Torque, RPMs, Porting...My Philosophy

[HuskStihl]

Oh you want someone to cuss you out huh Jon?

Thanks, but not required. I've been married for 15 years, so that part is handled just fine

 

[Mastermind]

I'd like to see all of the guys that port saws for other people share their ideas and tips. That way no matter who does the saw, you know it's gonna be top shelf.

In the past I've shared my whole notebook with Brad. And Brad sharing his findings with me has helped me build a better saw as well. We may not always agree, but we are always friends, and we will always be talking about the saws.

One guy I have to give major props to is Wigglesworth. Jeremy and I have spent many, many hours on the phone talking two stroke theory. I don't think I would be one fourth as good at what I do had he not been willing to take the time to brainstorm with me.

I've also built a good relationship with Dennis Cahoon, and Cliff Helsel. Those guys have also helped me by sharing their ideas with me. I remember a couple of years ago when Dennis called me up just to tell me that what I thought I had discovered was very wrong.......I was going the wrong way, and needed to be straightened out. When a world record breaking engine builder tells you that you are messing up.......you need to listen.

 

[blsnelling]

What Randy says is true. I lost all of my build notes last year with PC problems. Randy graciously sent me all of his notes! I hope you guys realize what a selfless act that was! That's no small thing. We do things very differently on many models, but his notes were a great help. I'm still amazed by this selfless act. I admittedly don't understand all of this stuff. I've tried some of Randy's techniques, and they haven't worked for me, and likewise, many things I do, he doesn't necessarily care for. That's the beauty of this thing. There are many ways to skin the cat. The saw buyer gets an option, and Randy keeps me on my toes!

 

[LowVolt]

Hey Brad! Any carb mods on this 361??

 

[blsnelling]

Hey Brad! Any carb mods on this 361??

No. Just a popup piston, porting, timing advance, and a muffler mod.

I need to talk you into sending some of your saws up to Chad

 

[LowVolt]

What about some of your saws? Get your 372 built and put it to the test...

So which one did you do???

 

[blsnelling]

Saturday ended up getting spent running the saws in the first post, so didn't get started on yours yet. I plan on doing the 461 first.

 

[LowVolt]

Yeah wigglesworth, I remember that guy. Where has he been hiding???

 

[Mastermind]

Working like a slave......

I talked to him this morning.

 

[LowVolt]

I sent him a text a while ago and he said the same thing.

Busy is good. Like a slave? Not so good.

 

[Deets066]

I think brad and randy should each port a saw of the the same model and send them to me for extensive testing.

 

[MustangMike]

Thanks, but not required. I've been married for 15 years, so that part is handled just fine

Got ya beat, been married twice longer that that both times!!!!! It's the divorce part that's no fun!!! Was even a Single Parent with 2 girls for 4 years, AHHHH!!!

 

[MustangMike]

I think brad and randy should each port a saw of the the same model and send them to me for extensive testing.

I'll bet the results differ per model, which is why Chad's info is so anticipated. Soon, we will have a database!

Changing gears, I found some information that says an MS-660 produces 7.0 Hp, an 066 7.3, Hp and a 066 Magnum (dual port muffler) 7.8 Hp. That is a substantial 11% difference from 660 to 066 Magnum. It also seems to me that the "0" series saws respond better to dual port mufflers & muffler mods. I'd be very interested to hear the builders (or anyone else with experience) take on this.

 

[chadihman]

Alright guys I just got cleaned up from lots of testing. I tested the 361, 461, 660 stock and 660 dual port. I have to leave at 5 am for Jersey work tomorrow. So sorry guys but the graphing will have to wait till after work. It takes time to go through all the video and scribble all the #s down then there's lots of calculations and entering #s into the graph program. Sorry again. I think you guys will like these #s.
I'm beat. I gotta start taking tips for this info.

 

[chadihman]

Shower time. I smell like I've been sitting inside the 660 muffler.

 

[Moparmyway]

OK, improper use of units and quantities leads to confusion and a lack of clarity.

Torque and horsepower are not unrelated quantities. Horsepower = Torque X rpm (times a scale factor, but forget that). I can make a couple of hundred ft-lbs at zero rpm, but that doesn't represent any power output because any torque X zero = zero. What matters here is power - the torque value isn't relevant because it is part of the power. Power is what gets the work done.

Because the cutter spacing is fixed, the load is proportional to the number of cutters passing a point per unit time. So if you want a 10% higher chain speed then you have roughly a 10% higher load. That means a 10% higher chain speed requires 10% more hp at a 10% higher rpm. However, if you manage to push on it, increase the load and drop the speed back down, then you won't want to have lost any power down there or it will stall (bog).

It is still just a question of power at rpm, not of torque.

10% more chainspeed and 10% higher RPM ............ OK, got that
BUT
10% more power ?????
Not at all
Power needed is a cubic relationship

You will need ALOT more power than 10% to see a 10% increase in chain speed !!

 

[CapitaineHaddoc]

I just have one ported saw (for now, i'm sure this will change soon ). What i want with a ported saw? More work at the end of the day, and be less tired as I use a smaller and lighter saw. Gas is not a problem if 1 full tank is enough to cut and limb a complete tree, i can take a second gas can and let it in my truck!

 

[blsnelling]

It also seems to me that the "0" series saws respond better to dual port mufflers & muffler mods. I'd be very interested to hear the builders (or anyone else with experience) take on this.

If anything, the 066 would respond the least. The 660 is the most chocked up and will therefore benefit the most from a MM. The early saws had a way larger opening in the muffler and a dual port cover to boot.

 

[Chris-PA]

10% more chainspeed and 10% higher RPM ............ OK, got that
BUT
10% more power ?????
Not at all
Power needed is a cubic relationship

You will need ALOT more power than 10% to see a 10% increase in chain speed !!

Can you show that cubic relationship of power with .... what? (i.e. an equation or somesuch)? The number of cutters passing a point will go up proportionately with increased chain speed, and that is the main load, so it would seem that the power required also increases linearly/proportionately. Certainly there will be other losses that increase and so in reality you will need more than a 10% increase in power, but mechanical engineering classes were a long time ago and I can't come up with a 3rd order relationship.

 

[HuskStihl]

If anything, the 066 would respond the least. The 660 is the most chocked up and will therefore benefit the most from a MM. The early saws had a way larger opening in the muffler and a dual port cover to boot.

Chads dyno will make guessing moot, but I'd bet the latest 660's problem lies more in the cylinder than the exhaust