What's The Story On Modified Mufflers On Stock Chainsaws?

[outdoortype]

Any more questions?

No point in being smart alec. Did you actually measure the engine temp? I know the cat mufflers get hot but most of that is around the cat plate. I tested a cat saw and the engine temp gain was not significant.

 

[exSW]

No point in being smart alec. Did you actually measure the engine temp? I know the cat mufflers get hot but most of that is around the cat plate. I tested a cat saw and the engine temp gain was not significant.

I actually do use an IR thermometer on friction points and bearing surfaces on many of the pieces of equipment I own and operate as 20-30 degree differences are harder to determine.On this saw however the difference was SO SIGNIFICANT that a test of that sort was pointless.When the heat of the cat equipped muffler scorches the saws adjacient plastic cladding and you can feel it heating up your left hand as you operate the saw you know it's to hot.What were the parameters of your test?Was it a cold or hot day?How long did you run the saw?How long did you run the saw under load?What was the nature of the wood you were cutting(hardwood,softwood,species)?I bought a brand new saw and cut aprx 10 cord of wood in a about a three week time frame.Ran several Gallons of gas through said saw before I voided the warranty and cut out the cat.

 

[Yukon Stihl]

What makes everyone think that the saw runs cooler with a muffler mod? Have any of you guys ever measured the engine temp on stock vs modified muffler? I would think that the increased air flow and increased rpm would increase friction and heat in the cylinder thus negating any gains from otherwise. Most of the cooling is done by the evaporation of fuel and the cylinder fins providing a heat sink.

It makes sence that a modded muff will run cooler because the hot gas can escape faster so the hot gases have less time to heat the cylinder and muff.
There shouldn't be any evaporation of fuel the idea is to burn it for power.
So the fins that are on the flywheel are just for looks?Maybe you should break them all off for extra power.Sometimes the saw builders will lighten a flywheel for more power.Looks like they can save some lathe time and just use a pair of vice grips and break the fins off the flywheel.They serve no real purpose,.....or do they hmmm.
Thomas

 

[Big_Wood]

Fuel does reduce heat but not because of evaoration. A properly tuned mixture will add a small amount of extra fuel displacing what would otherwise be air. This added fuel and less air makes for cooler combustion because not all of it can be combusted by the paricular engine being tuned. The end result is unburned gases that actually soak up some of the heat from combustion and send it out the exhaust. What i'm saying is this is very similar as an egr valve in a car works. The egr valve sends unburned exhaust gases back into the intake to displace the combustable mixture soaking up heat in the process. A 2 stroke without that extra fuel will not last long as they overheat which results in cylinder scoring. A 4 stroke on the other hand will actually run for quite a while, producing severe NOX emissions until you burn a hole in a piston. 2 strokes generally don't make it to that point but i have seen it happen on rare occasions. Muffler mods do make your engine run cooler. Yer pumping more but yer expelling heat faster. Heat from top end friction will be expelled out the cooling fins for the most part.

 

[outdoortype]

I actually do use an IR thermometer on friction points and bearing surfaces on many of the pieces of equipment I own and operate as 20-30 degree differences are harder to determine.On this saw however the difference was SO SIGNIFICANT that a test of that sort was pointless.When the heat of the cat equipped muffler scorches the saws adjacient plastic cladding and you can feel it heating up your left hand as you operate the saw you know it's to hot.What were the parameters of your test?Was it a cold or hot day?How long did you run the saw?How long did you run the saw under load?What was the nature of the wood you were cutting(hardwood,softwood,species)?I bought a brand new saw and cut aprx 10 cord of wood in a about a three week time frame.Ran several Gallons of gas through said saw before I voided the warranty and cut out the cat.

why would would it matter if it was a cold day or hot day or what size/type wood?
The adjacent plastic on a cat equipped saw is melted due to the extra heat of the exhaust gas. Awhile back another member tested this and the exhaust temperature was much higher on the cat equipped saw. This however, does not directly translate into the engine running hotter. My test was done on a 87 degree day with high humidity. I warmed the saw and made about 10-15 cuts. I bought a used saw with a cat muffler (359) and wanted to see just how hot that baby would get. The cut was done in a 20" chunk of pine and I measured the cylinder and the muffler with a fluke IR thermometer. The front of the muffler was around 400, the cat plate was around 700, and the top of the cylinder was 300. The transfer covers measured considerably less I don't remember exactly. Within a few seconds, the cylinder dropped to 250. Within about 15-20 seconds, it dropped to around 190. The saw was turning 9000-10000 RPMs in the cut. I don't remember the exact temp of the non cat 359 I tested before because I expected the difference to be much greater than it was. Regardless of wood type, I would bet that any saw turning 9-10,000 in a cut for a duration of 15-20 seconds in that kind of weather would measure fairly close regardless if it had a cat muffler or not. Most of the heat is generated by the friction and RPM.

Westcoaster,
Fuel does cool the engine because it can not turn to vapor without absorbing heat. The fins on the cylinder are there to help carry/dissipate the heat.
Yukon
I have no idea why you mentioned the fins on the flywheel.

 

[tolman_paul]

What makes everyone think that the saw runs cooler with a muffler mod? Have any of you guys ever measured the engine temp on stock vs modified muffler? I would think that the increased air flow and increased rpm would increase friction and heat in the cylinder thus negating any gains from otherwise. Most of the cooling is done by the evaporation of fuel and the cylinder fins providing a heat sink.

The hottest thing in an engine are the exhaust gasses that are at about 1200 deg F. If instead of completely purging them from the cylinder with a fresh charge of air and fuel part of them linger in the cylinder due to muffler back pressure then the engine will most definitely run hotter. So a restrictive muffler will makers power by limiting the amount of air and fuel you can put in the engine and will cause it to run hotter by not purging all the hot exhaust gasses.

 

[outdoortype]

The hottest thing in an engine are the exhaust gasses that are at about 1200 deg F. If instead of completely purging them from the cylinder with a fresh charge of air and fuel part of them linger in the cylinder due to muffler back pressure then the engine will most definitely run hotter. So a restrictive muffler will makers power by limiting the amount of air and fuel you can put in the engine and will cause it to run hotter by not purging all the hot exhaust gasses.

How would you ever know how much exhaust gas is being purged one way or another? However you do know that more rpms generate more friction which does equal heat. Most muffler mods increase performance by increasing RPM. If you're going to open the muffler and then richen mixture back to stock RPMs then I can believe the theory. But who does this?

 

[OH_Varmntr]

If you're going to open the muffler and then richen mixture back to stock RPMs then I can believe the theory. But who does this?

Folks that mill. And it helps, imagine that.

 

[1270d]

Could somebody provide a link to a video showing two identical saws, one stock with muff mod and one bone stock, running side by side. How many percent gain is there? 5?

 

[chadihman]

http://www.arboristsite.com/chainsaw/240387.htm

This was a test I did on my dyno with my oem MS 460. The muffler mod was very impressive.

 

[1270d]

I'm interested. Your test shows roughly 20% gain?

 

[z71mike]

Sounds about right.

 

[outdoortype]

Folks that mill. And it helps, imagine that.

how many muffler mod videos you see milling? Most mod to increase performance via rpms, imagine that.

 

[shawn.m]

Disagree

how many muffler mod videos you see milling? Most mod to increase performance via rpms, imagine that.

My 372 didn't really increase rpm as much as gain hp throughout the curve. This means I can take bigger bites of the wood without bogging down. Before muffler mod I was slower through the cut
That is why I did muffler mod with rejet . More power in cut as almost my wood is oak

 

[Yukon Stihl]

[QUOTEYukon
I have no idea why you mentioned the fins on the flywheel.[/QUOTE]

Hi Outdoortype
I mentioned them because they do most the cooling.They are the fan that blows cooler air past the fins on the cylinders.

 

[Stihlman441]

Could somebody provide a link to a video showing two identical saws, one stock with muff mod and one bone stock, running side by side. How many percent gain is there? 5?

Get your stop whatch out
Stock 441CMTronic same chain,bar in each vid,top wood is soft Pine bottom wood is hard Yellowbox.

Stock

[video=youtube;bKiNyhBS0OE]http://www.youtube.com/watch?v=bKiNyhBS0OE[/video]

 

[Stihlman441]

Stock with muff modd

[video=youtube;exwpA0mjccY]http://www.youtube.com/watch?v=exwpA0mjccY[/video]

 

[MCW]

how many muffler mod videos you see milling? Most mod to increase performance via rpms, imagine that.

Results vary between different saws but a muffler mod on my 3120 definitely helped when milling - very noticable with a 60" bar (55") cut and bar buried in hardwood. It won't rev any harder with a fixed high jet and rev limited coil but did noticably increase the torque.

 

[wyk]

I'm interested. Your test shows roughly 20% gain?

I was impressed as well, and that is with the stock dual ported muffler vs non dual stihl muffler. It goes to show how stopped up some of the newer saws are.
I don't know about less heat, or whatever. But I do know every saw I have modded the muffler on has shown an amazing improvement in performance and responsiveness.

 

[OH_Varmntr]

Results vary between different saws but a muffler mod on my 3120 definitely helped when milling - very noticable with a 60" bar (55") cut and bar buried in hardwood. It won't rev any harder with a fixed high jet and rev limited coil but did noticably increase the torque.

Exactly. More exhaust gases expelled equals more room for fresh air/fuel charge to be utilized by the same cylinder volume, which equals more power.

how many muffler mod videos you see milling? Most mod to increase performance via rpms, imagine that.

Many folks that mill run modded mufflers. I don't need to see videos to know that. A simple search will turn up plenty of examples for you. Nothing to do with higher RPMs for milling and the MM still impresses with more power.

ETA: My MS460 is all stock and I've been wanting to MM it for awhile now. I'll throw my tach on it, cut a round and video it. Then I'll MM it, tune it to the same RPMs as before, cut a round and video it. We will time it from there and see the results. Do you think it will be the same?