I would like to seek some other opinion from the turbo otai about this subject. As we know NA car compression ration is about 12-14:1. Bear in mind that is negetive pressure, the most is 0 bar or atmospheric pressure. Than piston compress it to the ratio say 13:1.
The turbo car say, 1 bar pressure going into the cylinder blok than piston compress it say to ratio 8.5:1, however the actual final compression is 17:1 relative to NA 13:1. And if we boost 2 bar it wil be 34:1 relative to NA 13:1
My point is nothing wrong if we upgrade NA car by 0.5 bar which the final net compression ratio will be 20.5:1 and if we boost 1 bar it will be 26:1. Provided that the block, piston and conrod be able to handle the load. That the reason many campro, Myvi & 4g18 BOT are common.
I believe this similar topic had been discussed before.
I want to hear the comments from Otai turbo and the tuner. Whay do you say!.
thats not how the calculation was done....
NA compression ratio turbo compression ratio those advertised was STATIC compression ratio...
and NA compression ratio actually range from 9:1~11.5 (12 maybe on high performance direct injection engine) 14~18:1 ratio was diesel engine.....
that was just static ratio....but what most important is the DYNAMIC compression ratio.... that involve calculation CFM intake port, CFM exhaust port, the amount of air coming in depend on camshaft intake degree opening-closing, then amount of air compressed after all that proccess compared to combustion chamber capacity....thats what matter..the dynamic compression ratio.... and almost impossible to calculate without complety measuring everything including TB,intake manifold, camshaft duration, intake port size, usual bore and stroke, valve size, intake flow dynamic....best done with simulation software that helps cutting down measuring and calculation time (done on computer)
and since camshaft for NA and turbo car were different in profile,timing etc etc...u CANNOT relate the CR by just simple adding-minus the number....
just make it easier to under stand..just take normal NA engine with CR 10:1.... then u BOT the engine let say boost 0.4bar....the stock NA CR at 0 vaccum or means at atmosphere pressure (1bar absalute pressure ATM).....add 0.4 bar to the equation..... it was cramming 1.4times of air inside the engine.... means it was 1.4 bar of air pressure......
so to simplify the calculation, static CR of 10:1 now multiple by 1.4 (10x1.4=14) which means now your BOT car running 14:1 static compression ratio.....
another example if u got NA engine static CR 9:1....install BOT boosting 0.3 bar (effective 1.3bar) means 9x1.3=11.7 that resulting u have effective static CR of 11.7:1
*****but also that my calculation wasnt exactly correct...its just much simpler way to describe how static CR change when switching NA to BOT..... the actual calculation was wayyyyyy difficult to explain..even me ignore how to calculate that thing
so i just use my simplified guide for rough estimation*****
thats why most people BOT would advice not to go more than 0.5 bar of boost when using stock NA engine internal especially without thicker head gasket.....
but u cant relate an OEM NA engine to OEM turbo engine even they based from same engine like the 4g93 gsr VS 4g93 putra/gti or 4g63 evo3 with 4g63 perdana sei...mainly because intake different, port size different, tb size different, camshaft also different, valve size also usually different...plus the usual piston deck height and combustion chamber different.....
me typing this also started to becum dizzy....so i should stop typing now :sleep::sleep::sleep:
