A friend pointed to a video showing a NEW hop up technic

[Timjus]

In a 4 stroke engine, if you increase air flow and don’t increase compression, you lose bottom end/throttle response.

you should re think this............

 

[Loony661]

you should re think this............

Dynamic compression goes up substantially in a running 4 stroke with boost added..

 

[davidwyby]

you should re think this............

I’m not talking boost. I’m talking increasing diameters for more flow (less velocity at low rpm)

It’s common knowledge that if you throw heads with big valves, big cam, intake, big carb, exhaust on an engine and increase flow without increasing compression you move the torque peak up and the bottom end gets soft.

 

[Stump Shot]

I’m not talking boost. I’m talking increasing diameters for more flow (less velocity at low rpm)

It’s common knowledge that if you throw heads big valves, big cam, intake, carb, exhaust on an engine and increase flow without increasing compression you move the torque peak up and the bottom end gets soft.

What's wrong with a soft bottom end? Better than a bony one.

 

[Ketchup]

What's wrong with a soft bottom end? Better than a bony one.

But not as good as a tight one.

 

[Stump Shot]

But not as good as a tight one.

Both.

 

[rogue60]

If he is a friend of yours can you please teach him how to sharpen chain. I have seen a few of his attempts to out cut new C83 and he is clearly lost.

A 7/32 file, 30 across, 10 down, side plate at 70-75, top plate cutting angle between 55-60, depth gauges with a husky progressive gauge. Forget about the gullet , it doesn't matter. Just focus on the part that actually cuts wood.

It would make his videos much less painful to watch.

Agree get the gullet is overrated.. Is way more important things guys should be focusing on if mastering sharpening chain is the actual goal.

 

[davidwyby]

Agree get the gullet is overrated.. Is way more important things guys should be focusing on if mastering sharpening chain is the actual goal.

For you Aussies and this wannabe Aussie it doesn’t matter in our wood…but I have gotten into fibrous stuff and found why west coast guys run skip square with the gullets cleaned out

Those chips act like safety chaps. Palm is horrible.

 

[Junk Meister]

He can quantitate all he likes, however, JUST the compression isn't the only thing that changes when installing a pop-up piston, the flow characteristics of the upper transfers are also altered, changing the efficiency of the loop scavenging effect. Mostly in the primary clearing of spent gasses from the top of the piston. It doesn't take a big imagination to imagine this especially after seeing wash patterns pop-ups create or the power created that never impressed me and is why I don't mess with them, as flat tops so better(here's your sign)
If you're going to make a decision about compression a better test should be devised, that's all I'm saying here, then going from a flat top to a pop-up, there's more going on than reading a gauge.
My thoughts lean to cutting the top off the cylinder and making a separate head that could have the combustion chamber turned down in stages and ran between those stages to really see what is happening and what's going on with just compression and compression alone, thus eliminating any other changes that go along with piston or cylinder alterations.
A simpler test could be possible with using one ring and grinding it down to increase the end gap to relieve compression.
Then again, having changed out countless worn-out sets of rings producing low compression, replacing them with new ring sets has always resulted in a better running saw.
Now someone is going to chime in and say, hey Stump Shot, race saws don't have high compression and look how fast they go. True. No load or low load speed can be increased with low compression. I started up and old completely worn out saw with no compression(took a bit of coaxing to start it) and it screamed until it quit making noise before I could shut it down. If a hair would have hit the chain that would have probably stopped it. Most race saws get by from being very large and the load applied fairly small. Increase the load and the cut speed will reduce dramatically.
Now that I've nearly written a book, do I believe super duper ultra high compression is everything, No I don't. Do I believe a bump in compression from stock is helpful, yes I do. Do I believe there is one number in PSI that is key to making power, no I do not, as engine sizes change as well as bore and stroke combinations, it's a variable number at best. Do I think it's interesting and even fun to mechanic on saws and find out for myself how things change from making alterations to the running components of the saw, absolutely. Do I have some ideas of what makes things tick, I'd hope after all the testing I've done over the years has learned me the tools of knowledge to allow me to work. What I really think the most is if you want to know something bad enough, try it out for yourself, then you'll really know something of use and can transpolate to the work you're doing rather than rely on someone else's efforts that may be different than your own for any number of reasons.
Carry on...

And You said what you said so well I only had to READ it ONCE.
Thanks Now to read the rest of this thread.

 

[Junk Meister]

I think a more proper test technique wise would be to one hand it. Get the chain just right so it doesn’t 4 stroke. I bet with more compression it could pull a more aggressive chain at the same rpm…if the popup isn’t fouling things up.


While back I think project farm did a chain test. He hung a weight from the bar tip to make the feed pressure consistent. That’s what gave me my idea for the “chassis dyno”. Maybe it’s more like a drag strip…

Hope I don't derail this thread as it is a good one BUT a DRAG STRIP concept ain't my bag of Beans.

 

[rogue60]

For you Aussies and this wannabe Aussie it doesn’t matter in our wood…but I have gotten into fibrous stuff and found why west coast guys run skip square with the gullets cleaned out

Those chips act like safety chaps. Palm is horrible.

Yeah but the guy who started the get the gullet movement leaves the gullet in on his square grind chains.. then he goes and proves without realising it getting the gullet does jack with his baby c chain lol

 

[Motorka]

this guy and get the gullet ponies are entertainment alike 90 % of the youtube

Waiting afleetcommand and spike 60 to do real video on this topic Or any other

 

[Ketchup]

I think of the gullet a lot like the clutch cover. Short bars and brittle wood it probably doesn’t matter. Big deep cuts, noodling or stringy wood need extra space.

I have seen people round file in a way that the top plate is sharp but there isn’t enough gullet. Cuts like crap.

 

[Woodslasher]

Hope I don't derail this thread as it is a good one BUT a DRAG STRIP concept ain't my bag of Beans.

Well, it's better than a drag stripper like Dallas.

 

[Stump Shot]

this guy and get the gullet ponies are entertainment alike 90 % of the youtube

Waiting afleetcommand and spike 60 to do real video on this topic Or any other

Not sure that is necessary. Most problems can be solved by nature. What makes more noise an uncompressed or a compressed fart? More noise equals more power, erevybody already knows that. Quite simple you see, now I'll just let everyone arrive at their own conclusions privately, we shouldn't have need of that kind of testing here. Lol

 

[pbillyi69]

in this test he only changed the piston....does the pop up piston measure the same on the sides.....is the didtance from the center of the wrist pin to the top edge of the piston the same? are the skirts the same? isnt there a knot in the wood that the lower compression cut didnt run through? or am i seeing things?

 

[ZERO]

He can quantitate all he likes, however, JUST the compression isn't the only thing that changes when installing a pop-up piston, the flow characteristics of the upper transfers are also altered, changing the efficiency of the loop scavenging effect. Mostly in the primary clearing of spent gasses from the top of the piston. It doesn't take a big imagination to imagine this especially after seeing wash patterns pop-ups create or the power created that never impressed me and is why I don't mess with them, as flat tops so better(here's your sign)
If you're going to make a decision about compression a better test should be devised, that's all I'm saying here, then going from a flat top to a pop-up, there's more going on than reading a gauge.
My thoughts lean to cutting the top off the cylinder and making a separate head that could have the combustion chamber turned down in stages and ran between those stages to really see what is happening and what's going on with just compression and compression alone, thus eliminating any other changes that go along with piston or cylinder alterations.
A simpler test could be possible with using one ring and grinding it down to increase the end gap to relieve compression.
Then again, having changed out countless worn-out sets of rings producing low compression, replacing them with new ring sets has always resulted in a better running saw.
Now someone is going to chime in and say, hey Stump Shot, race saws don't have high compression and look how fast they go. True. No load or low load speed can be increased with low compression. I started up and old completely worn out saw with no compression(took a bit of coaxing to start it) and it screamed until it quit making noise before I could shut it down. If a hair would have hit the chain that would have probably stopped it. Most race saws get by from being very large and the load applied fairly small. Increase the load and the cut speed will reduce dramatically.
Now that I've nearly written a book, do I believe super duper ultra high compression is everything, No I don't. Do I believe a bump in compression from stock is helpful, yes I do. Do I believe there is one number in PSI that is key to making power, no I do not, as engine sizes change as well as bore and stroke combinations, it's a variable number at best. Do I think it's interesting and even fun to mechanic on saws and find out for myself how things change from making alterations to the running components of the saw, absolutely. Do I have some ideas of what makes things tick, I'd hope after all the testing I've done over the years has learned me the tools of knowledge to allow me to work. What I really think the most is if you want to know something bad enough, try it out for yourself, then you'll really know something of use and can transpolate to the work you're doing rather than rely on someone else's efforts that may be different than your own for any number of reasons.
Carry on...

Steve can I sign up for one of your 2-stroke classes. It will only take three decades for me to understand 10% said here.

This is why you want to choose your builder carefully. And thank you for pushing the envelope on the various projects we worked on.

A true master at work.

 

[Maintenance Chief]

Personal experience for me is if the combustion chamber is designed well for a pop up it helps with power , like an 028 super.
My experience with saws like an 044 or an 066 is the flat top works best for me.
It's funny but some of the most famously good saws have been notoriously high compression, 2100, super xl925, Super Pro 80,and 66. I'd say that creature comfort aside most of these saws would run with their modern counter parts( up until recently, with the new generation of saws).

 

[drf256]

you should re think this............

4 strokes are a different animal all together. High static compression ratios are needed to restore bottom end power because of low dynamic compression at low rpm. Usually from intake valve closing degree and backflow of charge back into the intake manifold. You’re not getting a full chamber of charge and therefore less actual compression of the charge.

 

[Junk Meister]

Well, it's better than a drag stripper like Dallas.

You got my drift but I was thinking of the PROFESSIONALs out thar.