The exhaust is a huge bottleneck on these choked up saws.
Torque, RPMs, Porting...My Philosophy
- Thread starter blsnelling
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HuskStihl
Chairin'em for the sound
I bet the above post as well as the one it is in response to are both fairly accurate. The power thing comes from car world and top speed, again, no direct equation, but a well known fact that doubling power won't double top speed. Assuming a "cubic" relationship, a 10% increase would require roughly a third more power. For example, 100hp car max speed 100mph, to get 110 would require 135ish. To get 200mph it would need 800bhp. Obviously not a perfect equation, and likely cannot be directly extrapolated to saws, but a decent rough approximation. The graph of power to speed will become asymptotic well before einsteinian levels, but that topic has been well covered in the "not so pro" thread
Mastermind
Work Saw Specialist
I think it's both Jon.
The high exhaust, and tiny outlet seems like a way to burn more hydrocarbon in the muffler can.
Just a way to make the EPA happy.
Chris-PA
Where the Wild Things Are
That could be - in which case the cubed term would come from aerodynamic drag, but that is not really applicable here. Well, some of the chains we see might have some air resistance!
Trx250r180
Saw polisher
i tried a stock muffler on the 660 to try to quiet it down ,tuned correctly it was getting hot enough milling to burn the paint and discolor the front cover ,i pulled the muffler cover ,much dryer than i felt comfortable with milling in there from the heat ,muffler was very clean actually ,i can see the epa thing here for cleaner burning exhaust ,slapped just a dual port cover on there with no carb adjustments ,had oil in the muffler can now ,you would think with more airflow it would have to be richened up ,but it ran cooler and the piston was actually wetter just by putting the cover on
Mastermind
Work Saw Specialist
I gotta share something here........
We all like to think that we are building saws that are the strongest, fastest, meanest, etc.....
I have another consideration. After all, I just build saws for work.
Safety.
The days of getting every ounce of power I can find out of the work saws I build are pretty much over......and have been for a while now.
That's not something I really post about, but there it is. Can I make a saw that's a little faster? Oh yeah......I call those "extra spicy".
Here's the thing though.......a guy starts the backcut on a heavy head leaner.......the ultra high compression finely tuned "on the edge" machine in his hands decides to take a dump......
That's a bad day.
I still build the "extra spicy" saws for guys that want a "GTG" saw. But my true work saws are a little different. Toned down a wee bit....
These days I'm looking at ways to make them perform at least 30% better than stock, while keeping the unit as quiet as possible. Fuel economy is also a consideration, but most importantly is the unit's dependability.
Just keeping it real.......
We all like to think that we are building saws that are the strongest, fastest, meanest, etc.....
I have another consideration. After all, I just build saws for work.
Safety.
The days of getting every ounce of power I can find out of the work saws I build are pretty much over......and have been for a while now.
That's not something I really post about, but there it is. Can I make a saw that's a little faster? Oh yeah......I call those "extra spicy".
Here's the thing though.......a guy starts the backcut on a heavy head leaner.......the ultra high compression finely tuned "on the edge" machine in his hands decides to take a dump......
That's a bad day.
I still build the "extra spicy" saws for guys that want a "GTG" saw. But my true work saws are a little different. Toned down a wee bit....
These days I'm looking at ways to make them perform at least 30% better than stock, while keeping the unit as quiet as possible. Fuel economy is also a consideration, but most importantly is the unit's dependability.
Just keeping it real.......
And that is why it is so difficult to place the real value on experience. Sounds perfect.
hardpan
Addicted to ArboristSite
Perfect recipe and logic.
Porting for a pipe is totally unlike what would go in a GTG saw.
Hedgerow
HACK
And use a sharp chain...
But I still like the extra spicy ones from time to time...
Hedgerow
HACK
Though pipes can be made in all form and fashion...
Hence the term "tuned pipe"...
When someone is porting a saw to be run on pipe, is the standard M.O. to have an extremely high exhaust and insane intake duration?
In the last 5 years or so, I think I've only had 5 or 6 different saws fail. Three of those were saws that I had built for myself, which also had aftermarket topend on them. I will not port an AM topend for a customer. So when it really comes down to it, I've really only had a couple different saws fail. I don't see reliability as a real concern. My biggest concern is an operator tuning and using the saw properly. Fortunately, that hasn't been a problem either.
The exhaust is much higher and it will have much more blowdown. You want to keep static compression reasonable too.
Hedgerow
HACK
I wondered about having too little blow down in a saw meant for work... And it possibly messing with what the pipe was trying to do..
A piped saw will likely have >30° of blowdown.
MasterMech
ArboristSite Operative
And should be less of a problem going forward thanks to AT/MT. I bet you guys with grinders are sleeping good at night when one of those gets sent home.
Does that mean you have a good recipe?
I've never ported a 288. That would be better served in another thread too.
