mostlyharmless
Member
I have a question about a rebuild I am doing on a 2002 GTX-DI.
From most of what read on forums and the internet, even after a top end rebuild, the tested cylinder psi achieved is about 130-135.
Is there a reason that the desired cylinder psi is 155 on most every other 2 stroke Rotax engine, yet the direct injection set up seems to have the reduced cylinder psi when brand new and after a rebuild?
The reason I ask is that when I will do the bore/hone, there is a new process on my CNC at work that will, bore through, offset away from the bit and return to the initial cutting plane, then return to the bore center coordinates and do a synchronization of spindle and feed rate to create a cross hatch spring pass pattern that the manual says eliminates the honing process and creates a more consistent size and surface finish than achieved with the earlier process. I am hoping that using this new process, I will be able to size the cylinder to get the best compression possible (155 psi)?
If I achieve that type of cylinder pressure however, will I have to somehow modify/adjust the fuel and air pressures of 107 psi for a 130-135 psi, to something higher to more evenly feed a 155 psi cylinder?
I would guess that the new volume of the cylinder after being bored oversize, as well as any increased psi would change the requirements needed of the fuel/air system to correctly feed the engine.
Any insight would be greatly appreciated. I also would like to thank the members here for their advice and input with my questions since I became a member here. The assistance given has been invaluable.
From most of what read on forums and the internet, even after a top end rebuild, the tested cylinder psi achieved is about 130-135.
Is there a reason that the desired cylinder psi is 155 on most every other 2 stroke Rotax engine, yet the direct injection set up seems to have the reduced cylinder psi when brand new and after a rebuild?
The reason I ask is that when I will do the bore/hone, there is a new process on my CNC at work that will, bore through, offset away from the bit and return to the initial cutting plane, then return to the bore center coordinates and do a synchronization of spindle and feed rate to create a cross hatch spring pass pattern that the manual says eliminates the honing process and creates a more consistent size and surface finish than achieved with the earlier process. I am hoping that using this new process, I will be able to size the cylinder to get the best compression possible (155 psi)?
If I achieve that type of cylinder pressure however, will I have to somehow modify/adjust the fuel and air pressures of 107 psi for a 130-135 psi, to something higher to more evenly feed a 155 psi cylinder?
I would guess that the new volume of the cylinder after being bored oversize, as well as any increased psi would change the requirements needed of the fuel/air system to correctly feed the engine.
Any insight would be greatly appreciated. I also would like to thank the members here for their advice and input with my questions since I became a member here. The assistance given has been invaluable.