Question about fuel efficiency vs. performance

[drf256]

I was recently told that an 026 I ported gets just about the same amount of usage time on a full tank than a stock one does.

Not sure how that can be exactly, maybe it makes the same amount of cuts over less time than a stock 026 so it seems like it's the same. I just don't know.

I'm not trying to look a gift horse in the mouth here. I know treemonkey used to be about fuel efficiency and cutting ability at the same time. I'm happy the Saw is fuel efficient. Who needs a ported saw that needs to be filled every 3 cuts-that would waste any time saved.

My question is this, if the Saw is burning that small amount of fuel, there may be more potential to make more power and burn just a little more. What contributes to fuel efficiency in a Saw?

This 026 has a relatively small 194 carb, a stock boot and 105/122/78 timing. Compression around 230psi. Advanced timing. Exhaust outlet 100% of exhaust port.

I'm wondering if I could be filling the chamber better if I raised the transfers a few more degrees. Possibly moving the transfers up would fill it better.

It seems that if it's that good on fuel, I'm making less power than I can be.

Thoughts?

 

[jmssaws]

Intake shape is what I find that makes a difference,rounded floor or flat they run the same but the flat one will use more gas and have more spit back.

Wear the skirt faster also.

 

[Al Smith]

Well it goes back to the old adage that it takes fuel to make power .With a longer blow down it only makes sense it will blow some fuel straight through it .Plus if it has a hole in the muff at 100 percent you have nearly no equalization if any ,nothing to stop it from over running the carb unless it's a big one .

I tried an 038 mag with a cover with a big hole and it didn't run as well as one that was about 85 percent area .

The only one of my own I ever noticed on fuel usage is a 200T I reworked .The average 200 or most any other saw will hold about 40 minutes of run time .That one will blow through a tank in about 20 minutes .Which quite frankly would be a nuisance for a tree trimmer .Fun to run but what you might gain in speed would be lost having to refuel so often .

 

[paragonbuilder]

I was recently told that an 026 I ported gets just about the same amount of usage time on a full tank than a stock one does.

Not sure how that can be exactly, maybe it makes the same amount of cuts over less time than a stock 026 so it seems like it's the same. I just don't know.

I'm not trying to look a gift horse in the mouth here. I know treemonkey used to be about fuel efficiency and cutting ability at the same time. I'm happy the Saw is fuel efficient. Who needs a ported saw that needs to be filled every 3 cuts-that would waste any time saved.

My question is this, if the Saw is burning that small amount of fuel, there may be more potential to make more power and burn just a little more. What contributes to fuel efficiency in a Saw?

This 026 has a relatively small 194 carb, a stock boot and 105/122/78 timing. Compression around 230psi. Advanced timing. Exhaust outlet 100% of exhaust port.

I'm wondering if I could be filling the chamber better if I raised the transfers a few more degrees. Possibly moving the transfers up would fill it better.

It seems that if it's that good on fuel, I'm making less power than I can be.

Thoughts?

Al did he time how long it would run? Or just seat of the pants feels like it lasts as long?

 

[drf256]

Well it goes back to the old adage that it takes fuel to make power .With a longer blow down it only makes sense it will blow some fuel straight through it .Plus if it has a hole in the muff at 100 percent you have nearly no equalization if any ,nothing to stop it from over running the carb unless it's a big one .

I tried an 038 mag with a cover with a big hole and it didn't run as well as one that was about 85 percent area .

The only one of my own I ever noticed on fuel usage is a 200T I reworked .The average 200 or most any other saw will hold about 40 minutes of run time .That one will blow through a tank in about 20 minutes .Which quite frankly would be a nuisance for a tree trimmer .Fun to run but what you might gain in speed would be lost having to refuel so often .

Longer blowdown spitting fuel out of the muffler?

Got that backwards brother Al?

 

[drf256]

Al did he time how long it would run? Or just seat of the pants feels like it lasts as long?

Jeff said it's miserly. Cut 2 full trees up on one tank.

I fully understand it's a good thing. I'm just wondering if there's more power to be had if I sacrifice efficiency just a bit.

Wondering what steps that would take? Dropping intake to 80? Raising transfers to 118-120? Both?

 

[Brush Ape]

What contributes to fuel efficiency in a Saw?

Look into the Air/Fuel Ratio. Also see stoichiometry.

121⁄2 O2 + C8H18 → 8 CO2 + 9 H2O

 

[paragonbuilder]

Jeff said it's miserly. Cut 2 full trees up on one tank.

I fully understand it's a good thing. I'm just wondering if there's more power to be had if I sacrifice efficiency just a bit.

Wondering what steps that would take? Dropping intake to 80? Raising transfers to 118-120? Both?

Both could be tried with a sacrificial piston. Then your not messing up what you know works until you test it.

 

[dall]

al i could send you a saw you could test on i know my 026 runs good and gets good time on a tank also but i think its the best of both worlds

 

[drf256]

Both could be tried with a sacrificial piston. Then your not messing up what you know works until you test it.

Good Idea.

al i could send you a saw you could test on i know my 026 runs good and gets good time on a tank also but i think its the best of both worlds

Thanks for the offer Dallas, but I'm good.

I think I have about 20 of the model on hand at present.

 

[exSW]

Look into the Air/Fuel Ratio. Also see stoichiometry.

121⁄2 O2 + C8H18 → 8 CO2 + 9 H2O

We are now officially over my head. Stoichometric equations absolutely kicked my ass in school.

 

[Red97]

I don't think any saw is getting 100% available power out of the charge stock.

Let's just say 70% stock. once ported you get 85-90% power from the same fuel.

No so much using less fuel as it is doing more work from the same amount of fuel.

 

[drf256]

We are now officially over my head. Stoichometric equations absolutely licked my ass in school.

Means nothing in this question.

That's only the chemical breakdown and how much oxygen is needed to burn fuel.

 

[Mastermind]

Raising the transfers will make it use more fuel. A lot more.......it will also make it sorta peaky. It sounds like you should be happy with it as it is.

 

[Simondo]

Means nothing in this question.

That's only the chemical breakdown and how much oxygen is needed to burn fuel.

...and as we can change the amounts of both depending on the motors requirements and state of tune needed we'r good .

 

[Magic_Man]

I'm not certain what the problem is here. Let me get this straight, you have developed a recipie that runs like a scalded dog and gets great time on a rank of fuel ? Sounds like a win to me ! I understand what your saying, that possibly there is more power to be found. I for one wouldn't want a saw that was .1 seconds faster in a cut but used twice the fuel to do so.

 

[Simondo]

I was recently told that an 026 I ported gets just about the same amount of usage time on a full tank than a stock one does.

Not sure how that can be exactly, maybe it makes the same amount of cuts over less time than a stock 026 so it seems like it's the same. I just don't know.

I'm not trying to look a gift horse in the mouth here. I know treemonkey used to be about fuel efficiency and cutting ability at the same time. I'm happy the Saw is fuel efficient. Who needs a ported saw that needs to be filled every 3 cuts-that would waste any time saved.

My question is this, if the Saw is burning that small amount of fuel, there may be more potential to make more power and burn just a little more. What contributes to fuel efficiency in a Saw?

This 026 has a relatively small 194 carb, a stock boot and 105/122/78 timing. Compression around 230psi. Advanced timing. Exhaust outlet 100% of exhaust port.

I'm wondering if I could be filling the chamber better if I raised the transfers a few more degrees. Possibly moving the transfers up would fill it better.

It seems that if it's that good on fuel, I'm making less power than I can be.

Thoughts?

Your quote ...."What contributes to fuel efficiency in a Saw ? " ....not loosing unburnt fuel out the exhaust has got to be a big help.

 

[drf256]

I'm not certain what the problem is here. Let me get this straight, you have developed a recipie that runs like a scalded dog and gets great time on a rank of fuel ? Sounds like a win to me ! I understand what your saying, that possibly there is more power to be found. I for one wouldn't want a saw that was .1 seconds faster in a cut but used twice the fuel to do so.

It's not a problem, just quality control.

Trying to figure out how to gain more performance.

I certainly coulda stumbled upon the perfect recipe, but I tend to doubt that.

I think a bit more intake and transfer duration may be my next experiment.

 

[cus_deluxe]

Ill be the first to say i couldnt care less how much fuel my saw uses (within reason). I dont climb trees or do production felling, and i understand the utility of fuel efficiency for those guys, but, for cutting firewood and occasional felling, im usually ready for a break before my saw is, so burn it all!!

 

[Al Smith]

Longer blowdown spitting fuel out of the muffler?

Got that backwards brother Al?

If you had a big huge hole in the muffler it would stand to reason the escaping exhaust could never get to the point it equalized with the incoming transfer .It would therefore blow some of the fuel out the exhaust .Where else could it go ? I we can recall the newer saws use a fresh air blowdown to some extent which is not fuel laden air .

A pressure can is exactly that ,a pressure regulating device .If they would run better with no back pressure people would be running megaphone exhaust systems .I suppose you could if you had enough carboration behind it which you don't on a normal chainsaw .

Now don't get me wrong because I run relatively long blowdowns but I don't cut the front of the muffler off either .Tried that,didn't work .