Measuring Cylinder Capacity

[JohnD]

Yes, but a lot less messy than measuring oil!
John

[wnut]

Originally Posted by dtype38

I'have done some measuring of actual chamber volume (ie volume of chamber including gasket etc with piston at tdc) using oil down the plug hole. I simply set the piston at tdc firing stroke and measure oil in until it reaches the top of the spark plug hole. Subtracting the volume of metal in plug gives a pretty accurate measurement of real chamber volume. Taking the oil out is then just a matter of lowering the piston a bit then using a big syringe with a thin bit of plastic tube on the end. Any residual oil burns off pretty quickly.

Going back to the method I suggested though, if its just swept volume that's needed to be measured (not actual bore) then the maths is a doddle:

Swept Vol = Control volume of oil added x (stroke / height change in oil level)

"height change in oil level" being the difference between the two dipped heights when the control volume of oil is added (with the previously mentioned provisions about piston crown and chamber edges).

Ie if the stroke is 8cm and adding 100cc of oil give a rise in height of 2cm, then the swept vol = 100 x (8/2) = 400cc

I believe I'm correct in saying that this works even if the cylinder is inclined (so long as "height" is measured parallel to the bore).

Sounds good to me.
Just level the cylinder using a slope or a jack, slope and a jack.
Don't roll (overturn) the car down the slope!
Suck the bulk of the oil out with an extractor syringe, turn the engine over and blow the rest out into a rag.
Don't do it on anything with a catalytic convertor! The oil will kill the cat!

[DX20VT]

I did something similar a few years back when I was tech inspecting some cars for a series.

Was quite easy as all the cars that I had to check were DOHC engines,
mainly Mitsi Evo's 4G63.

I cam up with the theroy that how much extra capacity go you go with a standard stroke?
Answer was not a hell of a lot, and all I was trying to determine was which engines were 1800cc, 2000cc, and which were 2.2/2.3L.

You couldn't bore an engine far enough on standard stroke to make one into the other, adn so all I measured was stroke.

So I made a tool that screwed into the sparkplug hole and had a 6mm hole right through it. With a 6mm rod dwon the centre onto the piston found TDC and BDC and measured the difference to give stroke.

I measured those that were complaining and those who being complained about, and when both measurements were the same it ended the arguement.

So you originally stated within 10% accuracy,
maybe a similar method may work depending on what engines you have to do it on??

[Al Weyman]

Originally Posted by JohnD

Yes, but a lot less messy than measuring oil!
John

But no good if it don't work!

[graham bahr]

only applicable to engines where the spark plug is in the middle of the bore and vertically aligned, but ive seen scrutineers use a trellis type devise down a spark plug hole to meassure bore size, and another dti affair to measure stroke, its accurate enough give or take a few cc, so you might not find an engine thats a few cc too big, but youd certainly spot one much bigger.

thinking about it, it was scrutineers colin barnet and mike hibbins ive seen, colin on tv, mike ion the paddock at lydden