Gandini Pistons

Cylinder displacement vs combustion chamber volume,  what other way is there?
 
That makes sense Grant..but how do you actually measure the combustion chamber volume ? The piston may have a domed surface with cut outs for valves, the head is shaped with valve seats sticking out at least to some degree...no doubt it is simple for you engineers who can do sums, but i have visions of complicated maths..or filling it up with fluid?some of which would leak down...enlighten me please?!
 
As i thought after checking the intereweb, not so easy. On steps 5 6 7 of 11 ( 7 is find the dome/dishvolume of the piston)..get this info from the manufacturer. Likewise get the volume of the combustion chamber from them.Simples? I think not.
 
Assumed, the valves do close completely and liquid tight, you can do as follows for the nett combustion-chamber volume (nett would mean: total combustion-chamber volume (brutt) minus the part of the piston that protrudes into the combustion chamber):

-Mount the Pistons onto the rods and into the cylinders
-put the old head gasket on
-bring one piston in TDC
-measure how many Milimeters it measures above the head gasket (let's assume that is 5mm, just to explain the way to work...)
-now take that piston, a measuring or graduated jug slightly bigger than the piston and fill it to a certain mark with gas or any other liquid that has no or almost no surface tension.
-now you need a construction that is able to lower the piston very controlled for the 5mm (or what ever you measured the piston reaches above the old head gasket)
-now check how many ml the water rose due to that. If you want to have it very cranular, you can take a hose and a syringe and suck out water until you reach the level the water had without the piston...). Now you know what volume the piston takes in the combustion chamber.

Step 2: turn the head upside down, take a small (!!) syringe and gently fill the combustion chamber with the same liquid. Note the amount as brut volume. Now deduct this amount by the volume measured in Step 1 and you have the net combustion chamber volume.

This then can be put into relation to the diameter x stroke volume and you have the ratio. Easy, eh?  :D

this is not 100% accurate, but close enough for a xx,x:1 value I feel.
 
I saw it shown on a Slater Jota in Bike magazine in the 70s, just to show the bike was not anything other than a stock engine.
They brought the right cylinder to TDC, removed the spark plug and filled the combustion chamber with oil from a measuring cylinder.
Then it's a simple calculation of cylinder head volume vs swept volume.
 
Come on, Grant, I was giggling thinking of him getting started on this overcomplicated setup and you are telling him the easy way to get around?  :-[

:LOL: :LOL: :LOL:

There is a danger though that there is an airbubble hiding somewhere in this setup, as the Cylinders are some degrees leaned forward. But it might come as close as my setup above, so - depending on if you have the engine apart or not, one or the other way would be possible.  ;)
 
Cylinder displacement vs combustion chamber volume,  what other way is there?

As far as I learned it should be Cylinder displacement plus combustion chamber volume vs combustion chamber volume.  :'(
 
Yes, I didn't spell it out exactly, just gave the basic things required.
 
"it should be Cylinder displacement plus combustion chamber volume vs combustion chamber volume." Correct.
Checked with fluid usually, and best with the motor out so it can be positioned to avoid air bubbles etc. and get the plug hole at the top.
It is not hard to check and calculate if you have the motor out.
 
CLEMTOG said:
Davo
how did you measure the compression ratio of your sprint, to arrive at it being 12:1?
CLEM
Click to expand...

Measure?  :o I read it in the manufacturer's specs.
 
Grant said:
Apples and oranges, you know that.
Click to expand...

I know, just thought I would throw in the numbers without mentioning fuel injection, engine management system and liquid cooling.
 
"Measure?  :o I read it in the manufacturer's specs."

see reply 18

OK then, I bit on that didn't I

CLEM

ps the swept volume (bore X stroke) is not the same as the actual volume at BDC
see Lothars reply
 
Who sells JE pistons for Laverda? Are they made to Laverda or does they need something extra work to fit?

I have thought that JE is mostly making pistons for V8's in the US. Is that the same corporation?

Also who sells the Accralite for Laverda?
 
You must log in or register to reply here.
Back
Top