How to measure the compression ratio - the engine health condition

11/13/2018

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The health of your engine can be expressed through a seemingly simple piece of equipment: the Pressure gauge. Read inside how to measure it yourself!

If you don't know about this yet, engine's compression ratio is a very useful figure, especially when it comes to determining if your car is in good condition or not. By examining the engine you are able to tell this problem yourself and see if the condition of the car is actually in line with the distance it has traveled.

Today, Naijauto.com will provide you with some steps for you to be able to examine the engine yourself. Of course, when there's a problem with the engine, the car should be driven to an auto shop for servicing, but it doesn't hurt to know a little bit more about your car, so that you would at least have the sense of the condition of the car before taking it to any repairing shops.

Step 1

For a pressure measurement, one sure needs a pressure gauge. You can buy this device at almost any car shop or just go online and do a quick google search and you should be served.

 This small device can be bought at any shops that sell auto equipmenta pressure gauge

Step 2

Unlike other tests, this one can only be done when the engine has reached its normal temperature, which can be achieved by starting the engine for a few minutes to warm it up.

*Note: In case the problem is worse than you may think - the engine refuses to start, ghastly issues may be lying inside the vehicle and you must know what to do when car refuses to start.

Step 3

When the proper temperature is achieved, it's time to turn off the engine and also unplug a small wire near the spark plugs area for the test to be taken. At this point, remember to take a picture beforehand so that you wouldn't forget where it was previously located, and locating it again can be tricky.

4 dirty spark plugs

Grab a cloth and give it a go, it's probably pretty dirty from all the carbon residue

At the same time, if you have a cloth near you, have a good wipe on the spark plug as well. Or if you spot the signs of problematic spark plugs, have them replaced right away.

Step 4

When everything is all set, unplug the spark plug and put the tip of the gauge into the hole. Make sure that it covers the hole entirely for the measurement to be precise.

Step 5

Now it's time to crank the engine again, preferably you have another person to do this for you. Keep accelerating for 4 to 5 seconds and measure the pressure. When you're done with one spark plug, move on to another and all of them should have equal pressure reading, or not more than 1.5 bar difference, on the gauge, ideally equal to the number recommended in the manual. 

a pressure gauge

The figure on the gauge should be the same or insignificantly different

Step 6

When the manual is not around you, there's a quick trick you can do to roughly calculate the supposed number on the reading. Let's say the compression ratio is A:B, then the ideal reading should be around A + B.

Step 7

When the number shown on the gauge is not in line with the recommended number of your engine, there's only one way left, take it to a local auto to get it fixed. The issues with engines are often complicated and cannot be fixed at home.

Compression ratio fully explained

We hope you will be able to detect the problem with your engine after reading this article. You can also see more articles on car maintenance and have a better understanding on how to take care of your 4-wheel friend.

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