Up the compression or big bore

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Most guys think that if their saw runs faster on 95 octane, then 95 octane puts out more power. But it wasn’t an apples to apples comparison if that was the case. The 95 or 104 or 110 that they used was probably a racing fuel that had other additives in that made the power. It wasn’t the additional octane that created it. It’s actually a pretty simple test. Pick up some 87 octane fuel and run a dozen timed cuts. And then add a bottle of octane boost to the same batch of fuel and try it
 
Raising compression raises torque. Raising octane creates less power. Octane is a measurement of a fuel’s resistance to combust. Higher octane fuels burn slower creating less power in a chainsaw.


Yes I am aware of what octane does, but racing fuels are more the just higher/lower octane. They are blended with different combinations of additives be it higher or lower or the added or lack of them. That's why many are restricted to off road use only because the volume of fuels used are lower then the mass fuels that are run in everyday autos. There are plenty of low octane racing fuels that produce more power and octane rating alone is not always the mane factor. Pollution and fuel economy are not as much a concern with racing applications as they are with street cars. Racing fuels are of a higher quality because they use stricter guidelines and production volumes are lower.
 
Yes I am aware of what octane does, but racing fuels are more the just higher/lower octane. They are blended with different combinations of additives be it higher or lower or the added or lack of them. That's why many are restricted to off road use only because the volume of fuels used are lower then the mass fuels that are run in everyday autos. There are plenty of low octane racing fuels that produce more power and octane rating alone is not always the mane factor. Pollution and fuel economy are not as much a concern with racing applications as they are with street cars. Racing fuels are of a higher quality because they use stricter guidelines and production volumes are lower.
I believe most of that to be true. They also aren’t allowed on the road because there are no road taxes built into the sale price
 
Raising compression raises torque. Raising octane creates less power. Octane is a measurement of a fuel’s resistance to combust. Higher octane fuels burn slower creating less power in a chainsaw.
Whereby increasing torque.
Example being diesel vs gas.

Higher compression engines run higher octane fuels. Hence every performace application in modified engines.

The increased compression allows for higher octane fuels to burn faster and more efficiently increasing power.

That is why they make race engines higher compression and run higher octane fuels.
 
Hold on to your domes fellas...

Im not arguing with it being inefficient to run higher octane with lowrr compression but its not the case in an engine with higher compression such as one with a gasket delete or shaved head.
 
What would be your choice to pep up a 357xp? One or the other. A 47mm big bore kit or a higher comp piston.

Joe

There are two different styles of AM jugs advertised as "Big Bore Kit" for the 357. One 47mm style to avoid is a 359 copy. Not that the 359 is bad, but it would be a .5 hp downgrade even if on par with an OEM cylinder.

No experience with a AM 47mm xp jug. My woods ported OEM jug with a popup piston is an impressive saw.
 
If i was the op i would start with a base gasket delete if his current deck height allows it.
Assuming he already has done a muffler mod, that is.

Apart from time, all it costs is some solder to check squish and some sealant.

If he swaps the piston or p&c he will need to check the new deck height anyway...
 
If i was the op i would start with a base gasket delete if his current deck height allows it.
Assuming he already has done a muffler mod, that is.

Apart from time, all it costs is some solder to check squish and some sealant.

If he swaps the piston or p&c he will need to check the new deck height anyway...

I think the OP got smart and checked out hours ago.
 
Then why is it when I run 105 in my stock saw can I bear down way more on a full cut in big wood and it not bog down to a stop as easy as it does on pump fuel?

Yes I am aware of what octane does, but racing fuels are more the just higher/lower octane. They are blended with different combinations of additives be it higher or lower or the added or lack of them. That's why many are restricted to off road use only because the volume of fuels used are lower then the mass fuels that are run in everyday autos. There are plenty of low octane racing fuels that produce more power and octane rating alone is not always the mane factor. Pollution and fuel economy are not as much a concern with racing applications as they are with street cars. Racing fuels are of a higher quality because they use stricter guidelines and production volumes are lower.

Look at that, you answered your own question.
 
I believe most of that to be true. They also aren’t allowed on the road because there are no road taxes built into the sale price

Road taxes are the least of the issue, it's more of the EPA guidelines on pollution emissions and cars have so many sensors that are sensitive to particular additives or lack of. Besides, race fuel is expensive enough as it is. I have never seen a cop check a cars fuel to see if it is legal road fuel like they do 18 wheeler trucks that sometimes run farm diesel witch other then color is basically the same as road diesel.
 
Whereby increasing torque.
Example being diesel vs gas.

Higher compression engines run higher octane fuels. Hence every performace application in modified engines.

The increased compression allows for higher octane fuels to burn faster and more efficiently increasing power.

That is why they make race engines higher compression and run higher octane fuels.
Lol.
High compression ratios require higher octane fuels to prevent preignition. The added compression and heat tries to ignite the fuel too soon, hence the term “spark knock”. Therefore they need higher octane to slow the burn. The power doesn’t come from the octane, it’s actually the opposite. And so is your entire theory on compression and octane
 
Lol.
High compression ratios require higher octane fuels to prevent preignition. The added compression and heat tries to ignite the fuel too soon, hence the term “spark knock”. Therefore they need higher octane to slow the burn. The power doesn’t come from the octane, it’s actually the opposite. And so is your entire theory on compression and octane
Ok boss you win.
 
Lol.
High compression ratios require higher octane fuels to prevent preignition. The added compression and heat tries to ignite the fuel too soon, hence the term “spark knock”. Therefore they need higher octane to slow the burn. The power doesn’t come from the octane, it’s actually the opposite. And so is your entire theory on compression and octane


Well yes and no. Diesel takes a lot more heat to ignite, but it burns longer. As for how hot the fuel burns I'm not sure. My guess is diesel burn hotter inside the combustion chamber. Diesels have a longer stroke so the combined longer, hotter burn and longer stroke gives it's superior torque. Plus it's mass being heavier, once that weight gets moving, it creates kinetic energy witch equals even more tongue.
 
Love when peeps compare bikes and quads to saws. @Huskybill

A two stroke is a two stroke, we pizz’d off many riders when they couldn’t keep up with a ported ‘80’s husky 250cr.

I measured a ported 2100 in the ‘80’s then applied the porting to dirtbikes. I been porting drag race engines since my teens. I have learned it’s not porting alone it needs to be tuned correctly. That’s the hard part for most engine builders.

Like the bikes it took me trying different ways of porting on each bike by the third bike the husky 250 cr I had it down with all the changes in one engine. I’m doing the same thing with my 2100’s. A little at a time in porting it, more and more.

I just started up my ported 2100 build. Now I need to tweek the tuning. But she does sound bad azz. I need to mod the muffler yet too. I just had to fire her up.
 

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