[Inq] What is different between Cylinder Pressure And Compression Ratio

[Md Ekal]

Dear all ZTH members....

Recently I made a little mod to my SGTi.... so after that my pomen tell me he does a some pressure test... and the question is start here, I tell the people about the result and the said it is compression ratio (CR), and some other said it's cylinder pressure. So I go back to my pomen, and he said just make a pressure test, but he doesn't know either it CR o cylinder test, but he show me the method he do.... =

-remove all spark plug and put the gauge, and crank start my car, so the result came out.

erm so please all master2x, old2x timers here please guide me here.... and tell me the signification of this press test...

Thank you in advance...
~p/s - my pomen is "kedai pokok cherry" type, so he doesn't know the term is... but his workmanship is great....

 

[DivineWind]

ur pomen is correct, its pressure test, its to check for leaks in the cylinder chambers.

CR is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity

 

[xtremeleo]

he was testing the pressure, not ratio. u can get the ratio by deviding dat pressure with atmospheric pressure.. well, sort of

 

[Md Ekal]

Thx for the answer, erm may I know something, what purpose for that test, coz some said, more press u get, more power u gain... is that correct?

 

[6UE5t]

Thx for the answer, erm may I know something, what purpose for that test, coz some said, more press u get, more power u gain... is that correct?

To check if there's any leaks or worn out piston rings.

 

[Veloc]

It's best to have the maximum amount of pressure just below the knocking limit and your engine's limit.

 

[Shahardi]

Boleh bagi tahu tak antara enjin kia spectra dengan enjin black top yang mana penggunaan minyak yang lebih?..maintenance yang mana tinggi?

 

[0382]

it was call as compression test.

 

[Md Ekal]

Thx for all the answer... right now I understand about the term and for sure I admit that that more compression cylinder = more power gain, is just a myth....

 

[nan83]

From my knowledge :

Cylinder Pressure : pressure that been created by explotion of air&fuel inside the cylinder to move the engine (measure by special pressure sensor, unit in mpa). Normally for Four stroke diesel engine: 5 - 7 MPa , Two stroke petrol engine: 1.5 MPa & Four stroke petrol engine: 2 - 5MPa.

Compression Ratio : the pressure ratio of the compression ( calculated by pressure gauge reading)

Compression Pressure : the pressure of compression (measure by pressure gauge, unit in kpa)

if wrong, please correct it... thanks.

 

[GEFORCEXTREME]

From my knowledge :

Cylinder Pressure : pressure that been created by explotion of air&fuel inside the cylinder to move the engine (measure by special pressure sensor, unit in mpa). Normally for Four stroke diesel engine: 5 - 7 MPa , Two stroke petrol engine: 1.5 MPa & Four stroke petrol engine: 2 - 5MPa.

Compression Ratio : the pressure ratio of the compression ( calculated by pressure gauge reading)

Compression Pressure : the pressure of compression (measure by pressure gauge, unit in kpa)

if wrong, please correct it... thanks.

You DON'T get the compression ratio by using the pressure gauge reading. Compression ratio is the ratio of how much max volume of air is possible inside the combustion chamber over the min of it. When you take reading from pressure gauge, that is pressure, which has nothing to do with compression ratio. But of course, you can still test it if you know the typical values of a good engine vs a bad one. Say, you know a healthy engine got some number, if another car with same engine everything have worse, then you know the condition of engine.

Generally, the higher cylinder pressure during combustion, the more power you get. You can do this multiple ways, either you tune your car and advance the ignition timing, or you do it by raising the compression ratio.

---------- Post added at 07:27 AM ---------- 6 hour anti-bump limit - Previous post was at 07:26 AM ----------

Or you do force induction.

 

[sarutobi84]

If all 4 cylinder show almost similar reading than your engine good to go.reading should be around 250psi for slight modified engine head.relatively higher pressure(cylinder pressure test) shows higher cr which means good for peformance.