Porting - Performance Measured?

[Ron660]

I'm considering porting a larger saw but have a question concerning how this increase in performance is measured. I've read after porting you should see a 40% increase. How is this 40% measured? Is this increase measured with a gauge/instrument or a timed cut (before & after)? I know more HP (torque + rpms) will increase cutting speed and porting will also probably assist in lowering engine temperature. I know porting works just how is this "%" increase measured?

 

[troylee]

Dyno thread was around recently, but before and after seems to be most common

 

[treesmith]

I was under the impression it was an increase in cut speed - reduction in cutting time. Some have comparison videos with timings, others you just see and hear the difference. My 261 and 660 both hold rpms in the cut and don't bog easily when leaned on

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[sawfun]

My ported saws hold their rpm's in the cut where stock.they would drop or bog. Some saws Ive left stock as they cut fairly well. My 044 and 460 do well enough with dual port mufflers. My 880 really needed porting as it was a dog. Husky's seem to need porting to me, however they respond better to porting than Stihls. The porting gives a Husky the torque it lacks compared to a Stihl and then some. But thats my opinion.

 

[DanTheCanadian]

If you're wanting a numbers game you will be looking for awhile. Actual data seems to vary because even a thing like elevation can effect output. If you've ever ran a ported saw you just know it feels better. Its stronger, its faster, but best part is that it feels right. Its hard to explain but once you get it you get it.

 

[VinceGU05]

Dan, that's PSA !

 

[DanTheCanadian]

Dan, that's PSA !

I'm afraid I'm not sure what PSA is but I've probly got it.

 

[VinceGU05]

Ported saw addiction

 

[DanTheCanadian]

Yupp, I've definetly got it lol. You know its bad when you want to port your 6 month old dolmar lmao. My wife cannot understand how I like to let my saws scream and cut would all day on my day off, that's why I come here and feel normal.

 

[VinceGU05]

Lol I have the same problem/situation.

 

[chadihman]

99.999% use timed cuts and the other .001% use a dyno.

 

[bootboy]

I may be wrong, but I think the best way to dyno a chainsaw would be electronically measuring with an induction generator. If that makes sense. That seems like it would be very accurate and then simply converting the Kw to HP. (746watts to 1 HP, as I recall)

Just crank up the the current through an electric motor on the same shaft and measure the difference based on what the saw is able put out.

 

[old-cat]

My PSA is SO BAD, I even ported my wood stove vent!

 

[DanTheCanadian]

I ported a dirt bike engine and threw it on a crastsman 6hp lawn mower. Man did that baby fly. My uncle got a speeding ticket on it!

 

[chadihman]

I may be wrong, but I think the best way to dyno a chainsaw would be electronically measuring against an electric motor. If that makes sense. That seems like it would be very accurate and then simply converting the Kw to HP. (746watts to 1 HP, as I recall)

Just crank up the resistive current being passed through the motor and measure the difference based on what the saw is able put out.

I thought about building an electric generator dyno. I work with hydraulics every day and it makes sense to me. The sizing and availability of the rite size generator to apply a variable load on a saw from 6000 to 10000 rpms seemed difficult. Heat would seem to be hard to get rid of also on an electric dyno. I also wasn't sure how to use up all the electric being produced. I'm guessing discharged batteries that would consume the energy until there charged then the batteries would have to be discharged again. I also thought a generator would have a cooling fan in it that would create a drag that's not accounted for in the torque. The faster the generator is spun the more air it moves creating a variable drag. My hydraulic pump has some drag in the pump but all the drag in the pump is being applied to the torque reading because the pump rotates as the drag is increased. I'd build an electric dyno if it made sense to me.

 

[anlrolfe]

Just crank up the the current through an electric motor on the same shaft and measure the difference based on what the saw is able put out.

Problem now is that you need a mechanical load with a known HP demand connected to the electric motor.

It would be easier to dump the energy into a resistance like space heaters, electric range elements or banks of incandescent lights. Measure Volts x Amps = Watts

Generating equipment has internal losses that would slightly skew the results but would be much more consistent than mechanical measurements

 

[CR888]

I'm considering porting a larger saw but have a question concerning how this increase in performance is measured. I've read after porting you should esee a 40% increase. How is this 40% measured? Is this increase measured with a gauge/instrument or a timed cut (before & after)? I know more HP (torque + rpms) will increase cutting speed and porting will also probably assist in lowering engine temperature. I know porting works just how is this "%" increase measured?

Everyone who asks this question on AS gets shot to pieces however it is a more than reasonable question IMO. Saw Builders don't seem to like dyno's and prefer cut times, feel, rpms and the 'you can just tell' as a measure of performance gains. In any other motorsport this would almost be a laughable way of testing performance gains. A dyno can tell you a lot more than max hp. l think a 40% gain in hp is huge and if correct would turn a 50cc saw into somthing more like a 70cc saw. l'm not saying for a second that porting, increased compression, timing retard/advance and exhaust modification won't increase HP or better utilize the HP already there, but this standard 40% is a bit too vague for me. If l was a saw builder, l could not think of a more useful tool than a dyno to verify what is really going on. The poster above (Chad) is a very talented member and built his own dyno thats right friends...BUILT HIS OWN DYNO! His greatest achievement to date though was marrying a lady who quote "thinks the chainsaw testing machine is really cool". Now that's something special!

 

[Stormy]

Dyno thread was around recently, but before and after seems to be most common

"What did you shoot today, Ty?"
"Oh, I dunno judge. I don't really keep score."
"Really? Then how do you measure yourself against other golfers?"
"By height."

 

[SawTroll]

Reduction in cutting time is the usual way - and that means there are a large margin of error, and many variables involved.

I suspect that way of measuring results in more impressive numbers than a dyno test would.....

 

[Stormy]

I guess i understand the sentiment of the question, but it comes with a twinge of anxiety echoing back at me from my youth. We were taught in shop class to always use a torque wrench to put in plugs. Not long after I reminded someone of the importance of this, and that experienced mechanic shot me a grin that helped me to recover from my stupor. "Do you shift by your tach?" "Umm, no." "Maybe you did at first, but then other things took over. There's more than one way to know your car." BUT, would a dyno give info that would support a claim that ported saws stay stronger longer than stock saws? That porting is just plain better for the health of a saw? While it wouldn't be strictly quantifiable, it might be a more meaningful measure?