Wales
by Joske Vermeule, September 1
|
|
|
|
|
|
|
|
|
|
|
Forums39
Topics49,869
Posts837,665
Members9,596
| |
Most Online1,063
Jun 14th, 2026
|
|
|
|
Joined: Dec 2017
Posts: 2,223 Likes: 183
Talk Morgan Expert
|
OP
Talk Morgan Expert
Joined: Dec 2017
Posts: 2,223 Likes: 183 |
Bruce
1964 4/4 Series V Comp (Megan)
1994 +8 (Maurice) tis no more
2013 M3W (Olga)
|
|
|
|
|
Joined: Jul 2007
Posts: 27,816 Likes: 749
Member of the Inner Circle
|
|
Member of the Inner Circle
Joined: Jul 2007
Posts: 27,816 Likes: 749 |
And the engine should be fully warmed up.
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
|
|
|
|
|
Joined: Aug 2015
Posts: 1,616 Likes: 143
Talk Morgan Enthusiast
|
|
Talk Morgan Enthusiast
Joined: Aug 2015
Posts: 1,616 Likes: 143 |
Sometimes I'll do a compression test with the engine stone cold and then one with the engine fully warmed up and then compare the results. Diagnosed a cracked piston this way.
Arwyn
|
|
|
|
|
Joined: Jun 2015
Posts: 2,093 Likes: 74
Talk Morgan Expert
|
|
Talk Morgan Expert
Joined: Jun 2015
Posts: 2,093 Likes: 74 |
On this subject of compression testing...A question for anyone with thermo-dynamics expertise...Atmospheric pressure is about 14.6psi. So if I have an engine with 10:1 compression, in theory, the maximum cylinder pressure with no losses through valves etc would be 14.6 x 10=146psi. In practice, at BDC, the inlet valve is still open and the pressure in the cylinder is probably below atmospheric, so on the upward compression stroke, by the time the inlet valve closes there is even less swept volume to compress, which would result in something even lower than 146psi. So why do we achieve readings of 170psi upwards?
Is it something to do with heating of the trapped air under compression?
Simple explanations welcomed please.
Doug
2011 Plus 4 in Rich Maroon
1972 750 “ComDom” sprinter
1958 Triton 650
1992 Triumph Trophy 900
|
|
|
|
|
Joined: Jul 2007
Posts: 27,816 Likes: 749
Member of the Inner Circle
|
|
Member of the Inner Circle
Joined: Jul 2007
Posts: 27,816 Likes: 749 |
Yes the air is compressed & heats up & thus expands
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
|
|
|
|
|
