Ported 026 Squish Check

[Andyshine77]

I guarantee you 2 saws with the same numbers but one with 185lbs and the other with 220 the 185 saw won't be anywhere close to the other.
Tourqe, power,rpm,hp, whatever you want to call it compression is power plain and simple.

Compression is cheap power no doubt, but it isn't the end all be all, and if yo go too far you slow down.

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[drf255]

This is torque for a 50cc saw

 

[jmssaws]

Compression is cheap power no doubt, but it isn't the end all be all, and if yo go too far you slow down.

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I've heard that but I haven't cn it yet.

Port a saw without raising compression and it will gain but not like 50 lbs of extra compression.

 

[drf255]

Another. Zippier. 16,000 and 4 stroke

 

[blsnelling]

I've heard that but I haven't cn it yet.

Port a saw without raising compression and it will gain but not like 50 lbs of extra compression.

I disagree, but only because of personal first hand experience.

 

[Andyshine77]

I've heard that but I haven't cn it yet.

Port a saw without raising compression and it will gain but not like 50 lbs of extra compression.

I have.

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[jmssaws]

Are we talking about a saw that will miraculously last forever or a saw that will cut faster than the other one?

Compression isnt cheap either,mandrels and lathes are expensive.

 

[blsnelling]

I disagree, but only because of personal first hand experience.

Let me re-phrase that. I've seen several examples that would suggest otherwise. Compression is a key component, but not the be all, end all, that many have been come to believe.

 

[jmssaws]

I have.

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How much did it take? I've got some to almost 250 and they seem pretty strong.

 

[drf255]

In the case of the 026, the band cut also allows a lower exhaust, so the increased compression is a bit of a side effect of aiming for a lower exhasut.

You cant get that low exhaust without the comp bump.

 

[jmssaws]

I have a saw that's 225lb that will cut with or maybe even out cut my 240+ saw but it has fingers and the other dont.

 

[Chris-PA]

Combustion pressure makes power, but the pressure you read on a gauge while pulling on the rope at 50rpm is not directly related to the combustion pressure at 10,000rpm. That's why some saws have notches at the top of the exhaust port - it bleeds off pressure for easier starting but doesn't have time to do much at rpm.

Good to read something from you Chris. Havent seen you much lately. How have you been?

I've been good, if busy! I hope you've been well too? Mostly I don't log in here much anymore, but this topic interested me and I liked the link Brad posted to some decent 3rd party reference material.

 

[Deets066]

250cc? .040 would be very tight for a 250cc MX engine.

Not really, I run .040 on 700cc

 

[Andyshine77]

How much did it take? I've got some to almost 250 and they seem pretty strong.

175/180 psi.

Like Brad said compression is a key component, but everything has to come together. I personally would rather have proper squishband and squish clearance, than crazy high compression. On smaller saw I do like more compression, but I keep squish tight with proper taper. Huge squish band clearance, and a wide squishband will never make the best running engine IMHO.

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[drf255]

175/180 psi.

Like Brad said compression is a key component, but everything has to come together. I personally would rather have proper squishband and squish clearance, than higher compression. On smaller saw I do like more compression, but I keep squish tight with proper taper. Huge squish band clearance, and a wide squishband will never make the best running engine IMHO.

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Please explain why a wide band wont make power. More trapped unburned volume?

 

[blsnelling]

Not really, I run .040 on 700cc

How much in each cylinder?

 

[blsnelling]

Please explain why a wide band wont make power. More trapped unburned volume?

It's explained in the article I posted. Chris-PA can likely do a better job of explaining it though.

 

[jmssaws]

I port saws for a living and I can assure you that if my customers got there saw back with 185lbs of compression I would be out of business. I've ported a mountain of saws and shaping the squish and shinning on things don't work where I'm from.

 

[Andyshine77]

Yes Chris's post explained it better than I could ever hope to.

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[Andyshine77]

I port saws for a living and I can assure you that if my customers got there saw back with 185lbs of compression I would be out of business. I've ported a mountain of saws and shaping the squish and shinning on things don't work where I'm from.

Different strokes for different folks.

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