Compression test results - Page 3 - PeachParts Mercedes-Benz Forum

layback40 · #31 06-05-2011, 08:59 PM

Quote:

Originally Posted by funola

layback40, I don't think so and I stand by what I said, which was:

"There is no way in hell that engine will fire if there was fuel. With all glow plugs out, there is no compression except in the cylinder with the gauge. "

Notice I said "engine" and not "cylinder" will fire? An engine cannot run with fuel and compression in only one cylinder!

With a glow plug adapter, the compression ration is lowered due to the smaller volume of the adapter compared to a glow plug. I highly doublt that a cylinder with lowered compresion ratio than stock will ignite the fuel (with no glow plug heating) while the engine is cranked for only a few seconds during the test.

funola,
This is absolute garbage !!
Clearly you have no formal knowledge of the kinetics & thermodynamics of the operation of a diesel motor.
Semantics are great for the incompetent.
A diesel motor fires one cylinder at a time. They start by one cylinder firing. They may not continue to run.

Best you go get an education before commenting further.
I have previously referenced theory of combustion texts, but from the content of your posts its unlikely that you have the necessary education background to understand or provide informed comment.

Others have already emailed me explaining that you are trolling in a way similar to richc in a hope that you can generate an infraction.

Best you go pick on some one else.

For the benefit of others,
The primary purpose of the GP is to heat the injected fuel so that there is sufficient activation energy present to start the combustion process. Once the decomposition of the fuel molecules starts, the oxidation does not require much activation hence high air temperatures are not so important.

Stretch · #32 06-06-2011, 02:39 AM

Quote:

Originally Posted by leathermang

Please do find a link.... given how hot a glow plug can get...I am skeptical...
I hope that is not based on using the glow plug as a thermocouple.....LOL
And ....whatever happened to THAT project ?

Yes I'll look for the link...

I've still got plans for a bit of glow plug research but at the moment I'm busy getting the car back together again (transmission rebuild, paint, motor in etc etc etc). There's a lot of other stuff going on here in addition to my crazy plans and projects.

As for the tests - funola started making some measurements and the last I heard he was searching for a rotary switch so he could make in-car-whilst-driving-measurements... Now there's a new one for the law - no cell phones - no multimeters...

Stretch · #33 06-06-2011, 02:41 AM

Quote:

Originally Posted by 47dodge

The compression loss I do not think would be much with the tester verses a glow plug. Note that just the pencil part of the glow is the only differance between the tester and a glowplug as far as volume is concerned.

I have some pc's and glow plugs on the workbench so I measured the volume of the pc, and the glow plug. The pc is .529 ci (cubic inch) and the glow plug (pencil style) is .049. so with the glow plug removed this gives a drop of 9.26 % in the pc. I do not know the volume above the piston at tdc,but this would lower the differance even more.Just for arguements sake lets say no clearance above the piston. Then for just less then 10% pressure drop on 400psi would give us 360 psi. Still very good. Clearly there would still be enough compression to fire that cylinder if fuel were allowed in.

Thanks for the input - that's exactly what these types of discussions need - some measurements. I hate having to say "probably", "likely", or "possibly" because I don't have some supporting evidence.

Cheers!