What does a cars compression ratio actually mean???

Question

Say,like on my friends Sting Ray,it states 9.0:1.....

Answer 1

The compression ratio is a single number that can be used to predict the performance of any engine (such as an internal-combustion engine or a Stirling Engine). It is a ratio between the volume of a combustion chamber and cylinder, when the piston is at the bottom of its stroke and the volume when the piston is at the top of its stroke. The higher the compression ratio, the more mechanical energy an engine can squeeze from its air-fuel mixture. Higher compression ratios, however, also make detonation more likely.

The ratio is calculated by the following formula:
{CR} = \frac { ( pi b^2 s) / 4 + V_c } /{V_c}, where
b = cylinder bore (diameter)
s = piston stroke length
Vc = volume of the combustion chamber (including head gasket). This is the minimum volume of the space into which the fuel and air is compressed, prior to ignition. Because of the complex shape of this space, it usually is measured directly rather than calculated.

Answer 2

Engine Compression Ratio

Answer 3

Compression ratio is measured by comparing the volume of the engines cylinders at the bottom of it's stroke to the the volume at the top of it's stroke. For example if you were to fill a cylinder with liquid when the piston is all the way down and it holds...let's say...900 cc's and then you bring the piston to the top and again fill it with liquid and it held.... lets say... 100 cc's ...you would have a compression ratio of 9 to 1. In other words the engine compresses the air and fuel mixture in it's cylinder from 900 cc's to 100 cc's. Why is this important? Because the more an engine compresses it's fuel /air mixture the more cylinder pressure it creates which equates to more torque and horsepower. However, more cylinder pressure can result in pre-ignition and detonation knock. This can be overcome to a point with higher octane gas. Most modern average automobile engines have a compression ratio of around 9 to 1.... street performance motors are almost always less than 11 to 1 ... and race engines are often 12, 13 or 14 to 1. BTW ...Diesels are usually somewhere around 22 to 1. That's where they get their incredible torque.

Answer 4

The compression ratio is the ratio between the volume of the combustion chamber in the cylinder when it is at its largest (piston all the way down) compared to when it is at its smallest (piston all the way up).

Under the laws of physics, a higher compression ratio, which compresses the fuel-air mixture into a smaller volume, has greater potential for power, but also raises the temperature higher and requires higher grades of fuel else the fuel might ignite spontaneously before the spark plug wants it to.

Answer 5

What Is The Compression Ratio

Answer 6

For the best answers, search on this site https://shorturl.im/fJcmI

Compression ratio is the differential between the space between piston at top of the cylinder at TDC and BDC. So if the space left when the piston is at the top is 1/9th of the space when it's at the bottom then the engine has a 9:1 compression ratio. The higher the compression ratio, generally the more power is made. Higher compression also means a propensity to pre-detonate so higher compression engines usually require higher octane fuel. You are correct about bore and stroke. Generally speaking, increasing bore makes more horsepower than torque and increasing stroke makes more torque than horsepower. Engines designed to rev to high RPM's and make high horsepower usually have slightly higher bore than stroke. This is called an "oversquare" design. It's generally long lasting and can rev higher, but generates a bit more heat. This is what you'll find in motorcycles and a lot of sports cars. An extreme example would be the engines in Forumula one cars that have more than 2 times the bore than stroke and can rev to 19,000 RPM and make crazy horsepower. A long stroke makes it harder for an engine to rev high but it increases the amount of torque produced. An engine with longer stroke than bore is called "undersquare". This is a practical design for producing some low-end torque, like what you'd want in a small engined commuter car that you'd drive in traffic and also in a truck that's hauling stuff. Not designed for high revs and high horsepower, but good at making power at low RPMs and it's easier to have a higher compression ratio with a long stroke motor which makes up for some of the power loss in the high end. A "square" motor is an engine where the bore and stroke are equal.

Answer 7

This Site Might Help You.

RE:
What does a cars compression ratio actually mean???
Say,like on my friends Sting Ray,it states 9.0:1.....

Answer 8

the higher the compression ratio the higher grade gas you need. if you dont use a high grade on a high ratio motor then you will have a annoying knock after a while do to the gas igniting before the spark hits the cylinder

Answer 9

If you want the Practical Answer without the technical detail == what it means in practical terms to the non-mechanic == is the grade of gasoline you should burn. Higher compression ratios should burn higher octane fuels.