Porting torque vs hp

[jmssaws]

Build 20 the same and you will have a stand out for no other reason than its just a good one.

 

[jmssaws]

Porting mostly 1122 stihls over the years I doubt I've built more than a hand full the same numbers wise,those cylinders tell you where they need to be.
I'm not much of a build to a number guy and I've found in this particular model that numbers can be all over and still be just as strong. It's exciting to port a gillion of the same saw and not have to stock cylinders alike. It baffles me still

 

[CR888]

This subject was sure to get chins wiggling! I missed out the other week on a EBay auction bidding on a brand spanking new 4 stroke chainsaw. It was a chincy one but I wanted it all the same just to play with.

 

[Nitroman]

A wise old man once told me, "you don't take a Mercedes diesel to a bank robbery, you take a Corvette".

 

[Red97]

A wise old man once told me, "you don't take a Mercedes diesel to a bank robbery, you take a Corvette".

What if you have to drag the safe home to crack it??

 

[CR500]

Porting mostly 1122 stihls over the years I doubt I've built more than a hand full the same numbers wise,those cylinders tell you where they need to be.
I'm not much of a build to a number guy and I've found in this particular model that numbers can be all over and still be just as strong. It's exciting to port a gillion of the same saw and not have to stock cylinders alike. It baffles me still

Which is why we all enjoy your posts.

Feel free to express the good or bad numbers with the 064, if it is a turd cylinder we will cross that bridge.

Sent from my non internal combustion device.

 

[CR500]

What if you have to drag the safe home to crack it??

A vette stands out and will be caught, a Benz though now adays if you are driving one from the 80's people think you are old. I should know lol

I have a 87 300TE summer driver. Get some looks once in a while.

Sent from my non internal combustion device.

 

[jmssaws]

I would like to hear some techniques and theories on porting for tourqe.

Low numbers make tourqe?
High numbers make rpm?

The fastest tuning 064 I've done has the lowest exhaust I've ever used,everytime you think you have it figured out something tells you that you don't.

 

[jmssaws]

Which is why we all enjoy your posts.

Feel free to express the good or bad numbers with the 064, if it is a turd cylinder we will cross that bridge.

Sent from my non internal combustion device.

About every 064 cylinder is good,some better than others but no really bad ones.

 

[MustangMike]

I'll just apply my auto knowledge to saws, and bet it won't be too far off ... the largest ports may provide the best top #s, but more modest size may provide a broader power band and better throttle response, ditto with carbs.

I know a guy who had 2 - 4bbl carbs on a 283 street car, the stupidity of it still gets me. A 427 engine needs to be turning well over 7,000 RPM before it needs more than 850 CFM.

Matching the components to the engine is also key. A better breathing intake, and better breathing exhaust will almost always help.

Conversely, putting a stock muffler on a ported motor will not only diminish performance, but often build up an unwanted level of heat.

 

[Red97]

I would like to hear some techniques and theories on porting for tourqe.

Low numbers make tourqe?
High numbers make rpm?

The fastest tuning 064 I've done has the lowest exhaust I've ever used,everytime you think you have it figured out something tells you that you don't.

Area, shape, flow, is where I see the real power being made.

Seems lower exhaust, higher comp moderate blowdown equates to a rather torquey saw. All of my saws have been sub 70cc. So numbers are vastly different than what you are used to Jason.

106,125,(88,76) pointed intake. This saw has one of the most use able powerbands in any 50cc I have built.

32" 3/8 full comp rs.

Bore/stroke is similar to the 346, but a 346 dosent have the lug of the echo.

I like 105, 119, 78 ish on the 346.

That is why I am thinking it has a lot to do with area, shape, and flow more so than numbers...

 

[TJ the Chainsaw Mechanic]

HP VS Torque.....

I think that was No Weight Vs Weight. LOL! But a great example for sure!

 

[jmssaws]

I port saws everyday and never give tourqe any thought,I guess what I call hp could be what someone else calls tourqe,
Aug chainsaw lives and dies with rpm so to me it's more about hp and it takes tourqe to make hp.
I got a 98cc hybrid stihl i built that will turn a insane amount of rpm in the wood with a 50" bar and full comp 404,does it take tourqe or hp to do that?
There's a ported 2100 here to that runs it very well to but the higher rpm hybrid will destroy it and I don't think If the bar was twice as long it would make any difference. I'm sure on a dyno that the husky would have more tourqe than the hybrid but without rpm it's never going to catch it.

 

[Red97]

I port saws everyday and never give tourqe any thought,I guess what I call hp could be what someone else calls tourqe,
Aug chainsaw lives and dies with rpm so to me it's more about hp and it takes tourqe to make hp.
I got a 98cc hybrid stihl i built that will turn a insane amount of rpm in the wood with a 50" bar and full comp 404,does it take tourqe or hp to do that?
There's a ported 2100 here to that runs it very well to but the higher rpm hybrid will destroy it and I don't think If the bar was twice as long it would make any difference. I'm sure on a dyno that the husky would have more tourqe than the hybrid but without rpm it's never going to catch it.

Try a
" wood dyno" lol
Set saw to ideal tune.
Record max rpm at clean up in the wood.
Then set the dogs and see how low it will go, that has to be really close to max hp and max tq numbers.

It takes torque to turn the chain.

Let's pretend your hybrid makes 6ftlb at 11k spikes set pulling hard. Roughly 12.5 hp at 11k.

Now the 2100 makes the same 6ftlb but only holds 10k spikes set. Roughly 11.4 hp at 10k

Both are making the same torque but the 2100 is doing it 1k less, therefore way down on power, dosent matter how long the bar is l. Without turning more rpm it will never match the hp of the stihl.

Both being similar displacement, and compression. I wold bet they both have real close to the same max torque.

This is where setting the spikes should come in handy, more than likely the stihl will hold higher rpm throughout the test.

As long as you use the same chain and the same stick the numbers can't change as much as timed cut variables.

My goal is to raise those figures at least 1k from stock to ported,

The more you try to compare one saw to another the more confusing things get.

Don't know if the wood dyno will work to compare different models, but seems pretty consistent between the same model.

 

[Iron.and.bark]

I would like to hear some techniques and theories on porting for tourqe.

Low numbers make tourqe?
High numbers make rpm?

The fastest tuning 064 I've done has the lowest exhaust I've ever used,everytime you think you have it figured out something tells you that you don't.

Essentially what I am doing (unskillfully ) in my 603 thread.

Fundamentally the concept is that maximum torque achievable from an engine for the load that it will be operated in, is achieved from having the longest possible power stroke.

Will do a lot of elaboration later. Doing a 7 round trip to get some saws Dolmars

Oh and if HP and rpm was all that's important everyone would own a husky

 

[Chainsaw Jim]

It's amazing how much of a role mufflers play in all of this regarding chainsaws.

 

[drf256]

Torque wins races but horsepower sells.

Torque at a given rpm is horsepower. The amount of work that can be done over time. So torque is a 300 lb guy moving a pile of gravel with a 1 yard shovel. Hp is a 160 lb guy moving it with a standard shovel. At the end of an hour, the little guy will likely have moved more.

The only way to make torque is combustion pressure and the lever arm it exerts it's force against. So a long bike pedal will give you more ability to climb a hill, but will be a hindrance when trying to pedal fast on a flat surface.

WHERE you make the torque is what matters the most, but that will be where the cylinder fills the best dynamically.

So in a well done saw, making the same amount of torque at the highest rpm will win a race, cookies or bucking.

You guys know I like to build small saws. If I make one create its best torque at 10,000 rpm, it will be a dog. But if I can move the torque up in the rpm range, the mathematics are on my side and I can make power increases logarithmically.

Ever see a 3 liter Ferrari v12 crush a 454 LS6 Chevy? I have. It just happens later down the drag strip.

So they are interrelated and the entire package needs to work with what you produce. A lower rpm torque saw will do better with a larger rim sprocket. I'd rather have a saw that turns 16k with a 7 pin than one that turns 13k with a 9 pin.

My $.02

 

[Mastermind]

What numbers did that hybrid end up with Jason?

 

[jmssaws]

Torque wins races but horsepower sells.

Torque at a given rpm is horsepower. The amount of work that can be done over time. So torque is a 300 lb guy moving a pile of gravel with a 1 yard shovel. Hp is a 160 lb guy moving it with a standard shovel. At the end of an hour, the little guy will likely have moved more.

The only way to make torque is combustion pressure and the lever arm it exerts it's force against. So a long bike pedal will give you more ability to climb a hill, but will be a hindrance when trying to pedal fast on a flat surface.

WHERE you make the torque is what matters the most, but that will be where the cylinder fills the best dynamically.

So in a well done saw, making the same amount of torque at the highest rpm will win a race, cookies or bucking.

You guys know I like to build small saws. If I make one create its best torque at 10,000 rpm, it will be a dog. But if I can move the torque up in the rpm range, the mathematics are on my side and I can make power increases logarithmically.

Ever see a 3 liter Ferrari v12 crush a 454 LS6 Chevy? I have. It just happens later down the drag strip.

So they are interrelated and the entire package needs to work with what you produce. A lower rpm torque saw will do better with a larger rim sprocket. I'd rather have a saw that turns 16k with a 7 pin than one that turns 13k with a 9 pin.

My $.02

Morning al,we'll said.
Tourqe+rpm is horsepower.
I've said it a few times now,2 saws with the same tourqe but at different rpm will be night and day different,a saw with 8ft lbs at 8k will be a slow stinker that nobody would want to run because it's very low hp and no matter how long the bar or how big the sprocket it will never beat the saw that makes the same tourqe at a higher rpm. This is why I don't think about tourqe in a saw,sure it has to have it but it has to have hp or you just have a slow saw.

 

[jmssaws]

What numbers did that hybrid end up with Jason?

100 119 78
It was a battle to get enough bd so it could run proper,very high stock transfers.