hi sifu all

pls correct me if i am wrong with this...

normally thicker metal gasket is used when turbocharging a car to reduce the compression ratio rite?
in this case for na engine, can we elimitate the metal gasket to increase the compression ratio?

Remove completely no, use thinner ones yes. but you need to know what you are doing or you will kill the engine faster than anything, increasing the compression ratio increases stress tremendously.

what's the gasket for actually?

All gaskets are used to make sure that nothing will leak between two gaps cos the 2 surfaces are never perfect. Like your manifolds and block. The same goes for the head gasket. Its to prevent the leakage between the cylinder head and engine block.

anyone knows how thick a stock 4g13p head gasket is?what material is it?if i were to turbocharge it using a low boost turbine (0.4bar), should i change to a thicker metal head gasket?

the purpose of using a thicker head gasket is to reduce the compression ratio. it's not the matter of should or should not do it, it depends on your needs. but in my opinion, stock compression ratio will work just fine with just 0.4bar, provide everything else is tuned properly.

metal gaskets also help in heat dissipation, although just marginal but it helps.

so that means metal gasket itself is a flexible material (to a certain degree) coz it is needed to fill the gap between head n block?
unless the block and head is polished to achive 100% smoothness (if compression ratio is still in safety margin) , then we dun need a gasket rite?

if theres a perfect seal between the head and gasket (which i think is impossible to get a PERFECT seal) then im guessing no need la... but then again u have to keep in mind that the valves and piston heads will also be close to each other and possibly collide. aint too sure of this myself...but its still a possibility.

also take note that if u increase ur compression ratio too high u wont be able to use normal fuel...u might end up having to use racing fuel coz ull need the MUCH higher octane. i think that point would be somewhere around 13 if im not mistaken

gioven that the normal engines CR is at about 10.5, no gasket would probably push it up closer to 11. 11 is the max for normal petrol engines running on off the pump fuel. 11.5 requires 100 octane stuff unless its a GDI engine.

It is impossible to attain 100 perfection cos the amount of surface area is just too great. Also imagine everytime there is combustion, there is a mini explosion pushing the cylinder head upwards. So it might leak from that.

You cannot eliminate the gasket because during normal operation the engine might expand unevenly, so the gasket fills the gaps.