Spuds Porting and Tuning Thread

[Eddy_t]

I would be intrested to know what this porting does to the fuel consuption, longevity of the engine big end and side bearings, noise levels, emmisions, vibration,chain speed ( do they now need higher class trousers ) not knocking it just intrested.

 

 

The initial gains from a dual port (or jungle mufflers as they're known as by yourself) will extend the life of the saw, as it runs cooler (at the expense of fuel and noise), the actual porting itself increases the engine wear, but not considerably so, as the bearings and rings are steel, and harder than the piston.

Vibration doesn't increase as the engine generally doesn't run at a different rpm (or at least those ported to maintain the same rpm don't), which means the chain doesn't run faster, they produce more torque. Chain speed is generally controlled by sprocket gearing (7, 8, 9 toothed rims).

 

If you need anymore info, I believe Gary has a ton of stuff on porting, and a badly piped 576

[adw]

Yes i saw the 576 other than a lot of noise it was gutless, nice chrome pipe though, i always thought of porting as a black art, some good some bad, when ported the power band is changed so the full load cutting speed is surly going to be faster, and as chain speed is taken into account when choseing the class of trouser to wear this must become an issue, as for vibration pretty sure this will have increased, all sounds a little anal but it will only take one accident and the s t will hit the fan,how much faster can the operator honestly work with all this extra power? or is it just a matcho thing?

[wyk]

Yes i saw the 576 other than a lot of noise it was gutless, nice chrome pipe though, i always thought of porting as a black art, some good some bad, when ported the power band is changed so the full load cutting speed is surly going to be faster, and as chain speed is taken into account when choseing the class of trouser to wear this must become an issue, as for vibration pretty sure this will have increased, all sounds a little anal but it will only take one accident and the s t will hit the fan,how much faster can the operator honestly work with all this extra power? or is it just a matcho thing?

 

Porting has been around since two stroke engines have been around. If you don't get it, consider yourself lucky. You just saved yourself some duckets.

 

Hell, we haven't even mentioned nitrous yet...

 

[Eddy_t]

Yes i saw the 576 other than a lot of noise it was gutless, nice chrome pipe though, i always thought of porting as a black art, some good some bad, when ported the power band is changed so the full load cutting speed is surly going to be faster, and as chain speed is taken into account when choseing the class of trouser to wear this must become an issue, as for vibration pretty sure this will have increased, all sounds a little anal but it will only take one accident and the s t will hit the fan,how much faster can the operator honestly work with all this extra power? or is it just a matcho thing?

 

 

Yes, that because it's a stock saw with a pipe for a 3120xp!

The power band is raised, but it doesn't increase the terminal engine speed, that's controlled by the carburettor. What it does increase is the speed in the kerf, but that's not relevant to PPE. If you leave the cutting attachments the same, there is no increase in terminal speed, as porting generally affects torque.

With your comment about it being a black art, some things can be good, some can kill a saw's performance, it's trial and error. Luckily most things have been tried so we have a general idea of what will and won't work.

I'll move on to chain speed and PPE now... PPE should be chose regarding terminal velocity, so <20m/s is class one. .325 chains generally run at 14k rpm on saws out of the box (346, 357, 550 and 560 all run a touch above 14k rpm) which puts a 7t .325 saw at 21m/s unloaded - that's class 2 PPE. Most people don't run at full chat when they ding themselves so class 1 is adequate. By increasing the rim size by 1 tooth on the rim you increase the speed by 3m/s (this puts the saws above the class 2 limit) meaning class 3 PPE is required, but this is unavailable (for obvious reasons). Most people who change the rims know and understand this, but still do it anyway (saws are getting more powerful so a lot of power is redundant unless larger sprockets are fitted).

Vibration will not be increased as the rpm will not increase or decrease at idle and WOT, only in the kerf, where the wood absorbs a lot of the vibes. As the saw is running faster in the kerf, it actually decreases vibes (check husky vibe ratings at idle and WOT, you'll see what I mean).

A faster saw does also increase production, in fact I can double the production compared to my colleagues just by chain speed alone!

So the question could be, why don't the saws come out the factory like this? That also is an easy answer, you don't know who's buying the saw, either a pro, or a complete novice with a log burner, you have to comply with emissions regs! And finally, you don't make PPE good enough! Last I checked husky had stopped the technical 24's, leaving only Stihl's hi-flex 24's! Nobody makes 28's or 32's!

[adw]

Eddy, published chain speeds are done at max power, not max rpm, anyway i think we have done this to death, so i shall not mention it again, thak you anyway for your input, by the way how do you know so much about the 576?

[Eddy_t]

Eddy, published chain speeds are done at max power, not max rpm, anyway i think we have done this to death, so i shall not mention it again, thak you anyway for your input, by the way how do you know so much about the 576?

 

 

I ask questions, when I get the answer I remember it when I don't get the answer, I keep asking until I find someone who answers.

I have also spoken to you directly, iirc you gave me a very small can of coke at the APF.

 

Chain speed is calculated by multiplying the rpm, chain size and sprocket together in a formula. In terms of peak power, it would be around 10k rpm, which would produce a result below 20m/s.

 

But the 2 technicians at the APF spent a good amount of time chatting with me regarding porting, as did Gary. It was useful to have components available to look at prior to me doing the work (next week!) and hopefully it'll benefit the saw greatly (the crankcase overheats and warps the oil galleries on a 560, very common fault), if not, I'll be buying a new 560!

[adw]

Eddy, i think i must have missed somthing here, are you saying you are going to port a 560XP? if so how are you goin to get more fuel into it as this is controlled by the auto tune unit.

[wyk]

Eddy, i think i must have missed somthing here, are you saying you are going to port a 560XP? if so how are you goin to get more fuel into it as this is controlled by the auto tune unit.

 

The EL46 carbs can be reset. The owners manual explains it.

They will deliver plenty of mixture to a ported 560/562.

 

My problem was actually getting too much mix at idle in the WTF series used on the 241 MTronic. Though this saw seems to have had that issue long before it was ported.

[Eddy_t]

Eddy, i think i must have missed somthing here, are you saying you are going to port a 560XP? if so how are you goin to get more fuel into it as this is controlled by the auto tune unit.

 

 

You don't add more fuel, we actually lean the saws after porting, as the increased air flow draws more fuel out. The autotune will do this for me!

 

The best way to demonstrate the Venturi effect is with an airline and a McDonald's coke, blast the airline at 90 degrees to the straw and coke will spray out, that's what happens in a carburettor, the high and low control how much fuel can leave the carb via the jets, but as the air pressure is drawing more out anyway, it usually needs leaning off.

[Joe Newton]

You don't add more fuel, we actually lean the saws after porting, as the increased air flow draws more fuel out. The autotune will do this for me!

 

The best way to demonstrate the Venturi effect is with an airline and a McDonald's coke, blast the airline at 90 degrees to the straw and coke will spray out, that's what happens in a carburettor, the high and low control how much fuel can leave the carb via the jets, but as the air pressure is drawing more out anyway, it usually needs leaning off.

 

 

I've always thought you boffins had made up the "Venturi effect" as an in joke to confuse is regular thickos.

 

That analogy explained it in perfect laymans term, cheers!