Saw video thread

[RI Chevy]

You guys with e-free stations are lucky...[emoji106]

 

[Nutball]

You lose power with lower octane if it all burns up near TDC. My car has a noticeable increase in power and MPG when using 93 over 87 because it fries bacon on 87. But 87 does burn faster for better high rpm power.

 

[RI Chevy]

I thought we were talking about 2 stroke saws???

 

[BangBang77]

You guys with e-free stations are lucky...[emoji106]

Not lucky. Just communist-free brother...

 

[Nutball]

I thought we were talking about 2 stroke saws???

What's the difference? Gas is still being burned in an engine under load.

 

[RI Chevy]

Nope. Do your research...

 

[PA Dan]

You guys with e-free stations are lucky...[emoji106]

I feel lucky but its 90 or 110 octane and the 90 is $4.99 a gallon!

 

[RI Chevy]

Yikes!!! WTF

 

[MustangMike]

Big difference between a car and a chainsaw: 2 stroke vs 4 stroke, 15,000 RPM vs 7,000 RPM, Most cars have computer controls (knock sensors) to adjust timing and valve timing, etc. Most saws don't have computers, and a 2 stroke can not adjust port timing.

A two stroke often runs so fast there is no time for pre ignition unless the timing is way in advance. This is especially true if you increase the oil over 50:1 and increase the Centene rating (slows the burn).

A chainsaw almost always operates near max RPM, a car can easily be lugged at low RPMS … in a nutshell they are completely different!

New cars benefit a great deal from higher octane fuel, chainsaws usually do not. I do run high test in my saws, not because I think it will make them run stronger, but it will help them to run cooler and last longer.

 

[TreeLife]

What's the difference? Gas is still being burned in an engine under load.

Gasoline octane does not affect piston ported 2 cycle engines running at great rpm like you think it does. Jeff is correct, tests done have proven the lowest octane makes the most power in saws.

But 87 does burn faster for better high rpm power.

It does not burn faster, it is less resistant to detonation.

 

[Nutball]

I'll trust your guys' research on those low octane tests.

Just to be clear on that last part higher octane is less resistant to detonation. As for lower octane (87) burning faster, I think I read that around here somewhere, it could have been part of the conclusion that less octane makes more power.

Anyway, my point was, 1) if the saw is detonating, first check that you are using high enough octane, and 2) if an engine is experiencing detonation, and higher octane solves the problem, it will make more power because that power isn't being wasted by the fuel burning too soon.

 

[MustangMike]

Yes, that is correct, the octane rating is just the temp at which the fuel will ignite, but often when they increase the octane it also slows the burn rate (but not necessarily). Higher octane only provides more power if the timing and compression are increased to take advantage of the higher octane. But, higher compression will increase the burn rate … all else being equal.

The Centene rating is the burn rate, and adding oil increases it (but lowers the octane rating). Diesel has a lower octane rating than gasoline, which is why they use direct injection for diesel engines. But, diesel has a higher Centene rating, making it ideal for low RPM diesel engines.

 

[Onan18]

Big difference between a car and a chainsaw: 2 stroke vs 4 stroke, 15,000 RPM vs 7,000 RPM, Most cars have computer controls (knock sensors) to adjust timing and valve timing, etc. Most saws don't have computers, and a 2 stroke can not adjust port timing.

A two stroke often runs so fast there is no time for pre ignition unless the timing is way in advance. This is especially true if you increase the oil over 50:1 and increase the Centene rating (slows the burn).

A chainsaw almost always operates near max RPM, a car can easily be lugged at low RPMS … in a nutshell they are completely different!

New cars benefit a great deal from higher octane fuel, chainsaws usually do not. I do run high test in my saws, not because I think it will make them run stronger, but it will help them to run cooler and last longer.

Carroll Shelby to Ken Miles "7000+ GO LIKE HELL!!!"

 

[MustangMike]

I took my Grandson's to see that … and was able to tell them "Know what Grandpa used to shift his 427 Ford motor at …. 6,800 RPM"!!!

My motor was a 66 Holman and Moody cross bolted - side oiler block, but I did not have the Lemans Rods in it … they were stronger! (My crank had been trued, cut 10 + 20).

I had it is a 70 Boss 302 body. I remember going into a parking lot one time … and there is a Ferrari with the engine cover up and the guy griping about how hard the carbs were to tune. Then he looks at me and says "but it runs real great when I get them right". I responded, "Yea, almost as good as my 427 Ford Motor"! He said NOTHING!!!

 

[MustangMike]

A little known fact: Most passenger car motors have the piston pins slightly off center to help them idle more smoothly, including other FE Ford motors like the 390 and 428. 427 Ford motors had the piston pins dead center, they did not idle as smoothly, but they held up better at high RPM.

 

[Nutball]

Big difference between a car and a chainsaw: 2 stroke vs 4 stroke, 15,000 RPM vs 7,000 RPM, Most cars have computer controls (knock sensors) to adjust timing and valve timing, etc. Most saws don't have computers, and a 2 stroke can not adjust port timing.

A two stroke often runs so fast there is no time for pre ignition unless the timing is way in advance. This is especially true if you increase the oil over 50:1 and increase the Centene rating (slows the burn).

A chainsaw almost always operates near max RPM, a car can easily be lugged at low RPMS … in a nutshell they are completely different!

New cars benefit a great deal from higher octane fuel, chainsaws usually do not. I do run high test in my saws, not because I think it will make them run stronger, but it will help them to run cooler and last longer.

I missed your post. The way I see it, rpm isn't as important as relative piston speed when comparing engines. If a car engine spins half the speed as a chainsaw but has 3 times the stroke length... you see my point. It might mean nothing, but I think it does.

 

[MustangMike]

Look at it this way … and RPM takes the same amount of time regardless of the engine's stroke. Also, adding 2 stroke oil to gas slows the burn rate.

So now you have the combustion taking 1/2 the time with a slower burning fuel … octane rating in a saw is less critical.

The problem is even worse when the engine is at 1-2,000 RPM and under load, something that should never happen to a saw.

Generally, the saw goes to full power before it hits the wood, then keeps about 80% of it's RPMs (or it stalls). A chainsaw engine should never be stressed like a truck pulling a trailer.

 

[Nutball]

Good point on the time factor.

 

[huskyboy]

Something interesting to think about on the subject of rpms and piston speed..... Here’s the piston speed of a 9000/9010 and 462 at around there max rpm for example. The very short stroke of the 462 for its cc’s allows it to have a slower piston speed despite turning more max rpms. It’s interesting to think how stroke can affect the piston speed more than rpms do... really makes you think. 4629000/9010

 

[Duane(Pa)]

I take the octane to ditch the ethanol.