Modding and Porting Fundamentals

[moody]

I don't really see a big jump in production in tree service. I can see it in logging and cutting firewood off a pole of logs. If i
had a ported saw that was 40% faster than stock its still not gonna turn a 10 hour day into a 6 hour day. And if it does i'm losing over $600 in wages because i get paid hourly.


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The speed allows some tree services to book more work. And that's where they can see the difference.

 

[shootingarts]

Phil,

The tach readings are one more stream of data coming in. If you use it as an extra source of information I think it has a great deal of value. Experience, past history with this saw, cutting conditions when testing all have to be weighed into conclusions. My opinion, my little forty dollar tach gives me a lot of bang for the buck.

One example, changing brands or types of chain can affect RPM. Might or might not affect time in cut. A similar thing, I put great new tires on my dirt car once. With the same rear gears that were fine with the old tires the tires bit harder and the engine bogged. Sounded like an old log truck coming off the corners. My lap times were exactly the same as with the old tires! Vastly different set-up gave me "the same time in the cut". Got my RPM back up where it belonged and the car cut almost a second off of lap times with those tires! The tach lets us seek the same balance with a saw if we use it for that.

The tach's value depends on how we use it and how well we interpret results.

Hu

 

[tree monkey]

i've done lots of real world testing with stock and ported saws comparing time and milage.
the best way to do this is to fill my truck with wood keeping track of time and fuel.
after 20 loads before and after porting i have a pretty good idea of where each stands.
every saw i tested cut more wood in less time using less fuel.
my 046 uses 25% less fuel in30% less time to get the same work done.

another way to look at things.
if a ported 362 cuts with a stock 461 and uses about the same amount of fuel and the price is about the same, witch one would you rather carry all day?
this is the biggest reason pros use ported saws.

now i know people will say that can't be done,or that i'm full of ****.
if you want proof, take a saw of your choice, burn 5 gal of gas keeping track of time and wood cut.
send me the saw for porting and repete.

 

[WHSH]

Sorry, obout the sarcasm assumption. I thought handing me a link wich appeared, in a brief view, was random unrelated conversational jibberish or dead end. Then the double posting was meant be a slap. In other words if was a joke post of just gibberish that you would tell folks to read then you were poking that them. Sorry, Its just that folks have taken the forum "off the rails" often on this site so I had my back up. I was wrong, sorry. I will dig down in them more.

 

[CR888]

But you can't accurately measure the load put on both saws. Saws are funny critters. The only way to judge performance is in the cut. Dyno won't do anything but show ratings but are those ratings user friendly during operation?

would a dyno not be the only way to put a constant measureable load on a saw. Me thinks a dyno is the only accurate measure of HP increase/decrease. l know the builders don't want to know about them but to me, correct use of dyno=truth.

 

[Real1shepherd]

I think some people over think the fuel mileage on ported saws. Yes they use more fuel buy a properly ported saw will put that fuel to use. Say that you use 10% more fuel but your production is increased 40%. You still see 30% more in the truck. To some that's more heat and to others that's a bigger check. Am I saying that everyone needs a ported saw? Not at all. A lot of logging happens in my area. And one log is $300ish veneers are quite a bit higher. Say that you get on Average of 30 logs a day with a stock saw. A 30% increase in production will yield 9 more logs a day. That's $2700 increase in pay. Tell me where $250 is a waste of money? This is not me ranting just a little food for thought is all

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I wouldn't argue that, with a fully modded, ported saw. But you assume in your scenario that you're saving so much time on your cuts, that it's actually gonna yield on average 9 more logs in a day. I've run Husky 2100's in the woods with muffler mods only, back in the day. My scale wasn't significantly increased, but the power into the falling cuts was more spectacular and therefore, safer. Nobody was saying modding was a waste of money...my point was that home brew modding may not significant improve scale. And to just test modest modding by time of cut, is not enough.

It's not that complicated and much of a stretch to think that say, someone did a muffler mod....goes outside with expectations that his mod worked and therefore leaned into the cut a little heavier than normal. I've watched a LOT of vids on youtube of guys bucking logs and probably close to half of them are not getting the best from their saws by their cut methods. Again, a lot of human variables here.

I'm all for porting and modding....I would like to have all my saws ported. But I don't want some barnyard job either....so that means $$$, even if it's money well spent. I'm not working in the woods ten hrs a day anymore and I would need to justify the expense. If it's just who's got the biggest di**, I could care less. I don't want this to get ugly or misconstrued...so I'll just pass on anything further.

Kevin

 

[Chris-PA]

Well, a higher performance saw can only speed up the part of the job where actual cutting is involved. So for example if the saw is 30% faster but you only spend 10% of the actually cutting (numbers pulled out my ass) then your improvement is around 3%. I don't know what the real percentage of cutting time is for various jobs, but you get the idea.

 

[smalltime]

Hmmmm, So, what is the ideal, squish band? Hmmmm? Most saws have flat/non angled bands. Some have asymetrical combustom chambers, thus asymetrical squish bands. This propagates the flame front starting at the intake side. Some have a centered dome with the plug on the intake side. Some like the older stihls have domed pistons and bands. This would seem to make the volume of the squish band larger than a flat piston? Just regarding the flame front and skipping the piston smashing part. To small you don't get cooling of the piston crown, two large you get diminished turbulance. Then there the two flame front detonation concern. So given the saws combustion chamber design has any one worked out saw specific squish band mods? Does any one polish the combustion chamber or is this still concidered intake tract, if so were does intake track start and end? Do you polish the piston crown but leave the combustion chamber rough? I would think to knock down the real rough points that concentrate heat and thus act to propagate detonation.

I found this and thought it was good reading.

Source - http://www.ktm950.info/how/Orange Garage/detonation/Detonation_101.html

"It is important to realize the two important functions of reducing the squish band clearance: (a) to enhance turbulence due to rapid ingestion of gas into the combustion chamber, hence increasing the burning rate of the mixture and (b) to reduce the volume of the unburned gas in the boundary layer of cool gas near the piston top and cylinder head surfaces. Typically, gas trapped in the squish area doesn't burn, even if the squish band clearance is relatively large. The cooling effects of the large surface-area-to-volume ratio of this region will prevent any ignition of the fuel-air mix therein, even if the squish band clearance is rather large. Hence any gas caught in the squish band will not be burned near TDC when it does the most good, but later during the combustion process when one cannot extract as much work from the late-burning gases. The amount of gas trapped in the squish band can actually be a substantially greater amount than just the relative volume of the squish band because the pressure wave from the ignition process literally crams a lot of the unburned gas into crevice areas like the squish band. Reducing the squish band clearance will decrease the amount of unburned gas substantially, leading to more complete and faster combustion, lower emissions and improved power. It is one of the few "all gain with no pain" modifications one can carry out on racing or even street motorcycles.
Someone wondered: Is the extra cooling of the squish band less than the added heat?
Basically the mixture in the squish region is in thermal contact with the cylinder wall and piston top and at roughly the same temperature, which is quite lower than the burn temperature. Reducing squish will decrease the amount of the cool gas in the squish region and increase the amount of hot gas in the burn region. A reduced squish clearance will increase temperatures a little even if the compression ratio is held constant. There is no "extra cooling" mechanism if you reduce the squish band clearance. The cooling rate of the gas in the squish zone depends on the thermal conductivity of the gas-metal interface, on the total surface area of this interface and the temperature difference between gas and metal. Note that these factors are all essentially constant at TDC and don't depend on the squish clearance. Hence the cooling rate is the same for large squish clearances and for small squish clearances. Thus there is no "extra cooling" mechanism if you reduce squish band clearance"

 

[K-techcowboy]

Thanks Chris. That was also very clear.

This is a great site when guys share stuff like this.

Philbert

Most of us are here for the same passion and we've all been there not knowing much about a particular subject we find fascinating. I look at this place as a brotherhood where we can learn and share not only our experiences with power equipment but with life. This is a great site especially for someone like me who is pretty cut off from society after traumatic events.