Running Compression Test

[FiendFX]

Will a digital compression tester be able to test this accurately? Planning to pull the trigger on this..

http://www.ebay.com/itm/131107759758?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT

 

[heytrid]

Depends on the digital compression tester and its resolution, even the Innova 5612 would be the best thing for this but it is double what you are looking to spend.

Can you easily return the mityvac one if it does not work for you? For sure an analogue gauge one will work.

 

[FiendFX]

Depends on the digital compression tester and its resolution, even the Innova 5612 would be the best thing for this but it is double what you are looking to spend.

Can you easily return the mityvac one if it does not work for you? For sure an analogue gauge one will work.

Hi,

This is why I'm asking on here if anyone has used a digital compression gauge, wanting some insight about it.

The analog gauge tends to fail. Hence, I wanted a digital.

 

[heytrid]

oh, I must have erased my first line.

I have not used that mityvac but on any other digital one I used it did not have the resolution in order to test accurately.

 

[Bondo]

Running Compression Test

Ayuh,... The thread title,..?? What is a Running compression test,..??

If the motor is runnin', you ain't doin' a proper compression test,....

 

[heytrid]

Actually you are, it will dignose things like intake issues (carbon/coking, debris) and exhaust issues.

Basically you pull one plug, ground the wire, unhook the injector and start the engine while comrpession tester is hooked up, I normally remove the valve core so it gets a good "bounce"

Proper name is Dynamic Compression test.

http://www.misterfixit.com/dyncompr.htm

 

[purplezr2]

I have had no issues with dial gauge OTC version. Not sure digital is all that better in this case. As long as your reading is within few psi of actual you are fine. It not a precision type measurement.

 

[MrGiggles]

Done several with a digital gauge before. No problems with it, responded fast enough for throttle blip. I believe it was a Mityvac gauge, but I don't remember for sure.

The idle reading should be 50% of the static rating, and throttle blip should be 80%. High reading indicates problems with exhaust valve, low reading is an intake valve problem.

 

[GTA Matt]

Ayuh,... The thread title,..?? What is a Running compression test,..??

If the motor is runnin', you ain't doin' a proper compression test,....

As others have said, its a great way to see what is going on with the engine that may not show up in a cranking compression test. Used the running compression test just this week to ID a cam lobe that was worn just .030". Running compression test at idle was about 12-15 psi lower then the other cylinders. Cranking compression results were negligible.




I would like to see a digital compression gauge in action. I'm so used to the behavior of my mechanical gauge, I'd like to see how they compare. I also have a pressure transducer for my labscope that really does an excellent job of showing exactly what is going on inside the cylinder. If the resolution of that is packed into a digital gauge, I think it would work great.

 

[FiendFX]

Ayuh,... The thread title,..?? What is a Running compression test,..??

If the motor is runnin', you ain't doin' a proper compression test,....

Dry compression test is to check to see the engine's ability to seal.

Running compression test is to check to the engine's ability to breathe.

 

[FiendFX]

As others have said, its a great way to see what is going on with the engine that may not show up in a cranking compression test. Used the running compression test just this week to ID a cam lobe that was worn just .030". Running compression test at idle was about 12-15 psi lower then the other cylinders. Cranking compression results were negligible.




I would like to see a digital compression gauge in action. I'm so used to the behavior of my mechanical gauge, I'd like to see how they compare. I also have a pressure transducer for my labscope that really does an excellent job of showing exactly what is going on inside the cylinder. If the resolution of that is packed into a digital gauge, I think it would work great.

Hi Matt,

I would like to learn more about pressure transducer. Do you have any resources available? Did you build your own PT?

 

[GTA Matt]

I have the fluke pv350 transducer. There are several others out there, ranging in price. aeswave.com has a selection of them and probably some good literature as well. You can make your own for low pressure and vacuum out of a map sensor.

 

[ffast65]

Any mechanical unit will work well for the type of testing your trying to perform. Even consider the Actron ones sold at Advance.