Down-side of modified saws

[twistedtree]

What's the down-side to a modified saw? If modifications are so great, why don't saws engineered by the manufacturers ship that way? They aren't dummies, in fact I'll bet they know more about extracting engine performance than all of our saw builders put together.

I guess the obvious reasons would be emissions, and longevity, but it doesn't all add up for me. Here's why.

Emissions: If opening up a muffler, or porting, etc. makes a saw run stronger and cooler (that's what I've learned here), then why not manufacture them that way? If it's an emissions thing, then I'd expect older saws (pre-EPA) to come with opened mufflers, big-ass ports, etc.. Power to weight really matters in a saw, so why not extract every bit of power possible? The EPA wasn't stopping anyone. To the contrary, my pre-EPA 262 packs a good punch for a 62cc saw, but (proportional to CCs) no better than my brand new 346 or 385. So there must be another reason why. Anyone know?

Longevity: This I can see. If you are doing competition, the saw only needs to last a minute or so. It's like dragsters. But what about those of you who modify work saws? More power in the same package has to mean more stress, and shorter life. If it didn't, then wouldn't all saws come out of the box with double the power to weight ratio? We'd all want that, wouldn't we?

So what's the down-side to a modified saw?

 

[bwalker]

Why dont the OEMS build saws like the could?

A few reasons that come to mind are emmissions, noise levels, use of poor fuel/oil, and neglect.

 

[skwerl]

So what's the down-side to a modified saw?

It's loud and doesn't meet EPA regulations for noise or emissions guidelines. The new saws are better, faster, stronger than old saws due to technological advancements.

New cars and trucks are faster, safer and stronger than cars and trucks from the 60's and 70's. But an aftermarket exhaust system and a chip to modify fuel and timing parameters will still give you a 10-15% gain in performance over stock. Not legal in states where you have annual emissions testing though, it won't pass. But the vehicle will run faster, stronger and longer than stock.

Saws aren't as technologically advanced as cars, but they are choked down pretty bad through rudimentary changes to meet government regs. The restrictions also cause the saw to run much hotter. Marginally acceptable if you are a perfect operator, but disaster for those who lug the motor and run dull chains for hours. The saws burn up due to excessive heat.

Woods mods allow better flow for more power and cooler operation. The downsides are more noise, a slight increase in emissions (although one commercial airliner making one flight has more emissions than all the saws in the US for a year) and faster fuel consumption. Also the cost of having the mods done. The manufacturers cannot do it because the saws would not be legal to sell in the USA.

 

[ShoerFast]

Good Question,,,,,

twistedtree

Good question,,,,, and another .02 to Skwerl's reply, is the "NOX" emmision standereds.

Just like the auto ind. in the 70's, they needed to start reducing emmissions of NOX,,,, the easest way to do thay was to add exhoust into the intake, via an EGR valve,,, with less O2 to start with the less that would end up combining with a free nitrigon to make NOX,,,, but it cost a lot of power,,,,, just look at a mid 80's car.

In a 2 stroke, it was easy to restrict the exhaust flow to cause a back up, so to speak, and introduce exhaust to the incoming air/fuel.

That again comes with a huge cost of power, it would be my guess that we are 10 - 15 years out from seeing small engines with minni-prossers doing the fuel injection and ing timming. ,,,,And it's my guess that thell screem!

Kevin

 

[bwalker]

Two strokes have naturaly low NOX emmisions(comparitivly) by virtue of the way the are scavenged.
The main push with emmisions laws in regards to two strokes are unburnt HC.

 

[Jim Mesthene]

Nitrous oxides (NOX) are a result of high combustion temperatures. Oxygen and nitrogen will combine in various forms at elevated temperatures, this has nothing to do with the fuel. EGR systems reduce combustion temperatures by introducing foul air into the intake mixture.

 

[bwalker]

Nitrous oxides (NOX) are a result of high combustion temperatures. Oxygen and nitrogen will combine in various forms at elevated temperatures, this has nothing to do with the fuel.

Thats correct.

 

[ShoerFast]

Excelant point Jim,,,,

Nitrous oxides (NOX) are a result of high combustion temperatures. Oxygen and nitrogen will combine in various forms at elevated temperatures, this has nothing to do with the fuel. EGR systems reduce combustion temperatures by introducing foul air into the intake mixture.

Excelant point, as the muffler restriction (or EGR) adds CO2 to the Air/Fuel, it cant burn as hot, and has to work harder to get-r-done.

By cutting the combustion temp, HC emmisions would go up, but HC is not nearly as deadly as NOX. HC will disapate, while zero is the number they want for NOX

Kevin

 

[bwalker]

Excelant point, as the muffler restriction (or EGR) adds CO2 to the Air/Fuel, it cant burn as hot, and has to work harder to get-r-done.

By cutting the combustion temp, HC emmisions would go up, but HC is not nearly as deadly as NOX. HC will disapate, while zero is the number they want for NOX

A two stroke has a defacto EGR valve in the form of incomplete scevanging, which happens on all two strokes due to the way the exhaust gas is evacuated out of the cylinder. Two strokes as a result are naturally low in NOX.
Like I said before the main push of two cycle emmisions standards are reductions in unburnt HC.
FWIW choking up the muffler and lean carb settings actually increase NOX by virtue of the incresed combustion temps, but they also greatly reduce unburnt HC.

 

[twistedtree]

I get the emissions argument, but didn't the EPA just start regulating saws in the last 10 years or so? Before that wouldn't all factory saws have had these less restrictive flow designs?

EPA regulates noise level? I didn't know that.

 

[skwerl]

The first phase of EPA regulation happened back in the early 80's, when pretty much all manufacturers went from 32-1 to 50-1 mix ratios. Then in the late 80's, early 90's we got new carbs with adjustment limiters. This meant that they were setting the carbs lean and we weren't easily able to richen them up. Many saw models were dropped, replaced with newer, cleaner burning models. MY beloved 038 Magnum was one of the models dropped in the USA strictly based on emissions.

This phase is getting stricter, Stihl and others have gone to a hybrid 4 stroke design on some equipment (HT101).

 

[rahtreelimbs]

The way I see it.........the new Husky 575 and the Stihl MS441 (On the way) are the wave of the future.

Some growing pains will be had..........but iI think the end result will be good. Just how long that will take is anyones guess!

 

[ShoerFast]

1997 and the clean air ACT,,,,,

Twisted tree

In 1997 small off road engines were placed on the EPA's list as testable engines as part of the Clean Air Act ( http://www.epa.gov/oar/caa/caa.txt )

The Clinton era congress passed the act as a means of testing and reducing the amount of "toxic" emmissions, a lot of red state arguments were that it would cost too much to clean up smaller engines, while a lot of the blue states held the vote as a means of monaturing the effects of toxic waste on the Ozone layer, and measuring the hole in the ozone.

While the manufacture of small off road engines were placed on the same scale as off road eq. and didnt need to meet the requirments of more conjested areas. ( http://www.epa.gov/fedrgstr/EPA-AIR/1997/March/Day-21/a7218.htm )They did need to comply with the toxic or NOX emmissions, (NOX is perhaps the most toxic) as HC is on the list of testable emmissions, it has nothing to do with the reason that there tested, as HC disapates, it's no longer believed to effect the ozone.

At the time these measures were coming about, I watched them very closely as an aircraft tech, A/C's were on the orginal list of testable engines.

It would be intersting to see any sites that could say that small off road engines are listed as needing to reduce HC, as it's a secondary by product.
(propane is an HC, it is said that it will disapate within 4 miles of a huge leak)

Engine Mfgr's and other Mfgr's have strong lobbies that would shoot down the EPA and ammend the Clean Air Act, if they could prove that it was all due to HC emmisions.
It's the unknowns that support the Clean Air ACT.

My take, it would be hard to say that we could change the hole in the ozone, or that NOX CO1, CO2, or HC have any effect, I dont think so, but it would be hell if we were wrong!

Kevin

 

[bwalker]

Phase 1 took effect in 98 I believe, but before that there was a push to reduce noise and visable smoke which led to more restrictive mufflers and less higher numeric oil ratios.

 

[bwalker]

It would be intersting to see any sites that could say that small off road engines are listed as needing to reduce HC, as it's a secondary by product.
(propane is an HC, it is said that it will disapate within 4 miles of a huge leak)

I have seen this sort of info on differant sites that I cant recall. I do know that the 06 standards for snowmobiles is based on a percentage reduction of HC+ NOX. HC is the big one though as the number greatly excedes the NOX number.
Dissipation has nothing to do it with as all emmissions dissapate in one way or another.

 

[ShoerFast]

So witch is it?

Two strokes have naturaly low NOX emmisions(comparitivly) by virtue of the way the are scavenged.
The main push with emmisions laws in regards to two strokes are unburnt HC.

Or is it

"I have seen this sort of info on differant sites that I cant recall. I do know that the 06 standards for snowmobiles is based on a percentage reduction of HC+ NOX. HC is the big one though as the number greatly excedes the NOX number.
Dissipation has nothing to do it with as all emmissions dissapate in one way or another."
.

Do you know or just quoting what you think you know from other sites?

Here in real lynda, the reason "small off road engines " were placed on the list was it passed congress, and singed into the Clean Air Act, because of the whole Global Warming thing,,,, some are concerned!

ATV's and Sleds , everything fall scrutiney to the 1997 act,,, things that have fallowed will also,,,,, it would tell in the ATV's OM, or what have you, as thay also need to have an Emisisions Warranty, it should be 2 years for the first owner.

The kicker for HC would be for the toxicens in the unburnt oil, as that would directely effect there program.

The effects of HC were not the reason the can of worms tipper over.

Kevin

 

[Lakeside53]

EPA regulates noise level? I didn't know that.

OHSA regulates noise in the work place... Some States regulate noise, as do most cities.

 

[ShoerFast]

Noise and HC reduction,,,,,

It would be next,,,,, a Catelitic Converter is the best way to burn unburnt oil, and reduce the noise,,,, are they next?

It would also be the best way to reduce HC, if that were there first goal.

Kevin

 

[bwalker]

I know for a fact that two strokes have naturaly low nox when compared to a four cycle of equl technology.
I know for a fact that the emmissions standards as applied to snowmobiles and chain saws use a a measure of HC+NOX.
I do know that HC emmissions are the main push of the regulations.

singed into the Clean Air Act, because of the whole Global Warming thing,,,, some are concerned!

HC and NOX have very little to do with global warming. The only way to cut carbon from entering the atmosphere is to decrease the mount of fuel burnt, which is not currently regulated. Some emmissions related schemes like RFG fuel have actually increased the amount of carbon being emmited.

The effects of HC were not the reason the can of worms tipper over.

Respectfully, yes, it was.

 

[bwalker]

http://www.zenoah.net/tech/image/XE23.pdf