, the differences in the power curve could be illustrated.

Then to top it off, the best carb run with the air filter on and one with it off. See where the easy gains are.

 

[Agent Smith]

I look forward to seeing some everyday, common work saws put on the dyno for stock before then modified after runs to see how much gains are achieved. Dont get me wrong though im thoroughly enjoying this thread so far!

 

[Red97]

An interesting test would be a saw with different carburetors to see how the powerband is affected. If someone had a Dolmar 7900 with a stock carb, a Poleman Twin Jet Zama and perhaps a HD-12, the differences in the power curve could be illustrated.

Then to top it off, the best carb run with the air filter on and one with it off. See where the easy gains are.

Modded Carb swap today...

Easy to see how it changed.

And how well the different modded carbs performed.

Possibilities are endless...

 

[Red97]

Bone stock 620 (75 plus tanks)

Stock saw over performed the book specs.

 

[Bigmac]

View attachment 243815

Bone stock 620 (75 plus tanks)

Stock saw over performed the book specs.

Cool, thanks! That really shows the difference

 

[Terry Syd]

Modded Carb swap today...

Cool graphs, so, instead of hacking away at the jug, you just slip on a modded carb and pick up the extra power.

 

[pavel408]

View attachment 243815

Bone stock 620 (75 plus tanks)

Stock saw over performed the book specs.

The stock 620 shows on your dyno about 5.8 hp. What could be the reason that Echo officially states only 4.4 hp ( https://www.echo-usa.com/getattachment/38a12853-5bfb-43f7-b930-b11cd23747d1/CS-620P.pdf )? Or is the reason for 1.4 hp gain those "75 plus tanks"?

 

[Red97]

The stock 620 shows on your dyno about 5.8 hp. What could be the reason that Echo officially states only 4.4 hp ( https://www.echo-usa.com/getattachment/38a12853-5bfb-43f7-b930-b11cd23747d1/CS-620P.pdf )? Or is the reason for 1.4 hp gain those "75 plus tanks"?

Close to 5.6hp

It is not the break in, tested one out of the box around 5.5hp

Either they are under rated from factory, or tested against some other type of correction factor

Hard telling the exact reason.

Some are close, and some overperform.

Until I get a few of each model stock it is hard telling what the power is on the dyno.

 

[Red97]

The stock 620 shows on your dyno about 5.8 hp. What could be the reason that Echo officially states only 4.4 hp ( https://www.echo-usa.com/getattachment/38a12853-5bfb-43f7-b930-b11cd23747d1/CS-620P.pdf )? Or is the reason for 1.4 hp gain those "75 plus tanks"?

Look at the fine print on the hp rating.

Says baised on the epa website rating....

Could have detuned ones to meet emissions, or they are saws abroad.