Dayuan Compression Tester – Product Review
July 23, 2022
We do love the easy jobs here at Car & Classic. The quick wins. Yes we relish the challenge of the biggies too, the head gasket replacements, the turbo installs and the like but those simple little jobs that take a few minutes are as refreshing as an ice cold Callipo on a hot day. Case in point is the good old compression test. We picked up the Dayuan Compression Tester to check our Volvo 940’s figures. It’s one of the most uncomplicated and straightforward jobs out there that can also tell you a hell of a lot about the health of your engine. Information that is vitally important when it comes to your classic and the plans you may have for it.
Piston rings, valves, valve seats, valve seals, and cylinder head gaskets are all relied upon by your engine to hold pressure in the cylinders. If any of these begin to wear or fail then your engine will lose compression resulting in poor or rough running, amongst other things.
A healthy engine should maintain a compression reading of over 100 psi per cylinder, but more importantly there should be no more than a 10% difference between each cylinder. A decent compression tester will allow you to quickly and simply determine the amount of compression in each of your engine’s cylinders to ascertain the condition of those components listed above, the results of which are fundamental in checking the state of your engine. We deployed the Dayuan Compression Tester to see if we could get some decent readings before forging ahead with our planned power mods on the big Swede.
Get your Dayuan Compression Tester here.
The Product
A compression tester is an uncomplicated affair. Essentially it’s just a gauge that attaches via a hose in place of where the spark plug sits at the top of the engine’s cylinder. As the engine cranks over, pressure builds in the cylinder and the gauge then measures that pressure. If you can replace a spark plug then you can use the Dayuan Compression Tester. Along with the gauge itself, which is clear and easy to read in both bar and psi, the kit includes adapters to fit most vehicles, all of which comes in a convenient carry case, making it incredibly easy to carry out that all important compression test.
The Test
Our Volvo 940 is very much a daily driver/rolling project car. We have plans for it, big plans. Plans that involve, among other things, extracting more power from the 2.3-litre, four-cylinder Redblock engine. As reliable and robust as that motor is we thought it was still pertinent to carry out a compression test before cracking on blindly with our modifications. Peace of mind and all that. So, we decided to compete a compression test to determine the health of the thing and how much of a rebuild would potentially be required.
As mentioned, the process is a painless affair. It’s simply a case of pulling the fuel pump fuse to prevent the car from actually starting (or whichever method works for your vehicle) and removing the spark plugs one by one, then screwing the gauge into the spark plug hole at the top of each cylinder. Once in place it’s then necessary to crank the engine over a few times in order to get a stable reading on the gauge and make a note of the figure. For £18 and twenty minutes of our time we thought the juice would definitely be worth the squeeze. NB: We had our fingers crossed the whole time.
The Result
We were actually on tenterhooks while cranking the engine of the 940, waiting for the results to show themselves on the dial, but we’re pleased to report that all four cylinders showed healthy compression. Once the correct adapter was chosen among the ones included in the kit it was incredibly easy to install the gauge into the spark plug holes. The dial was clear to read and although we can’t testify as to the accuracy of the readings, having no frame of reference, the important thing was that the compression readings on all four cylinders were within 10% of each other.
The Verdict – 5 out of 5
The Dayuan Compression Tester does exactly what we bought it to do and that is to give us a clear indication of the pressure held in each cylinder of our Volvo’s engine. It’s simple to use and saved us a bunch on unnecessary garage bills. For less than £20 it’s excellent value for money. It’s well worth the investment to see what’s going on inside your engine and to identify just how healthy, or not, it really is in there, giving you either the peace of mind to continue to enjoy your classic or provide you with the information to make an informed decision as to any repairs or rebuilds that may be necessary. It will now stay in our garage ready to be used for any future classics we’re likely to pick up.
