COMPRESSION RATIO: HOW to CALCULATE, MODIFY and CHOOSE the BEST one

Compression ratio is one of the most important numbers in your entire engine — and getting it right can make the difference between a powerhouse and a ticking time bomb. In this Boost School episode I cover everything: the theory behind compression ratio, how to calculate it, how to modify it, and — most importantly — how to choose the BEST compression ratio for your specific build. What we cover: WHAT COMPRESSION RATIO IS — the simple definition (the ratio between your largest and smallest cylinder volume), and how packing the air-fuel molecules closer together speeds up combustion, improves the burn, and raises both power and efficiency. WHY YOU CAN'T JUST RUN INFINITE COMPRESSION — the two limits: rising combustion temperatures and NOx emissions, and the big one — KNOCK. Why higher compression makes knock more likely, and why forced-induction engines are even more limited. HOW TO CALCULATE IT — the seven things that determine your compression ratio (bore, stroke, gasket thickness, gasket bore, deck height, piston dish/dome volume, chamber volume), and a real worked example plugging my own turbo build's numbers into a calculator. HOW TO MODIFY IT — bore and stroke, stroker kits, head gasket thickness (the cheapest lever), decking the block/head, combustion chamber work, and dished vs domed pistons. The one golden rule: anything that increases cylinder volume lowers compression, anything that decreases it raises compression. HOW TO CHOOSE THE BEST ONE — the factors that actually matter: how accurately you're building the engine, your hardware and software (ECU, knock control, engine protection), and your goals. THE MOST USEFUL RULE IN THIS VIDEO — why boost makes power far more readily than compression (roughly 4% per point of compression vs ~7% per psi of boost), why max-power boosted builds run LOW compression to make room for big boost, and why high-boost/low-compression engines can feel lethargic then hit hard. REAL EXAMPLES — the exact compression ratios I'd choose for different power goals, displacements, and naturally aspirated vs boosted setups, plus special concerns like mid-engine intercooling. Compression ratio is always a compromise — this video gives you the tools to strike the right one for YOUR application. 👍 If this helped, hit like and subscribe for more Boost School. 💬 What compression ratio are you running, and why? Let me know in the comments. — Disclaimer: This video is for educational purposes only. Engine building carries risk — always consult qualified professionals and verify all measurements for your specific application. #compressionratio #boostschool #turbo #enginebuilding #boost #forcedinduction #howenginesworks #automotive #cartech #enginetuning #knock #horsepower #mechanic #enginetech