Compression meter

[kadora]

Hi engine addicted

On the market i have found small and cheap digital pressure meter
specific for checking car tyre pressure .
This device automatically put to the internal memory the highest pressure
value what is needed due to pulsing pressure in cylinder.
To smooth pressure pulses more /for exact measurement/
is good to connect bicycle valve to the old glow plug.
Using is easy - screw modify glow plug to the cylinder , connect it with
rubber tube to the digital meter and turn crankshaft few times.
Pictures say more than my terrible description.

 

[gbritnell]

Hi Kadora,
When using a compression meter/gauge on small engines it's necessary to have a check valve as close to the tip as possible otherwise you are reading the displacement of the engine plus the displacement of the hose leading up to the meter.
gbritnell

 

[kadora]

This device measure compression pressure
not displacement.
Compression pressure in cylinder show you how valves and piston seals in combustion chamber.

 

[Cogsy]

But you have the same swept volume being compressed into a larger volume (with the air volume in the hose and guage) so the resulting pressure will be lower than it should be. In a full size engine this small extra bit of volume is negligible but for very small displacement engines like ours it has a huge effect on the reading.

I guess you could disregard it, but it seems if you are going to all the trouble of checking the compression with a guage then you'd want it to be as accurate as possible. I guess if you were just comparing 2 or more cylinders then the actual reading may not be needed.

 

[tornitore45]

If the purpose is to check valve leaks then the one way valve must be leak-proof as well, which is easier said than done.