Porting torque vs hp

[jmssaws]

I've been running a 064/066 since Saturday that is to this point the best running one I've had my hands on,ahead of the hybrid up to a 36" 404,the strange thing about it is im using a basically stock muffler.
Stock dp cover with the factory screen and the hole in the can is maybe 3/4" long.

 

[paragonbuilder]

I've been running a 064/066 since Saturday that is to this point the best running one I've had my hands on,ahead of the hybrid up to a 36" 404,the strange thing about it is im using a basically stock muffler.
Stock dp cover with the factory screen and the hole in the can is maybe 3/4" long.

The mysteries continue...


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[jmssaws]

The mysteries continue...


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I'm gonna stop testing and trying new things,makes my head hurt.

 

[paragonbuilder]

I'm gonna stop testing and trying new things,makes my head hurt.

I cannot like this...[emoji107]


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[jmssaws]

I cannot like this...[emoji107]


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I'm to ocd to stop looking,it would be easier though.

 

[drf256]

I'm gonna stop testing and trying new things,makes my head hurt.

Yeah, right.....

 

[Fairways_and_Greens]

HP VS Torque.....

Hard to say without unlimited traction in that one. Weight has a huge advantage in tractor towing. I'm willing to bet the old iron had the advantage.

 

[Fairways_and_Greens]

I would think piston bore and stroke has a lot to do with it. A larger bore with shorter stroke for a given cc will have more torque than a narrow bore with longer stroke. It seems like the primary play for porting for torque is the transfer shape?

 

[MustangMike]

I am going to disagree with the bore/stroke statement. Generally, when they want torque, they increase the stroke, and a high RPM motor will often have a large bore & short stroke, the piston travels a lot slower that way.

 

[jmssaws]

I am going to disagree with the bore/stroke statement. Generally, when they want torque, they increase the stroke, and a high RPM motor will often have a large bore & short stroke, the piston travels a lot slower that way.

Agreed.

 

[paragonbuilder]

I am going to disagree with the bore/stroke statement. Generally, when they want torque, they increase the stroke, and a high RPM motor will often have a large bore & short stroke, the piston travels a lot slower that way.

This is how I always understood it. The longer stroke per revolution is like putting a pipe on a wrench.


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[Iron.and.bark]

8lbs of torque at 8k? No one wants to run that stinker? Dang, better give me all your 090's

Back from my 7 hr round trip, you stihl heads would drool at what this guy had (that he wouldn't part with).

Incidentally fallers here in my neck of the woods use 3120's, not hotted 395/660. Wonder why that is, time is money after all.

Seriously to tired, feeling overly sarcastic and should be asleep. Be back and civil tomorrow

 

[wcorey]

This is an oversimplification and I’m sure not entirely accurate but...

Peak torque occurs way before peak hp on the rpm scale, with saws a 5k spread is typical.
The area between these two point is, roughly, the ‘power band’.
More rpm at the same torque is more hp, so what we’re shooting for is of course higher peak torque
but also to move the peak torque up on the rpm scale.

Problem is that as peak torque moves up, the peak hp wants to move up with it at a slower rate (why? I dunno…).
This does result in more hp but at the expense of the power band width.

So a saw that makes peak torque at 5k rpm and peak hp at 9.5k will be the ‘grunty’ ‘user friendly’ feeling one
and one with the 8.5k to 11k spread will feel ‘faster’ but ‘peaky’.

 

[Mastermind]

8lbs of torque at 8k? No one wants to run that stinker? Dang, better give me all your 090's

Back from my 7 hr round trip, you stihl heads would drool at what this guy had (that he wouldn't part with).

Incidentally fallers here in my neck of the woods use 3120's, not hotted 395/660. Wonder why that is, time is money after all.

Seriously to tired, feeling overly sarcastic and should be asleep. Be back and civil tomorrow

Thanks for sleeping then. LOL

It's plain for me to see that these guys are building great and strong saws, so I try to stay open minded, and teachable. I really have learned more since Bruce started this site than I did in five years before it. Is that because of the positive attitude of our members? I think yes.

So Jason, from what I've seen lately, you are not really changing the numbers that much from what we've been using for quite awhile, but you are opening the lower transfers wider and bigger to promote flow? Forget velocity in these two port motors (cause they never had it anyway) and go for max flow. Does that sound about right?

 

[jmssaws]

Thanks for sleeping then. LOL

It's plain for me to see that these guys are building great and strong saws, so I try to stay open minded, and teachable. I really have learned more since Bruce started this site than I did in five years before it. Is that because of the positive attitude of our members? I think yes.

So Jason, from what I've seen lately, you are not really changing the numbers that much from what we've been using for quite awhile, but you are opening the lower transfers wider and bigger to promote flow? Forget velocity in these two port motors (cause they never had it anyway) and go for max flow. Does that sound about right?

Pretty much yes,numbers aren't different but the transfers are, same duration as always but most everything is changed.

Direction or the angle they dump is a big part of it and how they open.
It takes several hours to do but they seem to run great.

 

[jmssaws]

The saw I did over the weekend is the best 066 I've done but I did start with the best stock cylinder I've ever ported and that makes all the difference.

Be impossible for me to get one to run like it with a poor cylinder.

 

[Mastermind]

You are onto something for sure.......all you guys are. People ask me questions all the time about what numbers work, etc.....

I try to say that there really ain't no good numbers. But no one believes that. The numbers that work for me with my port shapes might be terrible for someone else. It's cool to see you trying different things, and most of all, sharing what you are learning. Big props to you dude.

 

[paragonbuilder]

The saw I did over the weekend is the best 066 I've done but I did start with the best stock cylinder I've ever ported and that makes all the difference.

Be impossible for me to get one to run like it with a poor cylinder.

I hear you guys say this all the time, that a better timed stock cylinder makes a stronger ported saw.
But if you are raising and shaping the exhaust and transfers, and intake can be filled if needed, what is it that makes one able to be stronger?


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[Mastermind]

I hear you guys say this all the time, that a better timed stock cylinder makes a stronger ported saw.
But if you are raising and shaping the exhaust and transfers, and intake can be filled if needed, what is it that makes one able to be stronger?


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The exhaust is just too high on some jugs. To get it down as far as I would like, it would end up free porting on the piston skirt. Then the intake would be lower than ideal too.......and....and.....lol

 

[paragonbuilder]

The exhaust is just too high on some jugs. To get it down as far as I would like, it would end up free porting on the piston skirt. Then the intake would be lower than ideal too.......and....and.....lol

I see. I need some more experience I guess...


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