Quote:
Originally Posted by micalk
Liquids are incompressible, that is to say, volume does not change in response to pressure. There may be some "flex" in the lines, but it is inconsequential. Pressure at one end of a line is the same as all points in a line and pressure transmits instantaneously. A difference of a few inches one way or another will not make one whit of difference in timing. Rate of flow is affected by distance as a result of resistance to flow at the walls of the tubes, but I'd seriously doubt that it would be affected at these short distances.
My guess for the reason the lengths are the same is more for cost - only one part to manufacture, track, and maintain in supply rather than five. No matter the length all would have to be formed so that cost is fixed.
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Pressure would transmit at the speed of sound in the medium, faster than you're driving, but not instantaneously. When you wind an engine out, keep in mind that an injector is firing 1200 times / minute or 20 times a second.
Back of envelope calculation based on speed of sound in oil = 1000 m/sec
length deviation of 5 cm gives delta T of 50 microseconds, or .1% of a 720 degree timing cycle at 4000 RPM. I may have dropped or added a factor of 2 someplace, but it looks like the injector timing would advance or retard .4 degrees at 4000 RPM. So, borderline significant, but when trying to design an engine correctly, I would match the injector line lengths.
I believe the design of the lines also takes reflection and interference of pressure waves in the lines.
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