Another chainsaw dyno...

[wcorey]

Signs/symptoms: popping, it’s not burning most of the fuel as it should.
likely solution posted also.
Read it again perhaps?

So that's it?
So if higher octane leads to improved power due to the ability to run more advanced timing then why doesn't using higher octane improve the situation if it's popping due to too much advance with deficient octane?

 

[d997tt]

So that's it?
So if higher octane leads to improved power due to the ability to run more advanced timing then why doesn't using higher octane improve the situation if it's popping due to too much advance with deficient octane?

Probably because you have an ignition issue, whether it’s the coil, wire, or plug. Or you need to gap the plug smaller.
It’s all relative to how much advance you have as well. Even high octane won’t help if you’ve advanced it too much. Do you know these numbers? Unknown setup and condition of your components and it’s anyone’s guess.

 

[Egg Shooter]

https://oneillbrothers.com/collecti...br-reed-case-engine-with-v2-reed-valve-design

Here is the premier 1/5 scale RC and goped engine builder. In the drop down menus there is one for compression / fuel type. They tailor the build to the fuel you plan on running. There is something to it.

 

[d997tt]

https://oneillbrothers.com/collecti...br-reed-case-engine-with-v2-reed-valve-design

Here is the premier 1/5 scale RC and goped engine builder. In the drop down menus there is one for compression / fuel type. They tailor the build to the fuel you plan on running. There is something to it.

Yeah but (excuses) “it’s not a chainsaw, derp derp” lol

 

[Egg Shooter]

Yeah but (excuses) “it’s not a chainsaw, derp derp” lol

Im sorry. I forget saws have special air cooled 2 stroke engines unlike anything else in the universe. Lol.

 

[wcorey]

Probably because you have an ignition issue, whether it’s the coil, wire, or plug. Or you need to gap the plug smaller.
It’s all relative to how much advance you have as well. Even high octane won’t help if you’ve advanced it too much. Do you know these numbers? Unknown setup and condition of your components and it’s anyone’s guess.

Not one particular saw I'm referencing but a few random ones I've tried it on over the years and haven't bothered since as it never resulted in an improvement. Guess I've just been unfortunate to have maybe had ignition problems on all of them...
When I port/build a saw and play with advance, I (and I'd bet most others here) generally just keep advancing incrementally until it starts popping and then back off a bit. A bit more if it looses power obviously but that's rare.
Or just file the key by a 1/4 or 1/3 and if I get some extra snappy throttle and no popping, call it good...
Seems if what you're preaching held water then instead of backing off the advance I could alternately just raise the octane.

I will try to pay more attention to plug gap though, again the few times here and there I've tried have had no noticeable difference but maybe in some instances it could be the trick.

I suspect a lot of these things only have a significant effect on engines tuned much closer to the hairy edge than where a typical work saw or even hot play saw port job ends up...

 

[redline4]

Back when I was messing with single cylinder and V-twin mower engines, the higher octane made less power.
We could never get enough compression to make it worth while and our ignition timing was always fixed as we were stuck using Briggs coils.
With the billet flywheels we used generally 30-32 degrees of timing was where we ran.
This was with 4 stroke 30ish ci singles and 42ci twins. Isky was grinding our cams.

 

[wcorey]

https://oneillbrothers.com/collecti...br-reed-case-engine-with-v2-reed-valve-design

Here is the premier 1/5 scale RC and goped engine builder. In the drop down menus there is one for compression / fuel type. They tailor the build to the fuel you plan on running. There is something to it.

Im sorry. I forget saws have special air cooled 2 stroke engines unlike anything else in the universe. Lol.

Yeah, looks to be just like a typical saw engine/application...

9.4HP FULL MOD G340RC 34CC +2MM STROKER TR/OBR REED CASE ENGINE WITH V2 REED CASE

And piped I'm sure...

 

[d997tt]

Seems if what you're preaching held water then instead of backing off the advance I could alternately just raise the octane.

I’m not preaching anything. Referring to obvious factors that may cause what you described....all along with unknown condition of components nor fuel/oil mix used, etc etc. You never specified any of those.
Stock saws are not optimized and are factory tuned within a broad safety area where they will “work fine” with average fuel and average oil. You modify beyond those parameters with higher compression, porting, advance, etc, and you have to have address the necessary supporting mods if you want it to work. You raise the compression significantly and you’ll need higher octane, you can’t just dump more 87 mix and expect to maximize the potential. Race engine builders don’t limit themselves to 87octane for a simple reason: it’s not a rule as it seems to be for chainsaws according to some (lol)

 

[MustangMike]

Theory is one thing, but EVERYTHING has it's limitations.

Generally, the ONLY reason higher octane can produce more power is because it PREVENTS destructive pre ignition in engines with high compression. Higher compression will often provide higher HP, but NOT ALWAYS.

Octane is simply the temp at which a fuel ignites, it DOES NOT MEAN IT BURNS SLOWER.

Chainsaws rev so fast that octane over 87 usually does not provide any benefit. By the time pre ignition starts your plug is firing anyway.

Also, too much compression can limit the saws RPMs, thus reducing power. THERE IS ALWAYS A BALANCE.

Flow is important, but so is timing the flow to the pulses of the engine. That is part of the reason tuned pipe exhaust saws can produce so much more power.

Just like opening the muffler on a saw will often have diminishing returns when opened too much. Everything is a balance, and must be in sync.

 

[d997tt]

Yeah, looks to be just like a typical saw engine/application...

9.4HP FULL MOD G340RC 34CC +2MM STROKER TR/OBR REED CASE ENGINE WITH V2 REED CASE

And piped I'm sure...

And there it is: “it ain’t a chainsaw” lol

 

[Egg Shooter]

Yeah, looks to be just like a typical saw engine/application...

9.4HP FULL MOD G340RC 34CC +2MM STROKER TR/OBR REED CASE ENGINE WITH V2 REED CASE

And piped I'm sure...

Still an air cooled 2 stroke that is built to a certain octane usage. There must be a reason they do this is all im saying. And I don't buy into saws are some anomaly in the 2 stroke engine world. Still an air pump. I also know that just because I personally haven't experienced something doesn't mean its not true.

 

[MustangMike]

Rails at the dragstrip will pay close attention to the length of those straight open exhaust pipes to tune the "pulse" to the desired engine RPM.

 

[Egg Shooter]

Im sorry Joe for contributing to this. Imma step aside and lurk again. Later fellers.

 

[srcarr52]

Is this the new oil thread?

 

[wcorey]

Yeah, sorry for continuing the derail and this will hopefully be it for me also.

Still an air cooled 2 stroke that is built to a certain octane usage. There must be a reason they do this is all im saying. And I don't buy into saws are some anomaly in the 2 stroke engine world. Still an air pump. I also know that just because I personally haven't experienced something doesn't mean its not true.

Yes, there is a reason.
But for some other reason saws seem to actually be a fairly consistent exception to it and I can only conjecture as to why.
You think this is something new? It's been mentioned/discussed as a thing many times over on many saw forums over many years and some actual testing/evidence has been presented to at least anecdotally prove it out. My own experience has also reflected it and I've yet to see any actual testing with saws that proves otherwise.
Somebody show me and I'll be a believer...

Is this the new oil thread?

Everyone knows that octane threads are the only thing that can almost hold a candle to oil threads...

 

[RI Chevy]

@d997tt
Maybe you could port a saw. Use high octane and show everyone here something new. Take over the saw cant cutting racket by storm.
Basically show all of us here how to make a better mouse trap.
Prove your theories.

 

[Red97]

See if this 661 gains...

Way different recipe than I would normally use, but we will see...

 

[d997tt]

@d997tt
Maybe you could port a saw. Use high octane and show everyone here something new. Take over the saw cant cutting racket by storm.
Basically show all of us here how to make a better mouse trap.
Prove your theories.

Low quality bait.
Not maybe. I could. But I won’t do that for several reasons:
1. What I’ve mentioned is nothing new, it’s old news and has worked for decades on all platforms of gas combustion engines (especially 2strokes, chainsaws included). There’s no magic “build a better mousetrap” here, to claim that is ignorant. I never claimed that. Are you implying I claimed that?
2. Factors that get forced into the excuses of availability or bs reasons against, interjecting rules, ignoring supporting mods especially, etc, will render these long proven modifications (not theories) a waste of time and the results will not be proven.
3. Not a long time established member, which means no authority according to keyboard commandos.
Therefore, bait ignored. Carry on.

 

[RI Chevy]

Aye. I give up bruh. Unreal.