I heard it does and i heard it does not :dunno:

 

Combustion chamber is still the same size but the stroke gets longer and sweeps through more volume.

Compression ratio will increase with a stroked motor unless the pistons are dished or the head volume increased.

Compression ratio is Max volume / Final volume = Static CR

45/5=9.0 CR

Now stroke it 5 more CI

50/5=10.0 CR

You need actual precise dimensions and measurements to figure static CR.

Z28

 

It depends on what your idea of "stroking" is. If it involves sticking a bigger crank into the bottom end, clearancing, and nothing more, then of course it'll raise the compression ratio.

If your idea is buying different rods, pistons, doing headwork, decking the block, etc, then it depends on the combination of parts.

You can either raise/lower the compression by stroking the motor based on how you set it up.

BTW, this isn't an Advanced Tech question

Mike

 

Lol.....

Compression ratio...

If you keep the same chamber volume and increase the compression volume it will increase the Compression RATIO. Compressionn Volu : Chamber Volume.

That's the simple way to put it.

Bret

 

according to my teacher stroking does not increase compression

 

Well, he is wrong. Or else not answering the same question. Go to a simple CR calculator like the one right here on cz28 at https://www.camaroz28.com/calcs/index.shtml and play around with it to see the effect of stroking a motor on CR.

Rich

 

Well, technically, teacher is correct, although has allowed you to draw inaccurate conclusions, from his/her short response. (This is trusting, your attention span was not broken prior to teacher's complete response.) What stroking does, as Bret and Z brought to your attention in their own respective way, is cause the same combustion chamber volume to have more impact on the final CR. With the variables; deck height of the piston, along with (negative or positive) dispacement of piston crown contour, and combustion chamber volume remaining the same, CR will be raised, due to increased 'swept volume' of the piston. SV is the volume displaced, in the distance the piston travels, sliding from TDC, to BDC.

 

Holy smoke!

If the teacher is seriously standing behind that answer, after totally understanding
your question, he/she should be shot and pissed on.

Are you sure you clarified the question?

Maybe your teacher understood connecting rod length?

Allow me to extend another angle on the subject from a peon's (<me)point of view.

For a visual, use a one ounce shot glass to represent your combustion chamber.

Another one ounce shot glass full of liquid represents swept volume 'A"

A 2.0L bottle of Coke represents swept volume 'B'. (< the stroked motor)
(~67.63 ounces)

Do the math for volume ratios between the shot glass and bottle .

That would be a nice painted picture if your teacher insists you are incorrect.

 

I don't know......Some people have tough enuf time, sober.

 

To be a bit more pragmatic showing a real world example:

My current combo has a 3.75 stroke, the static compression is 11.91 and I'm bumping up the motor adding a new crank and pistons keeping the same cc combustion chambers. By just putting in a 3.875 stroke crank with the same rods, deck height, gasket, quench, valve relief, etc. the compression jumps to 12.3.

 

This is such a basic question that it could be answered by simply thinking about what compression ratio is and how it is calculated. It does not belong on Advanced Tech.