parrisw
Tree Freak
I agree with Brad, run that thing like you stole it.
NWP piston for 066
- Thread starter mtngun
- Start date
Help Support Arborist Forum:
mtngun
Addicted to ArboristSite
Why, it runs richer and cooler at part throttle ? I've got it set so rich that fuel dribbles out of the muffler. :hmm3grin2orange:
parrisw
Tree Freak
I think it has something to do with the metering of the carbs on saws, their meant to run WOT, and midrange they can starve for fuel.
Oh you don't need it that rich, just a little rich is good for breakin.
AUSSIE1
Al.
- Joined
- Aug 25, 2006
- Messages
- 8,004
- Reaction score
- 1,979
Get some decent pressure in behind those rings.
mtngun
Addicted to ArboristSite
Normally I don't baby new engines, but this injured jug is indeed getting babied.
Pressure went down after the initial run, which included a few brief bursts of WOT. In hindsight, that's probably when the new flake/scratch occurred.
Pressure went up after the idling and part throttle firewood cutting. It probably smoothed out the scratches and pits.
I'm listening to what the saw is trying to tell me.
Not that I am optimistic -- it may continue to flake regardless.
Pressure went down after the initial run, which included a few brief bursts of WOT. In hindsight, that's probably when the new flake/scratch occurred.
Pressure went up after the idling and part throttle firewood cutting. It probably smoothed out the scratches and pits.
I'm listening to what the saw is trying to tell me.
Not that I am optimistic -- it may continue to flake regardless.
If you run it too rich you can risk carbon scoring.
mtngun
Addicted to ArboristSite
Finally had a chance to put a couple of tanks of fuel through the 066 after aggressively honing the cylinder.
Compression did get better -- 131 psi. Whoop - pee - doo.
This jug seems to have suffered too much damage to ever seal well. :rant: The jug was a known issue going into this project, and If it had been a good jug, I wouldn't have used it as a guinea pig for my first porting project.
No big deal.
I plan to go ahead and mill a few timed cuts through a cant, just to see how this top end's cutting speed compares to the previous top end, and then it'll be on to the next top end.
The serious milling season is still 2 - 3 months away, so I've got some time to dink around with the saw. Some ideas I am kicking around:
-- pop-up and woods port on the used 1st gen BB, which is in like-new condition. The pop-up would result in massive freeport, but it wouldn't cost me anything, it would be an interesting experiment, and it would give me more porting experience.
-- NWP 54mm kit, with pop-up and woods port.
-- used OEM jug, with pop-up and woods port. I would lean toward OEM if I could get a pre-emissions jug at a reasonable price, however, the 660 jugs seem to have tame compression and radical exhaust timing, so I wouldn't be willing to spend a lot of money on a 660 jug.
-- the 2nd generation BB is no longer a consideration because its exhaust timing has been advanced by 2mm. Duh. :monkey:
Compression did get better -- 131 psi. Whoop - pee - doo.
This jug seems to have suffered too much damage to ever seal well. :rant: The jug was a known issue going into this project, and If it had been a good jug, I wouldn't have used it as a guinea pig for my first porting project.
No big deal.I plan to go ahead and mill a few timed cuts through a cant, just to see how this top end's cutting speed compares to the previous top end, and then it'll be on to the next top end.
The serious milling season is still 2 - 3 months away, so I've got some time to dink around with the saw. Some ideas I am kicking around:
-- pop-up and woods port on the used 1st gen BB, which is in like-new condition. The pop-up would result in massive freeport, but it wouldn't cost me anything, it would be an interesting experiment, and it would give me more porting experience.
-- NWP 54mm kit, with pop-up and woods port.
-- used OEM jug, with pop-up and woods port. I would lean toward OEM if I could get a pre-emissions jug at a reasonable price, however, the 660 jugs seem to have tame compression and radical exhaust timing, so I wouldn't be willing to spend a lot of money on a 660 jug.
-- the 2nd generation BB is no longer a consideration because its exhaust timing has been advanced by 2mm. Duh. :monkey:
splitpost
Nothing but 32:1
Finally had a chance to put a couple of tanks of fuel through the 066 after aggressively honing the cylinder.
Compression did get better -- 131 psi. Whoop - pee - doo.
-- used OEM jug, with pop-up and woods port. I would lean toward OEM if I could get a pre-emissions jug at a reasonable price, however, the 660 jugs seem to have tame compression and radical exhaust timing, so I wouldn't be willing to spend a lot of money on a 660 jug.
not sure what you mean by pre emission jug? but my stock 660 with muff mod has 165psi cold,that seems good to me
mtngun
Addicted to ArboristSite
Rumor has it that older 066 jugs had more compression and less exhaust duration than current 660 jugs, and that Stihl detuned it somewhere along the way to comply with emission standards.not sure what you mean by pre emission jug? but my stock 660 with muff mod has 165psi cold,that seems good to me
I don't know if that rumor is really true, since I've yet to come across a port map for one of those older jugs.
165 psi would seem wonderful to me, too, but I've never had 165 psi.
The OEM P&C that was on this saw when I acquired it blew 135 psi, equivalent to 157 psi at sea level.
Timberwolf's 460/660 project reported less than 150 psi on a new-ish 660.
It seems, based on what has been reported here over the years, that the average 660 blows 150 - 155 psi near sea level.
Bring that average 660 up to my mountain and it would only blow 129 psi. That makes for a gutless milling saw.
I just ported my 064 with "almost" new rings and it has 170psi.
mtngun
Addicted to ArboristSite
If you are trying to make me jealous, you are succeeding. :hmm3grin2orange:
I'm not, my saw does rip though
. How big is the combustion chamber and how tight is the P to C clearance?
parrisw
Tree Freak
My 395 has about 200psi! Want me to build you one? LOL
My 460 I had and modified had 210psi, it was a real arm breaker.
parrisw
Tree Freak
Ya, that's pretty high. Though that is too much for a big saw. Mines a little high actually for a 95cc saw, but so far so good.
mtngun
Addicted to ArboristSite
A 0.0015" feeler gage would barely fit between the piston and cylinder at the beginning of this project, when the piston still had the moly coating.
If I had to do it over again, I'd probably get a 395 instead of an 066. I'm not sure what the chamber volume/timing specs are on the 395's, but I get the impression the 395 is a better design.parrisw said:
I can only dream about 210 psi.StumpStomper said:
BTW, according to TW's 460/660 thread, they both have about the same uncorrected compression ratio, but the 460 has saner port timing.
Maybe you should try a piston with a single dome on the pop up rather than a double. How much did you take off the base.
mtngun
Addicted to ArboristSite
I've long since decided to abandon this top end, but wanted to do a speed test before moving onto the next top end, and finally found time to do it.
Since this saw is used for milling, speed is tested by milling a cant. I use a 12.5" ponderosa pine cant. I had done a similar speed test with the previous BB top end so I had something to compare it to.
3/8 x 0.063 Woodland Pro milling chain -- First pass 0.565 inch/sec first pass, second pass 0.49 inch/sec. Revs began at 10,500 but gradually dropped off to 9,100 by the end of the second pass.
Compare that to 0.64 inch per second with the lame BB top end, and it would appear that the BB made more power.
lo-pro x 0.050 Woodland Pro milling chain -- 0.73 inch/sec first pass. Revs began at 11,000, then settled into 10,000. During the last foot of cutting the saw seemed to suddenly lose power and I had to baby it to maintain 9000 rpms. I was worried that another chunk of plating had flaked off so I did not attempt a 2nd pass with lo-pro.
Compare that to 0.69 inch per second with the lame BB top end, and it would appear that the BB made less power.
The discrepancy could be due to chain sharpness, or the cant itself -- same size cant, same species, same general condition, but not the same cant. I really need a dyno.
Since this saw is used for milling, speed is tested by milling a cant. I use a 12.5" ponderosa pine cant. I had done a similar speed test with the previous BB top end so I had something to compare it to.
3/8 x 0.063 Woodland Pro milling chain -- First pass 0.565 inch/sec first pass, second pass 0.49 inch/sec. Revs began at 10,500 but gradually dropped off to 9,100 by the end of the second pass.
Compare that to 0.64 inch per second with the lame BB top end, and it would appear that the BB made more power.
lo-pro x 0.050 Woodland Pro milling chain -- 0.73 inch/sec first pass. Revs began at 11,000, then settled into 10,000. During the last foot of cutting the saw seemed to suddenly lose power and I had to baby it to maintain 9000 rpms. I was worried that another chunk of plating had flaked off so I did not attempt a 2nd pass with lo-pro.
Compare that to 0.69 inch per second with the lame BB top end, and it would appear that the BB made less power.
The discrepancy could be due to chain sharpness, or the cant itself -- same size cant, same species, same general condition, but not the same cant. I really need a dyno.
mtngun
Addicted to ArboristSite
Just for my education, I glued a degree wheel on the flywheel and checked the port timing. Feel free to point out any math errors.
Note: ports had been widened but exhaust port height was just as it came from the factory. I don't think I dropped the intake port but wouldn't swear to it (getting old is hell). The pop-up piston tends to increase intake duration, right, because it makes the piston shorter ? ? ?
Exhaust
95 degrees before or after TDC
duration 170 degrees
Intake
85 degrees before or after TDC
duration 170 degrees
Transfers (shined a flashlight through exhaust port to view transfer open/close)
open 119 degrees before or after TDC
Blowdown (degrees between exhaust opening and transfer opening)
119 minus 95 = 24 degrees blowdown
Compare to Timberwolf's report on a 660 jug:
And...... compare that to Martinm210's OEM jug, based on a paper map. Martin shows less intake duration, otherwise he is close to my numbers.
I thought I did a paper map for this jug, but can't find it. Oh well, I'll make a paper map after I pull the jug, just for practice, and to compare the accuracy of the two methods.
Note: ports had been widened but exhaust port height was just as it came from the factory. I don't think I dropped the intake port but wouldn't swear to it (getting old is hell
). The pop-up piston tends to increase intake duration, right, because it makes the piston shorter ? ? ? Exhaust
95 degrees before or after TDC
duration 170 degrees
Intake
85 degrees before or after TDC
duration 170 degrees
Transfers (shined a flashlight through exhaust port to view transfer open/close)
open 119 degrees before or after TDC
Blowdown (degrees between exhaust opening and transfer opening)
119 minus 95 = 24 degrees blowdown
Compare to Timberwolf's report on a 660 jug:
timberwolf said:
And...... compare that to Martinm210's OEM jug, based on a paper map. Martin shows less intake duration, otherwise he is close to my numbers.
I thought I did a paper map for this jug, but can't find it. Oh well, I'll make a paper map after I pull the jug, just for practice, and to compare the accuracy of the two methods.
mtngun
Addicted to ArboristSite
Good news, no additional flaking on jug. No new scratches, no new damage. But ..... the pre-existing damage was enough, you could see light scufffing on the rings, argh ! ! !
Cold compression after today's speed test was 126 psi on my old gauge. I also tried a brand new made-in-usa gauge and got 127 psi. Pretty much the same as always for this top end.
Here's the port map.
I used this calculator to interpret the port map.
The calculator asks for a "pin offset", that is the distance from the center of the piston pin to the top of the piston. Normally 23mm for the OEM 066 piston but this pop-up was 22.43mm, as best I could measure.
Crank axis-to-top-of-squish = 20mm (1/2 the stroke) + 68mm (rod length) + 22.43mm (pin offset) + 0.5mm (actual squish) = 110.93 mm.
Top of exhaust to crank axis = 110.93 minus 24.5 = 86.43 mm
Top of transfer to crank axis = 110.93 minus 32.35 = 78.58
Bottom intake to crank axis = 110.93 minus 62.9 = 48.03
And here is what the calculator spit out:
To my way of thinking, there is no significant difference between the port map method and the degree wheel method, but to each his own.
Hope you learned something from this thread, I sure did.
Next experiment is the BB pop-up. I'm pretty sure I won't be happy with the BB pop-up due to the freeport, but once again, it'll be a good learning experience. Long term, I'm trying to scrounge up a previously owned OEM jug (and let's hope it turns out to be a pre-emissions jug) and will install a Meteor pop-up.
Cold compression after today's speed test was 126 psi on my old gauge. I also tried a brand new made-in-usa gauge and got 127 psi. Pretty much the same as always for this top end.
Here's the port map.
I used this calculator to interpret the port map.
The calculator asks for a "pin offset", that is the distance from the center of the piston pin to the top of the piston. Normally 23mm for the OEM 066 piston but this pop-up was 22.43mm, as best I could measure.
Crank axis-to-top-of-squish = 20mm (1/2 the stroke) + 68mm (rod length) + 22.43mm (pin offset) + 0.5mm (actual squish) = 110.93 mm.
Top of exhaust to crank axis = 110.93 minus 24.5 = 86.43 mm
Top of transfer to crank axis = 110.93 minus 32.35 = 78.58
Bottom intake to crank axis = 110.93 minus 62.9 = 48.03
And here is what the calculator spit out:
To my way of thinking, there is no significant difference between the port map method and the degree wheel method, but to each his own.
Hope you learned something from this thread, I sure did.
Next experiment is the BB pop-up. I'm pretty sure I won't be happy with the BB pop-up due to the freeport, but once again, it'll be a good learning experience. Long term, I'm trying to scrounge up a previously owned OEM jug (and let's hope it turns out to be a pre-emissions jug) and will install a Meteor pop-up.
