VVTLIKICK, where you at?

[Slant]

As for the displacement question, The 2ZZ has a bore/stroke of 82mm/85mm, the 1ZZ has 79mm/91.5mm. So the 2ZZ has room to be stroked, and the 1ZZ has room to be bored.

I took this quote of yours from the Gen. Dis. section.
Can you explain this in layman terms?
82mm/85mm ---> ???
bore/stroke ---> ???

[Unity112]

I'm not vvtlikick :) but I will answer your question as simply as possible.

The bore can be described as two things. First it is described as the "hole" for lack of a better word that forms your cylinder wall and where the piston is fitted. The bore is where your engine does its most important functions. (intake, compression, combustion, and exhaust). This is also the area that you normally would alter to gain a bit of displacement. Secondly, it the measurement of how wide that area is from one edge to the other. Since the area is a circle, the measurement can be described as the "diameter". For the GT-S, it is 82mm.

Stroke is basically the distance that the piston travels up and down the shaft. Generally, longer stroked engines make power in low to mid rpm, and shorter strokes make power up higher in the rpm range.

Basically, he is saying, there is room (are you sure there is enough clearance?) to add some stroke to the 2zz and some bore to the 1zz.

[vvtlikick]

Originally posted by Unity112
I'm not vvtlikick :) but I will answer your question as simply as possible.

The bore can be described as two things. First it is described as the "hole" for lack of a better word that forms your cylinder wall and where the piston is fitted. The bore is where your engine does its most important functions. (intake, compression, combustion, and exhaust). This is also the area that you normally would alter to gain a bit of displacement. Secondly, it the measurement of how wide that area is from one edge to the other. Since the area is a circle, the measurement can be described as the "diameter". For the GT-S, it is 82mm.

Stroke is basically the distance that the piston travels up and down the shaft. Generally, longer stroked engines make power in low to mid rpm, and shorter strokes make power up higher in the rpm range.

Basically, he is saying, there is room (are you sure there is enough clearance?) to add some stroke to the 2zz and some bore to the 1zz. Yep, the bore is the diameter of the hole in the block for each cylinder, and the stroke is how much the piston moves up and down in that hole.

I don't know for a fact that's there's enough clearance in the 2ZZ to accomodate a long stroke crank (like one with the 1ZZ's 91.5 stroke), but there was that Japanese "3ZZ" that put the 1ZZ crank in the 2ZZ (custom block work required?).

As for boring the 1ZZ, there should be enough room to do so, because both engines have the same distance between the centerlines of each cylinder, so I'm sure you could at least match the 2ZZ's bore in a 1ZZ.

[Slant]

both engines have the same distance between the centerlines of each cylinder
what do you mean by that?

[autxr]

Bore centers...

OK, look down at an engine block. There are holes (4 of them in the case of a 4 cylinder engine).

We have an inline 4, so the 4 holes are lined up in a row.

Now, imagine the center point of each bore, measur ethe distance from the center of each hole to the next and they are the same.

I need to draw a picture...

Scott

[vvtlikick]

Originally posted by autxr
I need to draw a picture...Took care of it for you. :)

<img src="http://216.12.31.28/forums/attachment.php?s=&postid=14013">

[Slant]

Ok. Pictures are always helpful. Bare with me, I trying to understand the whole engine thing.

So, the pistons from the two engines would have different diameter, right? What about the length? B/c they have different stroke.

[vvtlikick]

Originally posted by Slant
Ok. Pictures are always helpful. Bare with me, I trying to understand the whole engine thing.

So, the pistons from the two engines would have different diameter, right? What about the length? B/c they have different stroke. Yep, the pistons on the 2ZZ are wider than the pistons on the 1ZZ (They'll be just smaller than 82mm and 79mm, respectively). But the 2ZZ uses a shorter stroke than the 1ZZ (85mm vs. 91.5mm). The shorter stroke is used, because it's more friendly to high-rpm use.

The crankshaft determines the stroke, not the conrods or pistons, but conrods and pistons would have to be changed to fit a crankshaft with a different stroke. The conrods would have to be of the correct length to locate the piston correctly at the top of its new stroke, and the pistons would have to use a different top profile to adjust the compression ratio, because the combustion chamber size would otherwise be the same, but the amount of air being compressed would be greater (more displacement).

Here's (http://www.howstuffworks.com/engine2.htm) a good description and diagram of an automobile engine including the crank, rods, etc. (Note that it's only SOHC, however. All ZZ engines are DOHC.)

[Slant]

Ok, one more. I'm on a roll here.
Compression ratio. Is that's how much the air and gas is compressed by the piston? So how would higher/lower compression be achieved? Different sized pistons?
And lastly, why is lower compression better for forced induction? It is just that the parts aren't strong enough to handle all the pressure?

[vvtlikick]

Originally posted by Slant
Ok, one more. I'm on a roll here.
Compression ratio. Is that's how much the air and gas is compressed by the piston? So how would higher/lower compression be achieved? Different sized pistons?
And lastly, why is lower compression better for forced induction? It is just that the parts aren't strong enough to handle all the pressure? CR (Compression ratio) is the ratio between the volume of the cylinder when the piston's at TDC (Top Dead Center) and the volume of the cylinder whens the piston's at BDC (Bottom Dead Center). Note: the actual CR in practice is less than the listed CR, because the cylinder never gets a full breath of air (at best it only fills like 90%).

The volume of the cylinder at TDC is the volume of the combustion chamber. The volume of the cylinder at BDC is the volume of the combustion chamber plus the displacement of the cylinder.

CR can be increased by shaving the head (removing material on the bottom of the head) to bring it closer to the block, shrinking the combustion chamber. But this means piston/valve clearance is reduced. Or you can run a thinner head gasket to achieve similar results with the same concern about piston valve clearances. Or you can do it the right way ;), and buy high compression pistons (with a high domed top protruding into the combustion chamber). I don't know how/what you can do to reshape the combustion chamber itself to increase CR.

CR can be decreased by running a thicker head gasket, but this could impair its' ability to seal against combustion pressure. Or you can do it the right way ;), and buy low compression pistons (with a dished out top enlarging the combustion chamber). I don't know how/what you can do to reshape the combustion chamber itself to decrease CR.

I think CRs are limited mostly by concerns over self-ignition due to excessive compression (the air/fuel mixture ignites itself, before the spark plug fires). So boost requires a lower CR to avoid self/preignition, because there's more air and fuel being crammed into the cylinder.