Westra Aros skrev:What is a pop Up piston
Mange skrev:Is it from Husqvarna? If so you can order from any dealer. If not its harder...
Pop up pistons is were they take the outer parts of piston a bit and allow cylinder to be lower so they can loose a bit of the volume above TDC, right? Make less volume in a bigger volume...
vinterrojarn skrev:http://opeforum.com/threads/husqvarna-550xp-pop-up.14793/
Thats what I found on Google.
vinterrojarn skrev:http://opeforum.com/threads/husqvarna-550xp-pop-up.14793/
Thats what I found on Google.
Andrei M3P skrev:Ok thank you, but in this case the guy took a metal from a piston and droped a cylinder down, which affects a timing in cylinder and port opening.
For example for Stihl 261 you can find a normal piston with "extra metal disc" on it, which increases a squish and you won't need to drop the cylinder down and modify ports.
It is like a mild tunning with lower effort than porting. Together with muffler mod you can have more torque and use a bigger sprocket, which increases chain speed, etc.
Mange skrev:vinterrojarn skrev:http://opeforum.com/threads/husqvarna-550xp-pop-up.14793/
Thats what I found on Google.
I think thats the way most do it unless you cast piston yourself.Andrei M3P skrev:Ok thank you, but in this case the guy took a metal from a piston and droped a cylinder down, which affects a timing in cylinder and port opening.
For example for Stihl 261 you can find a normal piston with "extra metal disc" on it, which increases a squish and you won't need to drop the cylinder down and modify ports.
It is like a mild tunning with lower effort than porting. Together with muffler mod you can have more torque and use a bigger sprocket, which increases chain speed, etc.
When lowering cylinder they change the timing ports open and close. Thats part of the trick.
There is a lot of talk about squish and increasing it by removing compressed fuel air mix volume in TDC.
Were do you find 261 pistons with disk on them?
Most do the work themself on original parts.
Just raising compression is not the same as reducing/increasing squish.
Squish volume is the volume above piston at TDC.
Squish band is the clearance needed on the outer parts of piston top so it won't hit the top.
I rather fill the volume there is in TDC more than reduce volume.
Mange skrev:If it is explosions things go kaboom ansd is no more. Its uncontrolled.
The thing that happen after spark is a flame front that expand in volume. It is very controlled and cumbustion chamber, sparks position, flame, expansion is all very controlled.
Mange skrev:Can you find pop up pistons for 55, 346, 357, 372, 395, etc.
Were do you find them?