Turbo porting vs big bore porting??????????

[HardKor]

I've heard/read that porting needs to be completely different for turbos than for big bores. IS IT TRUE? I have an M1200 and TM1000. I'm thinking of a turbo-ed 1200... With a mild port job (203 degrees) on the 1200 jugs, could they be put on the turbo without any changes?

What major differences should be addressed with porting a 1200 cylinder for a big bore vs a turbo?

OK... Then the head. I would assume less compression on the turbo would be better...(12:1 vs 14:1)

Thanks for the input (an any porting secrets )
Kor

 

[JROD]

From what I understand the secret is in the port timing. Lower port timing for turbos and higher for a naturally aspirated engine.

Good thread.

 

[DBLE_O]

With the head, the lower the compression the more boost you can put in the motor. But, the more boost you put in, the more liable you are to blow jugs and piston rings. With the piston rings, find somewhere that makes pistons and have some double rings made with a mild dish, preferably forged or billet. Titanium head studs, NOT bolts, bolts back out because they never seat all the way. Studs bottom out and wont loosen, they might look ugly, but youll be good forever. Ceramic gaskets. But dont have too low of compression, because itll start easy but wont have the force necessary to keep running, so you would have to raise the idle, depending on what compression.

 

[Boyko]

With the head, the lower the compression the more boost you can put in the motor. But, the more boost you put in, the more liable you are to blow jugs and piston rings. With the piston rings, find somewhere that makes pistons and have some double rings made with a mild dish, preferably forged or billet. Titanium head studs, NOT bolts, bolts back out because they never seat all the way. Studs bottom out and wont loosen, they might look ugly, but youll be good forever. Ceramic gaskets. But dont have too low of compression, because itll start easy but wont have the force necessary to keep running, so you would have to raise the idle, depending on what compression.

Did you just make this up?

A stock rotating assembly works well on boosted 2-smokers.

I have been playing with boost on twin cycles engines since 2000 and use only OEM parts including pistons.

Of coarse there are no oem 1200 pistons so use what you got.

Guys are cutting the base of the jugs down on the larger 2-smokers this is shortening the blow down time by lowering the ports

Fly cut the squish area in the head, 14:1 is to much so the domes will have to be open up.

I would add another .007 to .010 to the squish depending what it is

I just do this for a hobby so a good engine builder will know the specs better