jmssaws
Addicted to ArboristSite
Most saws need some intake anyway
How much better is a 372xp with the cylinder skirt removed?
- Thread starter Adam08ski
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jmssaws
Addicted to ArboristSite
Big_Wood
westcoast dweller
everyone has their own way of porting which is cool. my opinion is their are 3 types of exhaust ports. stock, efficient, and hogged out. lol widening is good to allow tightened blow down but i find lots ends up lost out the exhaust port and you have a pig on fuel.
jmssaws
Addicted to ArboristSite
Everything should be lost out the exhaust port.
A big flat floored intake will make a pig
Big_Wood
westcoast dweller
Flat floored at 88 and that 372 is better on fuel then anyone might think. Of course you want to lose all your exhaust but you don't want to lose any of the transfer coming behind it otherwise that is inefficient. Can still make a strong saw that way though,Just real hard on fuel. This is just my opinion and what I discovered over the years of trial and error. I don't expect anyone to be the same.
jmssaws
Addicted to ArboristSite
I think we're talking about two different ports.
I was talking about the exhaust port
Big_Wood
westcoast dweller
I was responding to this statement. Fuel can be lost out the intake or exhaust. anything coming out as burnt gases is power, losing some of your transfer charge out the exhaust during scavenging because it's massive will make a saw hard on fuel. Still make a great running saw but i only do that on short bar screamers myself. I do still widen but no where near as much, a little goes a long way as far as moving volume of air.
What can be lost out the intake would be spit back which is then resucked into the intake next cycle. You don't really lose much but it would still make what the EPA would call non emission compliant i'm sure. So what if it's hard on fuel standing at your truck tailgate cutting cookies right? I've chased my gas can all over the hill, it's ****** lol.
So is this 268 piston set up you are suggesting best with a stock gasket, I am guessing the idea is to keep timing with a base gasket etc yet gain compression with the pop up?
Big_Wood
westcoast dweller
Nope, their are many ways to do it's. Stacking base gaskets will still make a saw better then a stock 372 but no where near what it could be. The cylinder also touches the top cover with the stacked as gaskets but can still all be tightened down. If you assemble the saw with the 266 piston with one base gasket it won't even turn over cause the piston will hit the squish band. Turn down the piston will keep the center (pop up) for added compression but the squish gap will need to be measured and set correctly. The pop up cut is what allows stock timing for the exhaust and transfers not the base gasket. I just like to run a base gasket and you intake would be close to 90 without it. So, thinking about the wrist pin the 268 piston is taller off the pin then the regular 372 piston taking care of the excessive squish issue that plaques 372's. Then the skirts are also shorter off the pin allowing for added intake duration but still no free porting. The piston is also significantly lighter. I have 372's that will pull a chain through a cut faster then the 268 piston saws but the 268 piston saw is a lot nicer to use as far as just a general work saw. It seems a lot of saws ported by guys here are all or nothing and fall on their face as soon as they drop in RPM. The 268 piston build does not do that and in fact is one of the best behaving 372's I have ever ran. The numbers in my OEM build are different then you get with a pop up but the pop up runs real good anyways.
I follow what you ate saying to the tee. What I am after is a 372 that doesn't have to be nailed full tilt to get it to work nicely. My 038 Mag nails the 372 when the revs drop and you dig the dogs in.. think the 268 route sound perfect for my needs 
Big_Wood
westcoast dweller
the 372 piston running a popup is more involved because you have to cut the base on a lathe but if you good with a lathe that could work for you as well. my reason for mentioning the 268 piston is because it's very simple and anyone can do it at the cost of a piston. all you do is turn down the crown of the piston to make proper clearance and then install it into a stock jug with a factory base gasket. no porting whatsoever and it will run with the ones in the vid above after tuning. the cool thing is you haven't actually modified the cylinder at all, just the piston so if you wanted the factory piston back later it just fits in. with excessive squish of course. lol
I don't see how a big exhaust port can hurt fuel economy at all. It's single purpose is to exhaust the spent gases as quickly and efficiently as possible. I go 65% of bore as well.
Big_Wood
westcoast dweller
Of course a big exhaust port will exhaust spent gases quickly and efficiently, it's huge! lol The transfers are open for a good period of time that the exhaust is open correct? At this exact same time the exhaust is exhausting correct? 2 strokes are dirty and lose raw fuel out the exhaust even stock. That is a well documented fact and the whole reason Xtorq technology even came to exist.
XT's sure are good on fuel aren't they? what's the difference? a pocket of fresh air in between the exhaust gases in fresh charge. the fresh pocket is then lost out the exhaust where mix otherwise would have losing minimal charge creating power out of more of the fuel then it loses. That is the only reason they are fuel efficient and i think is a prime example to use about what i'm talking about.
So now you have a guy go in there and widen the piss out of his exhaust and set his transfers to open a little sooner. What happens? Do you think the raw fuel lost out the exhaust port gets to be less or more? lol The wide exhaust does no doubt make a performer and with good transfer angles should minimize fuel lost out the exhaust but it still exists. I've ran saws with huge exhaust port with short blow down that were just insane on fuel. 2 tree's and your looking for your gas can.
Anybody can believe what they want to believe and that's cool. This is just what makes sense to me from running the saws where i want to get **** done on a tank, not be thinking of refueling right away, and my reply to you for failing to see how it can turn a saw into a fuel hog.
IMO for an intake to make a fuel hog it would have to lose the fuel some where and that only place is through spit back. Even with an intake of 88 on that 372 it doesn't get the filter wet at all. If you have some goof job running the saw at 1/2 throttle all the time even a stock saw will spit back. Some stihls will spit heavy which is why they have those plastic shield under the filter but the huskies hardly do at all or the filter neck stops it from coming up to the filter really well.
XT's sure are good on fuel aren't they? what's the difference? a pocket of fresh air in between the exhaust gases in fresh charge. the fresh pocket is then lost out the exhaust where mix otherwise would have losing minimal charge creating power out of more of the fuel then it loses. That is the only reason they are fuel efficient and i think is a prime example to use about what i'm talking about.
So now you have a guy go in there and widen the piss out of his exhaust and set his transfers to open a little sooner. What happens? Do you think the raw fuel lost out the exhaust port gets to be less or more? lol The wide exhaust does no doubt make a performer and with good transfer angles should minimize fuel lost out the exhaust but it still exists. I've ran saws with huge exhaust port with short blow down that were just insane on fuel. 2 tree's and your looking for your gas can.
Anybody can believe what they want to believe and that's cool. This is just what makes sense to me from running the saws where i want to get **** done on a tank, not be thinking of refueling right away, and my reply to you for failing to see how it can turn a saw into a fuel hog.
IMO for an intake to make a fuel hog it would have to lose the fuel some where and that only place is through spit back. Even with an intake of 88 on that 372 it doesn't get the filter wet at all. If you have some goof job running the saw at 1/2 throttle all the time even a stock saw will spit back. Some stihls will spit heavy which is why they have those plastic shield under the filter but the huskies hardly do at all or the filter neck stops it from coming up to the filter really well.
IMHO, you're describing a saw built with poor transfer timing...not a saw with too big of an exhaust port.
Big_Wood
westcoast dweller
so even the stock XT has poor enough transfer timing to need the XT technology just the pass emissions? were talking the basics of 2 strokes at this point. would you say the 2 stroke design was mostly abandoned because of it's stellar efficiency? lol i got a 390 with transfers way the hell up there with short blow down but a well thought out exhaust port and the thing flat out runs and very good on fuel. better then alot of 372's. a smaller port will of course not empty a cylinder as fast but to me it's not about being fast as that's how fuel ends up out the exhaust port, it's about being fast enough to get the old out and new in. to fast results in some of the new going out with the old. the smaller port will contain more of the charge in the cylinder. this is not saying a saw with a huge exhaust will not be strong. heck ya it will. i'm talking about fuel efficiency only. i'm sure if you kept those transfers low enough so that they fed at exact the right time so minimal loss it would work but at that point you've restricted them to the point where the top end isn't even being properly fueled just to avoid **** getting out the exhaust. the need to keep a saw usable quickly diminishes when a guy is chasing the fastest cookie time. i don't need mine to be the fastest in the world. i need mine to be usable, with good power, and good on fuel. some might say i need a work saw lol. i do what works for me as others will do what works for them. i have a couple saws ported with a maxed out exhaust port and they are great. i've caught on to a new way a porting that works better for me as i feel it makes a better overall work saw while still performing just as good and in most cases better when it comes to torque.
This 268 route is a done deal for me
Big_Wood
westcoast dweller
i can't even take credit for it. simon in campbell river started doing them the popup way years ago and fallers were very happy with the saw. he didn't port them either, all he did was the piston but used the windowed one. his 372's were a legend in BC for many years as being the ultimate 372 work saw. easy starting and good usable power curve not typical of many 372 port jobs. his saws were easily beat'n by cookie cutters counting seconds of course but were just a better all around saw for bush work. Simon doesn't build them much anymore i hear but lots of guys still talk about those simonized 372's in camp.
