Well i got a big question on changing engine compresion ratio?

i have a mitsubishi 4g15 sohc efi 1465 with a compression ration of 10:1 but i am changing the pistons to be able to accomidate 1600 or to1495 but i need to know how do i change the compression ratio to 7:5:1 for a turbo to be add what would i need to do this other than the turbo and alot of money and time mitsubitshi engine dodge colt plymoth colt mitsubishi mirage / lancer proton wira eagle summitWell i got a big question on changing engine compresion ratio?You need at least the pistons for the 7.5 compression ratio.Well i got a big question on changing engine compresion ratio?the big thing likely you will want to change is the pistons themselves. since going from 10/1 to 7.5/1 is quite a bit you will need to get pistons with quite a deep crater in the center compared to now. the combo of head volume and clearances from the head gasket vs the height of the piston at TDC will be the other things you can look at. the reason largely that special pistons are needed is cause you need to control the turbulence during the hottest part of combustion with a certain amount of %26quot;squish%26quot; turbulence which is induced by the outer edges of the piston coming next to the outer parts of the head space. this helps cool the %26quot;end gas%26quot; or the part of the mixture that often detonates. if you try to reduce your comp ratio too much by increasing the distance from the piston to the head you will lose turbulence at TDC and the tendency to knock will increase. how much squish/were you want it depends partly on how much boost you want for your comp ratio. if you want a huge boost pressure you won't often need as much squish. but for most purposes you likely want close to the clearance/squish area you have now or a little more clearence. less comp ratio means less turbulence all other things being equal too. there is likely a company that already knows what pistons to make for your app. i think that good ones should already exist for that engine if its the one i think it is. you probably can do what you want with just new pistons but i don't actually know about your engine. make sure your exhaust valves are up to your task and use good oils. you will want to consider looking into an oil cooler /intercooler in my opinion if a lot of boost is your desire. also think about what kind of fuel/ign management you will want to use for your level of turbocharging. good luck.