Saw porters: upper transfers and torque?

[mainer_in_ak]

Question for the saw porters:

When I ported my cs 8000, I didn't have a right angle piece to work the upper transfers. But on 2 tree jobs, I've bore cut heavy-leaning saw logs with a 28 inch bar/c83 chain and a 36 inch bar with full house 3/8 lgx chain!

Both saw logs were so big, the noses of the bars barely poked through the bark. As I square up my hinge wood or begin cutting out what could barber chair, the saw comes right on step when chain is leveraged tightly against the wood. You don't have to baby into the cut. It got all this low end torque and I REALLY like how it cuts on the job!

Its tuned at 13500rpms no load and is a tiny bit rich. I can't distinguish a difference from a 28" bar or a 36" bar, it pulls the same. I also cut down stumps with this saw, and it feels no different bar tip burried with full house chain.

If I fiddled with or raised upper transfers, would I loose that low end torque? To get more air/fuel to the saw, I upgraded to the larger HDA 45 carb. So I've got the carb to feed this saw.

 

[srcarr52]

You'll find gains in the upper transfer work.

This is an 800 but it's close to the 8000.

 

[Ketchup]

Its possible. It depends what your other numbers are and how much you raise the uppers. But I have a feeling you’re running the saw at the bottom of the good power band. Typically raising the uppers will raise the power band. So then your saw will cut faster with a shorter bar, but hit a wall and be less good once the cut gets really big. If you’re happy with it, I would leave it.

 

[mainer_in_ak]

Thanks for the input guys. Almost tempted to get another cheap/used cylinder, raise the transfers and simulate the cutting conditions:

Bore cut a log that uses the entire 36" bar. Leveraging the felling spikes against the tree, thin out my plunge cut and square up my hing wood, see if the saw comes to life or bogs.

Anyhow, so much more to cutting performance than buzzing through a cookie.

Was the only saw I have on hand with a chain brake, that could handle abore cut with a 36" bar. I was honestly surprised that it felt no different than the typical 28 inch bar it normally wears. Punches way above the $400 I paid for the darn thing.

 

[srcarr52]

It went from a cut time of 83s down to 50s with a 32" full comp chain buried in dead ash (very hard wood). Stock I had to baby it through the cut, after I wish the owner had put the bucking spikes on it as I had to press very hard to keep it loaded.

I raised the transfer ports 0.095" above the stock port height which brought them up to 119° transfer duration from 103°. Ex duration was 158°, Intake 156.5° with 0.030" taken out of the squish band.

 

[mainer_in_ak]

Thanks, I'm gonna try and condense my above post:

What will happen to my low end torque with the plunge cuts with a 36" bar?

Will the increase in upper transfer duration and decrease in blow down change my low end grunt?

I'm not concerned about cut speed on a cookie. Forgot to mention:this cs 8000 is dual port.

Ketchup, thanks for your insight. I may very well leave the saw alone, but still on the fence if I want to take the time to compare another cylinder. Cut speed is plenty fast on this saw. The puny 800p/late model 8000 carb was the biggest choke point. It was almost as if I wasted good port work. The HDA 45 carb was the biggest improvement:

 

[srcarr52]

Thanks, I'm gonna try and condense my above post:

What will happen to my low end torque with the plunge cuts with a 36" bar?

Will the increase in upper transfer duration and decrease in blow down change my low end grunt?

I'm not concerned about cut speed on a cookie. Forgot to mention:this cs 8000 is dual port.

I know the 8000 is a dual port but the 800 is the closest thing I've ported to it. Generally dual port versions of series like even more transfer duration than their quad port cousins.

It takes a lot more power to pull the chain in a full cut than bore cutting. This is why everyone time cuts cookies in a consistent log with minimal rocking around to verify gains.

Generally gains are across the whole power curve until you start chasing really high peak power (peak HP above 11000 rpm). This is because in stock form most saws peak torque is between 6-7k rpm, so anything you can do to raise the peak HP is going to be beneficial to the torque throughout the range where you are operating the saw. See attached graph from a Stihl 064 I ported.

In short... if you haven't altered the transfer timing there is a lot of power to be gained.

 

[Ketchup]

Well there’s most of a recipe for you, so that takes out the guesswork. @srcarr52 knows his stuff and he has proof. I’d do what he suggests if you have the tools.

Or just carry on with a saw you already like! Win/win.

 

[mainer_in_ak]

I'm gonna leave the saw alone. Pausing in a cut where the entire 36" bar with full house chain is against wood, pounding on wedges for a few minutes, while leaving the saw idling, then resuming my back cut and comes right to life with that much drag on the chain.

I guess after I've slept on it, the curiosity ain't worth the time to tear into it. If it ain't broke, don't fix it.

Saw has been making me money for 2 years.