I never thought of leak down and voltage drop testing as being on the same page like that Dave. Thanks for making me think about it, good food for thought. Take care -Glen
Great analogy. I find your videos engaging. You do your research, you know your subject, you speak clearly, your explain clearly and in the end you get the message across with a balanced mix of theory and practical. I'm pretty sure this is what most people want/need. Keep them coming. Thanks :)
I worked for an airline based in Miami Florida, I was working as a flight engineer back then. My instructor had me a two year F/E then teach a recurrent class, I had never learned so much from that experience. I had to go home and research all the questions I’ve received from the new class of F/E’s that it aided me In my own knowledge of the Boeing 727
Yeah, I know what you mean, teaching forces you to learn a topic in much greater depth, especially if you're lucky enough to find people who aren't afraid to ask difficult questions. Thanks again for stopping by, aircraft mechanics is a much more unforgiving job, ha ha.
Good video! Out of passing interest, see the Wikipedia 'Leak-down tester' entry for some gory details on these things. In the aircraft world they're often called 'Differential compression tester's'. Also, those two gauges employed on the tester are whats known as 'Bourdon Tube Gauges', and have been around for eons in various forms. (It's the 'Bourdon Tube' effect that makes garden hoses and the like jump when pressurized.) the Wikipedia 'Pressure measurement' entry for loads of details on them specifically. (Edit for typo)
When I watch a video, I always scroll through comments, for remarks like yours that give the topic more depth. Thank you so much for making this page worth viewers' time! Dave
Good day Dave, so nice to have someone really put thing in real life situation and perspective. Look forward to more videos from you Sir. Very well done too.
Love your videos intelligent, straight to the point and no BS. I have a leak down tester not dissimilar to yours I am hoping it has a 1mm ( 0.040” ) restrictor but instructions do not say. If I was to rig up a 1 mm restrictor on the output side and got a reading of 50% leakage from the gauge this should prove the the device has a 1 mm restrictor in it, analogous to the voltage drop across 2 of the same value resistors in a circuit just like yours. Can you see any problems in this method ? I believe it would work and if the restriction is bigger or smaller than 1mm it would give me a clue as to what it could be
That's a very interesting question! As with voltage drop testing in electronics, the actual value of the resistance is not as critical as one might think, as long as you're in the approximate range and you get movement of gas. Case in point, drop testing across fuses when screening for parasitic drain. The math for voltage drop testing shows greatest sensitivity when the resistance of your testing device is about the same as the resistance of the circuit, and I will guess the same would apply when you're using gas to assess leakdown of a cylinder. Yeah, I suppose a 50% figure when two devices were put into series would suggest a similar orifice, but details might be confusing. It would be complicated by the adjustable voltage regulator on the input side of the second tester.... I'd have more faith in a comparison test in various engines. As always, a tradesman knows his tools....
Thank you. An efficient way to learn a topic in much greater depth is to go through the effort of making a video. This one was no exception, the end result is incidental history, ha ha.
There's something very appealing when you can draw two seemingly unrelated topics together. Wyatt, thank you so much for stopping by, I truly value your opinion.
That's a clever idea to test the valves and piston ring gap leaks. Although the piston ring gaps may have less effect on a high speed gas expansion/explosion. I think...... ha ha :-D Are you supprised by the amount of information your memory has, and you don't even know it's there untill the right prompt/key is presented by life?. Frightens the hell out of me, the garbage my memory kicks up from nowhere lol. Sorry im waffling again.
I was always under the impression that compression at faster RPM's while the engine is running might be higher, or at least similar to the slow RPM's of the starter motor. Not so, compression while running is dramatically smaller (~50 psi) because of dynamic effects of air viscosity, etc. Nevertheless the slow test shows a lot about engine health. Thanks for stopping by!
