Another chainsaw dyno...

[drf256]

The dip is because yours was still extra rich. Both saws were tuned at 14k ish

Ranchdad was prolly around the 13.8k cfb was prolly 14.3k

More of a gradual quick "clean up" with the leaner tunes. Where the ranchdad still had a hard 4 stroke until clean up. The dip means nothing other than it was still rich at those rpm.

I cannot "see" what the curve will look like. Looking at the raw data scrolling across the screen. Just any crazy anomalies, or missing chunks of data. As long as I don't see those, and have a smooth run. I take it home and graph it.

My thoughts are as long as I have a couple thousand rpm of down slope from peak hp it shows the "powerband". No matter how lean/rich it is tuned those peak numbers don't seem to change.

Now with the screamers, 15k+ those shoe real well on the top end of the graph, as they already have a good load by 14k (where the graph starts) they look good. But the peaks are still the same. Long as the tune isn't so rich to be under peak hp rpm.

I would fully expect your saw to start pulling away at the 12k+ mark. Still going to need around 15k+ to show the top end well.

It would be fair to use the cfb curve and replace your "dip" from the 11.5k to the 14k where yours is pulling a bit harder.
If that makes sense.

Interesting.

So you see little change in peak power regardless of tune? The curve will change but the peak won’t?

 

[Deets066]

Interesting.

So you see little change in peak power regardless of tune? The curve will change but the peak won’t?

As long as it’s tuned above peak power, should be able to see the peak on the graph. Dyno puts a good load on it.

 

[Red97]

2 different saws.

Red line is around a 11.5k tune.

Yellow was over 16k

Didn't have a double d to adjust.

You can see the 9.5k peak power on the red and the 10k peak on the yellow.

The yellow line shows the extended range of the lean tune, but nowhere on that line is going to come close to the power. Take a good look at the tq height in the 13-14k range

At 14k and 6.5k the hp is about the same, look at the tq difference.

The red curve has a down slope in it as well. If it was tuning 15k+ like the other the graph would follow the same trend as the yellow curve starting at that down slope



These added lines are what the graph would look like if the tunes were swapped.

 

[Duane(Pa)]

One of my earliest wows was the visible transition from four stroke as the load picks up. Since it’s going high to low rpm wise, it can’t really be construed as a HP drop off. More like a huge pick up after cleaning up into two stroking.

 

[Red97]

One of my earliest wows was the visible transition from four stroke as the load picks up. Since it’s going high to low rpm wise, it can’t really be construed as a HP drop off. More like a huge pick up after cleaning up into two stroking.

That is prolly the best way to describe it. Massive pick up in power.

 

[NightRogue]

View attachment 252825

2 different saws.

Red line is around a 11.5k tune.

Yellow was over 16k

Didn't have a double d to adjust.

You can see the 9.5k peak power on the red and the 10k peak on the yellow.

The yellow line shows the extended range of the lean tune, but nowhere on that line is going to come close to the power. Take a good look at the tq height in the 13-14k range

At 14k and 6.5k the hp is about the same, look at the tq difference.

The red curve has a down slope in it as well. If it was tuning 15k+ like the other the graph would follow the same trend as the yellow curve starting at that down slope

View attachment 252827

These added lines are what the graph would look like if the tunes were swapped.

This question has been lingering in my head for awhile, field experience i had with what you described tallies perfectly. It's more prominent on top handles generally and huskies, you can only richen or lean within a boundary. Anything more or less the power loss will be massive, thank you bud!

Sent from my INE-LX2r using Tapatalk

 

[Sawrain]

The burn time on the premium is likely too long, especially mixed with the oil.

87 octane gas clearly made more power in the high compression engine than the premium high octane.

I know it’s not what you guys said, but fuel octane rating and flame front speed do not strongly correlate.

A higher octane fuel may have a slower combustion chamber flame front speed, but that is due to its particular molecular makeup, not necessarily octane rating.

Higher octane does not mean slower
Burning, simply more resistant to unwanted ignition events.

Ethanol & methanol both being higher octane and faster burning than standard pump fuel.

I had some old NACA studies to support this, I can’t find them, https://core.ac.uk/download/pdf/77014245.pdf seems to agree though, with testing completed in a real engine as apposed to “engine like conditions” that some others published papers have done.

Diagrams page 39.

Edit, NACA docs supported the general idea that Octane rating and flame speed do not have to trend together, not ethanol/methanol in particular.

 

[Bigmac]

I know it’s not what you guys said, but fuel octane rating and flame front speed do not strongly correlate.

A higher octane fuel may have a slower combustion chamber flame front speed, but that is due to its particular molecular makeup, not necessarily octane rating.

Higher octane does not mean slower
Burning, simply more resistant to unwanted ignition events.

Ethanol & methanol both being higher octane and faster burning than standard pump fuel.

I had some old NACA studies to support this, I can’t find them, https://core.ac.uk/download/pdf/77014245.pdf seems to agree though, with testing completed in a real engine as apposed to “engine like conditions” that some others published papers have done.

Diagrams page 39.

Edit, NACA docs supported the general idea that Octane rating and flame speed do not have to trend together, not ethanol/methanol in particular.

I talked to my local vp fuel vendor and he also stated that the vp110 was an extremely fast burning fuel and that it burned faster than pump, but was really resistant to detonation.he was say it’s a common misconception that pump burned faster than race, he was saying that some regular and premium pump fuels have different burn rates but in general is more of a fuel stability, and resistance to detonation....but he is a sales rep too! Lol

 

[jacob j.]

I talked to my local vp fuel vendor and he also stated that the vp110 was an extremely fast burning fuel and that it burned faster than pump, but was really resistant to detonation.he was say it’s a common misconception that pump burned faster than race, he was saying that some regular and premium pump fuels have different burn rates but in general is more of a fuel stability, and resistance to detonation....but he is a sales rep too! Lol

Yeah, no one trusts a sales rep...

 

[Terry Syd]

Ethanol & methanol both being higher octane and faster burning than standard pump fuel.

I haven't looked into this, but as I recall an alcohol burner needs more ignition advance than a gasser.

EDIT: OK, I did a bit of quick research and methanol does have a faster burn rate than gasoline. However, it is the need for a much RICHER mixture that slows down the flame front and requires more advance.

"Mixture enrichment is common for racing alcohol fuels. For rich alcohol mixtures, ignition delay is increased. As a result, usually more ignition timing is needed. The amount of increased timing for alcohol fuels is very dependent on the amount of enrichment."

 

[huskyboy]

I think the older gas gets... say maybe a couple weeks to a month old... the saws seem to make less power, start worse and run worse. I haven’t done any tests... but it seems so. Would be interesting to dyno test that theory. Fuel age/quality... it seems to matter. I’ll take fresh 87 over weeks old 93 octane... especially if it’s pump gas. The canned fuels seem to be more stable and deteriorate at a slower rate. Just a few observations I have made.

 

[Bigmac]

I haven't looked into this, but as I recall an alcohol burner needs more ignition advance than a gasser.

EDIT: OK, I did a bit of quick research and methanol does have a faster burn rate than gasoline. However, it is the need for a much RICHER mixture that slows down the flame front and requires more advance.

"Mixture enrichment is common for racing alcohol fuels. For rich alcohol mixtures, ignition delay is increased. As a result, usually more ignition timing is needed. The amount of increased timing for alcohol fuels is very dependent on the amount of enrichment."

I run methonal in my quad, it’s really interesting to tune, your optimal tune is between 6-7.5 to 1. Makes a lot more torque under load, way more than the dyno measures, I my opinion, the feel is like it has a lot more grunt but on the dyno it’s only 5% ish. I was able to go up two countershaft sprockets with the same domes and timing as race gas

 

[TreeLife]

I run methonal in my quad, it’s really interesting to tune, your optimal tune is between 6-7.5 to 1. Makes a lot more torque under load, way more than the dyno measures, I my opinion, the feel is like it has a lot more grunt but on the dyno it’s only 5% ish. I was able to go up two countershaft sprockets with the same domes and timing as race gas

What machine are you running?

 

[Johnmn]

View attachment 252510

2149 j red vs 501p echo

2149 has had machine work, and a 357 carb and elbow. Stock muffler and no port work.

Joe any plans for the 501? It would be nice to see what a muffler mod does and maybe a gasket delete. Personally I think it did pretty good considering it went up against one of the strongest 50cc saws out there.

 

[Bigmac]

What machine are you running?

Banshee 443cc for now

 

[dahmer]

Banshee 443cc for nowView attachment 252904

 

[Nutball]

Joe any plans for the 501? It would be nice to see what a muffler mod does and maybe a gasket delete. Personally I think it did pretty good considering it went up against one of the strongest 50cc saws out there.

I wonder about the air filter. The inlet hole is very restricted with the angles and size of the spit back catcher.

 

[Deets066]

Banshee 443cc for nowView attachment 252904

Wanna race?

 

[Deets066]

I talked to my local vp fuel vendor and he also stated that the vp110 was an extremely fast burning fuel and that it burned faster than pump, but was really resistant to detonation.he was say it’s a common misconception that pump burned faster than race, he was saying that some regular and premium pump fuels have different burn rates but in general is more of a fuel stability, and resistance to detonation....but he is a sales rep too! Lol

Oxygenated fuel increases burn rate also. I have some oxygenated 94 octane that is pretty stout.

 

[Bigmac]

Wanna race?

Let’s go!