Turn the crankshaft until the piston of the cylinder to be adjusted comes into ......

[JACEK1]

Hello everybody!

Turn the crankshaft until the piston of the cylinder to be adjusted comes into the ignition dead centre position.

Which shall be adjusted: piston or cylinder?

Suppose the piston of the cylinder is to be adjusted.

Then the sentence would read as follows:

Turn the crankshaft until the piston of the cylinder which shall be adjusted comes into the ignition dead centre position.

or a little awkwardly

Turn the crankshaft until there comes into the ignition dead centre position the piston of the cylinder which shall be adjusted.

What is your opinion?

Thank you.

 

[JACEK1]

"the piston of the cylinder to be adjusted" means "the piston of the cylinder that/which is to be adjusted", doesn't it?

 

[JACEK1]

What is ambiguous?

The fact that "the piston of the cylinder that/which is to be adjusted" or "the cylinder that/which is to be adjusted".

I am in two minds about it.

 

[JACEK1]

I would be grateful for help from an engine expert.

 

[Skrej]

I'm by no means any kind of engine expert, but I do know that the piston is the moving part. The cylinder is just a hole that the piston moves up and down in. You can't really adjust a cylinder, aside from boring them out to make them larger. You can however adjust the movable piston.

I think you want something like "Turn the crankshaft until the piston to be adjusted comes into (top) dead center of ignition."

However, that's a fuzzy guess based off the Wikipedia entry.

 

[BobK]

Yes - the cylinder‘s just a hole in the engine block. The piston and the crankshaft are the only relevant moving parts, and their relationship is fixed. When you turn the crankshaft, the piston moves (or, if the motor‘s running - when the piston moves, the crankshaft turns). ;-)

b

 

[Eckaslike]

Turn the crankshaft until the piston, of the cylinder to be adjusted, comes into the ignition dead centre position.

I am no engine expert, but I agree the piston and the crankshaft move, not the cylinder. I think your first sentence makes sense if two commas are added, because the piston and cylinder are almost one unit.

 

[J&K Tutoring]

Piston and cylinder relationship is fixed. It is desirable for ignition timing to vary with engine speed and temperature, and according to performance and emissions objectives. Thus, there is no ignition dead center. There is, however, a piston Top Dead Center (TDC)- the point at which the piston has reached its highest point and will begin to move down as the crankshaft continues to rotate. Ignition timing is adjusted as degrees of crankshaft rotation before (+) or after (-) that point.

Traditionally, one cylinder (often #1 cylinder of a multi-cylinder engine) was used for reference, as all pistons move at the same rate, but do not reach TDC at the same time. Ignition timing was adjusted for all cylinders by rotating the distributor and checking the timing of ignition at #1. Ignition timing was controlled by mechanical means.

Today's computer-controlled engines may have some programing to allow adjustment of ignition timing for each cylinder individually but still, ignition timing would be adjusted by reference to crankshaft/piston position, not the other way 'round.

 

[J&K Tutoring]

Now to address your question:

"Turn the crankshaft until the piston of the cylinder (which is) to be adjusted comes into the ignition dead centre position."

This is not ambiguous. It would be perfectly clear to a mechanic.
It is the ignition (or perhaps valve) timing that is to be adjusted, not the piston and not the cylinder. It could also be valve tappet clearance being adjusted.

If you want more explanation, I can provide it, but it gets a little abstruse...

 

[probus]

All it means is that the head of the particular piston needs to be at top dead centre. You get it there by turning the crankshaft, obviously. Again obviously, you cannot adjust the position of a piston without adjusting the position of the crank. The why and wherefore are undefined by the limited context you have given.