What is porting? I know it is a way to boost power out of a saw, but what is done to the saw to accomplish this? I'm not looking for a how to, more like a how is it done, if that makes sense. I'd just like to know what you guys are talking about. Also do the modifications affect the saws life or reliability? Why don't the saw manufacturers produce ported saws? Is it an emissions issue? I'm not mechanically inclined, if I bought a ported saw, would my local Stihl/Husqvarna shop know what the mods are and/or how to service the saw? How would I know whether to trust the local shop?
I've never even attempted it, but I believe porting loosely refers to modifications of the ports. Gas and air get sucked into the bottom of the engine through the intake port, move from below to above the piston via the transfer ports, and after combustion the gasses get ejected through the exhaust port. Changing the size, shape and surface qualities of those ports will affect the way the engine runs in all sorts of ways.
An engine is nothing more than a pump... Reducing restrictions makes it more efficient. Porting can include moving the ports, cutting the squish, enlarging and polishing the ports, advancing the timing and deleting the base gasket along with the requisite muffler modification. The goal is to produce more power while making the saw more efficient.
Everything you read above is true. There is a lot to it beyond what is above. Manufacturers have design budgets, longevity concerns, warranty costs, and market viability to contend with. HVA, Stihl and all the rest would certainly like to bring the advantages of fully utilizing their design to market focusing specifically on performance without regard to other concerns; however, in reality that is not possible. Lets' say that you want a saw that retails for $700 and has a 2 year warranty. Now we add $250 to that to cover all the concerns stated above, now your saw is very close to $1000, would you still buy it? What if it only had a 6 month warranty, would you still be willing to spend near $1000? Does the modification of a saw impact its' service life, my opinion is yes, if it did not; the manufacturer would be doing it. Are there gains available to you from a ported saw, yes however they carry a cost, if you are willing to accept that cost, then go for it. Most dealers, if they are worth their salt, will immediately recognize a saw that is not factory and void the warranty claim and/or refuse to work on it or both.
What Guido posted, which is very accurate. To elaborate a little more.. And if Randy, Mike (Mdavlee), KilliansRedLeo, or several others would care to comment more. Basically they take what the manufacturer had in mind and improve on it. They raise compression (cutting the head down/or in the case of a saw, the head/cylinder) which is cutting the squish band. This is the distance between the top of the piston and the cylinder head. The closer the piston comes to the top, the higher the compression. They also open the transfer ports (ports that let the fuel travel from the crankcase to the compression chamber/cylinder), may raise and or lower the ports (intake, exhaust, or transfers/ to get better compression, blow down, crankcase pressure, transfer velocity, etc), polish the ports (the intake as I know, is rougher to allow the fuel charge to mix better, but the exhaust should be as smooth as a baby's bottom), advancing the timing (well, this is based on what they do with the port timing and squish), and modding the muffler (the easier the saw can breathe, the easier it will be to make power). As for the life span? This all depends on the degree of modification. If it's a race saw? It won't last long. A good woods port will add some stress to the engine, but if taken care of? The length of service shouldn't be affected to much. And this is still the short version.. If we beg enough? Maybe Randy will do a full featured Port job to a saw here.
I have a 1986 Husqvarna model 61 that I bought new in 1986 that makes it 28 years old. Still running with no problems and no rebuilds. I'm not saying that a ported saw will not last a good amount of time but I'm not sure 28 years would be in the cards. One must also remember that a chainsaw is a highly stressed, high use tool that through normal use will fail before your grandpa's hammer, ported or not.
If Randy were to publish something like that, say on one of the 665s he has and go through all the steps he has to go through, it would be like reading War and Peace!
How about an answer for his last 2 questions? For me there's no way I'd let either of the dealers I use touch any moded saw let alone my only ported one.
Well, a dealer is required to fix anything they see fit. So if you took in a modified muffler? They would replace it with OEM. As to knowing if it was ported? Unless the mechanics really know what "Ported" is? They may not know unless they check compression.
OK here is my take on the last two questions. No, they won't know what any cylinder timing changes are, what they will know is 'this is not factory'. Knowing how to perform service on the saw will not matter, because once they know 'it is not factory' they will seldon touch it. Trust in your dealer is something your dealer has to earn, you won't know from the onset of your customer/dealer relationship, and trust is something you bestow on one who has earned it.
Some dealers will replace any modified arts to make it back to epa standards at your cost and then do repairs. I've heard of fallers getting 2 seasons out of ported saws and some that didn't last 2 months.
It is worth mentioning that like any machine that you can modify, it matters who did the mods and to what extent it was modified. A "woods port" generally will not significantly reduce a saws life expectancy IMO. But there are varying degrees of modification. I would venture to say that 90% of dealer techs would not know a ported saw from a stock saw as long as both were wearing factory mufflers. Hell, the muffler mod on my ported 441 is so clean, I probably could pass it off as stock. There is no reason a dealer couldn't repair a modified saw, at your expense of course, as the same tools, techniques, and usually parts all apply. If your saw had parts from another model, it would be up to you of course to make whomever is repairing the unit aware of that.
Good points MM +1. Like Mdavlee said above, your results may vary. I would venture to say that if you have only one saw and depend on it to heat your home, a port job on that saw may be risky business. However if you have several saws it wouldn't be a big deal to have one modified just to see what it is all about. Just find someone to whom you will trust your $500-$1000 saw to and be prepared to pay the price. In this case 'price' is defined as the cost of the saw modification and a possible reduction of the useful life of the saw. Probably the most cost effective scenario would be to wait until the saw is in need of a major repair/rebuild, then bundle the porting in with the repairs. No sense in taking a brand new saw out of the box and destroying the warranty by modifying it, although some of us have been known to do just that!
Thanks all, much clearer on what the mods entail. Sounds like if I owned a ported saw I would need to find a trusted private shop or have a very clear understanding with the local guy.
And a dealer for Husky/JRed... He'll service anything he mods or sells... On another note, the expected service life of a pro grade saw is about 2000 run hours... If a good woods port job up's the performance, but knocks 30% off the expected service life, what do you have? 1400 hours of run time... I would dare say, few saws ever make it there without something else happening to them first.. Only a man that goes out 5 days a week and drops trees for 8 hours a day needs to consider the life expectancy, and it's those exact fella's that started modding their own saws so many years ago... I mill with a ported saw... Life don't get much worse for a saw than that.. Set it rich and keep it as clean as possible..
I agree most day in day out use saws will fail from something else before the 1400 hours runs out! Just for laughs lets' put the 1400 hours into perspective by dividing by 8 hour days = 175 days, divide again by 5 days a week = 35 weeks, divide again by 4.3 weeks in a month = 8.2 months. Do it again using the 2000 hour figure which works out to be 11.62 months. In the case of a guy heating his home who only uses his saw a few hours a month, he will get tired of the saw before the 1400 hours runs out, CAD! Hedge, lets face it, you and I are both capeable of repairing/rebuilding our own equipment, some folks are dependent on others, so longevity is more important to them.
