Compression Testing and What You Can Learn From It

Here is a video on performing a compression test on an engine to assess it's mechanical condition. An engines ability to compress air and fuel is directly proportional to it's performance since an engine is nothing more than an air compressor once you take away all the controls. A compression test is a good general test that will give you an idea of the engine's overall health but it does not give specific information on what the problem is should there be one, for that a "leak down test" would be required, here is a link to that video.

http://www.youtube.com/watch?v=WgrfT0LFMhc

However if you find yourself looking for the source of a performance problem with an engine, this is a great place to start. This test is often overlooked in favor of looking at the fuel or ignition system, I think that's a mistake, if an engine can't perform mechanically no amount of electronics will make that better.

Recently, I hit the 500 subscriber mark and I'd like to thank all of my subscribers past, present, and hopefully in the future for that. I enjoy making these videos and the fact that you seem to like watching them means a lot to me. So, thanks for subscribing, rating, and commenting, those little contributions make it all worth while.

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http://ericthecarguy.com/

Also see the video I did, "Octane Ratings and the 4 Stroke Engine Cycle" for more information on how compression works and why it is important.

http://www.youtube.com/watch?v=8VWEwEveGTQ

Thanks for watching and stay dirty

ETCG

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[TeeWeeQcKsteel]

mhm low pressure :-( It also could be a hole in the piston crown :-D or in newly engines a hole where the knock sensor is placed. (some are placed in the cylinder wall) :-D xD hell yeah very, very informative but nothing is new for me ;-)

[EricTheCarGuy]

@TeeWeeQcKsteel Compression testing is just a start, if you really want to know where the leak is a leak down is the way to go. I believe I referred to that in the video and I believe I've posted a link in the description to it. Thanks for the comment.

[vTeChRDC5]

hey bro I got a k20a type-r my compression is 180 without the wet test is that good or bad cuming from a type-r

[EricTheCarGuy]

@vTeChRDC5 I don't know the exact spec for that engine off of the top of my head but that doesn't sound bad at all.

[EricTheCarGuy]

@vTeChRDC5 What you're really looking for with this test is a variance of more than 20% between cylinders.

[orville534]

ur videos are the best ive ever seen

[EricTheCarGuy]

@orville534 Thank you for that, glad you like them.

[turdsandwicher]

ood vid guy

[eddyzwy]

What is the oil you are using?

[Pendemic]

Hey Eric. There has always been a lot of talk about whether to do compression tests on a hot engine or a cold engine...what do you think?

[Philscbx]

@TeeWeeQcKsteel A hole in piston is closer to zero psi. Jazzing airhose into cylinder, large airflow out the oil fill cap will be heard/felt. Typically, the two stroke world has this issue, very rare in 4 stroke. * As Eric stated, the Leak Down Test, shows who is leaking by percentage. All Aircraft I inspect, this is the only excepted standard. * Great job on these Instructional Video's Eric. Perfect way to show detail, holding glove as background for the camera.

[toddler273]

Your awesome!

[jet62095]

Old video, but just a note. A K series honda (Civic SI, Acura RSX, etc) doesn't shut off the fuel if you push the gas pedal to the floor. 

[MyDucatiGT1000]

@ryder2shae it's a kawasaki...thats your problem to begin with!...check for wasp nests,little fucking barstards!.stuck carby floats,jets?...yeah i got nothin?,im sorry i'd like to but can't help ya,not in front of me and i don't know much about thoses bikes,try sendin this bloke a message instead of a comment he might not see?...i think asking in a motorcycle forum would be best as far as online goes.

safe ridin dude.

[ryder2shae]

Hey Eric,I have a question.Its not about a car but its about a Motorcycle.My 1983 Kawasaki GPZ 750.The bike which I picked up two weeks back has trouble getting it started.Has only 36K kilometers on it.The carbs are clean like new.Carbs getting gas all the time but the fuel is not getting into the cylinders.All the spark plugs are dry.Am pretty sure that there is nothing wrong with the carbs and ignition system.Does it have anything to do with poor compression or tight valves anything like that?

[TeeWeeQcKsteel]

@dansschurman mhmm you need power, you need torque and horses so you drive your car when it's warm\hot :-)! You should do the test when your engine is warm. Also using the right oil, original cylinder head measurements and check the right pressure against each other (the original values with the values of\from your test)

[TeeWeeQcKsteel]

@MyDucatiGT1000 yeahhh ;-) I've noticed the smile on ya face, mate! Well, my job now is to tell you some examples... Are there any?! O.O xD I am sorry I can't tell more than one example: the leak have to go through a hairline crack, on the way to the knock sensor. Can happen but must not. Some knock sensors are right next to the cyinder wall, the wall is thin, a hairline crack is easy to brake! Long story short?! In my loopy opinion my comment is not very helpful.. :-D