Understanding how the piston works in the engine enables you to comprehend far more about the engine including how they and the rings can fail.
As the piston goes down within the cylinder, the air and fuel are pulled (or injected) in the chamber. As the piston rises up the cylinder again, (called the power stroke), the air and fuel are compressed by the piston. The closer the piston is to the head of the cylinder, the more compressed the fuel and air end up being. As it gets to the top the spark plug ignites the fuel/air mixture causing the piston to be pushed back down the cylinder.
As the piston is pushed down by the explosion of gases back down it develops an area of low pressure within the cylinder, producing a vacuum. That’s exactly what draws the mix of air and fuel into the cylinder for the next power stroke, when it will certainly be compressed before being fired up again.
The connecting rods linking the bottom of the piston are linked to the crankshaft which transforms the up and down movement of the piston into a circular movement which is then connected through other drive shafts, gear boxes etc to the wheels.
Pistons Do Wear Out
Over time however, the pistons come under some stresses and get worn so they no longer make a good seal. At that point the piston rings need to be changed. It’s important that the pistons fit tightly within the cylinder in order to produce sufficient compression and vacuums.
Without that tight seal and resulting compressions etc it will not be possible to generate the right power and will lead to poor performance in terms of speed and fuel economy.
It is that stage you may find it useful to talk to Scott Cheyne of Croft Autotech in Ellon about the potential need for a full engine rebuild (or a partial top end engine rebuild). He will be able to carry out various compression tests to measure the performance of each piston/cylinder and run other diagnostic tests.
At that stage he will be able to recommend the best way forward to rectify any problems he found and your own feedback and experience of the falling performance you have noticed.
Phone Scott now on 01358 722112 or email him using our contact form.
Written By Scott Cheyne