Stihl 260 muffler mod data, temp, sound level and preformance

[sritzau]

Are there earlier versions of the 026 that did not have to meet the same EPA regulations as the current ones? If so, it would be interesting to see what they had for open areas in their mufflers and try to figure out how the folks at Stihl settled on that value.

Steve

 

[bwalker]

This is just a swag, but I would guess that pre EPA saws will benifit some from muffler mods also as the stock mufflers are restrictive for ANSI noise standards.

 

[046]

muffler mod coming up on my 026

 

[chowdozer]

Good information!

I'm guessing you used a Raytec or similiar non-contact infrared thermometer. A word of caution when using these type of instruments: It is very difficult to get an accurate temperature measurement unless you are able to obtain an emissivity value of the material you are pointing at and even then bare aluminum is a no-no. In layman's terms, the measurement of the muffler is probably within 10% of actual. The cylinder head temp is probably way off. Reason being that flat black is a good emitter, ie heat radiator with an emissivity of 0.90 or greater. Unpainted aluminum is a very poor emitter, (emissivity of <0.20) and in fact aluminum sanded with 100 grit sandpaper is a very good infrared mirror causing you to measure heat reflected from something else. (Just for info, emissivity + relectivity = 1) where emissivity is the ability to radiate heat and reflectivity is the ability to reflect heat. Think "space blanket" or one of those parabolic reflectors on an electrical heater. I'm reasonably certain that if you were to paint a cylinder with VHT Flameproof coating and use an emissivity # of 0.92 in your Raytec you would get a different number. The VHT would also help the saw to run cooler. Why engine manufaturer's don't paint them black, I have no idea. Woodstove manufacturer's know about flat black paint.

I do believe that your temperature differentials are valid.

Greg
(thermal non-contact measurements are my job)

 

[DanMan1]

Good information!

I'm guessing you used a Raytec or similiar non-contact infrared thermometer. A word of caution when using these type of instruments: It is very difficult to get an accurate temperature measurement unless you are able to obtain an emissivity value of the material you are pointing at and even then bare aluminum is a no-no. In layman's terms, the measurement of the muffler is probably within 10% of actual. The cylinder head temp is probably way off. Reason being that flat black is a good emitter, ie heat radiator with an emissivity of 0.90 or greater. Unpainted aluminum is a very poor emitter, (emissivity of <0.20) and in fact aluminum sanded with 100 grit sandpaper is a very good infrared mirror causing you to measure heat reflected from something else. (Just for info, emissivity + relectivity = 1) where emissivity is the ability to radiate heat and reflectivity is the ability to reflect heat. Think "space blanket" or one of those parabolic reflectors on an electrical heater. I'm reasonably certain that if you were to paint a cylinder with VHT Flameproof coating and use an emissivity # of 0.92 in your Raytec you would get a different number. The VHT would also help the saw to run cooler. Why engine manufaturer's don't paint them black, I have no idea. Woodstove manufacturer's know about flat black paint.

I do believe that your temperature differentials are valid.

Greg
(thermal non-contact measurements are my job)

Greg, My experience with infrared thero, is in total alignment with what you posted. On metals the reading is severly distorted by suface impuraties. Just a speck of paint or rust, or a small rough or smooth area throws off the reading. Different stainless steel formulas give totaly different results, even when you look up the emisivity from a chart and dial in the meter. I DO think they don't paint the heads because convection and conduction accounts for more cooling on engines than radiation. And any paint applied reduces conduction heat transfer. Painted woodstoves favor radiation because they want to heat object across rooms and can't rely on convection provided by a flywheel fan.

 

[bwalker]

Using a infared device to measure the heat of a motor is a scientific circle jerk.
I had a HVAC guy out at my place this winter and he basicly confirmed what I thought all along about the devices lack of accuracy.

 

[Al Smith]

Using a infared device to measure the heat of a motor is a scientific circle jerk.
I had a HVAC guy out at my place this winter and he basicly confirmed what I thought all along about the devices lack of accuracy.

Well Ben,are you a thermal expert?Most infrared measuring devices take the measurements with ambient,or background temperature as a reference.If your theory holds true,then American as well as world wide industry has spend billions of dollars on a fluke.If ,however,the calibration of these measuring devices are inaccurate,then so would be the measurements.I will admit that you can't compare the several hundred dollar device the furnace man had to the $40,000 one we have where I work,which I will say is very accurate.

 

[bwalker]

Al, dont be banal. Of course I am talking about the units bought at home depot and such and not the 40k units you have at work.
When I visited a test cell dyno at one of the large American auto companies a few years back I sure as heck didnt see any engineers taking readings with a infared device. Rather every thing was measured via digital temp gauges and thermcouples.

 

[chowdozer]

to Al. I have 8 thermal imagers at work and two portable IR spectrometers. The measly $60-80K per imager isn't the costly part, it's the $300-400K for the lenses. That's per imager. Raytec's are notoriously inaccurate, but with careful preparation, they can do in a pinch.

 

[Al Smith]

How then,may I ask,do they take measurements in the production of steel?

 

[chowdozer]

Ben, sometimes a test engineer can't wire up thermocouples to the test object. Something about strapping loose wires on a supersonic jet engine that's going to roll out at 30K feet in a 7G turn. And sometimes, it might be a non-cooperative target.

 

[chowdozer]

I need to clarify one of my previous posts. Anyone can take a top notch piece of equipment and produce results, often times undesirable results. Few people can take a less than top notch piece of equipment and produce good results. Nothing against Raytec, they are decent if the operator knows what he's doing. If the operator doesn't understand what he's doing, a $100K piece of equipment won't make his results any better. It's about preparation and understanding.

 

[Al Smith]

I will agree that high end thermocouple devices,properly calibrated ,are far more accurate,but the use of thermal imaging devices has saved industry tons and tons of money by being able to detect potential problems with machinery breakdowns,faulty electrical devices and the like.On the opposite end of the light spectrum ,the ultraviolet devices have became well accepted as a means for ignition detection,etc.This posses a bit of a puzzle.All of our dyno cells at work,have state of the art temperature measuring devices,several for comparison,tied through a goobly gook of computers,monitoring devices etc etc.How,may I ask,would one take the temperature of an exhaust valve,if not for a thermal imager.

 

[DanMan1]

Al, apples and oranges.

Yes temperature measurement based on light energy measurement can be accurate and repeatable in a controlled environment and on known pure (that's the important part) materials. But come on, you have to admit thats not what you have with a used chainsaw muffler, is it? We all know that even after a minute of running a muffler develops areas with discoloration. Even a slight bluing of metal changes the emisivity. Then spots of missing paint, rust etc... So you are looking at a non pure material. How can you get repeatable accurate results from a handheld IR gun. You can't. You can get good ballpark results, but that's it.

 

[chowdozer]

Several things to mention here Dan.

It is wrong to call infrared energy light energy. It is an electromagnetic wave, just as radar or sound are. The wavelength of the typical IR bands, 3-5 um and in the case we're talking, 8-12 um, are much higher than light. Your eye only "sees" to the high .7 um, low .8 um.

The higher the temperature, the less difference the coating makes. This is one of the reasons why a cavity blackbody is an optimum calibration source. (That and the elimination of reflections.)

Areas of discoloration aren't very important on a part under test - to some degree. One of the reasons I use VHT flameproof paint, is that it bakes into the metal somewhere around 300 C. It might look like crap, but it does perform well. When you paint a part, it's ok to slightly see the metal underneath. If you have too much coating, it may be insulating the part.

If you were going to perform a lower temp test, the best paint is Krylon ultra flat black. This is a high carbon paint and very emissive, E= 0.95 Trouble is, it doesn't stick to well either and flakes off at higher temperatures.

I agree that you can't get good results with Raytecs, or any other devices of that nature. The only instance I know of that they are used with some degree of accuracy is race car tires. But then, I don't think the E of the rubber varies much either.

 

[DanMan1]

Several things to mention here Dan.

It is wrong to call infrared energy light energy. It is an electromagnetic wave, just as radar or sound are. The wavelength of the typical IR bands, 3-5 um and in the case we're talking, 8-12 um, are much higher than light. Your eye only "sees" to the high .7 um, low .8 um.

The higher the temperature, the less difference the coating makes. This is one of the reasons why a cavity blackbody is an optimum calibration source. (That and the elimination of reflections.)

Areas of discoloration aren't very important on a part under test - to some degree. One of the reasons I use VHT flameproof paint, is that it bakes into the metal somewhere around 300 C. It might look like crap, but it does perform well. When you paint a part, it's ok to slightly see the metal underneath. If you have too much coating, it may be insulating the part.

If you were going to perform a lower temp test, the best paint is Krylon ultra flat black. This is a high carbon paint and very emissive, E= 0.95 Trouble is, it doesn't stick to well either and flakes off at higher temperatures.

I agree that you can't get good results with Raytecs, or any other devices of that nature. The only instance I know of that they are used with some degree of accuracy is race car tires. But then, I don't think the E of the rubber varies much either.

Chowdozer, Nice mix of fact and fiction.

"It is wrong to call infrared energy light energy"

Sorry, you are wrong, plain and simple.
Just because it's not visible to human eyes doesn't mean it's not light.
I'm sure like me you must have learned that in your first years at college.
To passify you I included a cople of random definitions I just grabed from the net below.

1)A band of the electromagnetic spectrum between the visible and the microwave.
2)Light of wavelength longer than the reddest part of the visible spectrum
3)Light waves just outside the visible spectrum; that is, waves slightly longer than those visible to the human eye. Infrared light is sometimes filtered out to reduce heat on film or slides. Also see Infrared control.

"It is an electromagnetic wave, just as radar or sound are"

Here is where I stopped reading your post. Sorry but on Earth, 'sound' is the result of physical movent of a solid, liquid or gas such as air, NOT an electromagnetic wave.

 

[chowdozer]

Sorry, you are wrong, plain and simple.
Just because it's not visible to human eyes doesn't mean it's not light.
I'm sure like me you must have learned that in your first years at college.
To passify you I included a cople of random definitions I just grabed from the net below.

1)A band of the electromagnetic spectrum between the visible and the microwave.
2)Light of wavelength longer than the reddest part of the visible spectrum
3)Light waves just outside the visible spectrum; that is, waves slightly longer than those visible to the human eye. Infrared light is sometimes filtered out to reduce heat on film or slides. Also see Infrared control.

That’s a riot. I punched “light definition” into Google and took the third site. I took the third site because the first site said something about "web definitions of light". The second site was called “definition of the speed of light” or some such. So I took the third hit because it said "light ( līt ) n. Physics". That looked good. I read the first definition, here it is:

Electromagnetic radiation that has a wavelength in the range from about 4,000 (violet) to about 7,700 (red) angstroms and may be perceived by the normal unaided human eye.

Sorry but on Earth, 'sound' is the result of physical movent of a solid, liquid or gas such as air, NOT an electromagnetic wave.

Yep, I brainfarted and I’m willing to admit it.

Since we’re going to nitpick Dan, I want to know where you got this fiction?

“…can be accurate and repeatable in a controlled environment and on known pure (that's the important part) materials.”

Why does it have to be “pure”? Exactly what is “pure”? The best measurement you can make is on a sooty part. It’s carbon and if it sticks, it’s the best material to get an IR measurement from. Period

Nice mix of fact and fiction.

Ditto to you, Dan!

ps, use the spell check

 

[BigUglySquirrel]

little carried away....

Hey fellas, I think it's great that you guys are so into the nuances of your respective technical fields. Is it possible to stop arguing with each other and try to come up with a variable for the equipment this fella is using? He's gone through all of the trouble of collecting data and establishing baselines and conducting tests to as strict a standard as he can. Obviously he's not using state of the art equipment in a controlled testing environment designed specifically for the application. ($40k thermocouples? I see them too...what's the chances one of us is going to obtain one and THEN use it properly at home?? When you get down to .001 of a degree, you'd better be able to control the ambient air temp down to that accuracy or your tests are crap anyway.) He's not using toys out of the Crackerjack box either. His testing methods are unbiased and consistent. So I pose this challenge to you, gentlemen: Can you put your heads together long enough to define a degree of accuracy? 5%? 15%? I know it's hard to set aside ingrained technical learning, but try to keep in mind...this is NOT a definitive thesis on the matter at hand. It IS a very well conducted test for the purpose of "heads-up" comparison. Make a few assumptions based on well conducted home testing.

 

[chowdozer]

Can't argue with you there Chris. Timberwolf, my suggestions for the best measurements in the future are as follows:

Give the cylinder a light fogging of VHT flameproof black paint. Degrease first. Ideally a sandblast would be nice but we all have our dreams. Scuff up the muff removing all the paint you can. Fog it with the VHT also. Perform your test as you have outlined. If your intsrument has an emissivity setting indicated by a capital Greek E, set it to 0.92

All told though Timber, I think your delta temps, or differences (on the head and on the muff. I don't believe comparing the head temp to the muff temp would be accurate), are as accurate as your equipment can be. I would call your test a success for the answers you were after.

 

[timberwolf]

Have not posted in a while, but this draws me out.

Given the objective is not to find the exact temprature, but to find the temprature change between each step much of the error canclels it self out.

When I did this test I found a spot on the head and one on the muffler that were giving the consistantly highest readings.

Since then I have looked at saws and pipes with a 20k thermal imaging camera, cool images, but they wouldn't shead one bit of additional light on the temprature change between 2 tests, as interpreting the color display is very subjective. However it was very interesting to see the hot spots where there is poor air cooling, where the xfer ports cool the jug, and where the exaust heats it. Might also be useful for pipe tuning.

I agree thermal couples would be better because they can be fixed in one location, can give constant output (heat curve), are not as affected by reflectivity but do have thermal lag that might need to be taken into account for.