However, that same 11:1 static compression ratio engine with the radical 259/269 duration camshaft would have a dynamic compression ratio in the neighborhood of 7. General rule of thumb for acceptable dynamic compression ratio to run safely on pump gas is 8:1 maximum for engines with cast iron cylinder heads and 8.5:1 with aluminum cylinder heads. Therefore with the mild cam it will have a high dynamic compression ratio, probably 9.5:1+ which would be way too high to run safely on 91 octane gas. However, that same 11:1 static compression ratio engine with the radical 259/269 duration camshaft would have a dynamic compression ratio in the neighborhood of 7.5:1, totally acceptable to run on pump gas. How many PSI is 9 to 1 compression For an engine with a 9:1 compression ratio, the cranking compression pressure is typically around 120 to 140 psi for gasoline engines. Therefore with the mild cam it will have a high dynamic compression ratio, probably 9.5:1+ which would be way too high to run safely on 91 octane gas. An engine with an 11:1 compression ratio typically requires high-octane fuel, such as 91 octane or higher, to prevent knocking and detonation. If you put a very mild camshaft (194/204 duration this cam will have an 'early' IVC (intake valve closing point), and will 'bleed off' less compression than a radical camshaft with 259/269 duration and a considerably 'later' IVC. To give an example, lets say you're considering only pump gas for your engine, and it has a static compression ratio of 11:1. Unlike Static Compression Ratio, Dynamic Compression Ratio takes into account camshaft timing by considering the intake valve closing point in relation to the piston position. Static Compression Ratio numbers are the ones you hear thrown around the most ('10:1 compression'), and it takes into consideration the full sweep volume of the cylinder in regard to its range of crankshaft stroke. Visit the nearest bp service station at this link and start filling your vehicle with fuel with ACTIVE technology which will always protect the engine from dirt piling up and the performance of your vehicle's engine.This calculator will calculate both Static and Dynamic compression ratioĬompression Ratio is the ratio of an engine's cylinder volume vs. Our fuel assistant will also help direct you to the appropriate fuel pump. BP fuel is available octane 90, 92, 95, and also diesel. Careful tuning is the best way to determine your actual octane needs. Modern engines can handle much higher compression at lower octanes. There are many other factors such as head material, timing, and direct injection that come into play. Make sure your vehicle uses the right fuel, taking into account the things above. These calculators are rough approximations and none of the numbers here are absolute. The compression ratio of your vehicle is from 11:1 to 12:1, you can use 95.The compression ratio of your vehicle is from 10:1 to 11:1, you can use 92.The compression ratio of your vehicle is from 9:1 to 10:1, you can use 90.Here are the exact compression ratio and octane numbers: Because, if the vehicle requires a high octane but the fuel used has a low octane, the vehicle engine will sound ticklish. The psi value depends on factors like engine efficiency and air density. How to use this calculator: Simply fill in all the boxes below with the requested figures and click on 'Calculate CR' to find your engine's compression ratio. Use: Wallace Racing: Dynamic Compression Ratio Calculator At 4200 feet. The higher the compression ratio, it also indicates that the car engine will produce lower emissions, so the octane of the fuel must be higher.ĭetermining the right octane for the vehicle is quite complicated. This compression ratio calculator can be used to work out the compression ratio of your engine. What octane gas will be required Thanks in advance. The compression ratio is the ratio between the volume of the cylinder is at its low or high point.The compression ratio also determines the type of fuel that is right for you. To get 8.0:1 with the preceding rod, stroke, and cam intake closing event, you would need about a.

Know the Compression Ratio of the Vehicle As a general rule, the best available pump gas will work with an 8.0:1 dynamic compression ratio.

Read this article to find out what to watch out for. Because there are many components of a vehicle's engine as well as certain compressions that determine which fuel is appropriate and safe. Many types of fuel, are not necessarily right for your vehicle.

Octane compression ratio calculator